Orgo Practice Exam

Chem 230 (Fall 2013)

Final Exam Name______________________________________________________ ID __________________ Section___________________ TA________________________________________ Problem 1 (20 pts)_____________ Problem 2 (20 pts)_____________ Problem 3 (20 pts) _____________ Problem 4 (20 pts)_____________ Problem 5 (20 pts)_____________ Problem 6 (20 pts)_____________ Problem 7 (20 pts)_____________ TOTAL (140 pts)___________________

1a. Rank the following compounds by acidity. 4 = most acidic; 1= least acidic (5 pts)

OH OHOHCl

SHCl

1b. Rank the following compounds by their order of reactivity in E2 reaction using a large base,

i.e. t-BuOK. 4 = most reactive; 1= least reactive (5 pts)

Cl BrCl Br

1c. Rank the following compounds by their order of reactivity in SN1 reaction. 4 = most reactive; 1=

least reactive (5 pts)

BrBr ClCl

1d. Rank the following compounds by their order or basicity. 4 = most basic; 1= least basic (5 pts)

LiH KH LiAlH4 NaBH4

2a. A student wanted to synthesize methyl tert-butyl ether, CH3–O–C(CH3)3. He attempted the

synthesis by adding sodium methoxide to tert-butyl chloride, but he obtained none of the desired product. Show the product that is formed in this reaction and propose a better synthesis of methyl tert-butyl ether from any other starting materials. (10 pts)

2b. Explain why compound A reacts with potassium tert-butoxide much faster than compound B and

predict the structure of the product of this reaction. (10 pts)

Br

H

H

H

Br

A B

3. Provide products of the following reactions and their detailed mechanisms. All reagents are used

in stoichiometric amounts (10 pts each).

OHNa2Cr2O7

H2SO4, H2O

Br2

h!

4. Predict products of each of the following reactions. (20 pts). (a) (b)

(c) (d)

(e) (f)

(g)(h)

(i) (j)

NaBH4

EtOH

O

OH

Br t-BuOK

OH

OH

PCC

CH2Cl2

DMF

O

O

OH

NADH

lactate dehydrogenase

LiAlH4O

Br

diethyl ether; followed by

D2O

O HBr

hexane

H2O

Cl NaOMe

MeOH

Me

O

SMe

NaOH

H2O

Br

Br MeNH2

NaHCO3

DMF

OH OH diethyl ether

MeLi

excess excess

excessexcess

(1 equiv.) (1 equiv.)

excess excess

(1 equiv.)(1 equiv.)

5a. Predict major products of solvolysis reactions of each of the compounds below with ethanol (6

pts).

Cl

Cl

5b. Which of the two compounds below would react faster with ethanol? Explain your answer using

Hammond postulate and knowledge of ring strain. (7 pts). 5c. Would such reactions proceed faster or slower upon addition of a less polar solvent, such as

hexane? Explain your answer using Hammond postulate. (7 pts).

6a. The following reaction produces a rearranged product. Also, the rate of the reaction is several

thousand times faster than the rate of nucleophilic substitution of 2-chlorobutane by the hydroxide ion. Propose the mechanism of this reaction (10 pts).

N

Cl

NaOH N

OH 6b Using your knowledge of conformational analysis of acyclic molecules and presuming that methyl group is sterically bulkier than a bromine atom, explain why the following E2 reaction produces a trans alkene as a major product (10 pts).

Br NaOMe

major

+

minor

7. Propose syntheses of each of the two compounds on the right starting from two reactants on the left as the only source of carbon atoms. You can use any other inorganic reagents. Try to devise the shortest syntheses in order to obtain maximum credit. (10 pts each).

andO

H H

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