Polar aspects of intramolecular interactions in 2‐amino‐5‐nitro‐4‐methylpyridines and 2‐amino‐3‐nitro‐4‐methylpyridines

Abstract

The dipole moments of twelve 2‐N‐substituted amino‐5‐nitro‐4‐methylpyridines (I‐XII) and three 2‐N‐substituted amino‐3‐nitro‐4‐methylpyridines (XIII‐XV) were determined in benzene. The polar aspects of intramolecular charge‐transfer and intramolecular hydrogen bonding were discussed. The interaction dipole moments, μint, were calculated for 2‐N‐alkyl(or aryl)amino‐5‐nitro‐4‐methylpyridines. Increased alkylation of amino nitrogen brought about an intensified push‐pull interaction between the amino and nitro groups. The solvent effects on the dipole moments of 2‐N‐methylamino‐5‐nitro‐4‐methyl‐(I), 2‐N,N‐dimethylamino‐5‐nitro‐4‐methyl‐ (II) and 2‐N‐methylamino‐3‐nitro‐4‐methylpyridines (XIII) were different. Specific hydrogen bond solute‐solvent interactions increased the charge‐transfer effect in I, but it did not disrupt the intramolecular hydrogen bond in XIII.