Correlation of IR parameters with reactivity characteristics for the hydrazides of carboxylic acids

Abstract

Measurements have been made of the frequencies of the N-H and C=O stretching modes in dilute solution in CCl4 for 23 aliphatic and aromatic substituted hydrazides of carboxylic acids. These are compared with the σ (σ0) Taft constants. Measurements have also been made of the basicity constants at 25‡ in water and the rate constants for reaction with phenyl isocyanate at 25‡. Correlation equations are derived for the transfer of electronic effects across the -CONH-bridge. It is found that the sign of the reaction constant ρ in the correlation of $$\upsilon _{{\text{NH}}_{\text{2}} } $$ with σ0 reverses on passing from aromatic amines to amides via the hydrazides of carboxylic acids.