APPLICATION OF ETHANOL-TRIFLUOROETHANOL METHOD TO SOLVOLYSES FOR WHICH NUCLEOPHILIC INVOLVEMENT IS QUESTIONED

The ethanol-trifluoroethanol (EtOH-TFE) method is applied to several solvolyses for which the extent of nucleophilic solvent assistance either has not been previously determined or is of sufficient importance and uncertainty as to warrant further investigation. The substrates examined and the mechanistic conclusions reached are as follows: benzyl chlorides (ks except possibly for the highly activated p-methoxy derivative), tert-butyl chloride and bromide (rate-determinirng elimination in trifluoroethanol), cyclooctyl tosylate (a kc substrate), 3-methyl-2-butyl tosylate (solvolysis by competitive ks and kΔ mechanisms), and 3,3-dimethyl-2-butyl tosylate (either a kc or weak ks substrate). In addition ²-deuterium isotope effects are reported for 3-methyl-2-butyl tosylate solvolysis in 80% ethanol, 97% trifluoroethanol, and 97% 1,1,1,3,3,3-hexafluoro-2-propanol in order to examine the possibility that carbocation destruction may become rate determining in highly ionizing, weakly nucleophilic solvents; it is concluded that this possibility is not realized. © 1978, American Chemical Society. All rights reserved.