Effects of Grinding on the Physical and Chemical Properties of Crystalline Medicinals with Microcrystalline Cellulose. IV. Comparison of the IR Spectra of Medicinals in the Solid State and in Solution

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The infrared (IR) spectra of aspirin, benzoic acid, and salicylic acid, which exhibit intermolecular hydrogen bonding in their crystals, were measured in dilute CCl_4 solution. Two carboxyl carbonyl stretching bands were observed in these spectra, due to monomeric and dimeric species. IR spectral changes of carbonyl stretching bands attributed to hydrogen bonding between monomeric medicinals and 1-butanol were also measured. This hydrogen-bonded band was always observed at higher frequency than the intermolecular hydrogen-bonded band (dimer), and at lower frequency than the band of the monomeric medicinal. The shifts of the carbonyl stretching bands measured in the ground mixtures were compared with those of the solution spectra. In the ground mixtures, it was confirmed that the medicinal molecules were dispersed monomolecularly and were hydrogen-bonded with hydroxyl groups of cellulose or β-cyclodextrin molecules. The new band observed at 1748 cm^<-1> in the β-cyclodextrin dispersed system of aspirin was considered to be due to overlapping of (i) the band of the acetoxyl group of aspirin hydrogen-bonded with hydroxyl groups of β-cyclodextrin, and (ii) the free carboxyl band of aspirin.
社団法人日本薬学会の論文
1980-02-25