Study and characterization of L–arginine halides (HCl/HBr)

Abstract The systems of L-arginine with halogen acids (hydrochloric and hydrobromic) in water solvent under the influence of acoustic waves and without them were investigated in this study. Nine compounds were obtained and identified: (I) L-arginine hydrobromide, (II) L-arginine hydrochloride (space group P1), (III) L-arginine hydrobromide, (IV) L-arginine hydrochloride (sp. gr. P21), (V) L-arginine hydrobromide monohydrate (sp. gr. P21), (VI) L-arginine hydrochloride monohydrate (sp. gr. P21), (VII) L-arginine dihydrobromide monohydrate (sp. gr. P1), (VIII) L-arginine dihydrochloride monohydrate (sp. gr. P212121) and (IX) L-arginine dihydrochloride (sp. gr. P21), of which (I), (III) and (IX) crystals were obtained and studied for the first time. The conditions for the formation of all the compounds were described. The FT-IR ATR spectra of obtained crystals were presented and compared. Based on the IR spectra, it can be assumed that the crystals of (II) and (I) are isostructural, the same for (IV) and (III). The crystal and molecular structure of L-arginine dihydrochloride (sp. gr. P21) was studied by X-ray diffraction method. Thermal and other properties were investigated. The efficiency of the second harmonic generation of all the crystals was measured and compared with that of the KDP.