Organic Chemistry

Problems 435

36. Rank the following compounds in order of decreasing reactivity in an E2 reaction:


37. Using the given starting material and any necessary organic or inorganic reagents, indicate how the desired compounds could be
    synthesized:

a. d.

b. e.

c.

38. When 2-bromo-2,3-dimethylbutane reacts with a base under E2 conditions, two alkenes (2,3-dimethyl-1-butene and 2,3-dimethyl-
    2-butene) are formed.
    a. Which of the bases shown would give the highest percentage of the 1-alkene?
    b. Which would give the highest percentage of the 2-alkene?


39. a. Give the structure of the products obtained from the reaction of each enantiomer of cis-1-chloro-2-isopropylcyclopentane with
    a high concentration of sodium methoxide in methanol.
    b. Are all the products optically active?
    c. How would the products differ if the starting material were the trans isomer? Are all these products optically active?
    d. Will the cis enantiomers or the trans enantiomers form substitution products more rapidly?
    e. Will the cis enantiomers or the trans enantiomers form elimination products more rapidly?


40. Starting with cyclohexane, how could the following compounds be prepared?
    a. trans-1,2-dichlorocyclohexane b. 2-cyclohexenol


41. The rate constant of an intramolecular reaction depends on the size of the ring (n) that is formed. Explain the relative rates of
    formation of the cyclic secondary ammonium ions.

42.cis-1-Bromo-4-tert-butylcyclohexane and trans-1-bromo-4-tert-butylcyclohexane both react with sodium ethoxide in ethanol to

give 4-tert-butylcyclohexene. Explain why the cis isomer reacts much more rapidly than the trans isomer.

43. Cardura®, a drug used to treat hypertension, is synthesized as follows:

Identify the intermediate (A), and show the mechanism for its formation. Also, show the mechanism for the conversion of A to B.

Which step do you think will occur most rapidly? Why? (The mechanism for the conversion of B to the final product is explained

in Chapter 17.)

Br

OH

OH COCH 3

BrCH 2 CHCOCH 3 A

B

O O

O

+ + CH 3 OH

K 2 CO 3 KOH

O

COH

O

O

O

Cardura

Br (CH 2 )n-1NH 2 (CH 2 )n-1 +NH 2 Br−

n =

relative rate:

3

1 × 10 −^1

4

2 × 10 −^3

7

3 × 10 −^3

10

1 × 10 −^8

5

100

6

1.7

CH 3 CO−

CH 3

CH 3

CH 3 CH 2 CO− CH 3 CH 2 O−

CH 2 CH 3

CH 2 CH 3

CH 3 CH 2 CO−

CH 3

CH 3

O

HOCH 2 CH 2 CH CH 2

CH 3 CH 2 CH CH 2 CH 2 CH 2 CH 2 CH 2 NH 2 CH 3 CH 2 CH“CH 2 ¡CH 2 “CHCH“CH 2

OCH 3

CH 2 CH 3 CH CH 2

CH 3

Br

CH 3

CH 3

Br

CH 3

Br

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