Yp. Tu et al., CHEMICAL-IONIZATION MASS-SPECTROMETRY OF BENZOYL PEROXIDE - A RADICALAROMATIC-SUBSTITUTION RESULTING IN BIPHENYLCARBOXYLIC ACID IN THE GAS-PHASE, Organic mass spectrometry, 28(12), 1993, pp. 1435-1439
A radical aromatic substitution resulting in biphenylcarboxylic acid i
s inferred for the decomposition of benzoyl peroxide from the chemical
ionization and collision-induced dissociation mass spectra. The therm
olysis of benzoyl peroxide gives rise to a benzoyloxy radical, which u
ndergoes rapid decarboxylation and hydrogen abstraction leading to phe
nyl radical and benzoic acid, respectively. Attack of the resulting ph
enyl radical on the benzoic acid results in bipbenylcarboxylic acid. O
n the other hand, the phenyl radical abstracts a hydrogen atom to yiel
d benzene, which is then subjected to the attack of a benzoyloxy radic
al, affording phenyl benzoate. This substitution reaction rather than
the recombination of benzoyloxy and phenyl radicals is found to be res
ponsible for the formation of phenyl benzoate under the present condit
ions.