The work is divided into four parts. In part one the pKa values of a series of acetophenones have been determined using a novel method which involved measuring the rate of detritiation of a weak carbon acid in hydroxide-water-dimethylsulphoxide media. The change in the rate due to hydroxide ion removal on ionisation of an added stronger carbon acid enabled the pKa for this acid to be determined. In part two the hydroxide-catalysed rates of detritiation (k[T]) and racemisation (k[H]) of phenylmethylacetophenone have been measured in various dimethylsulphoxide-water mixtures. The isotope effect (k[H]/k[T]) reaches a maximum at an H_ value of 16.5 and the Bronsted B exponent for the reactions is 0.49 +/- 0.02. Arrhenius parameters have been determined and E[T]-E[H] reaches a maximum at an H_ value of 16.8. Anomalous A[H]/A[T], values are discussed in terras of solvent reorganisation contributions. In part three the acid-catalysed rates of detritiation of some acetophenones have been determined in acidic and highly acidic media. Equilibrium protonation studies on the acetophenones have also been made using a nuclear magnetic resonance method. The two studies allowed an appraisal of current mechanistic criteria for reactions in highly acidic media. The equilibrium studies emphasise the elusiveness of true thermodynamic pK[BH][+] values. In part four kinetic and nuclear magnetic resonance studies of ion association effects in alkali-metal ethoxide-ethanol, t-butoxide-t-butanol media have been made. The tendency towards increasing ion-pair formation on going from potassium to sodium to lithium cations is most pronounced in t-butanol. The nuclear magnetic resonance studies suggest a greater tendency towards the formation of solvent-separated rather than contact ion-pairs in ethanol.

The nitration of aromatic compounds has been performed on an industrial scale since the turn of the century. The rapid development of nitroaromatics as explosives and their use today in the dye industry and as intermediates in organic syntheses makes nitration an important, large scale process. The importance of nitration as a model electrophilic aromatic substitution reaction for the investigation of electronic effects in organic molecules led to it being studied in great depth in the homogeneous phase. Until recently, however, there was a sparse amount of information on the industrially significant two-phase reaction with mixed sulphuric and nitric acids and little attempt had been made to apply the results of kinetic experiments in a single phase to the phenomena observed in two phase batch and continuous nitration plants. In the last few years, however, much progress has been made arid a better understanding of the processes involved in these systems is now possible. The rates of nitration in a miniature stirred batch reactor and stirred cell containing pure toluene and chlorobenzene have been successfully interpreted on the basis of Danckwerts' Surface Renewal Theory of mass transfer. Many of the factors which affect the rate in these systems have been investigated and suitable rate equations tested experimentally. Despite the progress, however, the results obtained are not totally conclusive and several anomalous features have become apparent. The object of this work is to account for these features and hence try to substantiate the Theory of Danckwerts as applied by Cox and Strachan to the nitration of aromatics in two-phase systems.

Restricted and repetitive behaviours and interests (RRBIs) are a broad and heterogeneous class of behaviours that are present in a number of neuro-developmental conditions, such as, autism spectrum disorder (ASD) and Prader-Willi syndrome (PWS), but also feature in early typical development. The management of maladaptive RRBIs may present a considerable challenge to parents and the behaviours themselves may hamper the acquisition of new skills in affected individuals. Despite early research being fraught with lack of consensus in terminology and item overlap on standardised measures, the past decade has seen a resurgence of research in the area. Most systematic research, however, has been conducted in children with ASD and there are few studies that attempt to make links across disorders. Furthermore, debate over the structure of RRBIs and the use of domain scores in research has led to inconsistencies in studies attempting to identify their neuro-cognitive correlates. The collection of studies in this thesis attempt to move away from domain scores of repetitive behaviour by using factor analysis to parse the RRBI domain into homogeneous behavioural factors. These factors form the basis of studies in later chapters examining the relationship between RRBIs and executive functions (EF) in ASD, PWS and typical development. Results show that there is a differential pattern of association between different types of EF and specific RRBIs and findings across groups indicate possible common executive correlates of behaviour.

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