In benzene solution the dielectric polarization and dipole moments have been measured for a number of tertiary and quaternary alkylammonium salts, and for some of the former the infrared absorption spectra have also been studied. The state in solution of the tertiary salts can be formulated by the equilibrium: [equation] Since the equilibrium between Steps 1 and 2 is concentration dependent, and that between steps 2 and 3 is not, and also because the equilibrium is shifted to the right on increasing acid strength, the polarization changes with both these variables. At low concentrations and for weak acids the polarization increases non-linearly with increasing concentration and acid strength. As this increases, a progressively larger part of the plot becomes linear and takes on anincreasingly negative slope for the stronger acids. The latter effect is due to polyions. From the polarization variation with concentration,the overall equilibrium constant between unassociated acid and amine and associated species has been evaluated; and by some assumptions as to the values of the dipole moments of hydrogen bonded species and ion pairs, and were estimated. Some of the quaternary salts showed a marked decrease of polarisation with concentration owing to association of the ion pairs; and a modified procedure, used by Pohl, Hobbs and Gross in studies of carboxylic acid dimerization, has been employed in the evaluation of the dipole moments. By an extension of Debye's theory the charge distances in ion pairs have been calculated and the results are in good agreement with the corresponding Bjerrum distances. The infrared measurements showed presence of free acid and amine, hydrogen bonded species and ionic species in a measure predicted by the above equilibrium.

The impact of conformational analysis in chemistry was clearly demonstrated in 1969, during the tenure of this work, when the Nobel Prize for Chemistry was awarded to Professor D. H. R. Barton. The first part of this thesis deals with the vibrational analysis of biphenyl and its 4,4,-dihalogeuo derlvstlves with respect to the dihedral angle between the two rings. It is clearly demonstrated that change in conformation for biphenyl and 4,4'-difluorobinhenyl from D (solid state) to D2 symmetry (solution, molten and gaseous states) is accompanied by changes in position and spectral activity of certain normal modes. These shifts, together with supplementary data derived from some deuterated derivatives of biphenyl, give an estimate of the dihedral angle in the solution state. The structure of 4,4'-dichioro and 4,4,-dibromobiphenyl is irrespective of phase. The second part of the thesis presents the vibrational analysis of tetrahydropyran and its 4-chloro and 4-bromo derivatives. Variable temperature NMR measurements give a quantitative estimate of the con format loaal equilibrium. The final part of this work presents the liquid band shape analysis of tine 215 cm-1 band of hexsfluorobensene in mixed benzene-cyelohexane solvents. It is shown from the computed correlation functions that vibrational relaxation occurs during the split of the hexafluorobenzene-benzene complex.

This thesis describes an attempt to demonstrate enantioselectivity in free-radical hydrogen transfer reactions and was designed to test a novel extension of the Hammond Postulate. It is proposed that the rates of two related reactions which are thermodynamically identical but kinetically distinct should differ most when the processes are thermoneutral since the transition state is remote from both reactant and product. Bysynthesis and subsequent oxidation of suitable chiral hydroxamic acids a series of persistent chiral acyl nitroxide radicals ArCON(R)O has been made. By reacting such a series of nitroxide radicals with suitable chiral benzylic alcohols ArCHOHR it was hoped that by varying the nature of, the bond strength of the alcohol would come within the compass of the 0-H bond strengths of ArCON(R)OH. It was predicted that such an alcohol should show a maximum in a plot of enantioselectivity vs. 0-H bond strength. The target molecules for this work were optically active N-alkylbenzohydroxamic acids in which the akyl substituent was both chiral and tertiary. Substitution of electron withdrawing and releasing groups, ranging from into the aroyl group of the hydroxamic acid and subsequent oxidation of the latter allowed the synthesis of radicals with varying bond strengths. UV-visible, e.s.r. and CD spectra were determined for these radicals. 0-H bond strengths of the hydroxamic acids were estimated using an e.s.r. technique which determined the equilibrium position for hydrogen atom transfer between the hydroxamic acid and a standard di-t-alkyl nitroxide radical which forms a bond of known strength to hydrogen. These estimated values range from 76 to 79 kcal mol. Enantoselectiviy was searched for in two ways. The first employed UV spectroscopy to determine the second order rate constants for the four possible reaction pairs of chiral nitroxide enantiomers with benzylic alcohol enantiomers. The second method involved reaction of racemic alcohol with chiral radical and subsequent examination of enantiomeric excess by high performance liquid chromatography (HPLC); two approaches to this are described. In the majority of cases studied, however, enantioselectivity was immeasurably small. In the case of 2-methyl-l-phenylpropan-l-ol, a small enantiomeric excess was observed but further work is needed to substantiate these results. Small chiral discriminations were observed in the oxidation reactions of only one alcohol. These results were insufficient to investigate the extension of the Hammond Postulate as originally planned.

Raman and infrared activities of aqueous sulphur dioxide solution and of the sodium salts of dithionate, disulphite, sulphite, sulphate, bisulphate, thiosulphate, tetrathionate and dithionite ions have been investigated in the crystal and aqueous states. On the basis of the data obtained, the following conclusions have been derived gauche configuration with group symmetry satisfactorily describes the vibrational activities of the dithionate ion both in the solid and in the aqueous states. Some evidence for the existence of crystalline sodium bisulphite has been revealed. In addition to the well-known H-SO form of bisulphite, the HO-SO tautomer has been identified in a very significant amount in aqueous disulphite solution. Employing progressive dilution measurements, characteristic bands of the, H-SO and HO-SO ions and of the constituent thionate and thionite units of disulphite have been assigned. The non-existence of the oxygen bridged disulphite ion and of the lithium, sodium and potassium salts of bisulphite have been rationalised. Eight bands have been identified with the HO-SO isomer of bisulphite, and on the basis of C group symmetry they have been assigned the infrared activity of the sulphate ion has revealed that even in the free state the ion does not assume full tetrahedral symmetry. Some fundamental vibrations of the bisulphate ion in the high frequency region have been re-assigned. The vibrational activities of the tetrathionate ion have been analysed in terms of two thiosulphate groups held together by an S-S bond. Its fundamental modes have been assigned on the basis of group symmetry. The vibrational spectra of the dithionite ion in aqueous solutions strongly suggests C-gauche symmetry. No evidence for adoption of the trans or the planar structure has been found. Thiosulphate has been identified among the disproportionation products of the dithionite ion. Its formation has been confirmed by ultraviolet spectroscopy. An auto-oxidation process involving free radicals and proceeding at a low rate has been suggested to account for its formation. Sulphurous acid, H2SO4 has been detected in a significant amount in standing aqueous sulphur dioxide solutions. Both of the tautomeric forms, HO-SO-OH and H-30-OH, have been1identified, and in addition to the bisulphite isomers, the formations of the sulphite, sulphate, bisulphate and of the dithionate ions have been indicated in such standing systems. G group symmetry has been assigned to both of the sulphurous acid isomers. Photographic fixation reactions have been calorimetrically investigated, and on the basis of the data derived the following points have been elucidated: (i) fixation is an irreversible, penta-stage process; (ii) the overall reaction has been quantitatively analysed and subsequently used to re-evaluate the standard molar enthlphies of formation; (iii) using the above value, the standard molar enthalpies of formation have been evaluated; (iv) baed upon the athermal property of the reaction, the standard molar enthalpy of formation has been calculated; (v) the structures of the above three silver-thiosulphate complexes have been elucidated on the basis of the spectral measurements performed. The aqueous solubility of sodium dithionate dihydrate crystals has been determined. From the temperature coefficient of solubility, the entropy and the differential heat of solution have been evaluated.

A general quadratic force field, using the overlay technique developed by Schachtschneider and Snyder, was determined for the in-plane vibrations of Benzene and fifteen Fluorine substituted Benzenes by the cyclic refinement of the initial guesses for the forceconstants, known as the perturbation method. It was necessary to assume a Kekule type C-C/C-C interaction relation (Ri Ri+1) = -(Ri Ri+2) = (Ri Ri+3), as first introduced by Schererand Overend. Removal of this constraint gave rise to linear relationships between the force constants, and satisfactory convergence onto one force field was not obtained. The appropriate force constantsof the derived field are compared with those obtained by Duinker for the in-plane vibrations of Benzene. Although the model used is similar to his, the transferability condition is a severe extra constraint, and the extent of agreement is better than anticipated. Reassignments of the fundamentals were made for most of the molecules, and spectra were re-examined, where necessary, to obtain Raman polarisation data, and vapour phase infra red band contours. Biphenyl is known to be planar in the crystal and twisted in solution. The force field for Biphenyl and two deuterated analogues was refined to minimise Assuming that the force field does not change with geometry, the vibrational frequencies were calculated for angles of twist and an estimate obtainedfor the dihedral angle of the molecule in solution. Similar calculations were tried for difluoro Biphenyl, but asthere is insufficient frequency data available, the results were inconclusiveThe combination hands arising from the out-of-plane deformations of the C-H bonds of eight Fluorine substituted Benzenes were investigated, to measure the absolute infra red intensities, and, by a least squares analysis, to derive values for bond moments and bond moment derivatives. Regrettably, studies were limited to 1,4 difluoro Benzene, and, because of experimental difficulties, the intensities measured were so inaccurate that it was impossible to obtain reliable values for the parameters. A valuable new technique is currently being developed by other workers. In a solution spectrum, bands arising from a deformation are observed to shift in frequency, and to broaden when is added to the solution. The effects of this phenomenon were investigated for all eight molecules.

Electron impact induced rearrangements have been observed in compounds containing either two arylthio groups or an arylthio group and an arylsulphonyl group. In addition to the loss of sulphur dioxide from the molecular ion and a sulphone-sulphinate rearrangement, 3-arylsulphonyl-2-arylthiopropenes exhibited the rearrangement a bisarylsulphide ion (analogous to that reported for the isomeric l-arylsulphonyl-2-arylthiopropenes). A series of l-arylsulphonyl-4-arylthio-2-butynes also underwent sulphone-sulphinate rearrangement and rearranged to the bisarylsulphide ions, in the absence of sulphur dioxide or sulphur extrusion. The formation of the bisarylsulphide ion from the molecular ion of these compounds is postulated to occur after an initial {1,3} arylthio shift giving an ion analogous to the molecular ion of 3-arylsulphonyl-2-arylthiopropene. A skeletal rearrangement of N-(4'-arylsulphonyl -2 '-butynyl)-N-(4"-arylthio-2"-butynyl)anilines resulted in the elimination of Ar1SO2SAr2 from the molecular ion, but notions arising from a sulphone-sulphinate rearrangement or extrusion of sulphur or sulphur dioxide. The rearrangement of N,N- bis(4'-arylthio-2'-butynyl)anilines via consecutive {1,3} arylthio shifts,followed by elimination of a bisaryldisulphide moiety, was supported by the behaviour of N-(4'-arylthio-2'-butynyl)-N-(2"-arylthio-2"-propenyl)-p-toluidines and N,N-bis(2'arylthio-2'-propenyl)-p-toluidines. Theirmolecular ions are analogous to the rearranged molecular ions of the N,N-bis(4'-arylthio-2'-butynyl)anilines after one or two arylthio shifts, respectively. No extrusion of sulphur is observed, but rather the elimination of a bisaryldisulphide moiety occurs. A series of 1,8-bis(arylthiomethyl)naph-thalenes and 1,2-bis(arylthio)acenaphthenes were1 2synthesised. Electron impact showed no loss of Ar SSAr from the naphthalene derivatives, owing to the predominance of C-S bond cleavage. However, the acenaph-thene derivatives readily eliminated a bisaryldi-sulphide moiety and a qualitative substituent effect was1 2 +observed for the formation of Ar SSAr ˙ ions. In a separate investigation, the kinetics of ion-molecule clustering reactions in a number of chemical ionisation reagent gases were studied. Rate coefficients were obtained at various ion-source field strengths for the formation of proton or deuteron bound dimers at pressures of ca.0.01-0.4 Torr (450°K).Changes from overall third to second order kinetics were observed with increasing pressure, in accord with an energy transfer mechanism. Using the higher values of pressure, rate coefficients were obtained and corresponded to the formation of the excited collision complexes. Rate coefficients for the association reaction of the MH (or MD ) ions in methylamine, dimethylamine, trimethyl-Simple kinetic methods for estimating the ion-source pressures of these gases are described. The disappearance rate coefficients for the major primary ions of the above gases were also determined.

The Interaction between boron trihalides (bromide, chloride) and benzene derivatives (benzene, m-xylene, mesitylene, hexamethylbenzene) has been studied using the techniques of cryoscopy, vapour pressure measurement, proton magnetic resonance and Raman spectroscopy. No evidence was found to support previous assertions of weak complex formation in solution. The reactions between carbonyl halides (bromide, chloride) and Group three halides (boron, aluminium; chloride, bromide, iodide) have been studied. No complexes could be isolated, in contrast to the system studied previously. No reaction was found using boron halides, but with aluminium halides rapid and extensive halogen exchange occurred at ambient temperatures. Aluminium halides also catalysed the decomposition of carbonyl bromides: [equation] the enthalpy of hydrolysis of carbonyl bromide was measured by adiabatic solution calorimetry [equation] From this was derived [equation] differing significantly from previous values. Estimates have been made of thermodynamic functions for carbonyl iodide. The standard enthalpies of formation of aluminium bromide and aluminium iodide have been determined as [equations] by isoperibol calorimetry of the reactions [equations] Infra-red studies on the complex) have confirmed its structure as dative covalent, with bonding from oxygen to boron. On running the infra-red spectrum at room temperature, there is considerable dissociation of the complex, and also reaction with the potassium bromide windows. Determination of the degree of dissociation has shown that there is only negligible association in the vapour.

This thesis describes an investigation of the redistribution of electronic charge that occurs during the molecular vibrations of 1,4-dioxan and related compounds. The infrared band intensities of dioxan-dg, dioxan-dg, cyclohexane-d0, cyclohexane-d12 and tetrahydropyran were measured in both solution and gas phases. In the solution phase, overlapping band systems were split into their components by assuming Lorentzian band contours and producing the absorbance maximum, band half width and peak frequency from a least squares procedure. The individual gas phase intensities in such spectral regions were then derived by assuming that the distribution of intensity across the region was the same in both phases. Normal coordinate calculations were performed and extended to reduce the dioxan and cyclo-hexane experimental intensities to parameters known as atomic polar tensors (APTs). Each element of the APT for an atom represents the change in a component (x, y or z) of the molecular dipole moment on moving the atom along one of the molecule-fixed Cartesian axes. The sign ambiguity of the experimental dipole derivatives was satisfactorily resolved using constraints provided by the intensities of the deuterated compounds: APTs were calculated from each possible choice of signs and these were used in turn to predict the intensity of the deuterated molecule - the APT was rejected if the agreement was unsatisfactory (as measured by a "fit factor").The Gaussian 76 package for MO calculations was used to calculate ab initio APTs, and also, for dioxan, to derive a general valence force field. The latter, after least-squares refinement to the frequencies, proved more appropriate for the analysis of the dioxan intensities than a field derived from the Snyder-Zerbi generalized ether force field alone. A reasonable correspondence exists between the APTs derived from experiment and those from the Gaussian 76 package, and certain trends are apparent along the series of molecules that hopefully will aid future studies and will provide a route to the prediction of spectra of related molecules.

The non-catalysed reaction of chlorine with biphenylene yields 2-chlorobiphenylene as the main product, and tetra-chloro-, and trichlorohydroxy-tetrahydrobiphenylenes. Dechlorination of the tetrachloride and hydroxychloride gives biphenylene. The reaction of biphenylene with sulphuryl chloride also gives 2-chlorobiphenylene and tetrachlorotetrahydro-biphenylene in very poor yield. An attempt to chlorinate biphenylene with phosphorus pentachloride was unsuccessful. Methoxybiphenylene has been made by combined hydrolysis and methylation of 2-benzoyloxybiphenylene. Mono-substitution occurs at the 3-position on chlorination of 2-methoxy-biphenylene with molecular chlorine, giving 2-methoxy-3-chlorobiphenylene, but no chlorination occurs with sulphuryl chloride, either on standing or on reflux. Direct chlorination of 2-nitrobiphenylene gives 2-nitro-6-chlorobiphenylene in poor yield, but nitration of 2-chlorobiphenylene gave a comjilex mixture. Attempts to chlorinate 2 ,6-dimethoxybipheiiyleiie, 2-chlorobiphenylene and 2-bromobiphenylene did not give identified substitution products, but chlorination of 2-chlorobiphenvlene with large excess of chlorine in acetic acid gave a tetrachlorobiphenylene. Direct chlorination of both 2-benzoyl- and 2-acetyl-biphenylenes, and chlorination after sulpl.onation, gave an inseparable mixture of mono- and dichloro-derivatives. 2-Benzoyl-7-chloro- and 2-acety 1-6-clilorobiphenylones were made by Friodel-Crafts benzoylation and acetylatiou respectively, of 2-chlorobiphenylene-Chlorobiphenylene has been made by pyrolysis of 2- and 3-chlorobiphenylone iodonium iodide with cuprous oxide in poor yield. Finally, pyrolysis of -4-chlorobiphenylene iodonium iodide and 2,4-dichlorobiphenylene iodonium iodide with cuprous oxide gave 1-chlorobiphenylene and 1,3-dichloro-biphenylene respectively. The comparative study of the N.M.R., U.V. and I.R. spectra of the chlorobiphenyleneSand those of their bromo-analogues was extensively and successfully used to distinguish between structural isomers.

Understanding structure-property relationship of molecules is imperative for designing efficient materials for organic semiconductors. Organic semiconductors are based on π-conjugated molecules, either small molecules or macromolecules such as dendrimers or polymers. Charge transport through organic materials is one of the most important processes that drive organic electronic devices. We have investigated the charge transport properties in various molecular designs based on dendrons, dendron-rod-coil molecular triads, and conjugated oligomers. The charge transport properties were studied using bottom contact field effect transistors, in which the material was deposited by spin coating. In case of dendrons, their generation and density of charge transporting functionalities were found to play a significant role in influencing the charge transport properties. In case of macromolecules such as dendron-rod-coil molecules, the solid state morphology plays a significant role in influencing the charge transport properties. While these molecules exhibit only electron transporting behavior in field-effect transistor measurements, ambipolar charge transport is observed in the diode configuration. Short conjugated oligomers, based on donor-acceptor-donor design, provide model systems for conjugated polymers. Effect of varying the donor functionality on optoelectronic and charge transport properties was studied in short donor-acceptor-donor molecules. While donor-acceptor-donor molecules are well known in the literature, the effect of molecular composition on the charge transport properties is not well understood. We designed molecules with 2,1,3-benzothiadiazole as the acceptor and thiophene based donor functionalities. These molecules exhibit a reduced bandgap, good solution processability and charge mobility making them interesting systems for application in organic photovoltaics. Cyclopentadithiophene (CPD) based materials have been widely utilized as organic semiconductors due to their planar nature which favors intermolecular charge transport. While most CPD based materials are hole transporting, incorporation of electron withdrawing fluorinated substituents imparts n-type behavior to these molecules. This change in charge transport properties has often been attributed to the lowering of the LUMO energy level due to the increased electron affinity in the molecule. We designed CPD based semiconductors in which the bridgehead position was functionalized with electron withdrawing ketone or dicyanomethylene group and the -positions were substituted with phenyl or pentafluorophenyl groups. Both the phenyl substituted molecules are p-type materials, even though the dicyanomethylene group lowers the LUMO by 500 meV as compared to the carbonyl compound. The pentafluorophenyl substituted molecules are n-type materials even as their LUMO energy levels are about 300 meV higher than the corresponding phenyl substituted molecules. This indicates that charge transport behavior is not an exclusive function of the frontier orbital energy levels.