Experimental and theoretical investigation of vibrational overtones of glycolic acid and its hydrogen bonding interactions with water.

The present work reports observations of the 4nu(1) and 4nu(2) O-H stretching transitions in glycolic acid, CH(2)OHCOOH, using a highly sensitive cavity ring-down spectrometer. Experimental and theoretical values for the harmonic frequencies and anharmonic constants of both O-H stretching transitions were extracted and are compared with theoretical calculations in the literature. Calculations of anharmonic frequencies, intensities, and relative energies have been performed and are presented for three conformers of glycolic acid. In the presence of water, an interesting broad spectral feature appeared underneath 4nu(1) and 4nu(2). New calculations for harmonic frequencies, intensities, and relative energies of four CH(2)OHCOOH-H(2)O complexes are reported to aid in understanding the observed spectrum. This work suggests that the perturbations are caused by intermolecular hydrogen bonding of glycolic acid with one or more water molecules.