Organic Chemistry

784 CHAPTER 18 Carbonyl Compounds II

60. Propose a reasonable mechanism for each of the following reactions:

a.

b.

61. a. In aqueous solution,D-glucose exists in equilibrium with two six-membered ring compounds. Draw the structures of these
    compounds.

b. Which of the six-membered ring compounds will be present in greater amount?

62. The spectrum of the alkyl bromide used to make the ylide to form a compound with molecular formula is shown
    below. What product is obtained from the Wittig reaction?


63. In the presence of an acid catalyst, acetaldehyde forms a trimer known as paraldehyde. Because it induces sleep when it is
    administered to animals in large doses, paraldehyde is used as a sedative or hypnotic. Propose a mechanism for the formation of
    paraldehyde.


64. The addition of hydrogen cyanide to benzaldehyde forms a compound called mandelonitrile. (R)-Mandelonitrile is formed from the
    hydrolysis of amygdalin, a compound found in the pits of peaches and apricots. Amygdalin is the principal constituent of laetrile, a
    compound that was once highly touted as a treatment for cancer. The drug was subsequently found to be ineffective. Is
    (R)-mandelonitrile formed by attack of cyanide ion on the Reface or the Siface of benzaldehyde?

CH

HCl

NaC

excess

N

O

CHC N

OH

mandelonitrile

CH 3 CH

HCl

O

OO

H 3 C O

CH 3

CH 3

paraldehyde

10 9 8765 4 3 210

3.2 3.1 3.0 PPM

3.6 3.5 3.4 PPM

δ (ppm)

frequency

(^1) H NMR C 11 H 14
CH 2 OH
HC O
OH
OH
H
H
H OH
HO
H
D-glucose
CH 3
O
CH 3 O
COH
O
O
CCH 3
O
HCl
CH 3 OH
CH 3 CCH 2 CH 2 COCH 2 CH 3 O CH 3 CH 2 OH
H 3 C O
H 3 C +
OO

1. CH 3 MgBr


2. H 3 O+