Spectroscopic probe studies of solvation.
2015-11-19T08:44:44Z (GMT) by
The major part of this thesis concerns the use of relatively simple compounds used in extremely dilute solution to study solvation phenomena. Use of many spectroscopic techniques such as infrared, NMR, ultraviolet, etc., have made it possible to follow the environment of the probe throughout various mixed and pure solvent states. Simple molecules such as acetone, triethylphosphine oxide, small amides, etc., yield similar results concerning the interaction of alcohol-base and water-base systems and also provide information as to the solvation state of the probes themselves. A comparative study of the various solvent scales is included, combining information obtained during the course of this research with the various literature values. The relative merits and demerits of most of the widely-used scales such as Gutmann's Donor and Acceptor numbers, Taft's ? and ? scales, Kosower's Z values and Dimroth's ET values, etc., are discussed in the light of the various solvation parameters obtained. Of particular interest was the formation of 'clathrate hydrate' compounds, already well-established in the literature. A suitable technique was developed and is demonstrated herein for following the formation of the acetone clathrate hydrate using infrared spectroscopy. Its relevance to some theories of water structure and solvation are discussed with suggestions as to acetone's solvation structure in liquid water. A final chapter is included where techniques from the probe studies are utilised in formulating a suggested mechanism for the solvolysis of alkyl halides. These reactions already having been extensively studied by kinetic means previously relied on simple mechanisms which gave adequate mathematical results to the various rate laws. The involvement of hydrogen bonding to the solvent in no way alters the mathematics but is highly relevant to the overall operating mechanism.