Mechanism of Racemisation

Abstract

IN some work shortly to be published, we have shown that the racemisation of Rochelle salt by caustic soda is accompanied, and probably conditioned, by complex formation. It was previously observed by Thomsen,¹ and confirmed by Winther ² and by ourselves, that the rotation of sodium tartrate is reduced by the addition of alkali. We have, therefore, in continuation of our work on racemisation, investigated the behaviour of the specific rotation of Rochelle salt with increasing concentrations of alkali, and we find that the specific rotation of Rochelle salt eventually becomes strongly negative. In other words, the complex is itself lævo-rotatory, and the progressive reduction in the rotation is due to increasing formation of complex with addition of alkali. The rotation changes sign at an alkali concentration of 10 N caustic soda (approx.). It should be stressed that these changes of rotation are prior to any racemisation, in the ordinary sense of the term, the rotations being quite stable in the strongest alkali, provided the solutions are kept at room temperature.