Kinetics and Stereochemistry of Elimination of Nitrous-Acid From 1-Para-Nitrophenyl-2-Nitroethyl Derivatives

Abstract

The eliminations of nitrous acid from the compounds (1) and (6) are E2 processes, which proceed with a large primary kinetic isotope effect and with antiperiplanar stereochemistry. The rate of elimination of HNO2 from (1) is intermediate between the rate of elimination of HCl from (4) and HBr from (5). This order of nucleofugality , namely Br- > NO2- > Cl -, results from a more positive entropy of activation for the elimination of nitrous acid. The presence of an α-chlorine, as in compounds (8), (28) and (29), leads to elimination processes which are E1cB-like, with low primary kinetic isotope effects and with lack of stereospecificity.