A Guidebook to Mechanism in Organic Chemistry

Autoxidation

(XXVII), cyclohexene (XXVIII) and diphenylmethane, (XXIX), re­

spectively :

OOH

(XXVII) (XXVIII) (XXIX)

Reference**^already been made to the large-scale conversion of

cumene (isopropylbenzene) into phenol+acetone via the hydro­

peroxide (p. 100); the air oxidation of tetralin (tetrahydronaphthalene)

to the ketone a-tetralone may also be accomplished preparatively via

the action of alkali on the first-formed hydroperoxide:

HO^H 0-Q>H

H.O 'OH

In addition, the corresponding alcohol a-tetralol may be obtained by
reductive fissions of the hydroperoxide.
Aldehydes also readily autoxidise: thus benzaldehyde, in air, is
extremely easily converted into benzoic acid (seep. 254). This reaction
is catalysed by light and also by a number of metal ions, provided
these are capable of a one electron oxidation/reduction transition
(e.g. Fe®ee->-Feee). The perbenzoate radical (XXXI), obtained by
addition of 'Oa* to the first-formedJ?enzoyl radical (XXX), removes
a hydrogen atom from a secomtmolecule of benzaldehyde to form
perbenzoic acid JXOCXII) plus a benzoyl radical (XXX) to continue
the reaction chain.

The perbenzoic acid reacts with a further molecule of benzaldehyde,
however, to yield two molecules of benzoic acid. This reaction is