88563-51-3Relevant articles and documents
Dynamics of reaction of ion pairs in aqueous solution: Racemization of the chiral ion pair intermediate of solvolysis of (S)-1-(4-methylphenyl)ethyl pentafluorobenzoate
Tsuji, Yutaka,Mori, Tetsuo,Toteva, Maria M.,Richard, John P.
, p. 484 - 490 (2007/10/03)
The chiral ester (S)-1-(4-methylphenyl)ethyl pentafluorobenzoate, (S)-1-OC(O)C6F5, was prepared and a value of k rac = 8.5 × 10-7 s-1 was determined for the rate constant for its racemization to (R)-1-OC(O)C6F5 in 50:50 (v/v) trifluoroethanol-water (I = 0.50, NaClO4). This rate constant is 12 times smaller than ksolv = 1.06 × 10 -5 s-1 for the stepwise solvolysis of 1-OC(O)C 6F5, which shows that inversion of the ion-pair intermediate is a relatively rare event during solvolysis in a largely aqueous solvent, and two times smaller than kiso = 1.6 × 10 -6 s-1 for degenerate isomerization which exchanges the position of the ester bridging and non-bridging oxygens of 1-OC(O)C 6F5. A simple relationship is derived between the empirical rate constant ratio krac/kiso and the microscopic rate constants for reaction of the ion-pair intermediate within its solvation shell. Substitution of estimated rate constants for reactions of the 1-(4-methylphenyl)ethyl carbocation-pentafluorobenzoate anion pair into this equation gives ki = 1.5 × 1010 s-1 for inversion of the chiral ion pair, which is similar to k-d = 1.6 × 1010 s-1 for its separation to free ions. Copyright
