Pressure, volume, temperature studies have been made of gas phase amine-methanol systems. An apparatus which allows such observations without the need for weighing of original samples to be mixed is described. Equilibrium constants for the formation of hydrogen bonded complexes over the temperature range 2545°C are reported and thermodynamic parameters have been evaluated for systems formed by methanol with methylamine, dimethylamine, trimethylamhe and triethylamine. The values obtained are discussed in comparison with solution values. Larger values of AH" are found for gas phase complexes than for the corresponding complexes in solution, and the effect is interpreted in terms of solvation. It is found that the electron donating powers of the amines, as measured by AH" values for hydrogen bond formation in the gas phase, increase with increasing methylation of the amine. Wavenumber displacement AV of the 0-H stretching frequency on formation of such hydrogen bonds, are found to correlate with AHo values, and it is suggested that AV values may be used to estimate AH' values.

An infrared investigation of hydrogen bonding by water in gaseous mixtures establishes the formation of gaseous nionohydrates of ammonia, amines and pyridines. A model has been developed which relates the infrared shifts A i l and ATs for the HzO molecule in such complexes to the change in stretching force constant of the 0-H bond involved in complex formation. The model has been tested against existing experimental results and used to relate the shifts observed for the gas phase complexes of water to those for N * * H-0 complexes formed by methanol. From the empirical relationship between A; and the enthalpy of complex formation for these complexes, it has been possible to obtain enthalpies of complex formation (with an estimated uncertainty of + 2 kJ mol-') of water with ammonia and with the amines and pyridines investigated. The main results for these gas phase N ---H-0 complexes formed by water may be summarised as follows :

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An infrared investigation has been made of gas-phase hydrogen-bonded complexes formed by both phenol and 2,2,2-trifluoroethanol. For trifluoroethanol, an investigation of a wide range of 0-H * * * 0 complexes shows that the electron donating power of an oxy-group increases along the series, esters, ketones and aldehydes, alcohols and ethers, and for any given class it is increased by increasing methylation. For phenol, investigation of selected complexes shows there is a very close similarity between the wavenumber displacements, A;, for the complexes formed by phenol and trifluoroethanol with any given base, the similarity extending also to a number of 0--H --* N complexes.It is shown that where vapour pressure of a component is a limitation on observing complex formation in the gas-phase, as in the case for phenol, it will generally be advantageous to work at higher temperatures.

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