W.J. Orville-Thomas

Studies of intermolecular interactions by matrix isolation vibrational spectroscopy: Self-association of water

Abstract The mid- and far-infrared spectra of water in argon and nitrogen matrices have been reinvestigated. The water molecule rotates in an argon matrix, but in a nitrogen matrix two low-frequency bands are attributed to libration of the water monomer about its A and C rotational axes. Combinations of these modes with the stretching and bending modes of the water monomer were observed. A detailed concentration-dependence study enabled bands to be attributed to dimer, trimer, and tetramer or higher multimers. The dimer and trimer were both found to have open chain structures, whereas tetramer or higher multimer species appear to be predominantly cyclic. Intermolecular modes, observed for dimer and trimer in the far-infrared spectra, are tentatively assigned.

Charge transfer theory of hydrogen bonds: relations between vibrational spectra and energy of hydrogen bonds

Correlations between the enthalpy of formation, ΔH, and the frequency shift and infrared intensity change of the XH stretching band in hydrogen bonded systems are presented. The correlations are discussed in terms of Mullikens charge transfer theory.

Charge‐transfer properties of hydrogen bonds. III. Charge‐transfer theory and the relation between the energy and the enhancement of dipole moment of hydrogen‐bonded complexes

An extension of Mullikens charge‐transfer theory leads to a relation between the enthalpy of formation and the enhancement of the dipole moment for hydrogen‐bonded complexes. Extensive experimental data are in accord with this theoretical prediction. It is shown conclusively that the proton transfer effect is not responsible for the enhancement of the dipole moment in these systems.

Relation between O—H stretching frequency and hydrogen bond energy: re-examination of the Badger–Bauer rule

Experimentally a large number of linear relations have been found between the change in OH stretching frequency, Δ, on hydrogen bonding and the hydrogen bond energy, ΔH. A least square treatment of these Δ against ΔH relations is carried out for constant acceptor, variable donor as well as constant donor, variable acceptor systems. Generally, the constant-acceptor plots have much higher values of intercepts than the constant-donor plots. The slopes of the constant-donor plots seem to vary with the basicity of the donor . However, since Δ should go to zero when there is no interaction, it is suggested that the complete Δ against ΔH, relation could be nonlinear. Molecular orbital calculations have been employed to throw light on the Δ against ΔH relation. It is also shown that charge transfer theory when applied to the hydrogen bond predicts a relation between shown that charge transfer theory when applied to the hydrogen bond predicts a relation between ΔH and the quantity (20–2)½ where 0 and , are the free and perturbed OH stretching frequencies.

The IR spectra and structure of XCH2CH2OH molecules

Abstract The ir spectra of 2-halogenated ethanols have been studied. A frequency assignment shows that the chloro, bromo and iodo derivatives exist as rotational isomers with the gauche conformer being the more stable due to an internal hydrogen bond. This internal hydrogen bond stabilizes the gauche form of the fluoro derivative to such an extent that there is no conclusive evidence for the occurrence of a trans form.

Infrared and Raman matrix isolation studies of methylamine

Abstract Infrared (4000-50 cm −1 ) and Raman spectra are reported of methylamine, methylamine- d 1 and methylamine- d 2 trapped in argon and nitrogen matrices at 4–20 K. An anomalous intensity variation was found for the NH 2 wagging mode of methylamine isolated in nitrogen matrices, while in argon matrices the NH 2 wagging absorption exhibited a complex structure due to matrix site effects. A normal coordinate analysis was carried out using a new assignment of the NHD twisting frequency. Barriers to internal rotation in argon and nitrogen matrices, calculated from the observed torsional frequencies, are compared with the gas phase value.

Studies of intermolecular interactions by matrix isolation vibrational spectroscopy and normal coordinate analysis: Self-association of hydrogen cyanide

Abstract A detailed study of the infrared spectra of hydrogen and deuterium cyanide in noble gas, nitrogen and carbon monoxide matrices at 4 K and 20 K has enabled the bands observed to be assigned to monomer, dimer, trimer, tetramer and higher multimer species. Force constants calculated for the linear dimer are used to predict the spectrum of the trimer. The nature of the trapping sites occupied by the monomer and linear dimer, and the structure and trapping site of a second type of dimer observed only in argon matrices, are discussed.

On the nature of electron donor-acceptor interactions: 1. Charge-transfer theory and the relation between the energy and the enhancement of dipole moments of amine-iodine complexes

Abstract A relation between the enthalpy of formation and the enhancement of the dipole moment is derived for electron donor-acceptor complexes. Experimental data for a number of amine-iodine complexes are in accord with theoretical predictions.

Infrared band intensities and bond polarities: Part I. Bond moment constants in CO2, OCS, CS2, CSe2 and SCSe

Abstract Bond moment constants have been calculated for CO 2 , OCS, CS 2 , CSe 2 and SCSe using zero-order bond moment theory.

Infrared and raman studies on the Hofmann-type clathrates Ni(NH3)2Pd(CN)4,2C6H6 and Cd(NH3)2Ni(CN)4,2C4H4S

Abstract The Hofmann-type clathrates, Ni(NH3)2Pd(CN)4,2C6H6 and Cd(NH3)2Ni(CN)4,2C4H4S have been prepared and their infrared and Raman spectra are reported. Vibrational assignments are proposed for the bands of the host lattice and guest molecules.