Premium
Dynamics for reactions of ion pairs in aqueous solution: reactivity of tosylate anion ion paired with the highly destabilized 1‐(4‐methylphenyl)‐2,2,2‐trifluoroethyl carbocation
Author(s) -
Teshima Minami,
Tsuji Yutaka,
Richard John P.
Publication year - 2010
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.1642
Subject(s) - chemistry , carbocation , reactivity (psychology) , ion , aqueous solution , counterion , computational chemistry , medicinal chemistry , organic chemistry , photochemistry , medicine , alternative medicine , pathology
Abstract The sum of the rate constants for solvolysis and scrambling of carbon bridging and nonbridging oxygen‐18 at 4‐MeC 6 H 4 CH(CF 3 )OS( 18 O 2 )Tos in 50/50 (v/v) trifluoroethanol/water, ( k solv + k iso ) = 5.4 × 10 −6 s −1 , is 50% larger than k solv = 3.6 × 10 −6 for the simple solvolysis reaction of the sulfonate ester. This shows that the ion‐pair intermediate of solvolysis undergoes significant internal return to form reactant. These data give a value of k ‐1 = 1.7 × 10 10 s −1 for internal return of the carbocation–anion pair to the substrate. This rate constant is larger than the value of k ‐1 = 7 × 10 9 s −1 reported for internal return of an ion pair between the 1‐(4‐methylphenyl)ethyl carbocation and pentafluorobenzoate anion to the neutral ester (4‐MeC 6 H 4 CH(CH 3 )O 2 CC 6 F 5 ) in the same solvent. The partitioning of ion pairs to the 1‐(4‐methylphenyl)ethyl carbocation and to the highly destabilized 1‐(4‐methylphenyl)2,2,2‐trifluoroethyl carbocation is compared and contrasted. Copyright © 2010 John Wiley & Sons, Ltd.