Crystalline Forms of Lactose Produced in Acidic Alcoholic Media

Abstract

ABSTRACT Crystalline forms of lactose containing both anomers in the ratios α:β= 4:1 or α:β= 5:3, prepared previously by treatment of α‐lactose monohydrate at 27°C with hydrogen chloride in methanol or 99 wt% aqueous methanol, respectively, are also formed when the reactions, are performed at reflux. The products from α‐lactose monohydrate in acidic ethanol or 99 wt% aqueous ethanol at 27°C are lactose with α:β= 5:3 or anhydrous α‐lactose, respectively. In acidic, absolute or 99 wt% aqueous ethanolic or methanolic media at ‐20°C, the product is anhydrous a‐lactose. The reactions are considered to be solid‐solid transformations, and the products from a‐lactose monohydrate depend on the extent of anomerization during loss of water of crystallization. X‐Ray powder diffraction measurements are of most value in the identification of the various crystalline forms of lactose.