Organic Chemistry

(known as dioxin) is a contaminant formed during the manufacture of Agent Orange.
TCDD has been implicated as the causative agent behind various symptoms suffered
by those exposed to Agent Orange during the war.

Because of the known physiological activities of adrenaline and mescaline,
chemists have synthesized compounds with similar structures. One such compound is
amphetamine, a central nervous system stimulant. Amphetamine and a close relative,
methamphetamine, are used clinically as appetite suppressants. Methamphetamine is
the street drug known as “speed”because of its rapid and intense psychological ef-
fects. Two other synthetic substituted benzenes, BHA and BHT, are preservatives (see
Section 9.8) found in a wide variety of packaged foods. These compounds represent
just a few of the many substituted benzenes that have been synthesized for commercial
use by the chemical and pharmaceutical industries.

In Chapter 15, we looked at the reactions benzene undergoes and we saw how
monosubstituted benzenes are named. Now we will see how disubstituted and
polysubstituted benzenes are named, and then we will look at the reactions of
substituted benzenes. The physical properties of several substituted benzenes are given
in Appendix I.

Introduction 623

CH 2 CHNHCH 2 CH 3

CF 3

fenfluramine

CH 3

CH 2 CNH 2

CH 3

phentermine

CH 3

saccharin

C(CH 3 ) 3

OCH 3
butylated
hydroxyanisole
BHA
a food antioxidant

O

O O

OH

Cl

p-dichlorobenzene

mothballs and

air fresheners

Cl

(CH 3 ) 3 C C(CH 3 ) 3

CH 3

butylated

hydroxytoluene

BHT

a food antioxidant

C

NH

S

OH

MEASURING TOXICITY

The toxicity of a compound is indicated by its

value—the quantity needed to kill 50% of

the test animals exposed to the compound. Dioxin, with an

value of for guinea pigs, is an extremely

toxic compound. Compare this with the LD 50 values of

LD 50 0.0006 mg>kg

LD 50

for strychnine and for sodium cyanide—

far less toxic compounds. One of the most toxic agents known

is the botulism toxin, with an value of about

1 * 10 -^8 mg>kg.

LD 50

0.96 mg>kg 15 mg>kg

OCH 2 COH

Cl Cl

2,4-dichlorophenoxyacetic acid

2,4-D

O

OCH 2 COH

Cl Cl

Cl

2,4,5-trichlorophenoxyacetic acid

2,4,5-T

O

O Cl

O Cl

Cl

Cl

2,3,7,8-tetrachlorodibenzo[b,e][1,4]dioxin

TCDD

CH 2 CHNH 2

amphetamine

CH 3 CH 3

CH 2 CHNHCH 3

methamphetamine

“speed”

COH

OCCH 3

acetylsalicylic acid

aspirin

hexachlorophene

a disinfectant

O

O

Cl Cl Cl Cl

Cl OH HO Cl

CH 2