Y. Ito, T. Matsuura, K. Tabata
1987
Citations
0
Influential Citations
18
Citations
Journal
Tetrahedron
Abstract
Abstract Upon UV irradiation in the solid-state 4,4'-dimethylbenzophenone ( 1a ) underwent intermolecular hydrogen abstraction, followed by radical coupling, to give solely a dimeric product, 4-(2-hydroxy-2,2-di-p-tolyl-ethyl)-4'-methylbenzophenone ( 2 ). By contrast, 3,3'-dimethylbenzophenone ( 1b ). 3,4'-dimethylbenzophenone ( 1c ), and 4-methylbenzophenone ( 1d ) were photostable under the same conditions. From X-ray crystallographic analysis of 1a and 1d , the distances between the C=0 group and the nearby methyl C-H bond are 3.32 A for 0..H and 3.87 A for C..C for reactive 1a and 2.77 (or 2.72) A for 0..H and 4.39 (or 4.53) A for C..C for unreactive 1d . The angle C=0..H is 92° for la and 121 or 137° for 1d . The long C..C distance or/and the large C=O..H angle is probably responsible for the photoinertness of 1d .