Organic Reactions Volume 4 - Sciencemadness Dot Org

306 ORGANIC REACTIONS
INTRODUCTION
p-Benzoquinone, or "quinone/' was discovered in 1838 as a product
of the action of manganese dioxide in sulfuric acid on the rare natural
product quinic acid/ a tetrahydroxycyclohexanecarboxylic acid; however,
benzoquinones generally are prepared by the oxidation of disubstituted
aromatic hydrocarbon derivatives having hydroxyl or amino groups in
the ortho or para positions. Thus quinone results from the oxidation of
hydroquinone, p-aminophenol, or p-phenylenediamine; in the two latter
instances the reaction proceeds through the formation and the rapid
hydrolysis of a quinonimine or quinonediimine. When such starting
OH O [ NHl NH2
Oil O L NH J NH2
materials or intermediates are available, conditions often can be defined
for the production of the desired quinone in high yield. Certain quinones
are obtainable in moderate or fair yield by the oxidation of starting
materials containing only one hydroxyl or amino group, as exemplified
by the industrial production of quinone from aniline. Other methods
that have been employed for the synthetic production of benzoquinones
are of less consequence.
Oxidation of phenols and amines constitutes the chief topic for discussion
in this chapter. Processes for the oxidation with dichromate in
sulfuric acid solution 2 ' 3 or with ferric chloride 4 were developed at an
early date, and Nietzki 5 found that a marked increase in yield results
if the substance oxidized contains an additional hydroxyl or amino group
in the para position. This investigator was the first to employ the
efficient method of introducing a para amino group into a phenol or an
amine by the process of diazo coupling and reduction.
1 Woskrensky, Ann., 27, 268 (1838).
2 Nietzki, Ber., 10, 1934 (1877).
8 Nietzki, Ber., 19, 1467 (1886).
4 Carstanjen, J, prakt. Chem., [2] 3, 54 (1871).
6 Nietzki, Ber., 10, 833 (1877).