No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

A detailed investigation into the thermodynamic properties of pure fluoroalcohols and binary mixtures containing fluoroalcohols is described. A batch calorimeter was used to measure excess enthalpies over the complete composition range and enthalpies of solution were obtained using an L.K.B. 8700 calorimeter. The excess volumes were determined using both batch and dilution dilatometers. Vapour-liquid equilibrium diagrams for binary mixtures have been determined from vapour pressure measurements using a static vapour pressure apparatus. Enthalpies of vaporisation of the fluoroalcohols were determined from the variation of the vapour pressure with temperature. Solid-liquid equilibrium phase diagrams have been determined using a simple freezing point cell, and liquid-liquid measurements obtained using a synthetic method. A new isothermal dilution calorimeter is also described. Unlike the batch calorimeter it allows a wide composition range to be studied from a single loading. The results for the test systems benzene + cyclo- hexane and benzene + tetrachloromethane obtained with this calorimeter are presented. The results obtained are in excellent agreement with those obtained by other workers.

The aims of this project were to investigate the influence of tertiary amine structure upon both intramolecular and intermolecular fluorescent exciplex formation with simple aromatic hydrocarbons and to probe the photophysical properties of a number of polychromo- phoric systems. In the latter, interest centred upon the possible formation of intramolecular fluorescent exciplexes involving the interaction of more than two chromophoric units. A series of 2-(1-naphthyl)ethyl- and 2-(phenylethyl)- azacycloalkanes were studied and results indicated that the extent of intramolecular exciplex formation, was influenced by the amine ring size. In the intermolecular interaction between benzene and a series of N-methylated azacycloalkanes in cyclohexane solution, the quenching of the aromatic hydrocarbon fluorescence was found in several cases, to be accompanied by energy transfer to the amino unit, which subsequently fluoresced. Variable temperature studies ruled out the intermediacy of a fluorescent exciplex in the energy transfer process. Further studies utilising high concentrations of benzene were found to favour the formation of inter- molecular fluorescent exciplexes, in which solvation by benzene plays a part. These results indicated that the energy of the amine and solvation of the exciplex were relevant to the pathway taken by the process. The photo-physical and nitrogen-15 Nmr properties of the N-methylated azacycloalkanes and closely related a,w-diaminoalkanes were examined. Finally our studies into the behaviour of poly- chromophoric systems containing an aromatic hydrocarbon and two amine groups indicated quite clearly the formation of an intramolecular exciplex involving all three groups.

By analogy with the established mechanism for the low pressure pyrolysis of tetramethylsilane (TMS)1, the decomposition of trimethylchlorosilane (3MCS) would be expected to proceed thus, The dimeric product, if formed, could be useful as a precursor to long chain polymers containing (-Si-C-)n units. Thus, 3MCS was pyrolysed, at low pressure in a static system, using quadrupole mass spectrometry as the principal method of analysis. First order Arrhenius parameters given by log10 k = (17. 03 +.34) - (366.5 + 7.2 KJ mol-1)/2 . 303RT were measured for the decomposition, the activation energy being assigned to the silicon-methyl bond strength. The dimeric product proposed above however, was not formed, dimethyldichlorosilane (2M2CS) being the major silicon-containing product. Since a small quantity of hydrogen chloride was invariably present in the experimental system, owing to some hydrolysis of the reactant by background water, it was suggested that the addition process, could prevent reaction (4). A series of experiments was devised to test this idea and it was shown to be a possible explanation. The decomposition of 1,1-dimethyl-l-silacyclobutane (DMSCB) is well known2. From the co-pyrolysis of DMSCB with hydrogen chloride3 it was found that the addition is a very efficient process, reaction (7) being suppressed until most of the hydrogen chloride had been used up. Since no competition between processes (7) and (8) could be observed, an unusual analysis method was devised, which involved a comparison of the "on-set time" for reaction (7) with the calculated amount of DMSCB decomposed. Computer simulation of the co-pyrolysis mechanism yielded values of log10 k7 = (7.5 + .3) - (12 + 5 KJ mol-1)/2.303 RT. The addition of hydrogen bromide to 1,1-dimethylsilaethene was also investigated. Finally, the decomposition of dimethylchlorosilane (DMCS) and of methyldichlorosilane (MDCS), was shown to proceed via a radical route, consistent with the proposed pyrolysis mechanism of trimethylsilane1. The co-pyrolysis of DMCS and of MDCS with sulphur hexafluoride provided evidence for the presence of silicon radicals, the hexafluoride being a good "trap" for such species.

There has recently been an increase in the amount of work on the theoretical side of ENDOR spectroscopy which has tried to give a more detailed understanding of the complex spectra obtained from solid solutions. The work presented here is an attempt to show how much more information can be extracted from such spectra with only a minimal increase in the amount of experimentation required. A simulation program is presented which, based on a simple model, predicts the form of the variation of the ENDOR spectra when the field Bo, at which the experiment is performed, is varied within the span of the ESR spectrum. These theoretical results are compared with the results from a study of the complex bis-(pentan-2, 4-dionato) oxovanaduim (IV). The results indicate that not only can we obtain more accurate values for the principal elements of the hyperfine interaction tensors, but that we can extract information as to the relative orientation of the g axis system and the axis system of the hyperfine interaction tensor. two copper complexes, bis-(pentan-2,4-dionato) copper (II) and bis-(2,2,6,6-tetramethylheptan-3,5-dionato) copper (II), and these results are compared with results from solid solution ENDOR spectra of the two complexes obtained by the author and by other workers. The comparison indicates that a certain amount of reinterpretation is required in the case of the published work on the bis-(pentan-2,4-dionato) copper (II) complex.