Chemistry S-20

Name:

Important Notes:

1. This exam consists of 18 problems on 18 pages, plus this cover sheet, and two pages for scratch work at the end of the exam.

2. All answers must be written in the spaces provided. Do not write anything in red ink. Answers written on the back of a page will not be graded. Anything written on the scratch pages will not be graded.

3. You are allowed to use a set of molecuar models for this exam.

Problem

1.

2.

3.

4.

5.

6.

7.

8.

9.

Score

____________ / 16

____________ / 16

____________ / 16

____________ / 16

____________ / 18

____________ / 18

____________ / 14

____________ / 14

____________ / 18

Total Score:

______________ / 300

Problem

10.

11.

12.

13.

14.

15.

16.

17.

18.

Score

____________ / 18

____________ / 18

____________ / 18

____________ / 18

____________ / 18

____________ / 16

____________ / 16

____________ / 16

____________ / 16

11. Each of the following transformations can be carried out in three or fewer steps. Fill in the reagents or conditions required for each step. If a step is not needed, please put an "X" through that step.

Name:

_______ / 16

a)

b)

c)

d)

1.

2.

3.

1.

2.

3.

1.

2.

3.

1.

2.

3.

OH

O

O

OCH3

OH NH2

22. Each of the following transformations can be carried out in three or fewer steps. Fill in the reagents or conditions required for each step. If a step is not needed, please put an "X" through that step.

Name:

_______ / 16

a)

b)

c)

d)

1.

2.

3.

1.

2.

3.

1.

2.

3.

C CH

Br Br

Br Br

OH

OCH3

O O

OCH3

O

1.

2.

3.

O O

CN

3 Name:

a)

b)

3. Fill in each box with the single major organic product of the indicated transformation. For full credit, your answer must conform to the molecular formula, if given. Be sure to indicate the correct stereochemistry if it is relevant!

_______ / 16

c)

d)

1. O3

2. (CH3)2S

1. Zn, HCl, Δ

2. AlCl3,Cl

O

(Mol. form. C13H18O2)

O

O

1. NaOCH3,

2.

3. H+ workup

CuLi

2

O

O

HN

, pH 5

(Mol. Form. C12H21N)

4 Name:

a)

b)

4. Fill in each box with the starting material or single major organic product of the indicated transformation. For full credit, you must use each reagent in a reasonable way. Be sure to indicate stereochemistry if it is relevant!

_______ / 16

c)

d)

1. mCPBA2. CH3OH, H+

3. TsCl4. NaCN

H

Et Me

OH

HMe

(+/–)

1. BH3, THF

2. H2O2, NaOH

1. Na0, liq. NH32. NBS, CCl4

3. NaSCH3

SCH3

(+/-)

HO

O

1. H+ ,

2. NaBH4, EtOH

OH

O

5 Name:

5. In the following question, we will explore the preparation of nitrile oxides.

_______ / 18

Ph

O

H

NH2OH

pH 5 Ph

N

H

OH

oximePh

N

Cl

OH

oxidation

Ph

C

N

O

nitrile oxide

NEt3

a) Draw a complete curved arrow mechanism for the formation of the oxime from benzaldehyde.

b) Draw a complete curved arrow mechanism for the formation of the nitrile oxide from the oxime chloride.

c) Only the (Z)-oxime chloride reacts as you showed in part b. Explain with clearly labeled diagrams why the (E)-oxime does not undergo this reaction. Label any relevant FMOs.

oxime chloride

Ph

N

Cl

OH

Ph

C

N

O

NEt3

Cl

N

Ph

OHNEt3

(E)-oxime chloride

no reaction

benzaldehyde

6 Name:

6. In the following question, we will explore the reactivity of nitrile oxides.

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Ph

C

N

O

nitrile oxide

a) Provide a full FMO analysis of the conjugated pi-system of the nitrile oxide. Please include all pi-orbitals and identify the HOMO and LUMO. You should ignore the phenyl group and consider only the conjugated pi system of the C-N-O atoms.

FMO Analysis:

Ph

C

N

O

b) Nitrile oxides are known to dimerize (react with itself) under thermal conditions. You and your study buddy come up with two possible dimerization reactions. On the structures below, show the curved arrow mechanism for the formation of each of the possible products.

c) Only one of these reaction pathways is observed. Predict below the pathway that should be favored under thermal conditions.

Ph

C

N

O

O

N O

N

Ph

Ph Ph

C

N

O

Ph

C

N

O

O

N

N

Ph

O

Ph

ΔΔ

Pathway 1: Pathway 2:

circle one: PATHWAY 1 or PATHWAY 2

d) Show the FMO orbital analysis for the interactions that would be required in each of these pathways:

Pathway 1: Pathway 2:

7. You have just synthesized a new compound, and the following spectroscopic data are obtained:• From the mass spectrum, you deduce that the molecular formula is: C10H12O2

• The proton NMR spectrum is:

• The infrared spectrum is:

Draw your best choice for the structure of this molecule in the box below.

From the infrared spectrum, circle the functional groups that are definitely present:

From the infrared spectrum, circle the functionalgroups that are definitely absent:

O H C O C C C N O H C O C C C N

7 Name:

_______ / 14

6H

1H5H

012345678PPM

8. You have just synthesized a new compound, and the following spectroscopic data are obtained:• From the mass spectrum, you deduce that the molecular formula is: C5H10O

• The proton NMR spectrum is:

• The infrared spectrum is:

Draw your best choice for the structure of this molecule in the box below.

From the infrared spectrum, circle the functional groups that are definitely present:

From the infrared spectrum, circle the functionalgroups that are definitely absent:

O H C O C C C N O H C O C C C N

8 Name:

_______ / 14

0123456PPM

1H 1H 1H 1H

3H 3H

0540060080001002100410061008100020022004200620082000300230043006300830004

2.5 2.6 2.7 2.8 2.9 3 3.5 4 4.5 5 5.5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 21 22

WAVENUMBERS

MICRONS

0

10

20

30

40

50

60

70

80

90

100 0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.80.91.0

2.0

.05

%TRANSMITTANCE

ABSORBANCE

NICOLET 20SX FT-IR

9 Name:

9. Provide a complete curved-arrow mechanism for all steps in the following transformation.

_______ / 18

O

1. Br2 , H+ 2.

KOtBu, tBuOH

Ph

O

H

OO

Ph

10 Name:

10. Provide a complete curved-arrow mechanism for all steps in the following transformation.

_______ / 18

NH

Me

1. CHCl3

KOtBu, tBuOH

2. LDA

N

Me

Cl

11 Name:

11. Provide a complete curved-arrow mechanism for the following transformation. A key intermediate is provided below.

_______ / 18

O

Ph H

O

NaCNKOtBu, tBuOH

O

CN

HO Ph

key intermediate

O

Ph

O

12 Name:

12. Provide a complete curved-arrow mechanism for all steps in the following transformation.

_______ / 18

Me

O

O

+Cl

Cl

NO2 1. AlCl3

2. NaOH

Me

O

Me

NO2

13 Name:

13. Aromatic amines can be converted into phenols using the following two-step transformation:

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NH2 N2 Cl

1. HCl,

NaNO2

OH

2. H2O

a) Provide a complete curved-arrow mechanism for the first step of the above mechanism (the formation of the diazonium salt).

b) Your friend suggests that the second step of the above mechanism (reaction with water) could proceed through an SN1 mechanism. Provide the curved arrows for this proposed mechanism, and then explain briefly why this mechanism is not likely to be the correct mechanism.

14 Name:

14. Phenol can be converted into an interesting product using the following two-step transformation. Provide a complete curved-arrow mechanism for both steps. If your mechanism contains any pericyclic reactions, please provide the complete classification (e.g. electrocyclic, 6πe–, thermal, disrotatory).

_______ / 18

O

OOH

1. TsCl, pyr

2. NaNH2, NH3 (l)

Note: You may represent TsCl as:

ArS

Cl

O O

where Ar = para-toluene

15 Name:

_______ / 16

Starting Material:

15. Provide a complete synthesis of the following desired product from the indicated starting materials. You may use any other inorganic and organic reagents that you need, but all of the carbon atoms from the starting materials must end up in the product. You do not need to show any mechanisms. Be sure that your synthesis accounts for the stereochemistry of the product. The best answer will require eight or fewer total steps.

Desired Product

(+/−)

O

and HO

16 Name:

_______ / 16

Starting Material:

16. Provide a complete synthesis of the following desired product from the starting materials with four or fewer carbon atoms. You may use any inorganic reagents. You do not need to show any mechanisms. Be sure that your synthesis accounts for the stereochemistry of the product. The best answer will require seven or fewer total steps.

Desired Product

anything with 4 or fewer C's

plus, any inorganic reagents

H3COOCH3

CN

CN

(+/−)

17 Name:

_______ / 16

Starting Material:

17. Provide a complete synthesis of the following desired product from the acyclic starting materials. You may use any inorganic reagents. You do not need to show any mechanisms. The best answer will require six or fewer total steps.

Desired Product

any ACYCLIC reagents

plus, any inorganic reagents

(+/−)

HN

O

NMe

18 Name:

_______ / 16

Starting Material:

18. Provide a complete synthesis of the following desired product from the the given starting material and any other organic or inorganic reagents you need. You do not need to show any mechanisms. The best answer will require eight or fewer total steps.

Desired Product

O

H3CO

(+/−)

SCRATCH PAPER ONLY - NOTHING ON THIS SHEET WILL BE GRADED

SCRATCH PAPER ONLY - NOTHING ON THIS SHEET WILL BE GRADED