1,1,1,2-tetrafluoroethane (HFC 134a) is one of the major replacement compounds for chlorofluorocarbons and is therefore of great industrial importance. This work describes a method of characterisation for HFC 134a. The method profiled the levels of synthesis by-products present in samples of HFC 134a using gas chromatography (GC) with detection by flame ionisation detector (FID) or electron capture detector (ECD). The principal method for identification of the by-products was EI GC-mass spectrometry. The multi-variate data produced by the profiling of samples were analysed using chemometric techniques. A training set of samples of HFC 134a, with known origins of production, was analysed by both GC-FID and GC-ECD. This training data set was used to investigate the different methods of chemometric analysis as applied to the raw data, normalised data and principal component analysed data. K-means clustering and Hierarchical clustering were investigated to find the optimum methods for the identification of samples' origins of production based on their chromatographic profiles. The FID chromatographic traces could be correctly identified by applying a two step principal component analysis (PCA) using a hierarchical clustering method to classify the samples. The ECD chromatographic data could be correctly identified by applying a PCA followed by classification using a hierarchical clustering method. The two classification techniques were used to identify further samples of HFC 134a into clusters belonging to the known origins of production or into new clusters representing samples of unknown origin. Classification of samples using the ECD data required the least amount of operator interpretation and provided the least amount of ambiguity in sample identification.

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This thesis is concerned with the determination of the structures of the polyboron fluorides B₄F₆CO, B₈F₁₂ and B₁₀F₁₂ and the carboranes <i>closo-</i>2,3-C₂B₉H₁₁, <i>nido</i>-2,9-C₂B₉H₁₃ and <i>arachno-</i>6,9-C₂B₈H₁₄ by experiment and theoretical calculations. B₈F₁₂ is the first fully characterised higher boron fluoride and we can also report the second - B₁₀F₁₂. Its crystal structure contains a tetrahedron of boron atoms, each with a BF₂ substituent, similar to the known B₄X₄ tetrahedra but with two additional BF₂ bridge bonds. <i>Ab initio</i> calculations identify a very different structure. The molecule is based upon a folded B₄ central core as in B₈F₁₂, but this core is highly symmetrical in B₁₀F₁₂. However, calculations involving sterically larger substituents such as in B₁₀Cl₁₂, B₁₀Br₁₂ and B₁₀I₁₂ show molecular structures as found in crystalline B₁₀F₁₂. Carboranes form a widely studied class of molecule but past structural studies have generally relied upon theoretical calculations or NMR spectroscopy whilst, due to a general inability to form single crystals, diffraction studies have been carried out on salts or derivatives of the parent cluster. To further the understanding of carborane cluster structures the compounds <i>closo-</i>2,3-C₂B₉H₁₁, <i>nido</i>-2,9-C₂B₉H₁₃ and <i>arachno-</i>6,9-C₂B₈H₁₄have been experimentally characterised using gas-phase electron diffraction; they show structures comparable to known carboranes.

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In this thesis the results of a series of fluorinations of polyfluoroazabenzenes with a 50:50 mixture of C0F3 and CaFg are described. Perfluoro-4-isopropyl, -2,4-di-isopropyl, -3-methyl and -4-methylpyridines reacted by the addition of two or four fluorine atoms to give high yields of -azacyclodienes and -monoenes. The observed products were thought to represent the thermodynamically more stable dienes and a mechanism is proposed for their formation. Pyrimidines exhibited a variety of behaviours in that a diene resulted from perfluoro-4,6-di-isopropylpyrimidine, 5-chlorotrifluoropyrimide behaved more like tetrafluoro- pyrmidine in that dimers were produced whilst perfluoro-4- isopropylpyrimidine gave a complicated mixture of fragmentation products. Perfluoro-4,5- aid 4,6-di-isopropyIpyridazines both gave products resulting from the loss of nitrogen whilst a diene was obtained in high yield upon fluorinating perfluoro-2,5-di-isopropylpyrazineo Cyanuric fluoride was resistant to fluorination. Some direct fluorinations have been performed but only tetrafluoropyrimidine and perfluoro-4,5-di-isopropylpyridazine were reactive, the former producing a dimer the latter products due to loss of nitrogen. Some of the new perfluoropolyazacyclodienes have been reacted with a variety of nucleophilic reagents and whilst imino fluorines were readily substituted imines bearing perfluoroisopropyl were resistant to reaction, Perfluoro-4- isopropyl-l-azacyclohexa-1,3-diene has a very labile fluorine at C-2 compared with the one at C-3 and it is thought that polarisation of the imine bond by nitrogen is responsible for this. Several of the new dienes have been subjected to photolysis and ring opening and fragmentation reactions were observed. Products with isolated double bonds were not reactive.