Solvent effects in the decomposition reaction of some products formed by the reaction of sorbic acid with sodium nitrite: 1,4‐dinitro‐2‐methylpyrrole and ethylnitrolic acid

Abstract

AbstractA kinetic study of the decomposition reaction of 1,4‐dinitro‐2‐methylpyrrole (NMP) and ethylnitrolic acid (ENA), both formed in the reaction between sorbic acid and sodium nitrite was performed in the 3.5–4.2 pH range in water/dioxane mixtures. Conclusions were drawn as follows: (i) The decomposition of NMP occurs through nucleophilic attack by OH− ions, the rate equation being: r = kdecNMP [OH− ][NMP]. (ii) The rate law for the decomposition of ENA is: r = $k_{dec}^{ENA}$ [ENA]Ka/(Ka + [H+]), Ka being the ENA dissociation constant. (iii) The value of Ka decreases when the water/dioxane ratio decreases, log Ka being proportional to the Onsager parameter (ϵ − 1)/(2ϵ + 1). This permits the equilibrium between non‐dissociated and the dissociated forms of ENA to be rationalized. (iv) No appreciable variation in the ΔH# and ΔS# values with composition of the medium was observed, either in the NMP decomposition reaction, or in the ENA decomposition reaction. Copyright © 2008 John Wiley & Sons, Ltd.