| Popis: |
Kilimi (1866) first showed that an aldehyde group was present in glucose, by forming the cyanhydrin, which on hydrolysis and reduction gave n-heptoic acid. Glucose was later represented by the straight chain, “Fischer Projection Formula” and this was in general use until 1926, when Haworth proposed the pyranose ring structure for sugars. [Diagram] A ring formula was given to the isomeric methyglucosides, by Fischer. (These derivatives were obtained by the reaction of glucose with 0.5% methyl alcoholic hydrogen chloride at 80%.) Fischer did not extend the ring formula to glucose itself and he wrongly assumed that the ring was a (1,4) or butylene oxide ring. By a consideration of the phenomenon of mutarotation, later workers were able to show that sugars themselves had ring structures. A study of the oxidation products of tetramethylglucose showed that normal glucose had a (1:5) ring. This pyranose ring was represented by a hexagonal formula and X-ray evidence in support of it has been obtained. |
