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Solvent Effects and Steric Course in the Solvolysis of 1,3,3-Trimethyl-2- oxocyclopentyl Mesylate in Comparison with 1,1,3,3-Tetramethyl-2- oxobutyl System Takeuchi, Ken'ichi Ushino, Takuhiro Okazaki, Takao Kitagawa, Toshikazu Kinoshita, Tomomi Ohga, Yasushi Tanaka, Koichi Toda, Fumio The rates of solvolysis in various solvents were determined for 1,1,3,3-tetramethyl-2-oxobutyl tosylate (1OTs) and 1,3,3-trimethyl-2-oxocyclopentyl mesylate (4 OMs). The rate data for 1OTs reinforced that the linear Grunwald−Winstein (GW) relationship of 1OMs previously reported by Creary for non-aqueous solvents must also hold for aqueous organic solvents.4OMs showed a markedly dispersed GW relationship that is, on the other hand, well correlated with an extended GW equation involving a nucleophilicity parameter. Such solvent dependence, such marked effects of added sodium azide on rates, and the 100% inversion of configuration of the solvolysis product showed that the solvolysis of 4OMs would be categorized to SN2(intermediate), whereas 1OMs and1OTs solvolyze via limiting S N1.The negligible susceptibility of 1OTs toward nucleophilicity of solvent and azide probe indicates that the nucleofuge leaves along the C=O axis in such a manner that the back-strain (B-strain) in the ground state is efficiently relieved in the transition state. Comparison of solvolysis rates of 1OMs and 4OMs with those of the corresponding parent substrates suggests that the transition states of these substrates would not be stabilized by carbonylπ conjugation. The origin of the unexpectedly fast rates of solvolysis of 1 OMs has been discussed. Chemical Society of Japan 2001 eng journal article VoR http://hdl.handle.net/10112/5606 https://kansai-u.repo.nii.ac.jp/records/11459 10.1246/bcsj.74.363 AA00580132 00092673 Bulletin of the Chemical Society of Japan 74 2 363 370 https://kansai-u.repo.nii.ac.jp/record/11459/files/KU-1100-20011207-21.pdf application/pdf 240.3 kB 2019-05-23