To pick up your graded exam from a box outside 5100A Pacific Hall sign here: ________________________

CHEMISTRY 140A NAME (please print) FINAL EXAM (V & S 6TH ED) FIRST LAST JULY 29, 2011 SIGNATURE ID NUMBER LAST NAME OF PERSON SEATED ON YOUR RIGHT: LAST NAME OF PERSON SEATED OPN YOUR LEFT:

DO NOT OPEN THE EXAM UNTIL YOU ARE TOLD TO DO SO

− Please sign your name on the top of each page. − Please check to see that you have 8 pages (including this one). The one blank page

may be used for scratch work, but DO NOT use the scratch page for answers. Answer in the space provided. Do not write answers on the back of a page.

Question Points Score ________________________________________ 1. 55 _____ 2. 60 _____ 3. 35 _____ 4. 50 _____ ________________________________________ Total 200 _____ ________________________________________

H HeLi Be B C N O F NeNa Mg Al Si P S Cl ArK Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br KrRb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I XeCs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

NAME:__________________________

2

1-i. (25 pts) For each of the following transformations, draw the structure of the product or intermediate

that is formed by the indicated curved-arrow notation for electron movement. Be sure to indicate any formal charges and clearly indicate stereochemistry where relevant.

NAME:__________________________

3

1-ii. (30 pts) For each of the following one-step transformations show the movement of electrons by

using the standard curved arrow notation. Show all formal charges for each structure to the left and to the right of the reaction arrows. In the box below each reaction arrow indicate which of the following reaction types includes that general type of mechanistic step: SN1, SN2, E1, E2, oxidation, or reduction. (2 pts for curved arrows, 2 pts for charges, 2 pts for boxes)

NAME:__________________________

4

2-i. (30 pts) In the boxes provided, draw the structure of the starting material needed for each of the

following transformations. In all cases the starting materials must be optically pure compounds. Be sure to clearly show stereochemistry.

d)

a)

b)

c)

e)

NaBH4

NaOtBu

Et

OH

tBuOH

Me

MeOH

HOMe

a mixture of twodiastereomers

PCl3Cl

a single enantiomer

OMe

H

O-D

Me

LiAlD4

a single enantiomer

Et

OMe

OH

H

Br

H

O

Me

Br

NAME:__________________________

5

2-ii. (30 pts) For each of the reactions shown below, draw the structure of the major product(s). Where

appropriate, write “No Reaction”. Assume all chiral starting materials are optically pure. Show stereochemistry where appropriate. If the major product is formed as a mixture of diastereomers then place an “x” in the small circle. If the major product is formed as a single enantiomer, place an “x” in the small box.

NAME:__________________________

6

3. i. (10 pts) Give an example of a chiral primary alkyl halide that undergoes an E2 reaction to give

an achiral product. Clearly show the structures of the alkyl halide, the reagent, and the product. Draw the transition state structure in the box provided.

Br

H

R1R2

KOMe R1R2

Br

H

R1R2

MeO

HH

!

!

ii. (5 pts) Give an example of a primary alkyl bromide that does not undergo an E2 reaction. (CH3)3CCH2Br

iii. (5 pts) Give an example of an alkyl bromide that does not undergo an SN2 reaction. (CH3)3CCH2Br or (CH3)3CBr

iv. (5 pts) For the following sets of ions circle the best leaving group and place a box around the poorest leaving group in SN2 reactions:

MeCO2- Me2N

- MeO- H3C- MeSO3

- boxed circled

v. (5 pts) For the following sets of ions circle the best nucleophile and place a box around the poorest nucleophile (assume a polar protic solvent in each case):

H3O+ F- HS- HO- Cl-

boxed circled

NAME:__________________________

7

4. i. (5 pts) Give the structures of two chiral stereoisomers of dichlorocyclobutane:

Cl

Cl

Cl

Cl

ii. (20 pts) For each of the following compounds provide a Lewis structure with octets at all non-hydrogen atoms:

a) DMSO S

O

CCHHH

HHH

b) Acetone C

O

CCHHH

HHH

c) THF (tetrahydrofuran)

OHHHH

HH

HH

d) HMPA

P

O

NNC

C

C

CNC C H

HHHH H

HHH

HHH

HH

HHHH

iii. (5 pts) Which type of solvent (apolar, protic polar, aprotic polar) would you employ to

maximize the rate of reaction for an SN2 reaction? Aprotic polar

iv. (5 pts) Which type of solvent (apolar, protic polar, aprotic polar) would you employ to maximize the rate of reaction for an SN1 reaction? Protic polar

v. (5 pts) Which of the following haloalkanes will undergo hydrolysis most rapidly (circle your

answer)? d

a. (CH3)3CF b. (CH3)3CCl c. (CH3)3CBr d. (CH3)3CI

vi. (5 pts) Which of the following compounds will exhibit the highest boiling point (circle your answer): b

a. CH3CH2CH3 b. CH3CH2CH2OH c. CH3CH2CH2Br d. CH3OCH3

vii. (5 pts) How many different hydrogen environments are there in cis-1,2-dibromocyclopropane? 3