Characterization and Structure Analysis of Thiamine Hydrochloride Methanol Solvate

oThiamine hydrochloride (THCl) forms a monomethanolate (MM) upon exposure of crystalline thiamine phases (thiamine hydrochloride hemihydrate/HH, nonstoichiometric hydrate/NSH, and anhydrate/AH) to anhydrous methanol (solvent and vapor). Desolvation or MM at 50-80 degrees C resulted in the formation of a poorly crystalline intermediate which crystallized to AH at elevated temperatures (>= 150 degrees C). When exposed to water vapor (11-75% RH, RT), MM transformed to HH (NSH was detected at <= 40% RH), while exposure to polar solvent vapor resulted in direct formation AH. MM was stable in the presence of nonpolar (benzene and hexane) solvent vapor. Crystal structure analysis revealed a near identical H-bonding network in the two solvate (MM, and NSH with 1 mol water/mol THCl) lattices. The structure of MM as well as the solvent properties were identified as the key;actors influencing both the kinetics of desolvation of MM and the nature of the product phase.