MUTAROTATIOK. I. J-elocity of RIutarotation of a Glucose in Methyl Alcohol and Water B Y FREDERICK F'ALLISER WORLET .IND J O H S CLARK ASDREWS
The mutarotation of sugars has received a great deal of attention during recent years. and various explanations of the mechanism of the action have been advanced, but none of these esplanations has been found entirely satisfactory, nor have they received wide acceptance. Baker, Ingold and Thorpel stimulated interest in the problem b>- an attempted critical investigation of the esplanations of the mechanism of mutarotation advanced by E. F. ilrmstrongZjLolvry3 and Jacobsen and Stelzner4. The present investigation was undertaken with a vieir to criticising conclusions arrived at by Raker, Ingold and Thorpe. Lon-ryj in the meantime has adversely criticized their work and has pointed out that their mathematical investigation of the problem is unsound. He also advanced the subject by pointing out the similarity between mutarotation and the hydrolysis and saponification of esters. In spite of the large amount of experimental work already carried out by numerous investigators it would appear that all the facts necessary for the solution of the problem have not been available, and a considerable amount of work has recently been carried out using various sugars and their methylated and other derivations in various solvents.6 The esperimental basis of the work of Baker. Ingold and Thorpe was the effect of mater on the velocity of mutarotation of a glucose in methyl alcohol. The proportion of water did not exceed and no account was taken, as was pointed out by Lowry, of minute accounts of catalysts present. I t appeared desirable to ascertain the velocity in mixtures of highly purified methyl alcohol and water in all proportions. This has been done in the present investigation but although special care was taken in the purification of materials used it is not likely that all traces of catalytic substances have been removed. Even were it possible to obtain the substances absolutely pure, unavoidable contact with the atmosphere introduces impurities likely to have some catalytic action. Purification of Materials a Glucose was three times recrystallised from specially purified ethyl alcohol, final traces of alcohol being removed by careful warming under reduced pressure. The product was stored in a flask connected to a second flask containing phosphorus pentoside. J. Chem. Soc.. 125, 268 (1924". J. Chem. Soc., 85, I j67 (1904). J. Chem. Soc., 83, 1316 '190.3'. "Organische Chemie", 2nd Ed., (1'8 2 , 866, 910. 91j , 927. E J. Chem. Soc.. 127, 1371 i192j~i. f i L o n r y and Richards: J. Chem. Soc.. 127, 1 3 8 j ; Lowry and Faulkner: 2883 ' 1 9 2 j l ; Jones and Lowry: 128, 7 2 0 ; Faulkner and Lowry: 1938 (1926). I
MUTAROTATION
743
3Llethyl alcohol A. R. obtained from British Drug Houses, was found to contain traces of acetone. The acetone was converted into iodoform by means of iodine and caustic potash. After filtering, the liquid was refluxed for eight hours over freshly burnt lime. It was then distilled through a Young's Evaporator column of eight sections and the middle portion collected in a waxed vessel after condensat,ionin a condenser having an inner tube of silica. The boiling point was constant 64.j6-64.57OC D2j0,. = 0.78646. Water was purified in the usual way and was kept only for short periods and always in waxed vessels. dppuratzts. The polarimetric apparatus, thermostat, and temperature control were similar to those previously described by one of us1 and the source of illumination was a Cooper Hen
