BERICHTE DER BUNSEN-GESEULSCHAFT FUR PHYSIKALISCHE CHEMIE AN INTERNATIONAL JOURNAL OF PHYSICAL

Jahresregister von Band 91 (1987)

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Inhaltsverzeichnis von Band 91 (1987) (Autorenverzeichnis, Sachverzeichnis, Buchbesprechungen, Personalnachrichten)

A. Autorenverzeichnis

Abrantes, L. ML, R. Peat, L. M. Pe­ter, A. Hamnett: Electroreflec-tance at the Semiconductor/Elec­trolyte Interface. A Comparison of Theory and Experiment for n-GaAs 369

Acs, Α., R. Schmidt, H.-D. Brauer: Generation and Deactivation of ' Ο ^ ' Δ ) by Helianthrene and He-lianthrene-Derivatives 1331

- siehe H.-D. Brauer 1337 Albers, P. W., G. H. Sicking, L. G.

Earwaker, J. B. A. England: Depth Profiling of Hydrogen Iso­topes in Metals by Elastic Recoil Detection and Nuclear Reaction Techniques under In-Situ Con­ditions 573

Allongue, P., H. Cachet: Photoca-pacitance Study of n-GaAs/Elec-trolyte Interfaces 386

Alonso, M. C , siehe Μ. Costas . . . 184 Anderko, Α., siehe A. Ksiazczak . . . 1048 Andrecv, Β. Μ., G. Η. Sicking: Hy­

drogen Equilibrium Separation Factors in Metal/Hydrogen Sys­tems, a Synopsis on the Basis of the Localized Harmonic Oscilla­tor Model 177

Andres, K., siehe Κ. Späth 909 Anic, S., Lj. Kolar-Anic: The Influ­

ence of Potassium lodate on Hy­drogen Peroxide Decomposition in the Bray-Liebhafsky Reaction 1010

Anik, S., M . G. Frohberg: Thermo­dynamics and Solubility of Oxy­gen in Liquid Bismuth-lead and Bismuth-antimony Alloys 790

Apelblat, Α., Ε. Manzurola: Ther­modynamic Analysis of Partition Data in the CaCl 2 -H 2 0-n-Oc-tanol and CaCl 2 -H 2 0-n-Bu-tanol Systems.at 298.15 Κ 1387

Appel, I . , Κ. Kleinermanns: Fluores­cence Excitation Spectra of Hy­drogen-Bonded Cresol-Isomers in Supersonic Free Jets 140

Aracil, J., R. G. Rubio, J. A. R. Re-nuncio, M . Diaz Pena: Vapour-Liquid Equilibrium of n-Tetra-decane and of n-Hexadecane with Hexafluorobenzene and with Hexafluorobenzene -I- Benzene at 323.15 Κ 603

Arendt, P.: Diffusion of Excess Elec­trons in Decomposing Liquid Metal-Ammonia Solutions in the High-Conducting State, Injected into a Zero-Electric Field Space . 1363

Armitage, H., U . Blömer, I . Genge, A. Khuen, Ε. E. Wille, D. Ziessow: Fortschritte in der 2D-NMR-Spektroskopie mit Rauschanre­gung 1115

Auweraer, Μ. Van der 869

Badiali, J. P.: The Jellium Model in Electrochemistry 270

— siehe M . L. Rosinberg 276 Bässler, H., siehe F. Stolzenburg . . . 853 Bagdasarian, V. V., siehe Α. A. Sha-

hinian 670

Bahr, Ch., G. Heppke: Ferroelectric Liquid Crystals — Properties of the Smectic C Phase and the Smectic Α Phase of Compounds with High Spontaneous Polari­zation 925

Balducci, G., G. Gigli, M . Guido: Thermochemical Study of the Gaseous Molecules EuNb0 3 , EuNbO,, EuNb 2 0 6 and of the Niobium Oxides NbO and N b 0 2 635

Bartsch, Ε., Η. Bertagnolli: Test of a Symmetry Reduced Extended R1SM (XRISM) Equation Against Diffraction Experiments on Liquid Benzene and Hexafluo­robenzene and Evaluation of Op­timized Potentials 745

Bäuerle, P., M . S. Wrighton, Ο. M . R. Chyan, C W. Spangler: New Conducting Polymers of Some Bithiophene- and Bis-N-Methyl-pyrrole Polyenes, Their Proper­ties and Their Application in M i -croelectrochemical Devices 889

Baumann, F., siehe S. Schneider . . . 1225 Beck, F., G. Heydecke: On the

Mechanism of the Cathodic Re­duction of Anthraquinone to An-throne 37

- P. Braun, Μ. Oberst: Organic Electrochemistry in the Solid State-Overoxidation of Polypyr-role 967

Becker, A. C, U. Schurath: NBr (b1 Σ + , a1 Δ) in Solid Argon: Effect of the Rare Gas Matrix on Ra­diative and Radiationless Proc­esses 1238

Becker, F., siehe Μ. Erol 731 Becker, Κ. D., F. Rau: High Tem­

perature Ligand Field Spectra in Spinels: Cation Disorder and Ca­tion Kinetics in N i A l 2 0 4 1279

Beden, B., siehe J.-M. Leger 336 Belkoura, L., siehe Μ. Jungk 507 - F. P. Harnisch, S. Kölchens, Th.

Müller-Kirschbaum, D. Woer-mann: Study of the System Nitro-benzene/Isooctane in the Vicinity of its Critical Point: Static and Dynamic Light Scattering and Reevaluation of Ultrasonic Ab­sorption Data 1036

Bertagnolli, H., siehe Ε. Bartsch . . . 745 - Τ Engelhardt, Β. Lengeier: Local

Order in Liquid Bromobenzene — EXAFS Measurement and its Combination with X-Ray and Neutron Diffraction Results 1287

Bethune, D. S., siehe J. K. Sass 320 Beuthien, H., A. Torkler, W. Gunßer,

W. Niemann: X-ray Investiga­tions of the Thulium-Iron Crys­tallization Process 1296

- siehe A. Torkler 1300 Bhat, S. N , siehe Ν. Van Nhu . . . . 525 Biasio, A. Di , siehe F. Bordi 737 Bignell, C. M. , siehe P. J. Dunlop . 156 - siehe P. J. Dunlop 817 Biswas, S. R , siehe Τ F. Sun 1013 Bitterling, Κ., siehe F. Willig 869

Blömer, U., siehe H. Armitage . . . . 1115 Blümich, B , C. Böflel, G. S. Harbi­

son, Y. Yang, H. W. Spiess: Two-Dimensional MAS NMR: New Prospects for the Investigation of Partially Oriented Polymers 1100

- siehe C. Chmidt 1141 Blume, Α., siehe W. Hübner 1127 Bockhorn, Η., F. Fetting, A. Hedd-

rich, G. Wannemacher: Untersu­chung der Bildung und des Wachstums von Rußteilchen in vorgemischten Kohlenwasserstoff — Sauerstoff Unterdruckflam­men 819

Bodensteiner, T , siehe R. Winter . . 1327 Böflel, C, siehe B. Blümich 1100 Böhm, M. C, R. Ramirez, Α. Μ.

Oles: The One-Dimensional Band Structure of (Tetrazapor-phyrinato)iron(Il) 717

- siehe S. Fleck 1167 Börsch-Pulm, Β., siehe G. Hohl-

neicher 929 Borchers, D., Al. Weiss: Structures

and Phase Transitions in Pipe-razinium Hcxachlorometallates, (C 4 HpN 2 ) [MCl 6 ] , Μ = Te, Pb, Pt, and (C 4 H 1 2 N 2 )[MC1 6 ] · 3 H 2 0 , Μ = Sn. A X-ray Diffraction and 3SC1 NQR Study 1182

Borczyskowski, C. von: Optically Detected NQR on Matrix-Iso­lated Organic Molecules . . . 1137

Bordi, F., C. Cametti, A. Di Biasio: Osmotic Pressure of Aqueous Rod-Like Polyelectrolyte Solu­tions with Mono- and Di-Valent Counterions 737

Borggreven, J. Μ. P. M., siehe Η. P. F. Scholberg 129

- siehe Η. P. F. Scholberg 135 Boudh'hir, Μ. Ε., siehe Μ. L. Rosin­

berg 276 Bougeard, D., siehe S. Schroetter . . 1217 - N . Le Calve, B. Pasquier: Crystal

Dynamics and Phase Transitions of Malonitrile 1273

Boyadjiev, B.: Der Einfluß der Nah-ordnungsstruktur auf die chemi­schen Verschiebungen der Aro-matenprotonen in flüssigen M i ­schungen von Acetonitril mit 5 aromatischen Lösungsmitteln . . . 225

Bräuchle, Chr.: Optical Solid State Spectroscopy by Holographie Grating Techniques with Quan­tum Limited Sensitivity 1247

Brandner, G., F. L. Dickert, Ε. Leh­mann: The Formation of Carben-ium Ions and Naked Anions by the Protonation of Phthalophen-one with a Super Acid 740

Brauer, H.-D., siehe A. Acs 1331 - A. Acs, R. Schmidt: The Role of

Geminate Reaction in the Self-Sensitized Photooxygenation of Helianthrene and Helianthrene-Derivatives/Encounter- and Re-encounter Probabilities 1337

Braun, D., siehe Η. Yersin 1228 Braun, P., siehe F. Beck 967

VI Inhaltsverzeichnis von Band 91 (1987) — Autoren Verzeichnis

Brei, Μ., H. Jander, H. Gg. Wagner: Integral Carbon Mass Balance in Premixed Sooting Flames 30

Brückner, W., K. Grande, Η. A. 0ye: Vapour Pressure of the AlCl r POCh System 561

Brummer, S., AI. Weiss: NQR Spec­troscopy and Structure of Pho-tochromic 2,3,4,4-Tetrachloro-1 -oxo-l,4-dihydronaphthaline and 2 ,4 ,4 -Tr i ch lo ro - l ,4-dihydro-naphth[l ,8-cd]isothiazole-l , l -dioxide 873

Buchberger, Ε. Μ., B. Mollay, W.-D. Weixelbaumer, H. F. Kauffmann, W. Klöpffer: Time-Resolved Flu­orescence of Bichromophoric Ro­tors — Conformational Dynam­ics of l,3-di(N-carbazolyl)pro-pane 1209

Buchmann, L.-M., E. Illenberger: The Interaction of CFCU and CF 2C1 2 with Solid Surfaces Stud­ied by Thermal Desorption Mass Spectroscopy 654

Büttner, H., siehe U. Sum 957

Cachet, Η., siehe P. Allongue 386 Calve, Ν. Le, siehe D. Bougeard . . . 1273 Cametti, S., siehe F. Bordi 737 Cardon, F., siehe L. S. Yun 390 Carnie, S. L.: Recent Developments

in Double Layer Theory 262 Castro, C. A. Nieto de, siehe U. V.

Mardolcar 152 Chang, R. K.: Surface Enhanced Ra­

man Scattering at Electrodes: A Status Report 296

Chyan, O. M . R., siehe P. Bäuerle . 889 Clausen, B. S., siehe W. Niemann . . 2192 Conrady, R., W. Müller-Warmuth,

B. Krebs, G. Schwetlik, M . Wien-. kenhöver: Nuclear Quadrupole Coupling and Electronic Struc­ture of Boron Trihalide Adducts with Chalcogen Ligands 1322

Conway, Β. Ε., T. C. Liu: Behaviour of Surface Intermediate States in Anodic 0 2 Evolution Electroca-talysis at C o 3 0 4 on N i and Ti Substrates 461

— D. P. Wilkinson, D. F. Tessier: Catastrophe Situation for Poten­tial-Assisted Electron Transfer in Relation to Temperature-De­pendence of Tafel Slopes 484

Costas, Μ., M . C. Alonso, A. Heintz: Experimental and Theoretical Study of the Apparent Molar Volumes of 1-Alcohols in Linear Hydrocarbons 184

Dachwitz, Ε., Μ. Stockhausen: A Dielectric Relaxation Study of Self and Heteroassociation in Bi­nary Liquid Mixtures of Three Pyrrolidinones with Alcoholes and Water 1347

DalFO, L., H . Heydtmann: Kinetic Study of Chemically Activated Fluorocyclopropane 24

Decker, F., J. R. Moro, J. L. S. Fer­reira, Μ. Vanzi: Growth and Morphology of Electrodeposited Semiconducting Films 408

Degen, J.: Application of Photon Count Statistical Measurements to the Stationary Fluorescence of Fluoranthene 1215

Denninger, G., siehe Th. Schimmel . 901 Deul, R., siehe R. Diguet 551

Dick, B.: Fluorescence Studies of Ex­cited State Intramolecular Proton Transfer (ESIPT) in Molecules Isolated in Solid Argon: 3-Hy-droxyfiavone and 2,5-Bis(2-ben-zoxazolyl)hydroquinone 1205

Dickert, F. L., siehe G. Brandner . . 740 Dieckmann, R., siehe P. Franke . . . 48 - Μ. R. Hilton, Τ. Ο. Mason: De­

fects and Cation Diffusion in Magnetite (VIII): Migration En­thalpies for Iron and Impurity Cations 59

Diguet, R., R. Deul, E. U. Franck: Static Dielectric Constant and Density of Supercritical Meth-ane-Methanol-Mixtures to 200 MPa 551

Dong, S., R. Jiang: Research on Chemically Modified Electrodes: Electrocatalytic Reduction of Dioxygen by Iron Tetraphenyl-porphyrin Modified Glassy Car­bon Electrode with Heat Treat­ment 479

Dormann, E., G. Sachs: The Low-Temperature Phase of the Or­ganic Conductor (Fluoranthe-ne)2PF6 879

- siehe P. Strohriegel 918 Dorris, S., siehe Μ. Martin 779 Driessens, F. C. M., siehe Η. P. F.

Scholberg 129 - siehe Η. P. F. Scholberg 135 Dunlop, P. J., H. L. Robjohns, C. M.

Bignell: Diffusion Coefficients and Thermal Diffusion Factors for the Systems He — CF 4 and N e - C F 4 156

- C M . Bignell: Diffusion in Binary Mixtures of Ammonia with No­ble Gases 817

Durfee, W. S., siehe F. Willig 869 Durham, W. Β., Η. Schmalzried:

Chemical Potential Measure­ments on Nonhydrostatically Stressed Solids 556

Earwaker, L. G., siehe P. W. Albers 573 Ehbrecht, J., W. Hack, P. Rouvei-

rolles, H. Gg. Wagner: Hydrogen Abstraction Reactions by NH2(X2B,)-Radicals from Hydro­carbons in the Gas Phase 700

Eichberger, R., siehe F. Willig 869 Elfenthal, L., Κ. Leitner, J. W.

Schultze, O. Meyer: Migration of High Energy Defects After Pd-Implantation in Oxide Films on Titanium 432

Elfmger, G , siehe S. Schneider 1222 Engelhardt, T , siehe H. Bertagnolli 1287 England, J. Β. Α., siehe P. W. Albers 573 Enkelmann, V., siehe P. Strohriegel 918 - K. Göckelmann: Structure and

Phase Transitions of Aromatic Radical Cation Salts — a New Class of Organic Metals 950

Ernst, R. R.: Advanced N M R Meth­ods for Liquids and Solids: Two-Dimensional Spectroscopy 1087

Erol, Μ., M . Kocak, P. Richter, A. Steiger, F. Becker: The Influence of Dissolved Electrolytes on the Miscibility of Binary Liquid Sys­tems with Closed Miscibility Gaps 731

Ewig, F., D. Rhäsa, R. Zellner: K i ­netics, Energetics, and OH Prod­uct Yield of the Reaction C H 3 0 + 0( 3 P) -> C H 3 0 2 -> Products 708

Ezquerra, Τ. Α., siehe J. Rühe 885

Fechter-Rink, Ε., siehe H.-G. Kuball 1266 Feiner, A. S., A. J. McEvoy, Ν.

Vlachopoulos, Μ. Grätzel: Elec­trochemical Photooxidation of Carboxylates on CdS Electrodes 399

Fernandez, Α.: Theory of Scaling for Fluctuations in Thermal Explo­sion Conditions 159

— Renormalization Group from a Center Manifold Reduction in Dynamic Critical Phenomena . . 570

— Statistical Weights for Primary Structures of Inhomogeneous Polymer Chains 611

— Statistics of Disordered Polymers: An Effective Hamiltonian and its Associated Gibbs Measure 753

— Intrinsic Fluctuations in Ma-cromolecular Self-Replicating Systems 1002

Ferrer, I . J., P. Salvador: Photoetch-ing of Polycrystalline n-CdS Film Electrodes in a Photoelectro-chemical Cell: an Electrolyte Electro reflectance Study 374

Fetting, F., siehe Η. Bockhorn . . . . 819 Ferreira, J. L. S., siehe F. Decker . . 408 Fesser, K., siehe U. Sum 957 Fleck, S., siehe AI. Weiss 913 — M. C Böhm, N. Weiden, AI.

Weiss: Hydrogen Bonds in Am­monium Hydrogen-DL-Malate Monohydrate Studied by 2 H -NMR, IR, and LCAO - MO Cal­culations 1167

— siehe A. Kehrer 1176 Förstcrling, H. D., siehe H. Schreiber 798 Fojtik, Α., siehe L. Spanhel 88 — siehe A. Henglein 441 Fontaine, F., siehe J. Ledent 112 Frahm, J., siehe K.-D. Merboldt . . . 1124 Franck, E. U., siehe R. Diguet . . . . 551 — siehe T. Krader 627 Franke, P., R. Dieckmann: Defect

Structure and Transport Proper­ties of Manganese Oxides: (III) Relaxation Kinetics of Manga-nosite ( M n ^ O ) in CO/C0 2 Gas Mixtures 49

Freeman, P. Α., siehe R. Hayes 231 Friedrich, J., siehe W. Köhler 858 Frohberg, Μ. G , siehe S. Anik . . . . 790 Furlong, D N., siehe R. Hayes . . . . 231 Furuya, N. , siehe S. Motoo 457

Gäl, D., siehe G. Moger 794 Gallhuber, E., siehe Η. Yersin 1228 Gamsjäger, Η., siehe Ε. Königsber­

ger 785 Garnier, F., siehe D. Gningue 402 Gaube, J., siehe L. König 116 Genge, I . , siehe H. Armitage 1115 Gerhard, W., siehe L. König 116 Gerischer, H., D. Kolb 262 — M . Lübke: The Electrochemical

Behaviour of η-Type Silicon (lll)-Surfaces in Fluoride Con­taining Aqueous Electrolytes . . . 394

— siehe Τ. Solomun 412 — siehe R. Mclntyre 488 Gerads, H., siehe K. Hilpert 190 Gigli, G , siehe G. Balducci 635 Gläser, W., siehe R. Winter 1327 Gliemann, G., siehe R. Schwarz . . . 1233 Gningue, D., G. Horowitz, F. Gar­

nier: Stabilization of CdS and CdSe Photoelectrodes Modified by a Catalyst-Containing Poly-thiophene Coating 402

Göckelmann, Κ., siehe V. Enkel­mann 950

Goez, Μ.: Extremely Sensitive Op-

Inhaltsverzeichnis von Band 91 (1987) — Autorenverzeichnis V I I

tical Detection System for Stopped-flow Measurements of Reactions with Very High Rate Constants or Small Absorbance Changes 616

Gogu, E., siehe D. Schweitzer 890 — siehe W. Kremer 896 Gomes, W. P., siehe L. S. Yun . . . . 390 Gordon, J. G , siehe Κ. A. Bunding

Lee 305 Goto, Ν., siehe Τ. Ohtsuka 313 Gottesfeld, S.: The Time-Resolved

Response of Semiconductor-Elec­trolyte Interfaces to Short Pulses of Illumination 362

Grätzel, M., siehe A. S. Feiner . . . . 399 Grande, K., siehe W. Brockner 561 Greger, M., L. Riekert: Nonequili-

brium Phase Transitions in Solid Catalysts for Oxidation 1007

Grieser, F., siehe R. Hayes 231 Gross, F., siehe K. Späth 909 Gruner-Bauer, P., siehe P. Strohrie­

gel 918 Grupp, Α., siehe M. Mehring 1132 Gütlich, P., siehe L. König 116 Guido, M., siehe G. Balducci 635 Gunßcr, W., siehe H. Beuthien 1296 — siehe A. Torkler 1300

Haak, R., siehe R. Tenne 597 Haarer, D., siehe H. Kaul 845 Hack, W.. siehe J. Ehbrecht 700 Hänickc, W., siehe K.-D. Merboldt. 1124 Hallcy, J. W., J. Hautman: Molecu­

lar Dynamics Study of Raman Scattering and Infrared Absorp­tion of Ferrous and Ferric Ions in Aqueous Solution 491

Hamnett, Α., A. R. Hillman: Ellip-sometric Study of the Growth of Thin Organic Polymer Films . . . 329

— siehe L. M . Abrantes 369 Hansen, G. J., W. N . Hansen: In­

frared Spectroscopy of the Elec­trochemical Double Layer Via Electrode Emersion 317

Hansen, W. N., siehe G. J. Hansen . 317 Harbison, G. S., siehe Β. Blümich . 1100 Harnisch, F. P., D. Woermann: En­

thalpy of Demixing of a Binary Liquid Mixture of Critical Com­position: Study of the System Iso-butyric Acid/Water 811

— siehe L. Belkoura 1036 Hartmann, J., Al . Weiss: Nuclear

Quadrupole Resonance of Sub­stituted Anilinium Halides. l 2 7 I and 7 9Br NQR Studies of Tolui-dinium and Paraphenylenediam-monium Halides 1195

Hautmann, J., siehe J. W. Halley . . 491 Hayes, R., P. A. Freeman, P. Mul-

vaney, F. Grieser, Τ. W. Healy, D. N . Furlong: The Effects of pH and Adsorbed Hydrolysed Metal Ions on the Photodissolution of Col­loidal Cadmium Sulphide 231

Healy, T. W., siehe R. Hayes 231 Heddrich, Α., siehe Η. Bockhorn . . 819 Heidmann, C. P., siehe K. Späth . . 909 Heindl, D., siehe P. Strohriegel 918 Heinze, J., M . Störzbach, J. Morten-

sen: Experimental and Theoreti­cal Studies on the Redox Prop­erties of Conducting Polymers . . 960

Helberg, Η. W., siehe W. Kremer . . 896 — Electronic Excitations in (BEDT-

TTF)-Salts 899 Heimle, Μ., siehe F. Hentsch 911 Heintz, Α., siehe M . Costas 184 — An Efficient Calculation Proce­

dure of Predicting Heat Conduc­tivities of Complex Gaseous Mix­tures 190

Heinze, J., siehe Κ. Hinkelmann . . . 243 Henderson, D., Ε. Leiva, W.

Schmickler: The Jellium/Hard Sphere Electrolyte Interface . . . . 280

Henglein, Α., siehe L. Spanhel 88 — A. Fojtik, H. Weiler: Reactions

On Colloidal Semiconductor Particles 441

— siehe L. Spanhel 1359 Henning, I . , siehe D. Schweitzer . . . 890 Hensel, F., siehe R. Winter 1327 Hensler, G., siehe Η. Yersin 1228 Hentsch, F., Μ. Heimle, D. Könge-

ter, Μ. Mehring: Knight Shift in the Organic Conductor (Fluoran-thenyl)2AsF6 911

Heppke, G , siehe Ch. Bahr 925 Hermann, W., A. Raith, H. Rau: Dif­

fusion of Fluorine in Silica 56 — siehe Η. Rau 833 Heusch, R., F. Kopp: Structures in

Mixtures of p-tert-Octylphenol Polyoxyethylene and Water. 1. Triton X-114R 806

Heydecke, G , siehe F. Beck 37 Heydtmann, Η., siehe L. DalPO . . . 24 — siehe U. Schwanke 1043 Hillmann, A. R., siehe A. Hamnett . 329 Hilpert, Κ., H. Gerads, D. Kobertz,

M. Miller: Composition and Thermochemistry of the Equilib­rium Vapour of the Systems Nal - Fel 2 and Nal - Pbl 2 200

— siehe Μ. Miller 642 — Κ. Ruthardt: Determination of

the Dissociation Energy of the Cr 2 Molecule 724

Hilton, M . R., siehe R. Dieckmann . 59 Hinkelmann, Κ., J. Heinze: Analysis

of "Two-electron" Transfer Proc­esses by Cyclic Voltammetry . . . 243

Höfer, P., siehe Μ. Mehring 1132 Hoffmann, Η., J. Kalus, Β. Schwand-

ner: Small-angle Neutron Scatter­ing-measurements on a Surfac­tant System Consisting of Cat-ionic and Anionic Surfactant Molecules 99

— J. Kalus: Small Angle Neutron Scattering Measurement on a M i -cellar Solution of Dodecylam-monium-Triiluoro-Acetate Mole­cules 546

Hohlneicher, G , B. Borsch-Pulm: Classification of Higher Excited States in (4N+ 2)-Annulenes and Related π-Electron Systems 929

Homann, Κ. H., siehe Μ, Schottler. 688 — siehe Ch. Kubitza 695 — J. Traube: Use of a Wien Filter

for Mass and Velocity Analysis of Charged Soot Particles in a Nozzle Beam 828

Horiuchi, K., R. Ikeda, D. Naka-mura: Phase Transition and Anionic Motion in Solid [(CH 3 ) 2 NH 2 ] 2 SnCl 6 as Studied by the Temperature Dependence of 3 5C1 NQR Frequencies and Chlorine Nuclear Relaxation Times Determined with a Pulsed NQR Spectrometer 1351

Horowitz, G., siehe D. Gningue . . . 402 Hoshi, T , J. Okubo, M . Yananoto,

S. Tanabe: Electronic Spectra and Structures of Cation Radicals Produced from p-Phenylenedi-amine and 2,7-Diaminonaphtha-lene 1069

Hsin-min, J., siehe U. Nickel 997 Hübner, W., A. Blume: 2 H-NMR-

Spectroscopic Investigations of Phospholipid Bilayers 1127

Hürth, Μ., D. Woermann: Deuter­ium Isotope Effects in Binary Critical Mixtures Study of the Systems Methanol/Isooctane and Acetonitril/Water 614

Hüsser, Ο. Ε., Η. von Känel: Opti­cally Generated Space Charge Layer in Insulators: Electrolyte Electroreflectance at the B i l 3 / Electrolyte Interface 379

Huck, H.: Die Messung der Ultra­schall-Diffusion an einer Elek­trode und ihre praktische Anwen­dung 647

Huth, M. , siehe O. Schrems 1261

Ikeda, R., siehe S. Sato 122 — siehe K. Horiuchi 1351 Ikegami, K., siehe N . Yoshida 666 Illenberger, E., siehe L . -M. Buch­

mann 654

Jaegermann, W., siehe M . Sander . 416 Jander, H., siehe M . Brei 30 Jöllenbeck, Κ. M. , J. U. Weidner:

Röntgen Strukturuntersuchung des flüssigen Silicium-, Germa­nium- und Zinntetrachlorids. Ein Beitrag zur Frage einer gemein­samen Flüssigkeitsstruktur. I . Streuexperimente an den reinen Komponenten und ihren binären Mischungen 11

Röntgenstrukturuntersuchung des flüssigen Silicium-, Germa­nium- und Zinntetrachlorids. Ein Beitrag zur Frage einer gemein­samen Flüssigkeitsstruktur. I I . Bestimmung der individuellen partiellen Paarkorrelationsfunk­tionen. Vorschlag eines einheit­lichen Strukturmodells 17

Jungermann, G , G. Luft: Vergleich der Perturbed-Hard-Chain-Theorie mit der Freien-Völumen-Theorie und der Flory-Huggins-Theorie zur Berechnung von Phasengleichgewichten von Ethy-len/Polyethylen-Mischungen un­ter Hochdruck 541

Jungk, M . , L. Belkoura, D. Woer­mann, U . Würz: Study of a Binary Critical Mixture of 2,6-Dimethyl Pyridine/Water: Measurements of Static and Dynamic Light Scattering and Specific Heat Near the Lower Critical Point 507

Kaiser, W., A. Seilmeier: Schwin­gungsenergieumverteilung in Lö­sung 1201

Känel, Η. von, siehe Ο. Ε. Hüsser . 379 Kalus, J., siehe H. Hoffmann 99 — siehe H . Hoffmann 546 Kappus, M . , siehe H.-G. Kuball . . . 1266 Karaaslan, H., siehe E. Yurtsever . . 600 Kassner, K., siehe P. Reineker . . . . 864 Kauffmann, H. F., siehe Ε. M . Buch-

berger 1209 Kaufmann, S., siehe C. Schmidt . . . 1141 Kaul, H., D. Haarer: Charge Carrier

Generation and Transport in Po-lyvinylcarbazole: A Model Sys­tem for Polymerie Photoconduc-tors 845

Kehrer, Α., S. Fleck, AI. Weiss: 7 9 ' 8 , Br and 1 2 7 I NQR Studies of Hydro-bromides and Hydroiodides of Amino Acids and Dipeptides . . . 1176

ν π ι

Keldenich, J., siehe G. Peschel 285 Keller, H. J., siehe D. Schweitzer . . 890 — siehe W. Kremer 896 Keller, J. U.: Thermodynamics of

Non-Isothermal Coadsorption Processes 528

Kersting, H.-J., siehe Η. Stegemeyer 3 Khuen, Α., siehe Η. Armitage 1115 Kishimoto, S., siehe N . Yoshida . . . 666 Kita, H., siehe K. Uosaki 447 Kiyan, Ν. Z., siehe Ο. A. El Seoud . 825 Klein, B., siehe U. Nickel 997 Kleinermanns, K., siehe I . Appel . . 140 Klöpffer, W., siehe Ε. M . Buchber-

ger 1209 Klüter, U., siehe S. Schneider 1225 Klump, Η. H.: Characterization of

Highly Repeated Sequences in Eukaryotic DNAs by Scanning Microcalorimetry 206

Klutz, T , siehe D. Schweitzer 890 Knözinger, Ε., siehe W. Langel 1257 — siehe Ο. Schrems 1261 Kobertz, D., siehe Κ. Hilpert 200 Kogak, Μ., siehe Μ. Erol 731 Koch, Ε., Zs. Nagy-Ungvarai: New

Strategies for Studies on the K i ­netics and Energetics of the Be-lousov-Zhabotinskii Reaction . . 1375

Köhler, W., J. Friedrich: Configura-tional Dynamics of Doped Low Temperature Glasses and Poly­mers 858

Kölchens, S., siehe L. Belkoura 1036 Köngeter, D., siehe F. Hentsch 911 König, U., Μ. Μ. Lohrengel, J. W.

Schultze: Computer Supported Pulse Measurements of Current and Capacity during Fast Oxide Formation on Iron 426

Königsberger, Ε., Η. Gamsjäger: Solid-Solute Phase Equilibria in Aqueous Solution. 1. Solubility Constant and Free Enthalpy of Formation of Huntite 785

Kohler, F., siehe Ν. Van Nhu 525 Kolar-Anic, Lj. , siehe S. Anic 1010 Kolb, D., siehe Η. Genscher 262 Kolb, D. Μ., siehe Μ. S. Zei 349 Kollhoff, Η., siehe W. Langel 1257 — siehe O. Schrems 1261 Kolodziejski, W.: Paramagnetic

Probe for Molecular Interactions: I I . 7 L i N M R Study of Lithium Cation Solvation by a Nitroxide Radical 95

Kopp, F., siehe R. Heusch 806 Kortbeek, P. J., siehe Τ. F. Sun . . . 1013 Krader, Τ., Ε. U . Franck: The Ter­

nary Systems H 2 0 - C H 4 - N a C l and H 2 0 - C H 4 - C a C l 2 to 800 Κ and 250 MPa 627

Krebs, Β., siehe R. Conrady 1322 Kremer, W., H. W. Helberg, Ε.

Gogu, D. Schweitzer, H . J. Keller: Microwave Conductivity in the Pure and Iodine-Doped Organic Conductor a-(BEDT-TTF)?I3 . . . 896

Kremnitz, W., siehe W. Nitsch 218 Kröhnke, C, siehe Η. Rühe 885 — Single Crystals from Optically

Active Diacetylenes and Polydi-acetylenes 982

Ksiazczak, Α., A. Anderko: Proper­ties of Polar Gases and Their D i ­mer Structures 1048

Kuball, H.-G, A. Strauss, M . Kap-pus, E. Fechter-Rink, A. Schön-hofer: The Orientation Axis. Comparison of Order Parameters of Anthraquinone Dyes in a Liq­uid Crystal Phase 1266

Kubitza, Ch., M. Schottler, Κ. Η. Homann: Scavenging of Radicals from the Gas Phase by Freezing with Dimethyl Disulfide. 2. Rad­icals from Discharges and a Flame of Acetylene 695

Kuczynski, W., siehe Η. Stegemeyer 3 Kuhn, Η., siehe Η. Schreiber . . . . . . 798 Kunimatsu, Κ., siehe Τ. Ohtsuka . . 313

Lamy, C, siehe J.-M. Leger 336 Lang, E. W., F. X. Prielmeier, H.

Radkowitsch, H.-D. Lüdemann: High Pressure NMR Study of the Molecular Dynamics of Liquid Methylfluoride and Deutero-Methylfluoride 1017

High Pressure NMR Study of the Molecular Dynamics of Liquid Fluoroform and Deutero-Fluoroform 1025

Langel, W., H. Kollhoff, E. Knözin­ger, M . Prager: Neutron Scatter­ing and Dynamics of Small Mol­ecules in Cryogenic Matrices . . . 1257

Latanowicz, L.: Dynamics of Proton Transfer in Solution by NMR Re­laxation 237

Leaist, D. G : Bidirectional Coupled Diffusion of Glycine Driven by pH Gradients 1059

Lee, Bunding, Κ. Α., G. McLennan, J. G. Gordon: Surface-Enhanced Raman Scattering from Ethyle-nediaminetetraacetic Acid 305

Leeuwen, H. P. van, J. Lyklema: In-terfacial Electrodynamics of In­teracting Colloidal Particles. Geometrical Aspects 288

Leger, J.-M., B. Beden, C. Lamy: The Adsorption of Carbon Monoxide on Platinum Single Crystals in Alkaline Medium 336

Lengeier, B., siehe Η. Bertagnolli . . 1287 Lehmann, Ε., siehe G. Brandner . . . 740 Lehmpfuhl, G , siehe M . S. Zei . . . . 349 Leitner, K., siehe L. Elfenthal 432 Leiva, E., siehe D. Henderson 280 Lewerenz, H.-J., siehe M . Sander . 416 Limbach, H.-H., siehe B. Wehrle . . 941 Lindner, M . , siehe R. Schwarz 1233 Liu, T. C , siehe Β. E. Conway . . . . 461 Lohrengel, Μ. M. , siehe U. König . 426 Lorenz, W. J., siehe G. Schöne 469 Ludwig, P., siehe G Peschel : 536 Lübke, M. , siehe H. Gerischer . . . . 394 Lüdemann, H.-D., siehe E. W. Lang 1017 - siehe E. W. Lang 1025 Luft, G., siehe G. Jungermann 541 — siehe U . Stanislawski 756 Luntz, A. C , siehe J.-K. Sass 320 Lupo, D. W., M . Quack: Absolute

Rate Coefficients in IR-Photo-chemistry: Simple Estimates of the Rate Constant from Molecu­lar Parameters 565

Lyklema, J., siehe Η. P. van Leeuwen 288 Lytle, F. W.: X-ray Absorption Spec­

troscopy 1251

Manzurola, E., siehe A. Apelblat . . 1387 Mardolcar, U. V., C. A. Nieto de

Castro: The Thermal Conductiv­ity of Liquid Methane 152

Markworth, Α., Ν. Weiden, ΑΙ. Weiss: Microcomputer Con­trolled 47U-Zeeman Split NQR Spectroscopy of 35C1 in Single Crystal p-Chloroanilinium Trich-loroacetate. Crystal Structure and Activation Energy for the Bleach­ing Out Process 1158

Martin, M.: Impurity Diffusion in a Chemical Potential Gradient (I): Theoretical Results 772

— S. Dorris: Impurity Diffusion in a Chemical Potential Gradient (II): Iron Tracer Diffusion in Cobalt Oxide in an Oxygen Potential Gradient 779

Mason, T. O., siehe R. Dieckmann . 59 Matano, K., siehe Τ. Nagamura . . . 759 Materlik, G , M. Schmäh, J. Zegen-

hagen, W. Uelhoff: Structure De­termination of Adsorbates on Single Crystal Electrodes with X-ray Standing Waves 292

Matsuda, H., siehe Ο. Uemura . . . . 43 Mayr, Η., siehe R. Schneider 1369 McEvoy, A. J., siehe A. S. Feiner . . 399 Mclntyre, R., D. K. Roe, J. K. Sass,

H. Genscher: Physical and Elec­trochemical Aspects of Charge Transfer Reaction Inverse Photoemission Spectroscopy (CTRIPS): Photon Energy En­hancement for High Injection Currents 488

McLennan, G , siehe K. A. Bunding Lee 305

Mehring, M., siehe F. Hentsch . . . . 911 — P. Höfer, A. Grupp: Pulsed Elec­

tron Nuclear Double and Triple Resonance Schemes 1132

Meisel, W., siehe L. König 116 Melzig, M., siehe S. Schneider 1222 — siehe S. Schneider 1225 Memming, R.: Charge Transfer K i ­

netics at Semiconductor Elec­trodes 353

Menzel, R., P. Witte: Photophysical Hole Burning on Dye Solutions in the Liquid Phase with ns-La-serpulses 1249

Merboldt, K . - D , W. Hänicke, J. Frahm: NMR Imaging of Re­stricted Diffusion 1124

Meyer, O., siehe L. Elfenthal 432 Miller, M., siehe Κ. Hilpert 200 — Κ. Hilpert: Analysis and Ther­

mochemistry of the Equilibrium Vapour of the Nal —Snl2 and S c l 3 - S n l 2 Systems 642

Mindl, Α., siehe S. Schneider 1222 Möller, W., E. Mozzhukhin, H. G.

Wagner: High Temperature Re­actions of C H 3 . 2. H-Abstraction from Alkanes 660

Moger, G , J. Paäl-Lukäcs, D. Gal: Studies on the Interaction of An­thraquinone Triplet and a-Phen-ylethyl Hydroperoxide in Ben­zene and Chlorobenzene 794

Mollay, B., siehe Ε. Μ. Buchberger 1209 Moro, J. R., siehe F. Decker 408 Mortensen, J., siehe J. Heinze 960 Motoo, S., N . Furuya: Effect of Ter­

races and Steps in the Electroca-talysis for Formic Acid Oxidation on Platinum 457

Mozzhukhin, E., siehe W. Möller . . 660 Müller-Kirschbaum, Th., siehe L.

Belkoura 1036 Müller-Warmuth, W., siehe R. Con­

rady 1322 Mulvaney, P., siehe R. Hayes 231

Nagamura, Τ , K. Matano, Τ Ogawa: Molecular Orientation and Photoelectric Properties of Alloxazine Monolayer Assem­blies 759

Nagy-Ungvarai, Zs., siehe Ε. Koch . 1375 Nakamura, D., siehe S. Sato 122

IX

— siehe Κ. Horiuchi 1351 Nakato, Υ., H. Tsubomura: Remark­

ably High Photovoltages Gener­ated at η-Type Silicon Semicon­ductor Electrodes Coated with Extremely Small Platinum Is­lands 405

Nhu, N. Van, S. N. Bhat, F. Kohler: Calculation of Isothermal Com­pressibilities of Mixtures. The Ex­ample Acetone + Chloroform . . 525

Nickel, U., B. Klein, J. Hsin-min: K i ­netics and Mechanism of the Ox­idation of N,N-Diethyl-p-pheny-lenediamine by 12-Tungstocobal-tate(III) 997

Niemann, W., siehe Η. Beuthien . . . 1296 — Β. S. Clausen, Η. Topsoe: EXAFS

Studies of Ammonia Catalysts at Synthesis Conditions 1292

— siehe A. Torkler 1300 Nitsch, W., W. Kremnitz, G.

Schweyer: Kinetische Untersu­chungen zur Reversibilität der Makromoleküladsorption an der Grenzfläche Wasser/Luft 218

Nakanishi, M., siehe N . Yoshida . . 666

Oberst, M., siehe F. Beck 967 Ogawa, T., siehe T. Nagamura 759 Ohtsuka, Τ., N . Goto, N . Sato, Κ.

Kunimatsu: IR Reflection and Raman Spectroscopies of the An­odic Oxide Films on Tungsten . 313

Okubo, J., siehe Τ. Hoshi 1069 Okubo, T.: Microscopic Observa­

tion of Crystallites in the Deion-ized Suspensions of Monodis-persed Polystyrene Spheres . . . . 516

— Determination of the Effective Charge Numbers of Colloidal Spheres by Electrophoretic Mo­bility Measurements 1064

Oles, A. M., siehe Μ. C. Böhm 717 Oranth, Ν., F. Strohbusch: Kinetics

of the Isotrop-Nematic Phase Transition in Liquid Crystals. I . Nucleation Theory of Phase Transition 211

0ye, H. Α., siehe W. Brockner 561

Paäl-Lukäcs, J., siehe G. Moger . . . 794 Pandolfi, P., siehe Β. Sesta 7 Pasquier, B., siehe D. Bougeard . . . 1273 Peat, R., siehe L. M . Abrantes 369 — L. M . Peter: Intensity Modulated

Photocurrent Spectroscopy of n-GaAs 381

Peschel, G., J. Keldenich: Electrical Double Layer Forces in Thin In-terlayers between Macroscopic Bodies of Different Materials when being Immersed in Electro­lyte Solutions 285

— P. Ludwig: Cation Exchange on Oxide Surfaces as Influenced by Surface Hydration Phenomena. I . Alkali Metal Ions on Silica . . . . 536

Peter, L. M., siehe L. M . Abrantes . 369 — siehe R. Peat 381 — Photocurrent Spectroscopy of

Anodic Films on Metal Elec­trodes 419

Pettinger, Β.: Quantum-Mechanical Model for Surface (Un-)-Enhanced Resonance Raman Scattering of Adsorbates at Met­als. Common Effects in SERRS and SURRS 308

Piazza, S., siehe F. D i Quarto 437 Plieth, W. J., siehe P. H. Schmidt . . 323 Plog, C, siehe L. König 116

Pena, M. D., siehe J. Aracil 603 Plesch, P. H., siehe R. Schneider . . 1369 Prager, Μ., siehe W. Langel 1257 — siehe D. Zhang 1283 Prielmeier, F. X., siehe E. W. Lang. 1017 - siehe E. W. Lang 1025 Qiao, G., siehe M. S. Zei 349 Quack, Μ., siehe D. W. Lupo 565 Quarto, F. Di, S. Piazza, C. Sunseri:

Amorphous Semiconductor-Elec­trolyte Junctions. Photoelectro-chemical Behaviour of Thin Nb 2 O s Anodic Films 437

Radkowitsch, H., siehe Ε. W. Lang. 1017 - siehe Ε. W. Lang 1025 Rahmann, Μ. M., siehe G. Schönle 66 Raith, Α., siehe W. Hermann 56 Ramirez, R., siehe Μ. C. Böhm 717 Rau, F., siehe Κ. D. Becker 1279 Rau, Η., siehe W. Hermann 56 — W. Hermann: The Nature of the

Reduced Defect and the Diffusion of Ge0 2 in Germania-doped Vitreous Silica 833

Reineker, P., K. Kassner: Homoge­neous Optical Linewidth of Im­purities in Organic Glasses in the Low Temperature Regime 864

Renuncio, J. A. R., siehe J. Aracil . . 603 Rettig, W., siehe Μ. Vogel 1241 Reynaers, Η., siehe J. Ledent 112 Rhäsa, D., siehe F. Ewig 708 Rice, F. O., J. Tweedeil: On the Re­

moval of Metallic Mirrors by Free Radicals 995

Richter, P., siehe Μ. Erol 731 Richtering, W., siehe Τ. Solomun . . 412 Riekert, L , siehe Μ. Greger 1007 Ries, Β., siehe F. Stolzenburg 853 Rieß, W., siehe Th. Schimmel 901 Robjohns, H. L., siehe P. J. Dunlop 156 Roe, D. K., siehe J.-K. Sass 320 — siehe R. Mclntyre 468 Rosenholm, J. B.: An Infrared-Spec-

troscopic Study on the State of Water in Alcohols and in In­verted Micelles 106

Rosinberg, Μ. L., V. Russier, J. P. Badiali, Μ. E. Boudh'hir: Model-ization of the Electrical Double Layer: Structure of an Ion-Dipole Mixture Near a Wall 276

Rouveirolles, P., siehe J. Ehbrecht . 700 Rubio, R. G., siehe J. Aracil 603 Rühe, J., C. Kröhnke, Τ. Α.

Ezquerra, G. Wegner: Conduct­ing Polymers from 3,4-Disubsti-tuted Poly pyrroles 885

Russier, V., siehe Μ. L. Rosinberg . 276 Ruthardt, Κ., siehe Κ. Hilpert 724 Sachs, G., siehe E. Dormann 879 Salvador, P., siehe I . J. Ferrer 374 - siehe D. Tafalla 475 Sander, M., H.-J. Lewerenz, W. Jae-

germann, D. Schmeißer: Simula­tion of Electrochemical Interface Properties: UHV-Investigation on CuInSe2 and CuInS 2 416

Sass, J.-K., D. K. Roe, D. S. Bethune, A. C. Luntz: Infrared Reflection-Absorption Spectroscopy of Ad­sorbed Species on Electrode Sur­faces Using a Laser Source 320

- siehe R. Mclntyre 488 Sato, N. , siehe Τ. Ohtsuka 313 Satow, T., siehe Ο. Uemura 43 Schäfer, Α., D. Ziessow: Rechnerge­

stützte Analyse komplexer NMR-Spektren. Untersuchungen zur spektralen Darstellung und Ver-gleichsfunktion 1104

Schimmel, Th., W. Rieß, G. Dennin-ger, M. Schwoerer: Precision Conductivity Measurements and DSC on Single Crystals of the Or­ganic Conductor (FA) 2PF 6 901

Schindler, R. N., siehe G. Schönle . 66 Schmäh, Μ., siehe G. Materlik 292 Schmalzried, H., siehe W. B. Dur­

ham 556 Schmeißer, D., siehe M . Sander . . . 416 Schmickler, W., siehe D. Henderson 280 Schmidt, C, B. Blümich, S. Wefing,

S. Kaufmann, H. W. Spiess: Mo­lecular Motions from Two-Di­mensional N M R of Powders: Comparison of Rotational Jumps and Diffusive Reorientations . . . 1141

Schmidt, M. , D. Ziessow: Nichtli­neare, quantitative NMR-Spek-tralanalyse in der Reaktionski­netik m o

Schmidt, P. H., W. J. Plieth: The In­fluence of the Double Layer Field on the Protonation Equilibrium of Adsorbed Methyl Orange . . . 323

Schmidt, R., siehe A. Acs 1331 - siehe H.-D. Brauer 1337 Schmidt, V., siehe D. Wöhrle . . . . . 975 Schneider, R., H. Mayr, P. H. Plesch:

Ionisation and Dissociation of Diarylmethyl Chlorides in BC1 3/ CH 2 C1 2 Solution: Spectroscopic Evidence for Carbenium Ion Pairs 1369

Schneider, S., A. Mindl, G. Elfmger, M . Melzig: Photochromism of Spirooxazines. I . Investigation of the Primary Processes in the Ring-opening Reaction by Pico­second Time-resolved Absorption and Emission Spectroscopy 1222

- F. Baumann, U. Klüter, Μ. Mel­zig: Photochromism of Spiroox­azines. I I . CARS-Investigation of Solvent Effects on the Isomeric Distribution 1225

Schöne, G., W. Wiesbeck, Μ. Stoll, W. J. Lorenz: The Kinetics of the Polycry stalline Ag/Ag +-Elec­trode Studied by High-Frequency Impedance Spectroscopy 469

Schönhofer, Α., siehe H.-G. Kubal l . 1266 Schönle, G., Μ. Μ. Rahman, R. Ν.

Schindler: Kinetics of the Reac­tion of Atomic Fluorine with H 2S and Elementary Reactions of the HS Radical 66

Scholberg, H . P. F., J. Μ. P. M . Borggreven, F. C. Μ. Driessens: A Structural Interpretation of Impedance Spectra and Radioiso­tope Diffusion in Dental Enamel 135

Scholz, Μ.: Laser Induced Thermal Diffusion 1054

Schottler, Μ., Κ. Η. Homann: Scav­enging of Radicals from the Gas Phase by Freezing with Dimethyl Disulfide. 1. Test of the Method for Light Radicals 688

- siehe Ch. Kubitza 695 Schouten, J. Α., siehe Τ. F. Sun . . . 1013 Schreiber, Η., Η. D. Försterling, Η.

Kuhn: Photospannung in mono­molekularen Schichtsystemen mit Farbstoffaggregaten 798

Schrems, Ο., M . Huth, H . Kollhoff, E. Knözinger: FTIR-Spectros-copy of Molecular Clusters in Liquid Solutions and Cryogenic Solids 1261

Schroetter, S., D. Bougeard: The Calculated and Observed Vibra-

χ Inhaltsverzeichnis von Band 91 (1987) - Autorenverzeichnis

tional Spectra of the Ordered Phase of Tris(hydroxymethyl)-aminomethane 1217

Schlütes, Η., siehe P. Strohriegel 918 Schultze, J. W., siehe U. König 426 — siehe L. Elfenthal 432 Schumacher, R., siehe W. Stockei . . 345 Schumann, B., siehe D. Wöhrle . . . 975 Schurath, U., siehe A. C. Becker . . . 1238 Schwandner, B., siehe Η. Hoffmann 99 Schwanke, U., Η. Heydtmann: IR-

Chemiluminescence in the Reac­tion Systems F + C H 3 I and F + C H 2 I 2 1043

Schwarz, R., M . Lindner, G. Glie-mann: Photophysics of Single Crystal [Pt(o-phen) (CN) 2]: Op­tical Properties at External Mag­netic Fields and at High Pres­sures 1233

Schweitzer, D., siehe W. Kremer . . 896 Schwetlik, G. siehe R. Conrady . . . 1322 Schweyer G , siehe W. Nitsch 218 Schweitzer, D., E. Gogu, I . Hennig,

T. Klutz, H. J. Keller: Electro-chemically Prepared Radical Salts of B E D T - T T F : Molecular Metals and Superconductors . . . 890

Schwoerer, M., siehe Th. Schimmel. 901 Seilmeier, Α., siehe W. Kaiser 1201 Seoud, Ο. A. El, Ν. Z. Kiyan: Α Pro­

ton NMR Study of the Deuter-ium-Protium Fractionation in Aqueous Solutions of Some Or­ganic Ions 825

Sesta, Β., P. Pandolfi: Enthalpie Be­haviour of Sodium Deoxycholate in Pure Water and in Water-Urea Solutions at 25°C 7

Shahinian, Α. Α., V. V. Bagdasarian: Cooperative Transfer of Excita­tion Energy and the Dynamic Structure of Micelles 670

Shigehara, K., siehe D. Wöhrle . . . . 975 Shimura, S., siehe Ν. Yoshida 666 Sicking, G. H., siehe Β. Μ. Andreev 177 Sicking, G H., siehe P. W. Albers . 573 Smith, J. A. S.: Nuclear Quadrupole

Interactions in Solids: A Survey . 1145 Solomun, T , W. Richtering, H. Ger-

ischer: Electrochemical Reactivity of Ordered and Disordered n-GaAs(llO) Surfaces. A Combined XPS, LEED and Electrochemical Study 412

Späth, Κ., F. Gross, C. P. Heidmann, Κ. Andres: In Situ Observation of a Phase Transformation in a-(BEDT-TTF) 2 I 3 using a Contact-less Technique 909

Spangler, C. W., siehe P. Bäuerle . . 889 Spanhel, L., A. Henglein, Η. Weller:

Photochemistry of Colloidal Semiconductors. 24. Interparticle Electron Transfer in Cd 3P 2 — T i 0 2 and C d 3 P 2 - Z n O Sandwich Structures 1359

Spiess, H . W., siehe Β. Blümich . . . 1100 - siehe C. Schmidt 1141 Stanislawski, U., G. Luft: Dynamic

Viscosity of Supercritical Ethene 756 Stegemeyer, Η., H.-J. Kersting, W.

Kuczynski: Helical Twisting Power of Induced Twisted Smec­tic C* Phases 3

Steiger, Α., siehe Μ. Erol 731 Stockhausen, Μ., siehe Ε. Dachwitz 1347 Stockei, W., R. Schumacher: In situ

Microweighing at the Junction Metal/Electrolyte 345

Störzbach, Μ., siehe Η. Heinze . . . . 960 Stoll, Μ., siehe G. Schöne 469

Stolzenburg, F., B. Ries, H. Bässler: Kinetics of Geminate Pair Re­combination in Polyvinylcarb-azole 853

Storck, W., süehe F. Willig 869 Strauss, Α., süehe H.-G Kuball . . . . 1266 Strehlow, H., siehe I . Wagner 1317 Strohbusch, F., siehe Ν. Oranth . . . 211 Strohriegl, P., Η. Schultes, D.

Heindl, P. Gruner-Bauer, V. En­kelmann, Ε. Dormann: Prepara­tion, Crystal Structure and Di­electric Properties of the New Unsymmettrically Substituted Diacetylenies NP/R 2 918

Sum, U., K. Fesser, H. Büttner: Op­tical Absorption and Symmetries in Conducting Polymers 957

Sun, T. F., P. J. Kortbeek, S. N . Bis­was, N. J. Trappeniers, J. A. Schouten: An Ultrasonic Method for the Accurate Determination of the Mel ting Line: Data for Cy-clohexane and Benzene 1013

Sunseri, C, süehe F. Di Quarto . . . . 437

Tafalla, D., P. Salvador: Mecha­nisms of Charge Transfer at the Semicondiactor-Electrolyte Inter­face: Oxygen Electroreduction at Naked and Platinized n-Ti0 2

Electrodes 475 Tan, A. C, G A. Wright: The Anodic

Formation of Lead Iodide. Evi­dence for the Underpotential Deposition of a Reversible Monolayer 341

Tanabe, S., sitehe T. Hoshi 1069 Tenne, R., Rl. Haak, R. Triboulet:

Electrochemical Photocapaci-tance of ZnSe: Effect of Photo-electrocheimical Etching 597

Tessier, D. F.., siehe Β. Ε. Conway . 484 Topsoe, Η., süehe W. Niemann . . . . 1292 Torkler, Α., süehe Η. Beuthien 1296 - Η. Beuthien, W. Gunßer, W. Nie­

mann: X-ray Absorption Spec­troscopy (of Amorphous Rare-Earth Tramsition-Metal Oxides . 1300

Trappeniers, N . J., siehe Τ F. Sun 1013 Traube, J., siehe Κ. H. Homann . . . 828 Triboulet, R., siehe R. Tenne 597 Tsubomura, H . , siehe Y. Nakato . . 405 Tweedeil, J., siehe F. O. Rice 995

Uelhoff, W , suehe G. Materlik . . . . 292 Uemura, Ο., H . Matsuda, T. Satow:

Semiconduiction in the Liquid Tl - SbTlX 3 System (X: Te, Se) . . 43

Uosaki, Κ., IH. Kita: Electrolumi­nescence ait p-Type Semiconduc­tor/Electrolyte Interfaces 447

Vanmaekelbergh, D., siehe L. S. Dun 390 Vanzi, M. , siehe F. Decker 408 Versmold, H.„ M . Zeidler: Hermann

G Hertz zuim 65. Geburtstag . . . 593 Vlachopoulosi, N., siehe A. S. Feiner 399 Vogel, M., W. Rettig: Excited State

Dynamics of Triphenylmethane-Dyes used for Investigation of Micro viscosity Effects 1241

Wagner, H. Gg., siehe Μ. Brei 30 — siehe W. Möller 660 — siehe J. Einbrecht 700 Wagner, L, H . Strehlow: On the

Flash Phottolysis of Bromide Ions in Aqueouts Solutions 1317

Walz, L., siehe D. Zhang 1283 - siehe S. Wügand 1189

Wannemacher, G., siehe H. Bock­horn 819

Weaver, Μ. J.: Some Nontraditional Approaches for Examining Strong- and Weak-Overlap Elec­tron-Transfer Processes at Elec­trodes 450

Wefing, S., siehe C. Schmidt 1141 Wegner, G , siehe J. Rühe 885 Wehrle, Β., H.-H. Limbach, Η. Zim­

mermann: Variable Temperature , 5 N CPMAS NMR Studies of Dye Tautomerism in Crystalline and Amorphous Environments . 941

Weiden, Ν., siehe Α. Markworth . . 1158 — siehe S. Fleck 1167 — siehe S. Wigand 1189 Weidner, J. U., siehe Κ. M. Jöllen­

beck 11 — siehe Κ. M. Jöllenbeck 17 Weil, K. G , siehe H. Wiese 619 Weiss, ΑΙ., siehe S. Brummer 873 — S. Fleck: Pyroelectricity of Solid

Aromatic Compounds 913 — siehe A. Markworth 1158 — siehe S. Fleck 1167 — siehe A. Kehrer 1176 — siehe D. Borchers 1182 — siehe S. Wigand 1189 — siehe J. Hartmann 1195 — siehe D. Zhang 1283 Weixelbaumer, W.-D., siehe Ε. M .

Buchberger 1209 Weller, H., siehe L. Spanhel 88 — siehe A. Henglein 441 — siehe L. Spanhel 1359 Wienkenhöver, M., siehe R. Conrady 1322 Wiesbeck, W., siehe G. Schöne — 469 Wiese, Η., K. G. Weil: On the Mech­

anism of Electroless Copper Dep­osition 619

Wigand, S.. L. Walz, Ν. Weiden, ΑΙ. Weiss: *5C1 NQR Spectra and Crystal Structures of 1,2,4,5-Te-trachloro-3,6-dinitrobenzene and of 1,3,5-Trichloro-2,4-dinitroben-zene 1189

Wilkinson, D. P., siehe Β. Ε. Conway 484 Willand, C. S., D. J. Williams: Non­

linear Optical Properties of Po­lymeric Materials 1304

Wille, Ε. Ε., siehe Η. Armitage 1115 Williams, D. J., siehe C. S. Willand. 1304 Willig, F., R. Eichberger, K. Bitter­

ling, W. S. Durfee, W. Storck, M . Van der Auweraer: Light-Induced Hole Transfer Across a Lang-muir-Blodgett Double-Layer Membrane with a Short Tunnel­ing Barrier 869

Winter, R., F. Hensel, T. Bodenstei­ner, W. Gläser: The Static Struc­ture Factor of Cesium over the Whole Liquid Range up to the Critical Point 1327

Witte, P., siehe R. Menzel 1249 Wöhrle, D , V Schmidt, B. Schu­

mann, A. Yamada, K. Shigehara: Polymeric Phthalocyanines and their Precursors, 13 Synthesis, Structure and Electrochemical Properties of Thin Films of Po­lymeric Phthalocyanines from Tetracarbonitriles 975

Woermann, D., siehe Μ. Jungk . . . 507 — siehe Μ. Hürth 614 — siehe F. P. Harnisch 811 — siehe L. Belkoura 1036 Woldan, M.: Ion-Solvent Interac­

tions in Water-Acetamide Mix­tures from Volume Data 519

Inhaltsverzeichnis von Band 91 (1987) — Autorenverzeichnis XI

Wright, G. Α., siehe A. C. Tan . . . . 341 Wrighton. M. S., siehe P. Bäuerle . 889 Würz, U.. siehe M. Jungk 507

Yamada, Α., siehe D. Wöhrle 975 Yananoto. M. , siehe T. Hoshi 1069 Yang, Υ., B. Blümich 1100 Yoshida, Ν., M . Nakanishi, K. Ike-

gami, S. Shimura, S. Kishimoto: Anomalous Behavior of Glassy Ge0 2 in the Reduction Process by Hydrogen 666

Yersin, H., D. Braun, Ε. Gallhuber, G. Hensler: Lowest Excited States of [Ru(bpyj 3]X 2 Host Material, [Os(bpy) 3]A + Guest Complexes,

and Radiationless Energy Trans­fer 1228

Yun, L. S., D. Vanmaekelbergh, W. P. Gomes, F. Cardon: The Par­ticipation of Surface Decomposi­tion Intermediates in Charge Transfer Processes at Dark p-Type GaP/Electrolyte Interfaces 390

Yurtsever, Ε., H. Karaaslan: Monte Carlo Stimulation of Model Three-Component Liquid Sys­tems 600

Zegenhagen, J., siehe G. Materlik . 292 Zei, M . S., G. Qiao, G. Lehmpfuhl,

D. M . Kolb: The Influence of An­

ions of the Structure of Under-potentially Deposited Cu on A u ( l l l ) : A LEED, RHEED and AES Study 349

Zeidler, M. , siehe Η. Versmold . . . . 593 Zellner, R., siehe F. Ewig 708 Zhang, D., L. Walz, M . Prager, AI.

Weiss: Rotational Tunnelling of Methyl Groups in Bis(trimcthyl-tin) Sulfate Dihydrate 1283

Ziessow, D., siehe A. Schäfer 1104 - siehe M . Schmidt 1110 — siehe H. Armitage 1115 Zimmermann, H., siehe B. Wehrle . 941 Zimmermann, H. W.: Plancks Strah­

lungsgesetz und die Quantisi­erung der Entropie 1033

R. Schneider et al.: Ionisation and Dissociation of Diarylmethyl Chlorides in BC1 3/CH 2CI 2 Solution etc. 1369

Ionisation and Dissociation of Diarylmethyl Chlorides in BC1 3/CH 2C1 2

Solution: Spectroscopic Evidence for Carbenium Ion Pairs Reinhard Schneider, Herbert Mayr

Institut für Chemie, Medizinische Universität zu Lübeck, Ratzeburger Allee 160, D-2400 Lübeck 1, Federal Republic of Germany

Peter Η. Plesch

Chemistry Department, The University, Keele, North Staffordshire ST5 5BG, United Kingdom

Carbocations / Electrochemistry / Ionisation / Spectroscopy, Visible / Thermodynamics The ionisation equilibria of diarylmethyl chlorides Ar 2 CHCl (Ar = p - C H 3 0 - C 6 H 4 , p -PhO-C 6 H 4 , p - C H 3 - C 6 H 4 ) reacting with BC13 in CH 2C1 2 to give ion-pairs Ar 2 CH + BCLr (K{), and the dissociation of these (ΚΌ) were studied by conductimetry and spectro-photometry. The molar conductivities are almost independent of the nature of the aryl group («3 .5 · 10~3 Sm2/mol at —70°C). The ionisation constants K\ increase strongly with increasing electron releasing ability of the p-substituents. The standard ionisation enthalpies and entropies for (p-CH 3 -C 6 H 4 ) 2 CHCl and (p-PhO-QH 4 )(Ph)CHCl, calculated from the K\ at different temperatures are negative. The dissociation constants KD [(1.9 — 2.9) · 10~4 mol/L at — 70°C] do not show a systematic dependence on the electron donating abilities of the substituents in the aryl groups. Small differences between the UV-vis absorption spectra of unpaired and paired ions were used to confirm the

conductimetrically determined values of KD.

Introduction Diarylcarbenium ions have been studied extensively in

solvents of low nucleophilicity, mostly by N M R and U V spectroscopy [1] , and several species have been isolated as crystalline hexachloroantimonates from CC1 4 solution [2] . The ionisation equilibria of various diarylmethanols have been determined in sulfuric acid/water mixtures (Eq. (1)) [3] .

A r 2 C H + + H 2 0 A r 2 C H O H + H + . (1)

The KR+ values show a linear correlation with the rates of the solvolyses of the corresponding diarylmethyl chlorides [4] and the enthalpies of ionisation of diarylmethyl chlorides and alcohols in superacidic media [5] .

A r 2 C H + B C 1 4 - + H 2 C = C R R 7 ' ( 2 )

— A r 2 C H - C H 2 - C R ' R ' C l + BC1 3 .

In the context of kinetic studies on the addition of carben­ium tetrachloroborates to alkenes (Eq. (2)) [6] , the Lübeck group required information on the ionisation and dissocia­tion equilibria (3), the equilibrium constants of which are given by Eqs. (4) and (5).

1 - X . V 1*-X,V B C I " 1+-X .Y Covotent I o n - P a i r Free I o n s

l o n i s o t i o n D i s s o c i a t i o n

Ber. Bunsenges. Phys. Chem. 91, 1369-1374 (1987) - © VCH Verlagsgesellschaft mbH, D-6940 Weinheim, 1987. 0005-9021/87/1212-1369 $ 02.50/0

R. Schneider et al.: Ionisation and Dissociation of Diarylmethy) Chlorides in BCI3/CH2CI2 Solution etc.

[ A r 2 C H + B C l 4 ] 1 [ A r , C H C l ] [ B C l 3 ] 1 '

[ A r 2 C H + ] [ B O , - ] K d ~ [ A r 2 C H + B C l 4 - ] ' ( 5 )

The investigation involved conduetimetric and spectropho-tometric measurements, and the results were analysed by means of the theory of Binary Ionogenic Equilibria [7]. A new and unexpected finding is, that there are small but quite definite differences between the U V-vis spectra of paired and unpaired diarylmethyl cations, which can be used to confirm the conductimetrically derived value of ΚΌ.

Experimental

Dichloromethane was purified and dried as described by Heub-lein and Bauerfeind [8] . Boron trichloride (>99%) was commer­cially available and was used without further purification. Benzyl-triethylammonium chloride was dried for 24 h in high vacuum at 130C and stored under dry nitrogen. The diarylmethyl chlorides were prepared from diarylkctones, which were obtained by the Fric-del-Crafts reaction of suitably substituted benzoyl chlorides with benzene derivates according to a standard literature procedure [9] , The reduction of the ketones was carried out with Zn/KOH in ethanol, following the method of Davies [10a]. Subsequent treat­ment of the diarylmethanols with gaseous HCl in dichloromethane at 0 C in the presence of CaCl 2 yielded the diarylmethyl chlorides. After recrystallization or distillation colourless materials were ob­tained. 1-CH,.H: bp. 110-112 C77 Pa (160- 164 C/(8-9) · 102

Pa [10a]); 1-CH,,CH,: pentane, mp. 45 -46 C (45-46 C [10b]); l-OPh,H: ether, mp. 52 -53 .5°C; l - O C H 3 , H : pentane, mp. 6 1 - 6 2 ° C (62-63°C [10c]); l -OPh,CH 3 : ether, mp. 67-68 .5°C; l -OCH 3 ,CH 3 : pentane, mp. 4 3 - 4 4 ° C ; 1-OPh,OCH3: pentane, mp. 54 -56°C ; l -OCH 3 ,OCH 3 : ether, mp. 8 0 - 8 2 ° C ( 8 3 - 8 4 ° C [10d]).

The UV-vis-Spectra were taken with the K O N T R O N U V I K O N 860 spectrometer at ambient temperature. Photometric measure­ments were carried out with a fibre optic system (Schölly KGS III) . The light of a 30 W halogen lamp is conducted in a liquid fibre, which splits the light into a probe channel and a reference channel. The probe (Fig. 1) consists of two parallel quartz rods, inserted into twin quartz sleeves, which dip into the solution to be analysed. The light travels down one rod, is totally reflected at its lower end to pass through the solution 5 mm) and then returns by the second rod, whence a liquid fibre conducts it through an interference filter (Bandpass-Filter Corion) with a band width of 10 nm to the signal monitor.

rvv burette

Fig. 1 Diagram of the reaction vessel

Conduetimetric measurements were carried out with a Tacussel CD 810 conductimeter and Pt plate electrodes. The cell constants, determined with 0.01 Μ and 0.001 Μ KCl solutions, ranged from 53 to 85 m - 1 . Conductances below 10 μ8 were determined with

62.5 Hz AC, and for those between 10 and 50 μ5 an AC of 2:0 Hz was used.

All experiments were carried out in a dry nitrogen atmosphere. All the concentrations quoted are those at the actual openting temperatures, the adjustments having been calculated from thecoef-ficient of thermal expansion of dichloromethane, 0.00137 Κ 1 11].

Results and Discussion

Ionisation of Diarylmethyl Chlorides by BC13 in Dichloromethane

The reactions of diarylmethyl chlorides 1-X,Y with 3C13

yield ion-pairs 1 + - X , Y BCLf in equilibrium with the free ions 1 + - X , Y and B O T (Eqs. (3)-(5)). Consequently, the UV-vis absorbance and the conductivity will grow vhen BC1 3 is added progressively to solutions of 1-X,Y.

n l 0 4 K / s m _ 1

1 -0CH 3 , 0CH 3 1-CH 3 ,CH 3

1 5 10 15

Fig. 2 Conductance of 1.1 · 10 3 Μ diarylmethyl chloride solutions in the

presence of various amounts of BC13 (CH 2C1 2, — 70°C)

As shown in Fig. 2, the conductance increases rapidly, when l - O C H 3 , O C H 3 is titrated with BC1 3 and reaches a limiting value after the addition of 1 equivalent of B C l 3 . These findings indicate a large value of Κι and a dissociation equilibrium, which is independent of the concentration of BC1 3 , as required by theory (Eqs. (3) —(5)).

When l - O C H 3 , O P h , l - O C H 3 , C H 3 (not shown in Fig. 2) and l - O C H 3 , H are titrated, 1—3 equivalents of BC1 3 are sufficient to reach the plateau in the titration curves, i. e., Ky

is large for all of these systems. For l - O P h , H and 1 - C H 3 , C H 3 , 100-120 equivalents of BC1 3 are needed to achieve complete ionisation, and 1 - C H 3 , H is not completely ionised even with 200 equivalents of BC1 3 . Note that "200 equivalents of BC1 3" amounts to only » 2 vol% of BC1 3 , so that any effect on the macroscopic dielectric constant of the mixture is in fact negligible.

When the titrations were monitored photometrically, curves closely similar to those in Fig. 2 were obtained. Pho­tometric studies over a range of temperatures showed, that l - O C H 3 , O C H 3 , l - O C H 3 , O P h and l - O C H 3 , C H 3 in the presence of excess BC1 3 remain fully ionised from —70 up to — 20°C, whereas for the less stabilised cations 1 + -O C H 3 , H , l + - O P h , H , and 1 + - C H 3 , C H 3 the formation of

R. Schneider et al.: Ionisation and Dissociation of Diarylmethyl Chlorides in BC1 3/CH 2C1 2 Solution etc. 1371

the molecules 1-X, Y becomes noticeable at the higher tem­peratures (Fig. 3).

As discussed below, 10 5 Μ solutions of diarylcarbenium tetrachloroborates contain less than 10% of ion-pairs, and therefore the absorbances shown in Fig. 3 are almost entirely due to unpaired ions. If deviations from Lambert-Beer's law, which are caused by the use of non-monochromatic light [12], are neglected, K' = Kx · KD for the dilute solutions of 1 - C H 3 , C H 3 , and l - O P h , H can be derived from Fig. 3. From a plot of In AT' vs. 1 /r the thermodynamic parameters AH0

and A S 0 for the equilibrium (6) were calculated (Table 1).

Κι — [ A r 2 C H + ] 2

[ B C l 3 ] ( c 0 - [ A r 2 C H + ])/(! + tf, [BC1 3])* (9)

As discussed by Grattan and Plesch [7 a] , the ionic con­ductivity A\ can be considered to be independent of the concentration in dilute solutions, so that A\ = AQ = κ/ [ A r 2 C H + ] . With this substitution, Eq. (9) can be rewritten to give:

Cp 1-f l / g , [ B C l 3 ] 1 ' K + A KDAr

(10)

A r 2 C H C l + BC1 3 ^ CH 2C1 2

A r 2 C H + + BC1 4~. (6)

Table 1 Standard-enthalpies and entropies for the ionogenic equilibrium (6) from pho­

tometric studies at different temperatures

1-X, Y AH°/k) m o r 1 AS°/)K~* mol-'

1-OPh, Η -47.5 -260 1-CH3. C H 3 -46.4 -260

This equation is equivalent to E q . (C.2.14) of Ref. [7a], if [BC1 3 ] * [ B C 1 3 ] 0 .

For fully ionised systems, in which / ^ [ Β 0 3 ] > 1, Eq. (10) is reduced to (11).

κ 1

KDA? κ +

_1_

A' (ID

Eqs. (10) and (11) can be used to derive the equilibrium constants and the molar conductivities as described [7].

1.00

0.50

0.10-

AIT) A(-70°C)

1 + - 0CH 3 ,H

[ 1 + - C H , , C H , ] » 1.1 · 1 0 " * mol/L / [ B C I , ] - 9 . 0 - 1 0 " 2 mol/L

[ 1 + - O P h f H ] - 1 . 1 · 1 ( Γ 5 mol/L / [ B C I , ] - 9 . 0 - 1 0 - 2 mol/L

[ 1 + - O C H , , H ] - 2 .2-10-" mol/L / [ B C I , ] = 2 . 2 - Κ Γ 2 mol/L

T/°C — ι ι 1 1 1 — - 8 0 - 7 0 - 6 0 - 5 0 -AO

—ι— - 3 0 - 2 0 - 1 0

Fig. 3 Temperature dependence of the UV-vis-absorbance of diarylcar­

benium tetrachloroborate solutions in dichloromethane (A = 490 nm)

Quantitative Analysis of the Conductivity Results [7] If the system is described by E q . (3), the total concentra­

tion (c0) of diarylmethyl species is

c 0 = [ A r 2 C H C l ] + [ A r 2 C H + B C L r ] + [ A r 2 C H + ] .

Substitute [ A r 2 C H + B C l 4 ~ ] from (4) into (7):

c 0 - [ A r 2 C H + ] [ A r 2 C H C l ] = •

l + j ^ C B c y

(7)

(8)

The product ΚχΚΌ is formed from Eqs. (4) and (5), [ A r 2 C H C l ] substituted from (8), and [ B C l f ] set equal to [ A r 2 C H + ] (electroneutrality); we thus obtain E q . (9):

^2./root S-W 2

•300

c=1.0 ·10' 4 mol/L I

c= 5.0-10"5 mol/L \

c = 5.0-10 mol/L

•200

5.0.· 10"U 10;10'*

Fig. 4 Evaluation of Ax and KD for l + - O C H 3 , O C H 3 in dichloromethane

at - 3 0 ° C

In a first series of experiments, diarylmethyl chlorides 1-X, Y were added gradually to solutions of BC1 3 in C H 2 C 1 2

while the conductance was determined. The concentration of BC1 3 and the temperature were selected so that ionisation was complete. A plot according to Eq . (11) (Fig. 4) was linear for c 0 < 5 10~ 4 mol /L, and its intercept yields 1/Ar With this value, the dissociation constant ΚΌ can be derived from the slope.

The dissociation constants thus obtained are of the same order as the ΚΌ values of other types of carbenium salts in C H 2 C 1 2 previously reported (Table 2). As expected, varia­tions of the substituents have little effect on the molar con­ductivities. The temperature dependence of ΚΌ indicates negative dissociation enthalpies and entropies. The positive A G 0 value of the ion-pair dissociation is thus due to the unfavourable dissociation entropy. The paucity of data ob­tained at different temperatures inhibits a detailed discus­sion. It seems, however, that for the less stabilised carbenium

1372 R. Schneider et al.: Ionisation and Dissociation of Diarylmethyl Chlorides in BCI3/CH2G2 Solution etc.

Table 2 Molar conductivities, ion-pair dissociation constants and thermodynamic parameters for the dissociation of carbenium ion salts in dichloromethate

Saltb> T/"C No of Expts.

At • 10V S m 2 m o l ~ , a )

104 Kol mol L " 1 a >

AH0/ kJ mol 1

AS0/ J K " 1 mor ' Lit.

Ρ - O C H 3 , O C H 3 B C l 4 - 7 0 6 3.50 ± 0 . 1 4 2.2 ± 0.2 -2.3 -81 - 6 0 1 4.23 2.1 - 5 0 2 5.33 ± 0.03 1.9 ± 0.3 - 4 0 2 6.17 ± 0.08 1.8 ± 0.0 - 3 0 6 7.15 ± 0.09 1.8 ± 0.2 - 2 0 1 8.42 1.6

l + - O C H 3 , O P h B C l 4 - - 70 2 3.15 ± 0.06 2.1 ± 0.4

l + - O C H 3 , C H 3 B C l 4 - 7 0 9 3.49 ± 0 . 1 4 2.4 ± 0.3 -3.8 -88 c

- 6 0 1 4.34 2.3 -50 2 5.21 ± 0.20 2.0 ± 0.1 - 3 0 2 7.18 ± 0.08 1.7 ± 0.1

l + - O P h , C H 3 B C L T - 7 0 3 2.99 ± 0 . 1 7 2.9 ± 0.5 CI

l + - O C H 3 , H B C L r - 8 0 5 2.45 ± 0.05 2.7 ± 0.2 -7.0 -105 ci

-70 15 3.37 ± 0.12 1.9 ± 0.2 - 6 5 2 3.95 ± 0.05 1.8 ± 0.1 - 6 0 3 4.29 ± 0 . 1 3 1.7 ± 0.1 - 5 0 4 5.28 ± 0 . 1 7 1.4 ± 0.2 - 4 0 3 6.09 ± 0.09 1.3 ± 0.1 - 3 0 4 7.03 ± 0.06 1.0 ± 0.1

l " - O P h , H B C l 4 - - 7 0 7 3.16 ± 0.14 2.0 ± 0.3 0

r - C H 3 , C H 3 B C 1 4 -70 3 3.31 ± 0.25 1.9 ± 0.1

T r ' SbCl 6 - 4 5 6.17 0.73 -10.5 -126 [13a] P y r SbCV -45 5.95 0.88 -13.0 -138 [13a] Et 4 N + SbCl6- - 4 5 5.53 1.2 -6.3 -100 [13a] P h 3 C + S b C l 6 - - 4 5 4.13 2.9 -3.3 -71 [13b]

- 4 5 4.43 5.3 -8.4 -96 [13a] 0 8.21 3.1

25 10.8 1.9

P h 3 C + S b F 6 " 0 9.71 2.4 -9.2 -105 [13c] P h 3 C + A s F r 0 9.69 1.9 -9.2 -105 [13c] Ph 3 C + C l - 0 - - « 0 -152 [8]

With standard deviations. Tr = Tropylium; Pyr = 2,4,6-Trimethylpyrylium; Et = Ethyl; Ph = Phenyl. This work, derived from Eq. [11].

Table 3 Molar conductivities and ionisation constants for solutions of diarylmethyl chlorides and BC13 in CH 2 C1 2 at — 70°C derived from conductivity measure­

ments on partially ionised systems

1-X, Y No of Expts.

A, · ΙΟ3/ S m 2 mol"1 a ) L mol- 1 a )

AG?(70°C) kJ mol-'

1-OPh, Η 2 2.97 ± 0.08 145 ± 7 -8.4 1-CH 3, C H 3 3 3.64 ± 0.99 64 ± 10 -7.0

I - C H 3 , H b ) 3 1.94 ± 0.43 0.49 ± 0.05 + 1.2 (0.17) ( + 3.0)

a ) With standard deviations. b ) Calculated for KD = 2.0· 10~4 mol/L; values in parentheses calculated for

Ai = 3.20· Ι Ο - 3 Sm2/mol (see text).

ions both AH° and AS0 are more negative, which indicates that in these systems the solvation of the free ions is more important.

In a second series of experiments, diarylmethyl chlorides 1-X,Y were added gradually to solutions of BC1 3 under con­ditions of incomplete ionisation. Large concentrations of

B C I 3 were again used, and the changes of [BC1 3 ] during the titrations were negligible. Again, linear plots of CQ/K V S . Κ were obtained (Eq. (10)), but the intercepts (ί/Λ{) observed in different experiments varied considerably, which dimin­ished the accuracy of the A{ values. However, the A{ values of l + - O P h , H and 1 + - C H 3 , C H 3 (Table 3) agree well with those in Table 2. Since Table 2 showed Ax to be almost independent of the nature of the para-substituents, we con­sider the low Ax value found for 1 + - C H 3 , H to be an artefact of unexplained origin.

The K\ values can be calculated from the slopes of the plots, [BC1 3 ] , A-, and ΚΌ (Eq. (10)). These values together with the KD in Table 2 give K' = ΚνΚΌ for l - O P h , H + BC1 3 (0.029) and 1 - C H 3 , C H 3 + BC1 3 (0.0122), corresponding to A G 0 ( - 7 0 ° C ) of 6.0 and 7.4 kJ mol" 1 , respectively. These numbers are closely similar to those derived from the tem­perature dependence of absorbance (5.3 and 6.4 kJ m o l - 1 , Table 1).

Furthermore, the difference between the AG? values of the lower two compounds of Table 3 (8 —10 kJ/mol) agrees

R. Schneider et al.: Ionisation and Dissociation of Diarylmethyl Chlorides in BCI3/CH7CI2 Solution etc. 1373

well with the corresponding value (7-11 kJ/mol) derived from the pKR, values of 1 - C H 3 , C H 3 (pKR+ = -10.4 [3b]) and 1 -CH 3 ,H ( p £ R , = -12.3 [3c]; -11.6 [3d]) at 25°C.

Spectroscopic Evidence for Ion-Pair ±? Free Ions Equilibria

It has long been known that the UV-vis absorption spec­tra of carbocations are influenced only slightly by the solvent and the state of the ions [14]. Consequently, many analyses of ionogenic equilibria have been based on the identity of the absorption spectra of unpaired and paired ions [15]. The differences in the absorption spectra shown in Fig. 5 enable us to progress beyond these conventional approxi­mations and to extract information on ion-pair dissociation from absorbance measurements.

The absorption spectrum A (Fig. 5) can be attributed to unpaired 1 + - O C H 3 , O C H 3 ions, since at a concentration of 10~ 5 M, the degree of dissociation exceeds 90% (from ΚΌ

in Table 2). The same solution, but containing also 10~ 2 Μ benzyltriethylammonium tetrachloroborate gave spectrum B, which showed a 2 nm blue shift of A m a x and a decrease of f-max (Fig. 5). Similar changes have been observed for the absorption spectrum of l + - O C H 3 , C H 3 .

This effect may be attributed a priori either to the for­mation of ion-pairs or to a more general solvatochromic

550 λ/nm

Fig. 5 Absorption spectrum of 1 + - O C H 3 , O C H 3 (1.0* 10~5 M) in CH 2C1 2

at 20°C (curve A) in presence of benzyltriethylammonium tetra­chloroborate (1.0· 10" 2 M) (curve B)

1.00

0.50-

0.10

curve II

curve I

1.00 5.00 10.00

Quantity of BClf/mmol

Fig. 6 Titration of 1 + -OCH 3 ,OCH 3 BClf (2.0· 10" 5 mmol) and BC13 (10 mmol) in 92 mL of CH 2C1 2 with benzyltriethylammonium chloride at — 70°C. Upper curve: 485 — 495 nm, lower curve: 515 — 525 nm

effect caused by the change of the medium. Since all spectra were taken in the presence of a large excess of BC1 3 , the differences are unlikely to arise from nucleophilic impurities.

In order to assign these spectral effects, solutions of 1 + -X , Y BC14~ with excess of BC1 3 were titrated with benzyl­triethylammonium chloride. When the ammonium chloride is added, the BC1 3 accepts C l ~ ions so that [ B C L f ] increases at the expense of [B C 1 3 ] . According to Eqs. (4) and (5), these concentration changes reduce the degree of ionisation of 1-X,Y and the degree of dissociation of the 1 + - X , Y B C L f ion pairs.

0.50-

0.10-

100 5.00 10.00 Quantity of BCl^/mmol

Fig. 7 Titration of 1 +-OCH 3 ,CH 3 BC14" (2.0· 10~5 mmol, Xm&x = 488 nm in CH2C12) and BC13 (10 mmol) in 92 mL of CH 2C1 2 with benzyl­triethylammonium chloride at — 70°C. Upper curve: 465 — 475 nm;

lower curve: 505 — 515 nm

Fig. 6 shows the change of the absorbance during the titration of 1 + - O C H 3 , O C H 3 / B C l 3 with C I " in two different spectral regions. If the titration is monitored in the 515 — 525 nm range (Fig. 5, area I) one observes an initial 8% decrease in absorbance, then a wide range in which the absorbance remains constant, and finally an abrupt decrease (Fig. 6, curve I). A similar behaviour was observed when the ab­sorbance was measured at 485 — 495 nm (Fig. 5, area II ) ; the only difference is that now an increase in absorbance was observed during the first phase of the titration (Fig. 6, curve II) . Similar titration curves were obtained with 1 + -O C H 3 , C H 3 (Fig. 7).

With all systems, an abrupt decrease of the absorbance occurs when the BC1 3 is used up and the chloride ions are then trapped by the 1 + - X , Y . This finding supports the pre­vious conclusion that the diarylmethyl chlorides with X = O C H 3 and Y = O C H 3 or C H 3 are completely ionised by one equivalent of BC1 3 , i.e. Κλ is relatively great.

It remains to find the reason for the changes of absorbance in the initial phase of the titration. If they were due to a change of the medium, i.e. a general solvatochromic effect, one would not expect the absorbance to remain constant while 90 — 95% of the ammonium chloride is added. How­ever, the noticeable change in the absorbance at the begin­ning and the long plateau while most of the C l ~ is added,

1374 R. Schneider et al.: Ionisation and Dissociation of Diarylmethyl Chlorides in BCI 3/CH 2C1 2 Solution etc.

are readily compatible with our explanation in terms of ion-pairs.

A Ao

1.05

1.00< ο experimental

<3 calculated

0.10 0.50 1.00 Quantity of BCI 4 /mmol

Fig. 8 Upper part: Spread out section of Fig. 6 and calculated changes of

absorbance (see text). Lower part: percentage of free ions

Fig. 8 shows an enlargement of the left part of Fig. 6 and the percentage of unpaired ions calculated by means of KD

[16]. It is obvious that the changes of absorption take place in the same range in which the percentage of unpaired ions decreases from » 9 0 % to less than 13%. From the absorb­ance observed before C l ~ was added (92% free ions and 8% ion-pairs) and the absorbance at the plateau (5% free ions and 95% ion-pairs), we can calculate the absorbance at different stages of the titration and, as Fig. 8 shows, the experimental and the calculated curves superimpose. The participation of 1:1 ion-pairs in binary ionogenic equilibria has thus been supported by an independent method.

We thank Ute Grabis for experimental assistance, the Deutsche Forschungsgemeinschaft for financial support, and the British Council for supporting the cooperation between Lübeck and Keele.

References

[1] Η. H. Freedman, "Arylcarbonium Ions", in: Carbonium Ions, Vol. IV, Chapt. 28, eds. G. A. Olah and P. v. R. Schleyer, Wiley, New York 1973.

[2] a) H. Volz, Angew. Chem. 75, 921 (1963); Angew. Chem Int. Ed. Engl. 2, 622 (1963); b) H. Volz and H. W. Schnell, Angew. Chem. 77, 864 (1965); Angew. Chem. Int. Ed. Engl. 4, 873 (1965).

[3] a) N . C . Deno and W. L. Evans, J. Am. Chem. Soc. 79, 5804 (1957); b) N . C . Deno, J. J. Jaruzelski, and A. Schriesheim, J. Am. Chem. Soc. 77, 3044 (1955); c) W. N . White and C. A. Stout, J. Org. Chem. 27, 2915 (1962); d) N . C . Deno and A. Schriesheim, J. Am. Chem. Soc. 77, 3051 (1955).

[4] S. Nishida, J. Org. Chem. 32, 2692, 2695, 2697 (1967). [5] Ε. M . Arnett and T. C . Hofelich, J. Am. Chem. Soc. 105, 2889

(1983). [6] a) R. Schneider, U. Grabis, and H. Mayr, Angew. Chem, 98,

94 (1986); Angew. Chem. Int. Ed. Engl. 25, 89 (1986); b) R. Schneider and H. Mayr, Angew. Chem. 98, 1033 (1986); An­gew. Chem. Int. Ed. Engl. 25, 1016 (1986); c) H. Mayr, R. Schneider, and U. Grabis, Angew. Chem. 98, 1034 (1986); An­gew. Chem. Int. Ed. Engl. 25, 1017 (1986).

[7] D. W. Grattan and P. H. Plesch, J. Electroanal. Chem. 103, 81 (1979); b) G. E. Holdcroft and P. H. Plesch, J. Chem. Res. (S) 36 (1985), (M) 401 (1985).

[8] G. Heublein and D. Bauerfeind, J. Prakt. Chem. 326,81 (1984). [9] Organikum, Autorenkollektiv, 15 t h edition, p. 404, VEB

Deutscher Verlag der Wissenschaften, Berlin 1977. [10] a) A. G. Da vies, J. Kenyon, Β. J. Lyons, and T. A. Rohan, J.

Chem. Soc. 1954, 3474; b) E. D. Hughes, C . K. Ingold, and N . A. Taher, J. Chem. Soc. 1940, 949; c) P. D. Bartlett and R. W. Nebel, J. Am. Chem. Soc. 62, 1345 (1940); d) E. Berg­mann and J. Hervey, Chem. Ber. 62, 893 (1929).

[11] Landolt-Börnstein, Zahlenwerte und Funktionen, Volume I I , first part, p. 651, Springer, Berlin 1971.

[12] G. Kortüm, Kalorimetrie, Photometrie und Spektrometrie, 4 , h

edition, Volume I I , p. 30, Springer, Berlin 1962. [13] a) P. M . Bowyer, A. Ledwith, and D. C . Sherrington, J. Chem.

Soc. (B) 1511 (1971); b) N . Kalfoglou and M . Szwarc, J. Phys. Chem. 72, 2233 (1968); c) W/Gogolczyk, S. Slomkowski, and S. Penczek, J. Chem. Soc. Perkin I I 1729 (1977).

[14] a) A. G. Evans, I . H . McEwan, A. Price, and J. H . Thomas, J. Chem. Soc. 1955, 3098; b) J. W. Bayles, J. L. Cotter, and A. G. Evans, J. Chem. Soc. 1955, 3104.

[15] a) S. D. Pask and O. Nuyken, Eur. Polym. J. 19, 159 (1983); b) A. G. Evans, J. A. G. Jones, and G. O. Osborne, J. Chem. Soc. 1954, 3803 and earlier papers in this series.

[16] For the calculation of the percentage of free ions we assumed KD of 1 + BC14~ and R 4 N + B C L r to be equal (see Table 2 and corresponding discussion).

(Eingegangen am 4. Mai 1987, Ε 6485 endgültige Fassung am 21. Juli 1987)