POLARIZED FT-IR SPECTRA OF WATER IN DODECYLBUTYLDIMETHYLAMMONIUM BROMIDE MONOHYDRATE

Polarized infrared spectra of well-oriented crystalline thin films of dodecylbutyldimethylammonium bromide monohydrate (DBDM.H2O) Were recor ded in the region 5400-250 cm-1. From the results of the polychroism m easurements and the X-ray analysis, water bands were divided into thre e symmetry species (A1, B1, and B2). With the aid of frequencies and i sotopic frequency ratios, the water bands were assigned to the three f undamental vibrations, two librations, and their overtones and combina tions. In the crystalline environment, we have observed the doublets f or each of the vibrationally isolated OH and OD stretching bands of HO D in isotopically diluted monohydrates DBDM.HOD. This spectral feature suggests the presence of two distinct configurations of the water mol ecule, one forming a strong and linear O1H...Br1 hydrogen bond and the other forming a weak and slightly bent O1H...Br2 hydrogen bond. The r esults in this work are discussed in connection with previous work. Th e OH stretcing bands in DBDM.H2O appear at higher frequency than in do decylpropyldimethylammonium bromide (DPDM).H2O or in DPDM.1/2H2O, whil e the HOH scissoring, rocking, and wagging modes occur at lower freque ncy. These are consistent with the weaker hydrogen bond of the water m olecule and the longer O...Br hydrogen bond distance in DBDM.H2O than in the DPDM hydrates. Correlation between nu(OD) and the O...Br distan ce is also argued.