The Effect of Tacticity on the Conformational Properties of Poly(1-olefin sulfone)s

The effect of tacticity on the conformational properties of poly(olefin sulfone)s was studied. Tactic polymers, prepared from racemic thiirane monomers using chiral inititators were compared with atactic polymers prepared by free radical co-polymerisation of the 1-olefin with sulfur dioxide. Analysis of the XRD patterns showed that the tactic polymers formed more ordered structures in the bulk with longer layer spacings, consistent with a model in which their side chains meet at the tips in contrast with the atactic polymers whose side chains interdigitate. 13C MAS nmr experiments suggest that as tacticity increases so too does the proportion of C-S bonds in the gauche conformation, however the proportion of S-C bonds in the trans conformation falls, in contrast to a reported molecular mechanics study. Finally, DSC measurements on the polymers with longer side chains showed the presence of two endotherms on heating, illustrating definite liquid crystalline behaviour.

The production and characterisation of an antibody to detect the coccidiostat toltrazuril and its metabolite ponazuril.

The production of an antibody to detect toltrazuril or its metabolite ponazuril is complicated due to structural constraints of conjugating these coccidiostats to a carrier protein. Therefore a search was carried out for a compound that shared a common substructure to use as an antigen mimic. The chosen compound, trifluoraminoether, was conjugated to two carrier proteins (HSA and BTG) and used in the immunisation of six rabbits. Two immunogen doses (1 mg and 0.1 mg) were also used. All six rabbits produced an immunological response to the hapten regardless of the carrier protein or immunogen dose used. The most sensitive polyclonal antibody produced, designated R609, was subsequently characterised. This antiserum exhibited an IC50 of 18 ng ml-1 using a competitive ELISA format. Cross reactivity studies show that this serum is specific for toltrazuril and its metabolites (toltrazuril sulfoxide and toltrazuril sulfone) but does not cross-react with other coccidiostats such as halofuginone, nitroimidazoles or nicarbazin. This is the first reported production of an antibody capable of specifically binding toltrazuril and ponazuril.

Second-order NMR spectra at high field of common organic functional groups

The proton NMR spectra of aryl n-propyl sulfides gave rise to what may appear to be first-order proton NMR spectra. Upon oxidation to the corresponding sulfone, the spectra changed appearance dramatically and were clearly second-order. A detailed analysis of these second-order spectra, in the sulfone series, provided vicinal coupling constants which indicated that these compounds had a moderate preference for the anti-conformer, reflecting the much greater size of the sulfone over the sulfide. It also emerged, from this study, that the criterion for observing large second-order effects in the proton NMR spectra of 1,2-disubstituted ethanes was that the difference in vicinal coupling constants must be large and the difference in geminal coupling constants must be small. n-Propyl triphenylphosphonium bromide and 2-trimethylsilylethanesulfonyl chloride, and derivatives thereof, also exhibited second-order spectra, again due to the bulky substituents. Since these spectra are second-order due to magnetic nonequivalence of the nuclei in question, not chemical shifts, the proton spectra are perpetually second-order and can never be rendered first-order by using higher field NMR spectrometers.

SULFOXIDES OF HIGH ENANTIOPURITY FROM BACTERIAL DIOXYGENASE-CATALYZED OXIDATION

Selected strains of the bacterium Pseudomonas putida (previously shown to effect dioxygenase-catalysed asymmetric cis-dihydroxylation of alkenes) have been found to yield chiral sulfoxides from the corresponding sulfides with a strong preference for the (R)- or (S)-configurations but without evidence of sulfone formation; similar results obtained using an Escherichia coli clone (pKST11, containing the Tod C1 C2 B and A genes encoding toluene dioxygenase from P. putida NCIMB 11767) are again consistent with a stereoselective dioxygenase-catalysed sulfoxidation.

Efficient and selective hydrogen peroxide-mediated oxidation of sulfides in batch and segmented and continuous flow using a peroxometalate-based polymer immobilised ionic liquid phase catalyst

The peroxometalate-based polymer immobilized ionic liquid phase catalyst [PO4{WO(O-2)(2)}(4)]@PIILP has been prepared by anion exchange of ring opening metathesis-derived pyrrolidinium-decorated norbornene/ cyclooctene copolymer and shown to be a remarkably efficient system for the selective oxidation of sulfides under mild conditions. A cartridge packed with a mixture of [PO4{WO(O-2)(2)}(4)]@PIILP and silica operated as a segmented or continuous flow process and gave good conversions and high selectivity for either sulfoxide (92% in methanol at 96% conversion for a residence time of 4 min) or sulfone (96% in acetonitrile at 96% conversion for a residence time of 15 min). The immobilized catalyst remained active for 8 h under continuous flow operation with a stable activity/selectivity profile that allowed 6.5 g of reactant to be processed (TON = 46 428) while a single catalyst cartridge could be used for the consecutive oxidation of multiple substrates giving activity-selectivity profiles that matched those obtained with fresh catalyst.