Co-host: The Chemical Society of Japan, The Society of Synthetic Organic Chemistry, Japan (Cooperation)
We have discussed the behavior of ion pair based on the products analysis for the solvolysis of 1-phenylethy thionobenzoates in 50/50 (v/v) TFE/H2O (I = 0.5, NaClO4) at 25oC, and proposed the mechanism that the solvents attack to ion pair competes with the position change of leaving anion without the rotation of carbocation. In order to clarify the rotation of carbocation, we have examined the stereochemistry of 1-(4-fluorophenyl)ethyl alcohol obtained in this solvolsis. The product alcohol generated from (S)-enantiomer was isolated and the stereochemistry of this was determined by the 1H NMR spectrum in the presence of (S)-(+)-2,2,2-trofluoro-1-(9-anthryl)ethanol. The ratio of (R)- and (S)-configuration was 1.2. This means that 91 % of product formation is accompanied with racemization. This value is much larger than that expected from the mechanism we proposed. The rotation of carbocation occurs in this solvolysis.
