Benzil has been irradiated in cyclohexane solution. The principal products are: benzoic acid; benzal-dehyde; phenyl cyclohexyl ketone; benzoin; benzoin benzoate; a compound tentatively identified as desyl benzoyloxydesyl ether; another compound not yet identified; and approximately one-third of the reacted benzil that was not accounted for. A small amount of unsaturation is also found. As long as there is enough benzil present (presumably to absorb all of the light) the benzil disappearance is linear with time. All products appear at the shortest times checked and so cannot be secondary products. If one neglects the benzoic acid approximately 19% of the benzoyl groups that react do so in the form of benzoyl radicals. No evidence for phenyl radical formation was found. The upper limit for the quantum yield of benzil disappearance at 366 mμ is 0.25. The benzoic acid does not arise directly during the photolysis but only when the solution is exposed to oxygen during the work-up. Preliminary experiments in cumene solution have shown that the amount of benzil lost for the same length of irradiation increases by a factor of about 1.5. In 2-propanol solution the increase is by a factor of 2.5. When 2-propanol is the solvent, a new product appears which is most probably the dimer of the ketyl radical which is formed when an excited benzil abstracts a hydrogen atom. This product is very unstable.
SynopsisThe rate of chemical-initiated solution copolymerization of acrylonitrile and styrene in toluene as solvent was studied theoretically and experimentally with a limiting conversion of about 50%. Taking into consideration industrial operation, the polymerization was carried out under an azeotropic composition of A N S t = 2575 by weight, and a new kinetic model is proposed for estimating the conversion and the rate of polymerization as well as the molecular weight distribution over the entire reaction course. It is shown that the experimental data of conversion and the rate of reaction, as well as average molecular weight, can be successfully correlated to limiting conversion by this model if the effect of change in the initiator efficiency during the reaction on the rate of reaction is taken into consideration. It was found that the effective initiator efficiency can be expressed as f
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