D.M.W. Anderson

Applications of infrared spectroscopy : The determination of small amounts of alcohols in aqueous solution

Abstract Recent developments in methods of analysing dilute solutions of alcohols are briefly reviewed, and a simple modification to the Zeisel reaction is described. This permits the analysis, on a 1 -ml aliquot, of dilute aqueous solutions of alcohols alone or in admixture.

Structural analysis of the gum polysaccharide from anacardium occidentale

Abstract The gum exudate from Anacardium occidentale contains galactose (61 %), arabinose (14 %), rhamnose (7 %), glucose (8 %) and glucuronic acid (5 %) in addition to small amounts ( component) and 6-O-β-D-galactopyranosyl-D-galactose (minor component). Degraded gum A, prepared by controlled acid hydrolysis, contained galactose, glucose, and uronic acid. A Smith-degradation of degraded gum A gave degraded gum B, which contained only galactose. Sequential Smith-degradations of Anacardium occidentale gum, and methylation analyses of the gum and of its degradation products indicated a highly-branched galactan framework consisting of chains of β-(1–3)-linked D-galactose residues branched and interspersed with β-(1–6) linkages. Arabinose is present as end-groups or in short (1–2)-linked chains up to five units long. Glucose, rhamnose, mannose xylose, and uronic acid are all present as end-groups.

Studies on uronic acid materials : The simultaneous determination of uronic acid and alkoxyl groups in polysaccharides by reflux with hydriodic acid

Abstract A reaction period of 2.5 h is required for the decarboxylation of uronic acid groups with 19% (w/w) hydrochloric acid, but 55% (w/w) hydriodic acid gives complete decarboxylation in 1.5 h. This rapid reaction can be carried out in a standard Zeisel reaction flask and condenser. Vapour phase infra-red spectroscopy gives a specific determination of the carbon dioxide evolved, and facilitates simultaneous determinations of any alkoxyl groups present. The proposed method is particularly useful for pectins and plant gums; it gives greater sensitivity and reproducibility than previous methods.

Studies on materials containing uronic acid—I: An apparatus for routine semi-micro estimations of uronic acid content

Abstract The design features of some of the many forms of apparatus previously proposed for the estimation of uronic acids using the Lefevre and Tollens decarboxylation reaction have been critically examined. Several sources of error have been eliminated, and a simple, yet reliable, apparatus facilitating routine estimations on a semi-micro scale has been developed. Details of the experimental procedure and apparatus finally devised are given.

Applications of infrared spectroscopy—IV1: The causes of anomalous alkoxyl determinations given by sugars and polyhydric alcohols

Abstract The volatile reaction products from Zeisel determinations on sugars and related compounds have been identified. One of the products from certain common sugars is 2,5 dimethylfuran, which interferes with the Viebock iodometric determination ofalkyl iodide, and has been shown to be a contributing cause of apparent alkoxyl values. Suggestions that hexyl iodide is evolved from sugars and that vinyl iodide is a product from polyhydric alcohols have been disproved.

Applications of infrared spectroscopy—III: The simultaneous determination of methoxyl and ethoxyl groups

Abstract Quantitative vapour-phase infrared spectroscopy permits the simultaneous determination of methoxyl and ethoxyl groups as alkyl iodides or bromides : when the methoxyl/ethoxyl ratio exceeds 4:1, determinations are only possible as bromides. The reaction-time involved is 30 min. Results, correct to within ±1 % for each alkoxyl group, can be obtained on the micro-scale. The presence of sulphur does not interfere.

Studies on uronic acid materials—II1: The variation in composition of gum nodules from combretum leonense

Abstract Several gum nodules from the Nigerian tree Combretum leonense have been individually investigated. The amount of material present in each nodule has permitted a study of the variation in constitution of both crude and purified forms of the gum. The variations found are much greater than can be explained by analytical error. They are considered to indicate that inter-nodule differences in fine structure exist.

Applications of infrared spectroscopy—II: Observations on some aspects of the zeisel alkoxyl determination

Abstract A sensitive infrared method for quantitative determination of vapours has been used to study some of the reaction variables in the Zeisel alkoxyl determination. Several conflicting reports in the literature have been clarified. Reaction conditions giving rapid and accurate determinations on solids and volatile liquids, even in presence of large sulphur concentrations, are described: for determinations on vanillin the standard deviation is 0.16%. Interaction between alkyl iodides and sulphuretted hydrogen has been found to occur only in aqueous solutions; the use of soda-asbestos as a solid scrubber therefore has fundamental advantages over aqueous solutions, and gives excellent results.

The degradation of acidic polysaccharides during structural analysis involving permethylation

Abstract The extent of the degradation of gum exudates from Acacia and Combretum spp. in different methylation procedures has been studied. Methylation of C. nigricans gum with the sodium hydride—iodomethane—dimethyl sulphoxide system caused losses of rhamnose and galacturonic acid that did not occur with two other systems. In a study of the extent of the degradation suffered by the gums from Acacia seyal and Combretum nigricans during methylation with the Haworth method, partially methylated products, isolated at intervals during the reaction, were analysed: C. nigricans gum suffered much more rapid and extensive degradation than A. seyal gum; this degradation must be taken into account in structural analyses of gums of the Combretum genus.

The determination of mixtures of hydrazine, monomethyl-hydrazine and 1,1-dimethylhydrazine

Abstract Admixtures of hydrazine and monomethylhydrazine (MMH) and of hydrazine with 1,1-dimethylhydrazine (UDMH) can be analysed by a titrimetric method in which two aliquots are titrated with potassium, iodate: ( a ) directly to determine the sum of the hydrazines present, and ( b ) to determine the MMH or UDMH after selective reaction of the hydrazine with salicylaldehyde. For ternary mixtures, three aliquots are required: the sum of the hydrazines is determined with potassium iodate; the sum of MMH and UDMH is found after selective reaction of the hydrazine present with salicylaldehyde ; and the UDMH content is obtained by non-aqueous solvent titrimetry after reaction of both hydrazine and MMH with acetic anhydride in dioxane.