Solid State Transformations of α-Lactose Monohydrate in Alcoholic Media

Crystalline a-lactose monohydrate was obtained from aqueous methanol or acetone solutions, and the amount of methanol or acetone retained in the crystals was measured by gas chromatography. Established procedures were used for conversion of a-lactose monohydrate containing methanol into anhydrous a-lactose, mixed anomeric form of lactose, and/3-lactose in neutral, acidic, and alkaline ethanolic media, respectively. The amount of methanol retained in the products was measured. Similarly, the amount of acetone retained in anhydrous a-lactose prepared by conversion of the acetone-containing a-lactose monohydrate in methanol was measured. The results were consistent with the view that the transformations are solid state reactions and not dissolution followed by recrystallization.