[IR spectral research on erythromycin mono- and dihydrates]

The IR spectra of crystalline and amorphous forms of erythromycin monohydrate and dihydrate were investigated and their characteristic spectral features were described. Differences in the system of the intermolecular hydrogen bonds and in the level of perfection of the crystalline structures of the monohydrate and dihydrate were detected. It was shown that both crystallohydrates of erythromycin might exist in two polymorphous modifications. The crystalline structure of the low temperature modification of the monohydrate was of low perfection. At 75-80 degrees C irreversible polymorphous conversion of erythromycin monohydrate and erythromycin dihydrate accompanied by changes in the hydration water state was observed. The crystalline structures of high temperature modifications of the erythromycin crystallohydrates were identical.