John McMurry, Professor Emeritus

Problem 5-1

Chiral: screw, shoe

Problem 5-2

(a)

The structure of coniine, in which N is in first position. C2 is labeled with asterisk and bonded to a propyl group.

(b)

The wedge-dash structure of menthol. C1, C2, and C5 are labeled with asterisks.

(c)

The wedge-dash structure of dextromethorphan. Two fused carbons of both cyclohexanes and one carbon of central cyclohexane (that is bonded to nitrogen) are labeled with asterisks.

Problem 5-3

The figure shows two enantiomers of alanine represented in wedge-dash form.

Problem 5-4

(a)

The wedge-dash structure of threose. C2 and C3 are labeled with asterisks.

(b)

The wedge-dash structure of enflurane. C1 is labeled with asterisk.

Problem 5-5

Levorotatory

Problem 5-6

+16.1°

Problem 5-7

(a)

−Br

(b)

−Br

(c)

−CH₂CH₃

(d)

−OH

(e)

−CH₂OH

(f)

−CH

\text{=}

O

Problem 5-8

(a)

−OH, −CH₂CH₂OH, −CH₂CH₃, −H

(b)

−OH, −CO₂CH₃, −CO₂H, −CH₂OH

(c)

−NH₂, −CN, −CH₂NHCH₃, −CH₂NH₂

(d)

−SSCH₃, −SH, −CH₂SCH₃, −CH₃

Problem 5-9

(a)

S

(b)

R

(c)

S

Problem 5-10

(a)

S

(b)

S

(c)

R

Problem 5-11

A central carbon atom is single bonded to hydrogen and a propyl group, wedge bonded to a methyl group, and dash bonded to a hydroxyl group (clockwise).

Problem 5-12

S

Problem 5-13

Compound (a) is D-erythrose 4-phosphate, (d) is its enantiomer, and (b) and (c) are diastereomers.

Problem 5-14

Five chirality centers and 2⁵ = 32 stereoisomers

Problem 5-15

S,S

Problem 5-16

Compounds (a) and (d) are meso.

Problem 5-17

Compounds (a) and (c) have meso forms.

Problem 5-18

Meso compound has a cyclopentane ring. C1 is bonded to hydroxyl group. C3 and C4 are each wedge bonded to a methyl group. The symmetry plane passes through hydroxyl group and the C-C bond.

Problem 5-20

Two diastereomeric salts: (R)-lactic acid plus (S)-1-phenylethylamine and (S)-lactic acid plus (S)-1-phenylethylamine

Problem 5-21

(a)

Constitutional isomers

(b)

Diastereomers

Problem 5-22

(a)

The wedge-dash structure of (S)-glyceraldehyde. The dash bonded hydrogen at C3 is labeled pro-R and wedge bonded hydrogen is labeled pro-S.

(b)

The wedge-dash structure of an amino acid. The wedge bonded hydrogen at C3 is labeled pro-R and the dash bonded hydrogen is labeled pro-S.

Problem 5-23

(a)

The structure of hydroxyacetone. The central carbon is labeled Re face at the top and Si face at the bottom.

(b)

The structure of crotyl alcohol. The central carbon is labeled Re face at the top and Si face at the bottom.

Problem 5-24

(S)-Lactate

Problem 5-25

The −OH adds to the Re face of C2, and −H adds to the Re face of C3. The overall addition has anti stereochemistry.

Chapter 5