E. Baciocchi*, M. Bietti, G. Ercolani
Jan 27, 2003
Citations
0
Influential Citations
8
Citations
Journal
Tetrahedron
Abstract
Abstract DFT calculations have been carried out for 2-, 3- and 4-methoxybenzyl alcohol radical cations ( 1 + , 3 + and 4 + , respectively) and the α-methyl derivatives 2 + and 5 + using the UB3LYP/6-31G(d) method. The theoretical results have been compared with the experimental rate constants for deprotonation of 1 + – 5 + under acidic and basic conditions. In acidic solution, the decay of 1 + – 5 + proceeds by cleavage of the C–H bond, while in the presence of − OH all the radical cations undergo deprotonation from the α-OH group. This pH-dependent change in mechanism has been interpreted qualitatively in terms of simple frontier molecular orbital theory. The − OH induced α-O–H deprotonation is consistent with a charge controlled reaction, whereas the C–H deprotonation, observed when the base is H 2 O, appears to be affected by frontier orbital interactions.