M. Aoki, Mikio Nakamura, M. Ōki
Aug 1, 1982
Citations
0
Influential Citations
8
Citations
Journal
Bulletin of the Chemical Society of Japan
Abstract
9-(2-Methoxy-4,6-dimethylphenyl)fluorenes carrying one or two bromo groups on the phenyl ring were prepared and the buttressing effect on the rotational barrier about the C9–Cph bond were investigated. The free energies of activation for rotation were 26.5, 25.9, and 27.2 kcal/mol at 56 °C for 3-bromo, 5-bromo, and 3,5-dibromo compounds, respectively. The buttressing effect was enhanced when the bromo group was next to the methoxyl group relative to that given to the methyl group. The results were attributed to the fact that a methoxyl group, which gives its steric effect by the oxygen atom in the normal cases, has to take conformations, not coplanar with the phenyl ring, caused by the presence of the bromo group.