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1616778 
Journal Article 
On the yield of intermediates formed in the photoreduction of benzophenone 
Costa, CV; Grela, MA; Churio, MS 
1996 
Yes 
Journal of Photochemistry and Photobiology A: Chemistry
ISSN: 1010-6030
EISSN: 1873-2666 
Elsevier 
LAUSANNE 1 
99 
1 
51-56 
English 
WOS:A1996VH90200008 
The production of intermediates (light absorbing transients,
LAT) has been examined in the photoreduction of benzophenone by different hydrogen donors in
inert solvents (acetonitrile and benzene). For 2-propanol in acetonitrile, a branching ratio of
0.3 for the coupling reaction between dimethyl- and diphenylketyl radicals was extracted by
computer model simulations considering inner filter effects and the quenching of triplet
benzophenone by LAT. Experimental evidence is presented that indicates that LAT could be an
efficient H-donor. Steady-state quantum yields for LAT production, Phi(LAT), and benzophenone
conversion, -Phi(Ph2CO), were determined for the donors 2-propanol, n- and c-hexane, benzhydrol
and tetrahydrofuran. The relative quantum yield, -Phi(LAT)/Phi(Ph2CO), which indicates the
differential partitioning of the products, shows that 2-propanol and tetrahydrofuran are nearly
ten times more efficient than alkanes. From the analysis of the mechanism we derived an upper
limit for the rate constant for the coupling reaction of two diphenylketyl radicals to yield LAT:
k(6d) less than or equal to 5 x 10(5) M(-1) s(-1). 
photoreduction; kinetics; condensed phase; benzophenone; light absorbing transients; intermediates; ketyl radicals