The mutarotation and ionization of D‐glucose in alkaline solution II

Abstract

AbstractMeasurements of the rate of mutarotation of D‐glucose in unbuffered alkaline solutions, with a pH meter, have been continued with a more sensitive instrument. All available data have been reinterpreted on the basis of the following assumptions: (a) The mutarotation in alkaline solution of D‐glucose is first order in the glucose concentration and the specific rate constant is given by (b) The catalytic constants kGα and kGβ are related by an expression derived from the Brønsted catalysis law where c was taken as equal to 0.4. It has been shown that the latter assumption (b) could eliminate the difficulty experienced in the preceeding communication 1) of a kOH value which was strongly dependent on the glucose concentration.The results provide new values for the catalytic constants of hydroxyl ions, of the α and β glucosate ions, and for the hydrolysis and ionization constants of α and β D‐glucose. Corresponding equations have been given.A critical discussion of the errors in the method has been included.The results prove, among other things, that the reason for the greater acidity of β D‐glucose than of the corresponding α form (as established in this investigation) lies in the considerable difference in entropy change upon ionization for the two different isomers.