This thesis is split into three sections. The first presents the discovery and development of a novel photochemical cycloaddition/rearrangement sequence of electron deficient N-butenyl pyrroles to form fused tricyclic aziridines. The reaction proceeds via two photochemical steps, the first of which is reversible and is mediated in the forward direction by short wavelength DV around 254 run. The backwards reaction and the second step of the sequence are facilitated at longer wavelengths around 312 nm. Detailed mechanistic studies have shown that the second step proceeds via a triplet mechanism as it is quenched by isoprene The scope of this reaction has been studied thoroughly. An electron withdrawing group is required at the 2-position of pyrrole, and extra functionality around the ring is well tolerated. The use of indoles and imidazoles as alternative heterocycles has been investigated, and a number of alkene and non-alkene tethers of branched, linear and cyclic nature have been applied. Pyrroles containing the alkene tether at the C3 position have also been subjected to this reaction and have been found to yield interesting cyclobutane structures. The second section describes the application of this methodology to the synthesis of alkaloid natural product dendrobine. While the synthesis was not completed, important observations were made, leading to the identification of limitations within this methodology. Complex, cyclic tethers are not always tolerated and can facilitate an alternative reaction pathway Finally, a thorough and comprehensive investigation into flow vs. batch photochemistry is presented. Twelve photochemical reactions, after independent optimisation under both batch and flow conditions, were found to give strikingly similar yields with the productivity of a three layer FEP flow reactor being around 20% higher than batch. The safety advantage of carrying out hazardous reactions on flow is also illustrated. In light of the results, a set of general guidelines for first time and experienced photochemists alike is presented

The regioselective activation of C-H bonds and subsequent transformation into desirable functional groupS is an attractive prospect in organic synthesis. We have developed two novel C-H functionalisation reactions; the first is an intramolecular, sulfonamide directed, C-H amination reaction for the synthesis of 3_phenylisoindolinone derivates and the second is a sulfonamide directed ortho C-H acetoxylation reaction. Both isoindolinones and phenol derivatives of sulfonamides are important motifs in numerous pharmaceutically relevant compounds. The Cull-catalysed intramolecular C-H amination reaction for the synthesis of substituted 3-phenylisolindolinone derivatives (Scheme i) was found to be tolerant to substitution on both aromatic rings, however, no reaction was observed on exchanging the tethered aryl group for an alkyl group. Mechanistic investigations revealed that C-H cleavage was not part of the rate-determining step which is likely to be coordination of the copper catalyst to the sulfonyl amide. Substitution of the tethered phenyl ring (R2 ) and a subsequent Hammett analysis indicated that this coordination may be accelerated by a cation-IT interaction between CU11 and the pie system of the aryl group.

I report the development of a technique for the measurement of mass-dependent Mo isotope ratios. This is used to significantly expand the limited existing dataset of mass-dependent Mo isotope ratios in igneous samples with the aim of better constraining the processes which fractionate Mo isotopes at high-temperatures. Mid-ocean ridge basalts (MORBs) from the Atlantic and Pacific basins have a uniform δ⁹⁸/⁹⁵Mo -0.24 ± 0.02 0/00 (2 s.e.) and provide a new reference value for the upper convecting mantle. This mean value is isotopically lighter than the mean of measured chondrites (Burkhardt et al., 2014) which is seemingly at odds with the prediction that core formation should leave the mantle preferentially enriched in isotopically heavy Mo (Hin et al., 2013). This may be a result of preferential extraction of isotopically heavy Mo to the continental crust. 3.7 Gyr samples from Isua, Greenland have δ⁹⁸/⁹⁵Mo values within error of the MORB value. If this signature is primary, rather than an artefact caused by later disturbance, it could suggest that the upper mantle Mo isotope signature was instead established prior to 3.7 Gyr. Indeed, by measuring more recent altered samples from La Palma and Hawaii, I show that δ⁹⁸/⁹⁵Mo values can be perturbed by alteration. Ocean island basalts show substantial Mo isotope variability δ⁹⁸/⁹⁵Mo -0.59 - 0.03 %0, this study; M. Willbold, unpublished; Lai, 2013). However δ⁹⁸/⁹⁵Mo does not correlate with traditional tracers of recycled material in the mantle such as Pb and Sr isotopes. The observed variability may reflect mixing of an isotopically light subducted component into a deep mantle source which is isotopically heavier than MORB . I also report a technique for measurement of mass-independent Mo isotope ratios with the aim of constraining the influence of the late veneer on mantle Mo, however the reproducibility obtained was insufficient to resolve addition of chondritic material given estimates for the size of the late veneer.

Studies of the dynamics of chemical reactions reveal a great deal about their mechanisms and the forces that control the chemistry. However, most of these studies have been performed on isolated reactions in the gas-phase, either experimentally or using computational methods. This thesis presents experimental results for the dynamics of both gas and liquid phase reactions. The results are compared in an attempt to understand the effects a solvent has on the course of a chemical reaction. The gas phase experiments focussed on the reactions of Cl atoms with alkenes, in an extension of previous gas-phase dynamical studies of Cl + alkane reactions. The velocity map imaging (VMI) technique was applied to observe the state resolved scattering distributions of the HCI product of the Cl + propene, isobutene and 2,3-dimethyl but-2-ene reactions. The experimental results were compared to trajectory simulations and it is shown that reactions can proceed by direct hydrogen absh·action or an addition-elimination mechanism. The Cl + 2,3-dimethyl but-2-ene reaction has previously been studied in solution and comparison with the gas-phase results presented here provides direct and quantitative evidence about the influence of the solvent on energy release in a reactive system. Solution phase studies involved the reactions of F-atoms with the organic solvents CD2Cb, CD3CN and CH3CN. Computational and experimental studies of the reactions of F+ H2 and F + CH4, and their deuterated isotopologues, have been at the forefront of advances in understanding the classical and quantum mechanical contributions to a chemical reaction. The 266-nm photolysis ofXeF2 was used as a source of fluorine atoms in solution and required characterisation of the photodissociation dynamics on picosecond timescales. The reactions of F-atoms with CD3CN and CD2Cb solvent were studied with the use of time-resolved infra-red (TRIR) and time-resolved ultraviolet-visible (TRUV-Vis) spectroscopy. Efficient energy flow into the vibrational motion of the DF product competes with dissipation of the energy to the solvent bath within a few picoseconds, and bimolecular reaction rate coefficients, DF vibrational level branching ratios and vibrational cooling rates of DF extracted. Results are also presented for the reaction of CN radicals with acetone in chloroform solution. The HCN and 2-oxy-propyl products of the reaction were probed with TRIR spectroscopy, and much of the excess energy of this exothermic reaction is deposited in vibrational modes of both products. Coupling of these vibrational modes to the solvent bath then thermalizes the product on timescales of tens or hundreds of picoseconds. The results from this thesis are combined with previous studies of reactions in the gas and liquid phases to provide a picture of how the solvent can alter the potential energy surface of a reaction. Possible roles of solvent-solute complexes, solvent caging, solvent restructuring to accommodate reactions, and friction associated with the fluxional motion of the solvent bath are discussed

Stabilizing charged species in nonpolar solvents is difficult due to their low relative permittivity (Er); therefore, surfactants that form inverse micelles are often used as charge control additives (CCAs). In this Thesis, the structural and electrokinetic properties of surfactants and surfactant-charged colloids in nonpolar solvents were studied. The aggregation of surfactants was studied using high-resolution small-angle neutron scattering (SANS) measurements. Critical micelle concentrations (CMCs) for inverse micelle formation were measured for an anionic and a nonionic surfactant, and the transition was different for the two types. However, variations to the surfactant counterion and the solvent did not influence the CMC. Contrast-variation SANS (CV-SANS) was used to study the interaction of surfactant with polymer latexes. The surfactant did not strongly interact with the steric stabilizer polymer and, rather, was located throughout the entire latex. Such a distribution of surfactant differs from other model colloids in nonaqueous solvents where the surfactant is assumed to be adsorbed at the core-solvent interface. Molecular variations to the surfactant structure resulted in differences to the charge of particles. Modifying the surfactant tail groups resulted in more effective CCAs. Triple-chain surfactants were more effective, and this may be due to the larger number of inverse micelles. Changing the surfactant counterion resulted in instability of the particles. This may be due to decreased particle charge and increased electrolyte screening. The results presented in this Thesis provide much-needed structural information and systematic variations to the field of charging in nonpolar solvents. Determining the chemical interactions between surfactants and solvents or colloids is important for understanding how surfactants form inverse micelles, stabilize particles, and generate charge.

Aerosols play a crucial role in many areas of scientific relevance including in new technologies to deliver medicine to the lungs, and in fuel injection and spray drying. Aerosols have a profound impact on the atmosphere, influencing radiative forcing both by scattering solar radiation and by influencing cloud properties. Organic aerosols are a major component, making up 20 - 90 % of the submicron mass by region, and are emitted from many natural and anthropogenic sources. This thesis presents new measurements of the hygroscopic behaviour of single organic droplets confined using two techniques: aerosol optical tweezers (AOT) and an electrodynamic balance (EDB). Values of the hygroscopicity parameter (K) are derived and added to a comprehensive literature survey to elucidate a relationship with droplet composition, in terms of the molecular ratio of oxygen to carbon atoms (OIC). These data are shown to be in broad qualitative agreement. However, variation in K for droplets of the same OIC is found to be significant, and discrepancies between subsaturated and supersaturated data are evident. The variabilities and uncertainties associated with characterising the kinetics of water transport in ultraviscous sucrose droplets are also presented. Droplets are exposed to a perturbation in relative humidity, and the resultant characteristic relaxation timescale (r) is determined from stimulated Raman spectra. Comparison of the experimental· evaporation data with simulated timescales shows excellent agreement, and r is shown to increase strongly with droplet radius. Qualitative agreement between experimental condensation data and simulated timescales is presented, and r is shown to increase with wait time (the time the perturbation is applied for). Finally, factors influencing the ability to perform controlled chemical synthesis in single droplets are investigated. The formation of Nylon-6,1 0 at the droplet-gas phase interface is used as a test case of the system, and the interplay between droplet volatility and reactivity is shown to be crucial for controlling the reaction. Further investigations demonstrate synthesis of picomolar concentrations (equivalent to a single dose) of a functionalised caprolactam anti-cancer drug. The challenges in reliably validating drug formation in aerosol are presented.

Chiral boronate complexes, derived from the addition of an aryllithium to a secondary benzylic pinacol boronic ester, had previously been shown to act as chiral nucleophiles towards a range of electrophiles, giving the products with inversion of stereochemistry.

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