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.