Richard A. Hancock

Structure of the levan elaborated by Streptococcus salivarius strain 51: An application of chemical-ionisation mass-spectrometry

The polysaccharide elaborated by Streptococcus salivarius strain 51 contains beta-D-fructofuranose residues linked through positions 2 and 6, as well as 1, 2, and 6. The approximate numbers of terminal, non-reducing D-fructofuranose residues and those linked through positions 2 and 6, and through 1, 2, and 6 in the average repeating-unit are 1, 7, and 1, respectively. The branches through the beta-(2 leads to 1)-linkage contain up to at least four D-fructofuranose residues. Chemical-ionisation mass-spectrometry aids the assignment of structures to O-acetyl-O-methylalditols obtained in methylation analysis.

The interaction of hexafluoroacetic anhydride with methane sulphonic acid and with sulphuric acid

Abstract The reaction between methanesulphonic acid and hexafluoroacetic anhydride yields methanesulphonyltrifluoroacetic anhydride. The reaction of an excess of sulphuric acid with hexafluoroacetic anhydride in a 1:1 mixture of nitromethane and dichloromethane results in the formation of trifluoroacetyl hydrogen sulphate. However, at higher concentrations of hexafluoroacetic anhydride, bis-trifluoroacetyl sulphate is formed. The rates of the reactions are dependent on the concentration of hexafluoroacetic anhydride and independent of the concentration of the acids when these are in excess. At low concentration of sulphuric acid a more complex relationship is observed.

Evidence for non-biradicaloid transition states in Diels–Alder reactions

Linear free energy relationships and a measure of the degree of asynchronicity in Diels–Alder reactions of cyclopentadiene with some arylsulphonyl ethenes support a synchronous mechanism.

Diaryl sulphones : a synthesis from arylthalliums

Abstract 2,4-dimethyl-, 2,4,6-trimethyl- and 4-chloro- phenylthallium bis (trifluoracetate) separately react with cupric benzenesulphinate to give unsymmetrical sulphones. An explanation for the requirement of Cu2+ in the reaction is given.

Novel sulphonylating reagent: sulphuric acid–hexafluoroacetic anhydride

A mixture of sulphuric acid and hexafluoroacetic anhydride is an efficient reagent for the sulphonylaction of aromatic compounds.