Infrared absorption spectra for liquid and ice H 2O and D 2O and for protonated and deuterated glycerol/water glasses are compared in the spectral range of 1000-4000 cm -1 and the temperature range of 295-12 K. As temperature decreases, the absorbance bands of the OH and OD stretching modes of glycerol/water solution shift to lower frequency and the band intensifies and narrows. The center of the absorption band for OH stretch for glycerol/D 2O/H 2O solution (60/32/8 v/v) is at 3364 cm -1 at 295 K and at 3277 cm -1 at 25 K. The full width at half-maximum (fwhm) of the band is 259 cm -1 at 295 K and 186 cm -1 at 25 K. The width of the OH stretch band for D 2O that is doped with H 2O is 193 cm -1 in liquid (295 K) and 24 cm -1 in ice (12 K). The broader width for the OH stretch at 12 K for glycerol/water relative to that seen in ice is consistent with inhomogeneous broadening due to the glassy nature of glycerol/water solutions. The HOH and DOD bending (scissoring) bands for water in glycerol shift to higher frequency, and the band broadens as temperature decreases. In contrast, in water below the ice transition, the HOH bending band can no longer be seen. Glycerol C-H and C-D stretching and bending modes are temperature independent between 295 and 12 K. Absorption between 1350 and 1450 cm -1 was seen in glycerol when the hydroxyls are protonated, but not deuterated. This band is assigned to a bending motion involving the glycerol hydroxyl. Both ice and glycerol/water glass show temperature-dependent infrared changes, but for the glass shifts in bands are continuous and are consistent with an increase in the H-bonding strength with lowering temperature.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry