Organic reactions in ionic liquids:A simple and highly regioselective N-substitution of pyrrole

In ionic liquids [Bmim][PF6] or [Bmim][BF4], pyrrole replaced the halogen atom of an alkyl halide to give the corresponding N-substituted pyrrole in excellent yield. Benzenesulfonyl chloride, p-methylbenzenesulfonyl chloride and benzoyl chloride reacted similarly with pyrroles to afford the N-substituted pyrroles in quantitative yield. Michael addition reaction of pyrrole with electrophilic olefins was completed in a highly regioselective manner to afford the N-alkylpyrroles.

Characterization and cytotoxicity studies of thiol-modified polystyrene microbeads doped with [(Mo6X8)(NO3)6]2- (X=Cl, Br, I)

Halide octahedral molybdenum clusters [(Mo6X8)L6]n- possess luminescence properties that are highly promising for biological applications. These properties are rather dependent on the nature of both the inner ligands X (i.e. Cl, Br, or I) and the apical organic or inorganic ligands L. Herein, the luminescence properties and the toxicity of thiol-modified polystyrene microbeads (PS-SH) doped with [(Mo6X8)(NO3)6]2- (X=Cl, Br, I) were studied and evaluated using human epidermoid larynx carcinoma (Hep2) cell cultures. According to our data, the photoluminescence quantum yield of (Mo6I8)@PS-SH is significantly higher (0.04) than that of (Mo6Cl8)@PS-SH (6Br8)@PS-SH (6X8)@PS-SH showed that all three types of doped microbeads had no significant effect on the viability and proliferation of the cells.

Sulphide ore minerals:surface chemical properties

The surfaces of iron-containing sulphide minerals were oxidised by a range of inorganic oxidants, and the resultant surface alteration products studied using various spectroscopic techniques. The characterisation of surface oxidation is relevant to the alteration of ores in nature and their behaviour during flotation and leaching, of importance to the metallurgical industry. The sulphides investigated included pyrite (FeS2), hexagonal pyrrhotine (Fe9S10), monoclinic pyrrhotine (Fe7Se), violarite (FeNi2S4), pentlandite ((FeiNi)9Se), chalcopyrite (CuFeS2) and arsenopyrite (FeAsS). The surfaces were oxidised by various methods including acid (sulphuric), alkali (ammonium hydroxide), hydrogen peroxide, steam, electrochemical and air/oxygen (in a low-temperature (150ºC) furnace), The surfaces were examined using surface sensitive chemical spectroscopic methods including x-ray photoelectron spectroscopy (ms), Auger electron spectroscopy (LES) and conversion electron Mössbauer spectroscopy (CEKS). Physical characterisation of the surfaces was undertaken using scanning electron microscopy (SM), spectral reflectance measurements and optical microscopy. Bulk characterisation of the sulphide minerals was undertaken using x-ray diffraction and electron microprobe techniques. Observed phases suggested to form in most of the sulphide surfaces include Fe204, Fe1-x0, Fe202, Fe00H, Fe(OH)3, with iron II & III oxy-sulphates. The iron sulphides show variable extents of oxidation, indicating pyrite to be the most stable. Violarite shows stability to oxidation, suggested to result from both its stable spinel crystal structure, and from the rapid formation of sulphur at the surface protecting the sub-surface from further oxidation. The phenomenon of sub-surface enrichment (in metals), forming secondary sulphides, is exhibited by pentlandite and chalcopyrite, forming violarite and copper sulphides respectively. The consequences of this enrichment with regard to processing and leaching are discussed. Arsenopyrite, often a hindrance in ore processing, exhibits the formation of arsenic compounds at the surface, the dissolution of which is discussed in view of the possible environmental hazard caused by the local pollution of water systems. The results obtained allow a characterisation of the sulphides in terms of their relative stability to oxidation, and an order of stability of the sulphide surfaces is proposed. Models were constructed to explain the chemical compositions of the surfaces, and the inter-relationships between the phases determined at the surface and in the sub-surface. These were compared to the thermo-chemically predicted phases shown in Eh/pH and partial pressure diagrams! The results are discussed, both in terms of the mineralogy and geochemistry of natural ores, and the implications for extraction and processing of these ore minerals.

A systematic study of the kinetics of lignin pyrolysis

The pyrolysis kinetics of four types of lignin (Alkali lignin, Hydrolytic lignin, Organosolv lignin, and Klason lignin) were investigated using thermogravimetric analysis (TGA). Kissinger's method was used to derive the kinetic parameters (activation energy, order of reaction and frequency factor). It has been shown that the pyrolysis of all the lignins except Klason lignin was first order with respect to solid decomposition, while for Klason lignin, the reaction had an order of 1.5. The activation energy depends on both separation methods and the plant species from which the lignin was isolated, while the frequency factor did not indicate the dependence of either plant species or separation methods.

Measurement of key compositional parameters in two species of energy grass by Fourier transform infrared spectroscopy

Two energy grass species, switch grass, a North American tuft grass, and reed canary grass, a European native, are likely to be important sources of biomass in Western Europe for the production of biorenewable energy. Matching chemical composition to conversion efficiency is a primary goal for improvement programmes and for determining the quality of biomass feed-stocks prior to use and there is a need for methods which allow cost effective characterisation of chemical composition at high rates of sample through-put. In this paper we demonstrate that nitrogen content and alkali index, parameters greatly influencing thermal conversion efficiency, can be accurately predicted in dried samples of these species grown under a range of agronomic conditions by partial least square regression of Fourier transform infrared spectra (R2 values for plots of predicted vs. measured values of 0.938 and 0.937, respectively). We also discuss the prediction of carbon and ash content in these samples and the application of infrared based predictive methods for the breeding improvement of energy grasses.

Effect of the Hofmeister anions upon the swelling of a self-assembled pH-responsive hydrogel

We report the effect of a range of monovalent sodium salts on the molecular equilibrium swelling of a simple synthetic microphase separated poly(methyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate)-block-poly(methyl methacrylate) (PMMA88-b-PDEA223-b-PMMA88) pH-responsive hydrogel. Sodium acetate, sodium chloride, sodium bromide, sodium iodide, sodium nitrate and sodium thiocyanate were selected for study at controlled ionic strength and pH; all salts are taken from the Hofmeister series (HS). The influence of the anions on the expansion of the hydrogel was found to follow the reverse order of the classical HS. The expansion ratio of the gel measured in solutions containing the simple sodium halide salts (NaCl, NaBr, and NaI) was found to be strongly related to parameters which describe the interaction of the ion with water; surface charge density, viscosity coefficient, and entropy of hydration. A global study which also included nonspherical ions (NaAce, NaNO3 and NaSCN) showed the strongest correlation with the viscosity coefficient. Our results are interpreted in terms of the Collins model,(1) where larger ions have more mobile water in the first hydration cage immediately surrounding the gel, therefore making them more adhesive to the surface of the stationary phase of the gel and ultimately reducing the level of expansion.

The synthesis of novel biodegradable polyesters and copolyesters from anhydrosulfites

This thesis was concerned primarily with the synthesis and the ring-opening polymerisation of anhydrosulfites (1,3,2-dioxa-thiolan-4-one-2-oxides), and secondly with the copolymerisation of anhydrosulfites with -caprolactone. The polyesters and copolyesters synthesised are of considerable interest in medical applications and also for use as environmental friendly packaging. A range of anhydrosulfites were prepared according to an established method. Aliphatic anhydrosulfites were obtained with a level of purity satisfactory for polymerisation whereas aromatic anhydrosulfites decomposed during distillation and purification by chromatographic techniques. Aliphatic anhydrosulfites with a substituent, such as methyl, isopropyl, n-butyl and isobutyl were studied by NMR spectroscopy. Analysis of these spectra revealed that the five-membered anhydrosulfite ring was puckered and that when the substituent was bulky, rotations about the alkyl chains were restricted. A wide range of anionic initiators may be used to initiate anhydrosulfites. Lithium alkyls turned out to be more successful than alkali metal alkoxides and amides. The molecular weights were found to depend on the basicity of the initiator, the monomer-to-initiator ratio, the nature of the solvent and the polymerisation temperature. The molecular weight M0 of poly(L-lactic acid) ranged from (0.5 to 6)x104. Highly crystalline and purely isotactic poly(lactic acid) was synthesised from L-lactic acid anhydrosulfite (L-LAAS) whereas DL-LAAS led to an amorphous polymer with randomly distributed D-and L-lactic units. This indicated that this polymerisation was not stereoselective. However, the bulkiness of the substituent in the anhydrosulfites molecule was found to influence the stereoselectivity of the polymerisation, thus polyesters with isobutyl or n-butyl pendant group were preferentially isotactic. Block-copolymers of ε-caprolactone and several anhydrosulfites were successfully produced. Block-copolymers of LAAS with ε-caprolactone were also synthesised, but the incorporation of caprolactone units was rather small. In contrast, random copolymerisation of LAAS and ε-caprolactone led to polymers with blocky structures similar to those obtained in the block-copolymerisation of LAAS with  ε-caprolactone.

Transport phenomena in hydrogel membranes

In this thesis the factors surrounding the permeation of alkali and alkaline earth metal salts through hydrogel membranes are investigated. Although of relevance to aqueous separations in general, it was with their potential application in sensors that this work was particularly concerned. In order to study the effect that the nature of the solute has on the transport process, a single polymer matrix, poly (2-hydroxyethyl methacrylate), was initially studied. The influence of cation variation in the presence of a fixed anion was looked at, followed by the effect of the anion in the presence of a fixed cation. The anion was found to possess the dominant influence and tended to subsume any influence by the cation. This is explained in terms of the structure-making and structure-breaking characteristics of the ions in their solute-water interactions. Analogies in the transport behaviour of the salts are made with the Hofmeister series. The effect of the chemical composition of the polymer backbone on the water structuring in the hydrogel and, consequently, transport through the membrane, was investigated by preparing a series of poly (2-hydroxyethyl methacrylate) copolymer membranes and determining the permeability coefficient of salts with a fixed anion. The results were discussed in terms of the `free-volume' model of permeation and the water structuring of the polymer backbone. The ability of ionophores to selectively modulate the permeation of salts through hydrogel membranes was also examined. The results indicated that a dualsorption model was in operation. Finally, hydrogels were used as membrane overlays on coated wire ion-selective electrodes that employed conventional plasticised-PVC-valinomycin based sensing membranes. The hydrogel overlays were found to affect the access of the analyte but not the underlying electrochemistry.

Organometallic precursors for pillared clay synthesis

The synthetic hectorite, laponite has been used within the paper industry to produce mildly conducting paper for use in electrographic printing. The aim of this research was to modify laponite in order to improve the electrical conductivity. In a continuation of a previous investigation involving organotin intercalation of laponite, the organotin precursor (p-CH3,OC6H4)4Sn was synthesised and characterised using Mass Spectroscopy, Infrared Spectroscopy and elemental analysis. Results of intercalation with this compound and a range of organobismuth and organoantimony compounds suggested that a halide content within the precursor was necessary for improvement in conductivity to be observed. Organometallic intercalation of a range of organotellurium compounds with laponite provided evidence that a hydrolysis reaction on the clay surface followed by the release of hydrochloric acid was an important first step if a reaction was to occur with the clay. Atomic Absorption Spectroscopy studies have shown that the acid protons underwent exchange with the interlayer sodium ions in the clay to varying degrees. Gas-liquid Chromatography and Infrared Spectroscopy revealed that the carbon-tellurium bond remained intact. Powder X-ray diffraction revealed that there had been no increase in the basal spacing. The a.c. conductivity of the modified clays in the form of pressed discs was studied over a frequency range of 12Hz - 100kHz using two electrode systems, silver paste and stainless steel. The a.c. conductivity consists of two components, ionic and reactive. The conductivity of laponite was increased by intercalation with organometallic compounds. The most impressive increase was gained using the organotellurium precursor (p-CH3OC6H4)2TeCl2. Conductivity investigations using the stainless steel electrode where measurements are made under pressure showed that in the case of laponite, where poor particle-particle contact exists at ambient pressure, there is a two order of magnitude increase in the measured a.c. conductivity. This significant increase was not seen in modified laponites where the particle-particle contact had already been improved upon. Investigations of the clay surface using Scanning Electron Microscopy suggested that the improvement in particle-particle contact is the largest factor in the determination of the conductivity. The other important factor is the nature and the concentration of the interlayer cations. A range of clays were synthesised in order to increase the concentration of sodium interlayer cations. A sol-gel method was employed to carry out these syntheses. A conductivity evaluation showed that increasing the concentration of the sodium cations within the clay led to an increase in the conductivity.

Prediction of Klason lignin and lignin thermal degradation products by Py-GC/MS in a collection of Lolium and Festuca grasses

A rapid method for the analysis of biomass feedstocks was established to identify the quality of the pyrolysis products likely to impact on bio-oil production. A total of 15 Lolium and Festuca grasses known to exhibit a range of Klason lignin contents were analysed by pyroprobe-GC/MS (Py-GC/MS) to determine the composition of the thermal degradation products of lignin. The identification of key marker compounds which are the derivatives of the three major lignin subunits (G, H, and S) allowed pyroprobe-GC/MS to be statistically correlated to the Klason lignin content of the biomass using the partial least-square method to produce a calibration model. Data from this multivariate modelling procedure was then applied to identify likely "key marker" ions representative of the lignin subunits from the mass spectral data. The combined total abundance of the identified key markers for the lignin subunits exhibited a linear relationship with the Klason lignin content. In addition the effect of alkali metal concentration on optimum pyrolysis characteristics was also examined. Washing of the grass samples removed approximately 70% of the metals and changed the characteristics of the thermal degradation process and products. Overall the data indicate that both the organic and inorganic specification of the biofuel impacts on the pyrolysis process and that pyroprobe-GC/MS is a suitable analytical technique to asses lignin composition. © 2007 Elsevier B.V. All rights reserved.

The chemistry of some organotellurium compounds

Tbe formation of Pd(TeR)n and (CuTeR)n from the reaction between telluroesters and Pd(II)or Cu(II) suggested that these organa­tellurium reagents may be useful precursors of RTe- ligands in reactions with transition-metal substrates. Also the formation of telluronium salts Me2RTeI- from the reaction between telluroesters and methyl iodide, together with the above, confirm the cleavage of -cõ-Te bonds rather than -C-Te bonds. The formation of a carboxylic acid from the toluene solution of a ditelluride d palladium(O) complex in the presence of light oxygen (from air) is demonstrated. When the solvent employed is p-xylene an aldehyde is formed.The reaction proceeds via the free radical, RTeO, with Pd(PPh3)4 as a catalyst.It has also been shown that the oxidation of aldehydes to carboxylic acids is catalysed by ditelluride. Spin trapping experiments with PhCH=N(O)But (phenyl-t-butyl-nitrone) have provided evidence that the oxidative addition of an alkyl halide (RX=Mei, BunBr, BusecBr, ButBr, BrCH2-CH=CHCH2Br, and Br(CH2)4Br) to diphenyltelluride and reductive elimination of CH3SCN from Ph2(CH3)Te(NCS) proceeds via radical pathways. A mechanism is proposed for oxidative addition which involves the preformation of a charge transfer complex of alkyl halide and diphenyltelluride.The first step is the formation of a charge transfer complex, and the initial product of the oxidative addition is a "covalent" form of the tellurium(IV)compound. When the radical R is more stable, Ph2TeX2 may be the major tellurium(IV)product. The reaction of RTeNa (R=p-EtOC6H4, Ph) with organic dihalides X2(CH2)n (n=1,2,3,4) affords telluronium salts (n=3,4; X=Cl, Br) the nature of which is discussed.For n=l (X=Br, I)the products are formulated as charge transfer complexes of stoichiometry (RTe)2(CH2).CH2X2• For n=2, elimination of ditelluride occurs with the formation of an alkene. Some 125’Te Mõssbauer data are discussed and it is suggested that the unusually low value of 6 (7.58 mm.s-1 ) for  p-EtO.C6H4.Te)2(cH2)cH2Br2 relates to removal of 5's electronsfrom the spare pair orbltal via the charge transfer interaction. 125Te Mossbauer data for (p-EtO.C6H4)Te(CH2)4Br are typical of a tellurium (IV) compound and in particular ∇ is in the expected range for a telluronium salt. The product of the reaction of Na Te (C6H4.OEt), with 1,3-dibromopropane is, from the Mössbauer data, also a telluronium salt.

The durability of glass fibre reinforced cements made with new cementitious matrices

Widespread use of glass fibre reinforced cement (GRC) has been impeded by concerns over its durability. Three degradation mechanisms are proposed - fibre corrosion, Ca(OHh precipitation and matrix densification - although their relative importance is debated. Matrices with reduced alkalinities and Ca(OH)2 contents are being developed; the aim of this study was to investigate their hydration and interaction with alkali-resistant fibres to determine the factors controlling their long-term durability, and assess the relevancy of accelerated ageing. The matrices studied were: OPC/calcium-sulphoaluminate cement plus metakaolin (C); OPC plus metakaolin (M); blast-furnace slag cement plus a micro-silica based additive (D); and OPC (O). Accelerated ageing included hot water and cyclic regimes prior to tensile testing. Investigations included pore solution expression, XRD, DTA/TG, SEM and optical petrography. Bond strength was determined from crack spacings using microstructural parameters obtained from a unique image analysis technique. It was found that, for the new matrices - pore solution alkalinities were lower; Ca(OH)2 was absent or quickly consumed; different hydrates were formed at higher immersion temperatures; degradation under 65°C immersion was an order of magnitude slower, and no interfilamental Ca(OH)2 was observed .It was concluded that: fibre weakening caused by flaw growth was the primary degradation mechanism and was successfully modelled on stress corrosion/static fatigue principles. OPC inferiority was attributed partly to its higher alkalinity but chiefly to the growth of Ca(OH)2 aggravating the degradation; and hot water ageing although useful in model formulation and contrasting the matrices, changed the intrinsic nature of the composites rather than simply accelerating the degradation mechanisms.

Metakaolin as a cement extender

The effect of 10% and 20% replacement metakaolin on a number of aspects of hydration chemistry and service performance of ordinary Portland cement pastes has been investigated. The analysis of expressed pore solutions has revealed that metakaolin-blended specimen pastes possess enhanced chloride binding capacities and reduced pore solution pH values when compared with their unblended counterparts. The implications of the observed changes in pore solution chemistry with respect to chloride induced reinforcement corrosion and the reduction in expansion associated with the alkali aggregate reaction are discussed. Differential thermal analysis, mercury intrusion porosimetry, and nuclear magnetic resonance spectroscopy have been employed in the analysis of the solid phase. It is suggested that hydrated gehlenite (a product of pozzolanic reaction) is operative in the removal and solid state binding of chloride ions from the pore solution of metakaolin-blended pastes. Diffusion coefficients obtained in a non-steady state chloride ion diffusion investigation have indicated that cement pastes containing 10% and 20% replacement metakaolin exhibit superior resistance to the penetration of chloride ions in comparison with those of plain OPC of the same water:cement ratio. The chloride induced corrosion behaviour of cement paste samples, of water:cement ratio 0.4, containing 0% , 10%, and 20% replacement metakaolin, has been monitored using the linear polarization technique. No significant corrosion of embedded mild steel was observed over a 200 day period.

Electrochemical chloride extraction to halt corrosion of reinforcement

This thesis presents results of experiments designed to study the effect of applying electrochemical chloride extraction (ECE) to a range of different hardened cement pastes. Rectangular prism specimens of hydrated cement paste containing sodium chloride at different concentrations were subjected to electrolysis between the embedded steel cathodes and external anodes of activated titanium mesh. The cathodic current density used was in the range of 1 to 5 A/m2 with treatment periods of 4 to 12 weeks. After treatment, the specimens were cut into sections which were subjected to pore-solution expression and analysis in order to determine changes in the distribution of free and total ionic species. The effect of the ECE treatment on the physical and microstructural properties of the cements was studied by using microhardness and MIP techniques. XRD was employed to look at the possibility of ettringite redistribution as a result of the accumulation of soluble sulphate ions in the cement matrix near the cathode during ECE. Remigration of chloride which remains after the ECE treatment and distribution of other ions were studied by analysing specimens which had been stored for several months, after undergoing ECE treatment. The potentials of the steel cathodes were also monitored over the period to detect any changes in their corrosion state. The main findings of this research were as follows: 1, ECE, as applied in this investigation, was capable of removing both free and bound chloride. The removal process occurred relatively quickly and an equilibrium between free and bound chlorides in the specimens was maintained throughout. At the same time, alkali concentrations in the pore solution near the steel cathode increased. The soluble sulphate ionic concentration near the cathode also increased due to the local increase in the pH of the pore solution. 2, ECE caused some changes in physical and microstructural of the cement matrix. However these changes were minimal and in the case of microhardness, the results were highly scattered. Ettringite in the bulk material well away from the cathode was found not to increase significantly with the increase in charge passed.3, Remigration of chloride and other ionic species occurred slowly after cessation of ECE with a resultant gradual increase in the Cl-/OH- ratio around the steel.4, The removal of chloride from blended cements was slower than that from OPC.

Technology of repair for corroded reinforced concrete

A number of factors relating to various methods of repair for chloride initiated corrosion damage of reinforced concrete have been studied. A novel methodology has been developed to facilitate the measurement of macro and micro-cell corrosion rates for steel electrodes embedded in mortar prisms containing a chloride gradient. The galvanic bar specimen comprised electrically isolatable segmental mild steel electrodes and was constructed such that macro-cell corrosion currents were determinable for a number of electrode combinations. From this, the conditions giving rise to an incipient anode were established. The influence of several reinforcement and substrate primer systems upon macro-cell corrosion, arising from an incipient anode, within a patch repair have been investigated. Measurements of electrochemical noise were made in order to investigate the suitability of the technique as an on-site means of assessing corrosion activity within chloride contaminated reinforced concrete. For this purpose the standard deviation of potential noise was compared to macro-cell galvanic current data and micro-cell corrosion intensity determined by linear polarisation. Hydroxyl ion pore solution analyses were carried out on mortar taken from cathodically protected specimens. These specimens, containing sodium chloride, were cathodically protected over a range of polarisation potentials. Measurement of the hydroxyl ion concentrations were made in order to examine the possibility of alkali-silica reactions initiated by cathodic protection of reinfored concrete. A range of mortars containing a variety of generic type additives were examined in order to establish their resistances to chloride ion diffusion. The effect of surfactant addition rate was investigated within a cement paste containing various dosages of naphthalene sulphonate.