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Solvolysis of 3‐substituted 4‐homoadamantyl methanesulphonates. Can the β‐substituent effect distinguish between classical and non‐classical ion intermediates?
Author(s) -
Okazaki Takao,
Kitagawa Toshikazu,
Takeuchi Ken'Ichi
Publication year - 1994
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610070904
Subject(s) - solvolysis , chemistry , substituent , reaction rate constant , 2 norbornyl cation , aqueous solution , medicinal chemistry , computational chemistry , additive function , logarithm , stereochemistry , organic chemistry , kinetics , hydrolysis , mathematical analysis , physics , mathematics , quantum mechanics
Abstract The rates of the solvolysis of 3‐R‐4‐homoadamantyl methanesulphonates (mesylates) (3) were determined in 80% aqueous ethanol. The relative first‐order rate constants at 25 °C were 1·0 (R = H), 2·29 (R = Ph), 3·26 (R = p ‐anisyl), 73·6 (R = Me) and 209 (R = Et). The methanolysis of 3 gave rearranged methyl ethers and rearranged olefins as major products together with small amounts (0·9–3·4%) of unrearranged products. The order of the accelerating effect suggests that the transition states involve significant σ‐participation, despite the fact that 3 (R = H) solvolyses via a classical ion intermediate. The logarithms of the solvolysis rate constants of 3 showed linear correlations with those of 1‐R‐2‐adamantyl tosylates (1) and 1‐R‐ exo ‐2‐norbornyl tosylates (2), indicating that the linear free‐energy relationship between the β‐substituent effects on the solvolysis rate is not a definite measure to distinguish between classical and non‐classical intermediates.