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Organic Chemistry I Exam 3 Fall 2011

(Klein Chapters 5, 7, 8)

I. _________ / 16 (General Questions)

II. _________ / 20 (Nomenclature and Stereochemistry)

III. _________ / 16 (Stereochemistry)

IV. _________ / 5 (Spectroscopy)

V. _________ / 39 (Reactions)

VI. _________/ 6 (Mechanisms)

Total _________ / 100

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I. General questions: (16 points / 2 points each ) Circle the correct answer or fill in the appropriate blank. 1. Rearrangements can occur in SN1 and E1 because ________________ form as an intermediate. 2. The process of separating enantiomers is called ____________________.

3. Compounds that have the same molecular formula and same connectivity but differ in their 3-dimensional orientation in space are called __________________. a. isomers b. stereoisomers c. constitutional isomers d. conformational isomers 4. Which of the following substrates will react fastest by an SN1 reaction? a. tert-butyl iodide b. 2-bromopropane c. 1-iodopentane d. 1-bromobutane 5. Define the term “achiral”? 6. A 50/50 mixture of two enantiomers is called a _____________ mixture. 7. An SN2 reaction always results in the _________________ of stereochemistry.

8. The rate of production of a product in an SN1 reaction is 10 mM/min. If the concentration of the nucleophile is doubled, what effect will it have on the rate?

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II. Nomenclature and Stereochemistry: (20 points total / 4 points each) Part A. For the following structures give the correct IUPAC name indicating the correct stereochemistry. 9. (a) (b) (c)

Part B. For the following IUPAC name give the correct structure. 10. (2S,3R)-2-bromo-3-iodoheptane

Br

H3C H

H

F

H

Br

CH3

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III. Fischer Projections (16 points) . 11. For the following Fischer projection give the stereochemistry (R) or (S) by placing a “R” or “S” with a circle around it next to the stereocenter. Make it clearly legible and easy to find. (4 points)

12. For the following compounds use Compound A as the reference compound. Relative to compound A state whether compounds B, C, and D are the same compound, a diastereomer or an enantiomer. (6 points).

13. For the following structure give its corresponding Fischer Projection. (4 points).

14. For the following structure give its mirror image. (2 points)

CH2CH3

H2N Br

CH3

HO H

FHHO Br

F H HBr

F H Br H F H

F

H

H HBr

Br

Compound A(reference compound)

Compound B

Compound CCompound D

OH

H

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IV. Spectroscopy (5 points). For the following IR and NMR spectra, provide a compound that is consistent with the spectra. Both the IR and NMR are for the same compound. 15.

C10H12O2

d, 2H

d, 2H t, 2H

sext, 2H

t, 3H

s, 1H

Disregard the stretches at 2400‐2600.

NaOCH3, Acetone

H3O+, H2O, heat

16

17

18

19

20

21

22

V. Substitution and Elimination Reactions: For the following reactions give either the product, reactionconditions, or reactant indicating the correct stereochemistry where appropriate. "Racemic mixture" is apossible answer for stereochemistry. "No reaction" is also a possible answer only if I am asking you forthe product of the reaction. (39 points/ 3 pts each)

CH3OH

CH3O-,

CH3OH,

I

Major Minor

CH2CH3

CH3H3C

H3CH2C

H Cl

CH3CH2OH, heat

Br

OCH3

Major product

OCH3

+

H OCH3

OH

H

CH3CH2S-, DMSO

Cl CH3 C N ,DMSO

6

after rearrangment

+ CH3OH2+

+ OTs-

+ Br-

23

24

Major Product Minor Product

CH3O-, CH3OH, heat

26

27

28

,DMF

H3O+, H2O, heat

25

NaN3

OTs

CH3CH2OH

2 constitutional isomers

OTs

Br AgNO3, CH3OH

2 constitutional isomers

NH2

+

+

H3CH2C

OMs

7

+ H2O

VI. Mechanisms: Complete ONE of the following mechanisms. Use the curved arrow formalism todenote the movement of electrons. Also be sure to show all lone pairs and formal charges. Do not showeverything in one step. (6 points).

H3O+, heat, H2O

29

30

8

+ H2O+OH

Br

CH3OH OCH3

OCH3

+

+ CH3OH2+

+ Br-