Page 597 - Carrahers_Polymer_Chemistry,_Eighth_Edition

560 Carraher’s Polymer Chemistry

Phthalic acid (1,2-benzene dicarboxylic acid), isophthalic acid (1,3-benzene dicarboxylic acid),
and terephthalic acid (1,4-benzene dicarboxylic acid) are made by the selective oxidation of the cor-
responding xylenes. Terephthalic acid may also be produced from the oxidation of naphthalene and
by the hydrolysis of terephthalonitrile. The oxidation of p-xylene by oxygen from the air is generally
done using acetic acid as a solvent in the presence of a catalyst such as cobalt–manganese. The yield
is close to 100%.

O OH O OH
CH 3
CH 3

O
CH 3
CH 3 OH
HO O
p -Xylene Terephthalic acid (17.6) m -Xylene Isophthalic acid (17.7)

Malic anhydride (2,5-furandione) is made as a byproduct in the production of phthalic anhyd-
ride, and by the vapor phase oxidation of butylene or crotonaldehyde. It is also obtained by the
dehydration of maleic acid and by the oxidation of benzene. Maleic anhydride is used for the pro-
duction of unsaturated polyester resin. This reactant, like many reactants, is fairly toxic and should
be treated as such.

O O

OH
O
OH (17.8)

O
O
Benzene Maleic acid Maleic anhydride

2-Pyrrolidone is a lactone used for the production of nylon-4. This reactant may be produced by
the reduction ammoniation of maleic anhydride. ε-Caprolactam, used in the production of nylon-6,
may be produced by the Beckman rearrangement of cyclohexanone oxime (Equation 17.11). The
oxime may be produced by the catalytic hydrogenation of nitrobenzene, the photolytic nitrosyla-
tion of cyclohexane (Equation 17.9), or the reaction of cyclohexanone and hydroxylamine (Equation
17.10). Nearly one-half of the production of caprolactam is derived from phenol.

N
OH
+ NOCl, HCl (17.9)

O N
OH
+ O 2 (17.10)

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