Gluconic acid-6-lactone

The initial product is gluconic acid lactone. Perlmutter-Hayman and Persky showed that at pH 1.25 and 0 °C, the rate coefficient for attack of hypobromous acid on glucose is 2.04x10" l.mole" sec" (the corresponding rate coefficient for attack by molecular bromine is 7 times greater). The rate coefficients both for attack by HBrO and Br2 increase with increase of pH beyond 3. This increase is attributed to the much greater reactivity of the glucose anion. 

Lactobionic acid. This derivative is produced by oxidation of the free carbonyl group of lactose (Figure 2.25), chemically (Pt, Pd or Bi), electro-lytically, enzymatically or by fermentation. Its lactone crystallizes readily. Lactobionic acid has found only limited application its lactone could be used as an acidogen but it is probably not cost-competitive with gluconic acid- -lactone. It is used in preservation solutions for organs prior to transplants. 

The main product of reaction between D-ribono-y-lactone and benzaldehyde dimethylacetal is the 2,3-acetal and not the 2, -acetal of the 6-lactone as previously proposed.Long chain aliphatic amines (Cg-C g) have been condensed with D-gluconic acid lactone to give amphlpathic products which form gels at low concentrations in aqueous solution. The morphology of the gels has been Investigated by electron microscopy. 

Colourless crystals m.p. I25°C, soluble in water and alcohol. In aqueous solution forms equilibrium with its lactones. Gluconic acid is made by the oxidation of glucose by halogens, by electrolysis, by various moulds or by bacteria of the Acetobacter groups. 

Note D-Gluconic acid and other aldonic acids exist in equilibrium with lactone structures. 

The ability of bacteria - particularly Pseudomonas spp. and Glucottobader spp. - to produce gluconolactone and gluconic acid has been exploited and the process is used commerdally, mainly in the production of the lactone. 

Precipitation of Fe(IIl) compounds from acid solutions as the pH increases above 2.2 is a particular problem. Complexing agents that have been used include 5-sulfosalicylic acid and citric acid (136) dihydroxymaleic acid (137) ethylenediaminetetraacetic acid (138) lactic acid (138) blends of hydroxylamine hydrochloride, citric acid, and glucono-delta-lactone (139) nitriloacetic acid blends of citric acid and acetic acid lactic acid and gluconic acid (140). 

---