published_or_final_version / Chemistry / Master / Master of Science

In recent years, much attention has been focused on the application of alternutive gaseoas fuels, particularly natural gas (lVG), to diesel engines. This is due to the promisiog results obtained from the resesrch on NG as an internal combustion engine fuel throughout the world which hus shown that there is potential fo, minimizing air pollution and noise by replacing diesel fuel in existing engines by lfc fuel. For partial substitution of diesel fuel with IfG fuel in a diesel engine, a mixed combustion process called daal-fuelling approach has been adopted. Dual fuelling is the method whereby an alternative gaseous fuel such as IYG is induced into the cylinder as a primary fuel, with oir, and is subsequently ignited with a pilot injection of diesel fael. Extensive tests on emissions, performonce and dilferent umounts of NG substitution in a direct injection (DI) diesel engine have been carried out fo, both diesel fuel only and dual fuel (DF) operations. The results show that 86 % NG could be substituted for diesel fuel at low speeds over the whole load range. Maximum IfG operotion showed higher corbon monoxide (CO) emissions than the diesel fuel only operution while smoke was reduced with DF operation. The maximum vulues of smoke emission were 30 Hutridge smoke numbers (HSIV) with the maximum IfG and 28.5 HSIY in diesel fael only opeFation

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The allylic bromide functionality within brominated poly(isobutylene-co-isoprene), or BIIR, is amenable to substitution by a wide range of nucleophiles. The objective of this work was to gain insight into the dynamics of these substitution reactions, and to develop methods for accelerating these processes. Of particular interest was the reactivity of exomethylene (Exo-Br) and bromomethyl (BrMe) isomers found within BIIR toward various nucleophiles, and catalytic techniques for affecting the proportion of these isomers. BIIR isomerization can be catalyzed through ionic chemistry involving soluble Lewis acids such as zinc stearate and through a nucleophilic SN2’ rearrangement with soluble bromide salts such as tetrabuylammonium bromide (TBAB). The compatibility of TBAB with other nucleophiles makes it a preferable choice, but further rate enhancements can be realized using the corresponding iodide salt (TBAI). TBAI serves not only as nucleophilic isomerization catalyst, but also accelerates halide displacement from BIIR by an in-situ formation of an allylic iodide intermediate. Studies of BIIR isomerization and substitution reactions involved solvent-borne reactions of tetrabutylammonium acetate (TBAAc) and solvent-free reactions with PPh3 and 2-[2-(dimethylaminoethoxy)ethanol]. In all cases, the BrMe isomers were more reactive to nucleophilic substitution than Exo-Br. Since the esterification of BIIR with TBAAc generates TBAB as a reaction by-product, displaced bromide catalyzes the isomerization of Exo-Br to the more reactive BrMe isomers. As a result, these esterifications exhibit auto-accelerating dynamics. Similar behaviour is observed for solvent-fee alkylations of PPh3 and tertiary amines, since the resulting onium bromide salts are effective isomerization catalysts. All reactions show some increase in rate with the addition of TBAI, supporting the concept of nucleophilic catalysis. / Thesis (Master, Chemical Engineering) -- Queen's University, 2009-09-28 09:50:26.649

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This thesis deals with the palladium-catalyzed nucleophilic substitution of π-activated alcohols in which the C–O bond of a non-manipulated hydroxyl group is cleaved. The thesis is divided in two chapters describing two different catalytic systems. Chapter 2 describes a heterogeneous palladium-catalyzed transfer hydrogenolysis of primary, secondary, and tertiary benzylic alcohols to generate the corresponding aromatic hydrocarbons using formic acid as the hydrogen donor. A detailed mechanistic investigation of this reaction has been conducted that establish the kinetic order of each reaction component and also the deuterium kinetic isotope effects. This data provide a mechanistic picture that the hydride transfer from formic acid to palladium, and not the C–O bond cleavage, is involved in the rate-determining step and that a catalytic amount of a base promotes the transfer hydrogenolysis. Chapter 3 describes the development, mechanistic studies and synthetic scope of a homogeneous palladium-catalyzed amination of allylic alcohols. Isolation of the catalyst precursor and equilibrium studies of the palladium and π-acidic triphenylphosphite ligand show unique properties of this catalytic system. Stereochemical, kinetic, and kinetic isotope studies have been performed to provide insight into the mechanism of C–O bond cleavage of allylic alcohol and C–N bond formation catalyzed by the palladium complex. Interestingly, both O–H and C–O bond cleavages are involved in rate-determining steps.