Yes / Sonochemistry, i.e., the application of mechanical energy in the form of sound waves, has recently been recognised for its similarity to mechanochemistry and is now included under the umbrella term of mechanochemistry. Typically, due to the hypothesised cavitation mechanism, a liquid medium is considered as a necessity for a process to take place as a result of ultrasonic irradiation. In view of this, condensation reactions between solid reagents in the complete absence of solvent were carried out successfully by ultrasonic irradiation with the importance of particle size being highlighted. This work increases the potential of sonochemistry in the drive towards a sustainable future. / EPSRC (EP/L019655/1)

Non-covalent interactions in solution are subject to modulation by surrounding solvent molecules. This thesis presents two experimental molecular balances that have been used to quantify solvent effects on non-covalent interactions, including electrostatic and dispersion interactions. The first chapter introduces literature where non-covalent interactions have been studied in a range of solvents, particularly those where the effects of aqueous or fluorous solvents have been investigated. These solvents are of particular interest as they both invoke solvophobic effects on organic molecules, but have differing chemical and physical properties. The second chapter describes the adaptation of the Wilcox molecular torsion balance to study interactions between organic and fluorinated carbon chains in a range of solvents. Solvent cohesion was found to be the principle force driving both the alkyl and fluorous chains together in aqueous solvents, where no contribution to the interaction energy arising from dispersion forces could be detected. In fluorous and polar organic solvents evidence was found for weak favourable dispersion interactions between the alkyl chains. In contrast dispersion forces between the chains were found to be disrupted by competitive van der Waals interactions with surrounding solvent molecules in apolar organic solvents. Association of the fluorous chains was found to be solely driven by solvent cohesion. The final chapter describes the design and synthesis of a novel synthetic molecular-balance framework and describes its application to simultaneously measure solvent and substituent effects on the position of conformational equilibria. Despite the simplicity of the model system, surprisingly complicated behaviour emerged from the interplay of conformational, intramolecular and solvent effects. Nonetheless, a large data set of experimental equilibrium constants was analysed using a simple solvent model, which was able to account for both the intuitive and more unusual patterns observed. A means of dissecting electrostatic and solvent effects to reveal pseudo gas-phase behaviour has resulted from the analysis of experimental data obtained in many solvents.

Radicals are core reactive species that occur in almost every subfield of chemistry. In particular, solution phase radicals find their way into biochemistry (e.g. vitamin B12), and in polymer chemistry (e.g. radical polymerizations) just to name a few. Yet, given the proliferation of radical chemistry, there are still fundamental aspects of it that are poorly understood. This dissertation probed factors that influence the solvent cage effect. The solvent cage effect is where two radicals are held in close proximity to one another and prevented from easily escaping (to form free radicals) by a cage of solvent molecules. A convenient metric of the solvent cage effect is the radical recombination efficiency (FcP). Typically, FcP correlates with the bulk viscosity of the solution, however, this parameter only produces qualitative assessments. This dissertation outlines a method to quantitatively predict FcP using the microviscosity. This microviscosity dependence holds for non polar, aromatic, polar, and hydrogen-bonding solvents, along with solutions that contain polymers. Microviscosity is a great metric because it addresses an underlying reason for the solvent cage effect, the strength of the cage. Not only does the strength of the solvent cage around the radical pair affect FcP, but so does the identity of the radicals themselves. That is, the strength of the solvent cage is one piece to forming a total predictive model. FcP for the Cp'2Mo2(CO)6 dimer also varies with the wavelength of irradiation. Identifying the mechanism by which this wavelength dependence occurs may also provide another factor to include in an overall model of the solvent cage effect. Also, an attempt at synthesizing an asymmetric molybdenum dimer was performed. This asymmetric dimer would allow the study of solvent caged radical pairs that are different from each other. Predicting the photochemical cage pair recombination efficiency (FcP) is the major topic of this dissertation. However, there is also the collisional cage recombination efficiency (Fcʹ). This is where free radicals come together in what is called a collisional solvent cage pair. A method and values of Fcʹ are detailed later in this dissertation. This dissertation contains previously published and unpublished co-authored material.

Lignocellulosic biomass represents the largest potential volume and lowest cost for biofuel and biochemical production. Harnessing the full potential of the lignocellulosic biomass for low-carbon energy requires the knowledge of efficient breakdown and fractionation of its carbohydrates and lignin. Organic solvent pretreatment is recognized as an emerging way ahead because of its inherent advantages, such as the ability to fractionate lignocellulosic biomass into cellulose, lignin, and hemicellulose components with high purity, as well as easy solvent recovery and solvent reuse. Through all-atom MD simulation, we analyze the conformational transition of diverse lignin molecules in varying concentration of Methanol/water , DMSO/water mixtures and neat DMSO , neat methanol and water. From our work, it appears that in 40 mol% DMSO and 40 mol% methanol mixture (’theta solvent’) hardwood lignin(G/S=1.35) conforms random coil like structure, while 60 mol% DMSO and 60 mol% methanol solution (at 300 K) appears to be ’good solvent’ forhardwood lignin since it conforms extended chain like structure. While 80 mol% methanol is proven to be ’theta solvent’ and 80 mol% DMSO is proven to be ’good solvent’ for softwood lignin. We find that, major functional moieties of both lignin preferentially coordinated by methanol and DMSO molecules in increased organic solvents concentration which induces the conformational transition from crumbled globule to coil and prevent self-aggregation of lignin in binary mixtures. Chain dynamics of lignin explain the relaxation and subsequently elongated in addition of organic solvents into water.

No description available.

In order to meet the energy needs of a growing world in a sustainable manner, new high efficiency, carbon-neutral fuels and chemical feedstocks are required. An emerging approach that shows promise for high efficiency production of renewable fuels and chemicals is the use of purified enzymes combined in one pot to catalyze complex conversions: synthetic pathway biotransformations (SyPaB). An exemplary technology in this burgeoning field is the production of hydrogen from biomass sugars. Lignocellulosic biomass, which includes agricultural residues, energy crops, and industrial waste streams, is an ideal substrate for SyPaB conversion, as it is abundant and cheap, second only to untaxed coal on a $/energy content basis. But the structure of biomass is highly recalcitrant, making high-yield biological conversion difficult to achieve. In order to increase susceptibility to enzymatic digestion, thermochemical pretreatments are applied, with the goals of removing of lignin, the simplest example being soaking in aqueous ammonia (SAA); hemicellulose removal, most often using dilute acid (DA); and increasing cellulose accessibility by cellulose solvent-based pretreatments, such as cellulose solvent- and organic solvent-based lignocellulose fractionation (COSLIF). In a comparison of the lignin removal (SAA) and accessibility increase (COSLIF) approaches, we found that certain levels of lignin removal (~15%) were important, but further lignin removal was less effective at achieving digestibility gains than increasing cellulose accessibility. Pretreated biomass forms an excellent substrate for SyPaB hydrogen generation, due to low cost and high sugar content. Following experiments demonstrating the high yield conversion of sucrose to hydrogen (97%) and SyPaB generation of hydrogen at a rate commensurate with the best biological rates achieved, 157 mmol/L/h. SyPaB was combined with enzymatic hydrolysis to enable the direct conversion of cellulosic biomass, including untreated, DA, and COSLIF corn stover. In addition, an updated kinetic model of the system was used to rationally increase the maximum hydrogen production rate by 70% while minimizing total enzyme loading and without increasing substrate concentration. Together, these results demonstrate the high level of engineering control in cell-free systems, which can enable conversion of a variety of substrates to hydrogen at the highest possible yield and rates as high as any biohydrogen production method. / Ph. D.

Yes / Literature data on solubilities of adamantane in organic solvents have been used to obtain properties, or descriptors, of adamantane. There is much less data on substituted adamantanes but we have been able to obtain descriptors for some 40 substituted adamantanes. These descriptors can then be used to estimate a wide range of physicochemical, environmental and other properties of the adamantanes. For the first time, the water-solvent partition coefficient and the gas-solvent partition coefficient into a large range of solvents, can be estimated, the latter being equivalent to Henry's Law constants. A variety of other important properties can also be estimated. These include vapor pressures, enthalpies of vaporization and sublimation, partitions from air and from blood into biological tissues, and skin permeability from water. The descriptors themselves are not exceptional. Adamantane itself has a rather low dipolarity, zero hydrogen bond acidity and a very low hydrogen bond basicity, in common with other multicyclic aliphatic compounds. These lead to adamantane being a very hydrophobic compound, as is evident from our estimated water-octanol partition coefficient.

No / Originally developed as a heat exchange fluid, Volasil 245 (decamethylcyclopentasiloxane) has been found to dissolve 10 times more ozone than water does. This article proposes and investigates the extraction of wastewater contaminants to ozone-loaded Volasil 245 as a means of providing rapid treatment. In a series of bench-scale tests, the effectiveness of ozone-loaded Volasil 245 contact was compared with that of conventional gas contact. Tests were conducted with respect to a range of organic compounds: namely, phenol, 2-chlorophenol, 2,3-dichlorophenol, 1,3-dichlorobenzene, o-nitrotoluene, and nitrobenzene. Contact with the ozone-loaded solvent was suggested to be the more rapid technique, reducing aqueous concentrations by at least 85% within 30 s. In the case of 2-chlorophenol, Volasil 245 contact was shown to require just ~0.5 min to achieve a residual aqueous fraction of 5%, as opposed to ~4.5 min of gas contact. However, water/solvent interfacial mass transfer resistance was suggested to limit the degree of aqueous decontamination ultimately achieved.

No description available.

The solvent extraction of yttrium and neodymium from copper pregnant leach solutions (PLS) using Primene JM-T, a primary aliphatic amine, has been studied. Effect of contact time, pH, sulfate concentration, and extractant concentration were investigated using synthetic and actual PLS systems. Standard experimental conditions were 5 minute contact time, pH ~2.5, 10% v/v Primene JM-T concentration, and 1:1 O:A phase ratio. Distribution isotherms were constructed for the pure systems and for actual copper leach solutions. Synthetic solutions contained 100 ppm Y and ~75 ppm Nd. Copper PLS contained 2.1 ppm Nd and 14.9 ppm Y. Results showed that complete extraction of both yttrium and neodymium occurred within five minutes and at pH values greater than 1. It was also found that sulfate concentration does not inhibit extraction at any concentration. Additionally, the distribution isotherms created show that extraction for these metals can operationally take place in one stage from both synthetic solutions and copper leach solutions.