Abstract
Deprotonation reaction of triphenylmethane cation radical has been studied in detail by PM 3 level semi-empirical molecular orbital calculations. The calculations show that the benzyl hydrogen undergoing the deprotonation is positively charged, suggesting that the triphenylmethanecation radical has high aptitude to undergoing the deprotnation reaction. Most interestingly, the C-H bond elongation with energy minimization gave three different energy minima, which respectively corresponds to isomeric proton adducts on a phenyl ring formed by the deprotonation from the benzyl carbon followed by intramolecular electrophilic proton addition. We have also studied the effect of water on the course of the deprotonation pathway, and found that the even in the presence of water at thevicinity of triphenylmethane cation radical, the proton undergoes the transfer to the phenyl ring, and it does not migrate to the water molecule. These results strongly suggest that deprotonation in the actual photochemical reaction conditions also occurs as a intramolecular proton transfer to the phenyl ring, and that does not occur as a simple proton transfer to a third molecule which is as a base strong enough to accept the proton in solution.
