Gas phase FT-IR spectra and structure of aminoalcohols with intramolecularhydrogen bonds I. The shape of the v(OH) vibrational bands in R2NC3H6OH (R= H, CH3)

Gas phase FT-IR spectra of 3-dimethylamino-1-propanol (1) and 3-amino-1-pro panol (2) are recorded. It is found that the forms with intramolecular hydr ogen bonds strongly predominate up to 100 degrees C in both compounds. The origin of multicomponent structure of nu(OH) bands is discussed on the assu mption of conformational equilibria as well as the coupling between the nu( OH) vibration mode with the low frequency chelate ring deformation modes af fecting the N ... O distance. DFT ab initio calculations are performed at 6 -31G(d,p) and 6-311 + + G(2d,2p) levels. It is concluded that the nu(OH) ba nd structure in 1 results from high/low frequency modes coupling. (C) 1999 Elsevier Science B.V. All rights reserved.