C. Eaborn, Z. Lasocki, J. Sperry
Feb 16, 1972
Citations
0
Influential Citations
18
Citations
Journal
Journal of Organometallic Chemistry
Abstract
Abstract Rates of cleavage by aqueous methanolic perchloric acid have been measured for 4-(trimethylsilyl)diphenylmethane, 2-, 3-, and 9-(trimethylsilyl)phenanthrene, 2-(trimethylsilyl)-9,10-dihydrophenanthrene, and 1-(trimethylsilyl)pyrene. The values of the rates, k rel , relative to those for trimethylsilylbenzene at 50δ are 7.9, 1.76, 2.1, 4.5, 12.8, and 223, respectively. In a plot of log k rel against log f , where f is the corresponding rate factor for detritiation in trifluoroacetic acid at 70δ, the points for single-ring systems (mono-substituted benzenes and thiophene) mainly fall about a straight line through the origin, but those for polycyclic systems (including heterocycles) lie, with a large scatter, about a different line which lies well away from the origin. It is suggested that in these systems resonance effects are unusually large, and that a measure of these resonance effects σ Res [=σ + −σ)] is give by the equation −1.85 σ Res = 0.6 log f −log k rel .