Infra-red spectra between 4000 and 40cm-I are reported for EtOH and EtOD suspended in argon matrices at 20 K. The small bandwidths in the low-temperature matrix reveal the presence of bands due to both trans and gauche conformers, and a complete vibrational assignment for the more stable trans conformer is made. The ratio of trans to gauche conformers in the vapour phase at room temperature is estimated to be 2 : 1. Concentration studies result in the identification of open chain dimer, trimer and tetramer, and cyclic tetramer, species from their OH stretching vibrations. The effect of association on other regions of the spectrum is examined.Two conformers of the ethanol molecule may exist, with the OH group trans (I) or gauche (11) with respect to the methyl group :The monomer OH stretching frequency in solution has been reported by some authors as displaying a~ymmetry,l-~ while others report that the band is ~ymmetrical.~ A detailed study of 12 isotopic species from 4000 to 400 cm-l in vapour, liquid and solid phases as well as in solution was inconclusive, the authors tentatively suggesting that the molecule is essentially in the gauche form, on the basis that strong interaction occurs between modes which would be of different symmetry for the trans conformer. However, Michielsen-Effinger reports, from microwave studies, the existence of both trans and gauche conformers of ethanol in the vapour phase, the trans form being the more stable. Takano, Sasada and Satoh6 confirm the existence of a gauche conformer, from similar studies.

Infra-red spectra are reported between 4000 and 40 cm-l for CH30H and CH30D, and between 4000 and 650 cm-l for CD30D, I3CH30H and CH3180D, suspended in argon matrices at 20 K. The small bandwidths in the low-temperature matrix allow a revised vibrational assignment to be made. Concentration studies have been performed on CH30H, resulting in the identification of open chain dimer, trimer and tetramer, and cyclic tetramer, species from their OH stretching vibrations. The effect of association on other regions of the spectrum is examined.

It is shown that the frequency shifts of the NH stretching mode of pyrrole in a variety of different solvents can be plotted directly against the corresponding shifts of many X-H stretching vibrations in the same solvents. The significance of the results obtained is discussed in relation to complex formation and hydrogen bonding.

Infra-red spectra are reported of HCl, HBr and HI in argon and other matrices at 20 K. Studies have been made over a wide concentration range from matrix/absorber ratio 2000 to 50 which, together with diffusion (" warm-up ") experiments, enable an interpretation to be offered of the complex pattern of frequencies. The first two intense association bands which arise are assigned to cyclic dimers and trimers respectively. Bands are also assigned to various multimeric species and the frequencies compare favourably with values calculated on the basis of a model based on that proposed by Keyser and Robinson.

The photolysis of trans-t-butyl nitrite in an argon matrix at 20 K gave rise to absorptions due to acetone, nitrosomethane and cis-t-butyl nitrite. Isomerisation was dominant at higher concentrations ; decomposition was dominant at lower concentrations. Vaporisation of nitrosomethane dimer and trapping of the products at 20 K yielded the spectrum of nitrosomethane monomer and the trans dimer. Ultra-violet irradiation dissociated the dimer, leaving nitrosomethane monomer. On warming to room temperature and recooling to 20 K the cis-nitrosomethane dimer was obtained, which could be dissociated by photolysis to regenerate the monomer. A vibrational assignment of the monomer is presented.