Ferrari P, Nebuloni M, Pelizza G, Gallo G G
Farmaco Sci. 1977 Aug;32(8):560-9.
The three crystalline and one amorphous forms of the title compound, so far isolated, have been characterized by differential scanning calorimetry, thermomicroscopy, infrared spectroscopy and X-ray powder diffraction. From I was obtained by solidification of the melt at 200 degrees; form II by crystallization from water/ethanol 1/1; form III by grinding of II; the amorphous form by rapid cooling of the melt or by evaporation to dryness of a chloroform solution. From II melts of about 200 degrees and immediately crystallizes into form I, which melts at 210 degrees. Form III transforms into I at 165 degrees. The infrared spectra of form I is different from that of forms II and III, while each form has a different X-ray powder diffraction. From consideration of the infrared functional absorption bands, it can be derived that form I is a dimer with H-bonds between the carboxylic groups, forms II and III are monomers with intramolecular H-bond between the carboxylic group and the hydrazide carbonyl, displaying different crystal packings, and the amorphous form is a mixture of both monomers and dimers, the latters in greater amount.
迄今为止分离得到的标题化合物的三种晶型和一种无定形形式，已通过差示扫描量热法、热显微镜、红外光谱和X射线粉末衍射进行了表征。晶型I通过熔体在200℃固化得到；晶型II通过从水/乙醇1/1中结晶得到；晶型III通过研磨晶型II得到；无定形形式通过熔体快速冷却或通过氯仿溶液蒸发至干得到。晶型II在约200℃熔融并立即结晶为晶型I，晶型I在210℃熔融。晶型III在165℃转变为晶型I。晶型I的红外光谱与晶型II和III的不同，而每种晶型都有不同的X射线粉末衍射。从红外官能团吸收带考虑，可以得出晶型I是一种在羧基之间具有氢键的二聚体，晶型II和III是在羧基与酰肼羰基之间具有分子内氢键的单体，表现出不同的晶体堆积，无定形形式是单体和二聚体的混合物，二聚体含量更多。
