Tautomerism and rotamerism in 2‐methylamino‐, 2‐anilino‐, 2‐acetamido‐, and 2‐benzamido‐pyridines

Abstract

Abstract Quantum chemical (CNDO‐CI‐1) simulation and theoretical analysis of UV absorption spectra of 2‐amino‐, 2‐methylamino‐, 2‐anilino‐, 2‐acetamido‐, and 2‐benzamido‐pyridines were carried out. A comparison of results with experiment provided information on tautomerism and rotamerism in abovementioned compounds in solution. Contrary to some literature data 2‐aminopyridine in solution exists in dimeric form of 2‐pyridylamine. Also 2‐methylaminopyridine in solution forms a similar dimer. 2‐Anilinopyridine appears in solution as cis ‐1 H ‐pyridine‐2‐phenylimine tautomer. Both acylamino derivatives of 2‐aminopyridine tautomerize with involvement solely of the carbonyl group to form hydroxyethylideno‐ and hydroxybenzylideno‐2‐aminopyridines, respectively.