CHEM230-2 W15 Lab Lecture #6 DIELS-ALDER

Diels-Alder/Lactone Formation

- REACTION SEQUENCE

CHEM230-2 W15 Experiment #7: Diels-Alder Reaction

! Reaction will be run neat (no solvent)

! Sequence starts with a Diels-Alder cycloaddition

! Lactone formation occurs spontaneously

lactone- forms fast

how to purify product to make sure to get high quality spectrum

Diels-Alder Reaction Template – additional information posted to Canvas

Lactone Formation


! The lactone forms spontaneously at room temperature.

optimize pi stacking

sigma-cis is required for a diels-alder reaction

when you have substituents on alkenes, those won’t change in configuration (E or Z)

the interior substutient gets pushed up


Techniques - Recrystallization: Purification of solids

! The recrystallization will be done using

warm solvent

! When recrystallizing, keep the solvent WARM (not boiling hot)

! Use the bare minimum amount of solvent to

dissolve the crude product.

! After dissolving the crude product, remove the flask from the heat.

! Let cool until crystals form – agitate if necessary

! Collect product by vacuum filtration

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SAFETY

1.  (2E,4E)-hexa-2,4-dien-1-ol A. Flammable liquid

B. Skin, eye, respiratory irritant

2.  Maleic Anhydride A. Toxic if swallowed

B. Sever Irritant to skin and eyes

C. Causes chemical burns

3.  Toluene A. Flammable liquid

B.  Skin, eye, respiratory irritant

Diels-Alder Reaction – Conformation of Product


The energy minimized structure is not a well-define half-chair conformation.

we need to validate our hypothetical transition state model; going to get your dihedral bond angles (which will have an effect on your NMR data)

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Most of these resonances have well-resolved first-order splitting patterns.

sequential- all protons not magnetically equivlent

multiplet

multiplet

that’s 2 hydrogens that are multiplets


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1H NMR (400 MHz, Chloroform-d) δ 5.90 (ddd, J = ?, ?, ? Hz, 1H), 5.56 (ddd, J = …

1H NMR Spectroscopy


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NOTE: These data were generated from a spectrum in a different NMR solvent.

DO NOT USE THESE DATA N

LAB REPORTS

big peak

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EXPERIMENTAL PRODUCTS

1. DATA/CHARACTERIZATION:

A. Determine mass of product

B. Place crude product in 4 mL vial and label

C. Obtain an IR spectrum

D. Prepare a sample for 1H NMR (1 mg of solid in 1 mL CDCl3)

E. Place sample in product rack before leaving.

F. Record observations/data in worksheet (get TA initials)

2. FAILURE TO TURN IN PRODUCT WILL RESULT IN LOSS OF CREDIT



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LABORATORY CHECK-OUT PROCEDURE

! Students must check-out of lab during the week of 16-20 Feb

FAILURE TO CHECK OUT CORRECTLY WILL RESULT IN A LOSS OF 50 POINTS

! Clean all glassware

! Check equipment /glassware inventory for completeness

- replace any missing items

! Remove all personal belongings (calculators, lab coats, goggles, etc)

! Get approval form TA and sign out on form (both lab partners)

! Place laminated card with lock combination in bench and turn lock around


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LABORATORY COMMON FINAL EXAM

! DATE: Monday, 23 February 2015

! TIME: 7:00-9:00pm

! LOCATION: RYAN AUDITORIUM TECH

ALTERNATE FINAL EXAM

! DATE: To Be Announced

! MAKE-UP FINAL ONLY PERMITTED WITH VALID, DOCUMENTED EXCUSES PROVIDED IN ADVANCE

CHEM230-2 W15 Lab Lecture #6 DIELS-ALDER

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