The sorption of the gases, hydrogen chloride and ammonia, and their mixture resulting from the dissociation of vapourized ammonium chloride, at temperatures between 200-350°C, has been studied in molecular sieve zeolites such as H-Zeolon, NaY and KL. The sorption of hydrogen chloride in an ion-exchanged zeolite is accompanied by an exchange reaction of part of its cations by protons while the chloride salt of the cation is formed. Depending upon the silica content of the zeolite, this can cause decomposition of its crystal structure. The salt produced from the exchange reaction can either remain molecularly dispersed in the crystal cavities or migrate outside the crystals. In hydrogen zeolites a reaction of hydrogen chloride with the aluminium of the zeolitic framework takes place. Due to these reactions, the sorption isotherms of hydrogen chloride were irreversible. Reversible isotherms of ammonia were obtained in most zeolites. The affinity of hydrogen zeolites for ammonia was higher than that of ion-exchanged zeolites because of the formation of the ammonium-zeolite. The sorption of the mixture is governed by the recombination reaction of ammonia and hydrogen chloride to form ammonium chloride and the sorption of the pure gases. If one of the gases is sorbed more strongly than the other, a disproportionation arises in the gas and sorbed phases, which decreases with increasing pressure. In an ion-exchanged zeolite an exchange reaction of its cations by ammonium ions also takes place. All the isotherms showed strong interaction between ammonia and. hydrogen chloride. The partial isotherms of ammonia and hydrogen chloride were calculated from the isotherms of the mixture in most cases. The sorption from the mixture was several times higher than from the pure gases. In view of these findings, a mechanism was suggested for the Clark-Steiger preparation of ammonium zeolites.

Aerosols have an inhomogeneous distribution across the globe because of their short lifetimes in the atmosphere. They impose a localised radiative forcing close to their emission source that is effective at driving circulation changes and influencing the hydrological cycle. One such type of circulation that has recently been suggested to be affected by aerosols is the South Asian summer monsoon, which provides 80% of annual rainfall to over a billion people during the summer months. I used the UK Met Office HadGEM3 coupled global climate model to investigate, for the first time, the centennial-scale South Asian precipitation responses to removing regional anthropogenic sulphur dioxide emissions. This study is unique since these experiments have never been attempted on a scale that is multi-regional, centennial and in a fully coupled ocean-atmosphere model setup. Despite the imposed localised heating in my experiments resulting from emissions removals over the United States, Europe, East Asia, South Asia or the northern mid-latitudes as a whole, the large-scale spatial pattern and magnitude of the precipitation response over South Asia was similar for all experiments. This was due to the ocean responding to the atmosphere enabling the full response to be realised and the ocean dynamics driving a structurally similar global climate response. The sum of the responses from the experiments where the emissions are removed from the United States, Europe and East Asia resemble the response seen in the experiment where emissions are removed in the entire northern mid-latitude band, suggesting that the response is roughly linear, with East Asia being the largest contributor to the response. East Asia’s proximity to South Asia meant that it was more effective at influencing the land-sea thermal contrast, pressure gradients, and therefore the local monsoon circulation itself. On the other hand, local emissions removals, i.e. over South Asia itself, led to decreases in precipitation over central and northern India, a result not seen in any other experiment. Moreover, the response of the circulation was still found to be the main driver of the response in this case, despite changes to the clouds making them thinner and less reflective. In the future, further work is warranted to allow for comparisons with other coupled ocean-atmosphere models performing similar multi-regional experiments, to enhance confidence in our results and to further our understanding of the processes involved. Similar experiments can also be performed to explore the role of other short-lived pollutants, such as tropospheric ozone. The insight provided could prove invaluable for informing emissions reduction policies and for understanding the implications for short-term regional climate prediction.

The synthesis of a number of novel polyaromatic compounds are reported, starting with novel polyheterocyclic systems containing sulphur and oxygen, otherwise known as thienoacenes and furanoacenes. These were generally produced via a four-step synthetic strategy utilising palladium-catalysed cross-coupling reactions such as Sonogashira and Suzuki cross-couplings to build the precursors, which were then subjected to a base-catalysed cycloisomerisation to give the final angular systems of several fused aromatic rings. Eight thienoacenes and seven furanoacenes, all consisting of between five and eight fused rings, were synthesised, as well as a mixed system featuring a thiophene and furan ring at either end of the molecule. Use of a five-ring thienoacene as a building block allowed for extension of the aromatic framework, and a stable fifteen-ring thienoacene was synthesised in a total of nine steps. The same synthetic method was applied in producing a series of polycyclic aromatic hydrocarbons (PAHs) with phenyl and naphthyl substituents replacing thiophene and furan. Within this chapter, significant work was carried out in investigating the final cyclisation mechanism. Six highly crystalline PAHs are reported, consisting of five to eight fused benzene rings, and the addition of extra steps enabled longer polyaromatics of nine, eleven and twelve rings to be created. The final challenge was the design and synthesis of a series of polyaromatic compounds for use as molecular wires. Similar approaches were used to build systems containing terminal pyridine and nitrile substituents which can act as anchoring groups to secure the molecule to a metal surface. Nine compounds containing five to eight fused aromatic rings with a suitable anchoring group were brought through, and the development of strategies for significantly lengthening these wires gave five systems of either nine or twelve rings. Optical and electrochemical characterisation of the compounds was carried out at the University of Caen Lower Normandy, France, in collaboration with Prof. Bernhard Witulski. The results of these measurements generally gave good correlation with computationally calculated values.

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Reaction of PtCl2(PR3)2 with a solution of SOCl2 in NH3(1) is known to yield compounds of the type Pt(NSO)2(PR3)2. Reaction of PtCl2(PR3)2 with a solution of S02 in NH3(1) is known to yield compounds of the type Pt(S02(NH)2(PR3)2). The initial part of this work was to try and expand this field of synthetic chemistry, and investigate whether metal dichlorides would be amenable starting material for the production of metal bis-thionylimide compounds via a liquid ammonia route, as opposed to more traditional wet chemical methods. This was largely unsuccessful, with the exception of the production of Hg(NSO)2, which was verified by i.r. and Raman spectroscopy and mass spectroscopy. Reaction of PtCl2(PR3)2 with SeOCl2 in NH3(1) was also tried, in an attempt to produce a selenium analogue of the thionylimide compounds. This was not successful. Much Raman-spectroscopic work was undertaken to try and expand upon the data previously published by authors such as Chivers and Lelieur, with respect to the species present in solutions of S, SOCl2, SO2Cl2, S/Se and mixtures thereof in liquid ammonia. We were unfortunately unable to improve upon previously published work.