Res. Chem. Intermed.
, Vol. 32, No. 8, pp. 749–758 (2006)
Also available online - www.brill.nl/rci
Laser photolysis studies of β-bond cleavage of phenacyl
phenyl sulﬁde in acetonitrile
, SAYAKA WAKABAYASHI and SEIJI TOBITA
Department of Chemistry, Gunma University, Kiryu 376-8515, Japan
Received 19 January 2006; accepted 14 April 2006
Abstract—Photo-induced β-bond dissociation of phenacyl phenyl sulﬁde (PPS) has been investi-
gated in acetonitrile by laser photolysis techniques. Direct excitation of PPS at 295 K provided the
acetylmethyl and phenylthiyl radicals with a quantum yield (
) of 0.18, whereas triplet sensiti-
zation using xanthone revealed an efﬁciency for β-cleavage of triplet PPS (α
disagreement between the
values, it was concluded that both the lowest excited single
and triplet states are reactive for β-bond dissociation in PPS. The photochemical processes of excited
PPS, including β-cleavage, are discussed in detail.
Keywords: Laser photolysis; phenacyl phenyl sulﬁde; β-bond dissociation; excited state.
Primary photochemical reactions of carbonyl compounds are often used as photoini-
tiators for polymerization. The radical formation through those photochemical reac-
tions results mainly from three processes, i.e., H-atom abstraction, β-cleavage and
α-cleavage. Norrish type-I and -II reactions where carbon–carbon bond ﬁssion oc-
curs at the α-andβ-positions of the carbonyl, respectively, have been widely stud-
ied [1, 2]. As with β-cleavage of the carbon–sulfur bond in carbonyl compounds,
photochemistry of phenacyl sulﬁdes has been studied mainly by product analy-
sis [3– 10]. Wagner et al. systematically investigated photochemistry of phenacyl
phenyl sulﬁdes based on measurements of formation yields of acetophenone in the
presence of thiophenol upon stationary photolysis . The quantum yields of
β-cleavage depend on the substituent groups on the phenacyl ring, varying from
0.19 to 0.41. The reactive states for the β-cleavage of phenacyl phenyl sulﬁde (PPS,
Scheme 1) derivatives were suggested to be both the n,π
singlet and triplet states.
However, the efﬁciencies of β-dissociation in each reactive state are not known.
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