THE CF3CH2O- ADDUCTS OF ALPHA-NITRO-BETA-(2,2,2-TRIFLUOROETHOXY)STILBENE AND BETA-METHOXY-ALPHA-NITROSTILBENE, AND THE MEO- ADDUCT OF BETA-METHOXY-ALPHA-NITROSTILBENE - KINETICS OF COMPETITION BETWEEN PROTONATION AND ACID-CATALYZED ALKOXIDE ION DEPARTURE

The reaction of aqueous acids with the CF3CH2O- adduct, Ph(OCH2CF3)(2) CC(Ph)=NO2-, of alpha-nitro-beta(2,2,2-trifluoroethoxy)stilbene leads virtually exclusively to the corresponding acetal, Ph(OCH2CF3)(2)CCH(P h)NO2, by carbon protonation, whereas reaction of acid with the CH3O- adduct, Ph(OCH3)(2)CC(Ph)=NO2-, of beta-methoxy-alpha-nitrostilbene le ads virtually exclusively to recovery of the beta-methoxy-alpha-nitros tilbene by acid catalyzed CH3O- expulsion. In the case of Ph(OCH3)(OCH 2CF3)CC(Ph)=NO2-, reaction with HCl produces a mixture of the correspo nding acetal, Ph(OCH3, OCH2CF3)CCH(Ph)NO2, beta-methoxy-alpha-nitrosti lbene and alpha-nitro-beta-(2,2,2-trifluoroethoxy)stilbene. Rate const ants for these processes as well as for the deprotonation of the vario us acetals by OH- and amines are reported. The large difference in the kinetic behavior of the various adducts as a function of the alkoxy g roups is attributed to a combination of factors. They include the stro ng dependence of acid catalysis on leaving group basicity, the much st ronger push by the methoxy compared to the trifluoroethoxy group, and the manifestation of the nitroalkane anomaly according to which a more basic nitronate ion is protonated more slowly than a less basic one.