Integrated intensity of nu(s)(OH) absorption bands in bent hydrogen bonds in ortho-dialkylaminomethyl phenols

The FT-IR spectra of 16 ortho-Mannich bases and its deuteroanalogues in the region of nu(s)(OH/OD) absorption bands were determined in CCl4 solution. Separation of nu(s)(CH) bands was achieved by applying the technique of deuterium substitution at the phenolic OH group. The spectroscopic effect of this substitution on the nu(s)(CH) absorption bands was discovered, which demonstrates that the OH ... N hydrogen bonds are stronger than in the analogous OD ... N complexes. It was shown that the integrated intensity of the nu(s)(OH) bands in bent hydrogen bonds is distinctly lower than in the respective linear ones. A good correlation of the integrated intensity with the hydrogen bond strength was obtained.