Study On Crystal Growth、 Character And Structure Of Esters Of Maleate Acid For X-ray Spectroscopy

Tetradecyl hydrogen maleate (THM), hexadecyl hydrogen maleate (HHM) and octadecylhydrogen maleate (OHM) are a series of analyzer crystals with long-carbon chains. This kind ofcrystals has high resolution, suitable reflectivity and reasonable mechanical properties. And thespace distances become larger with the increase of carbon chains. From the character of crystals,this paper discussed the relationship of the three crystals′habits, property and structure. It didgive some directions in the X-ray analyzer crystals.In order to obtain the high-quality crystal, the pure raw materials are quite important. In afivefold excess of benzene (based on weight of the alcohol), pure THM, HHM and OHM wereprepared by reaction of maleic anhydride and corresponding alcohol with the stoichiometricratio at about95-100°C. Then the basic physical and chemical properties of raw materials forcrystal growth were determined by the infrared spectroscopy, X-ray power diffraction, thermalanalysis, and so on. Through the crystallization experiments, the relations of the three crystalswere got and the best solvent was benzene for crystal growth. The single crystals were THM，HHM and OHM were got using the method of slow cooling in solution.Moreover, the nucleated experiment for the three crystals were carried out, and thenucleated induction period were measured under differ super saturation, also the nucleate rateaffected by the temperature and super saturation ratio was discussed. According to the classicalhomogeneous nucleation theory, the crystal surface tension, nucleation free energy and thecritical nucleation radius were calculated. The results show that the solution tends tospontaneously nucleate can be overcome while the low-temperature is selected and a smallersupersaturating ratio is controlled.In order to further understand the relationship about the crystal structure, performance andcomposition, this paper also carried out the single crystal structure determination for thecrystals, the results indicate that the three crystals are triclinic, space group P1_. The twomolecular united together by the link of hydrogen bond forming a structural motif. But the cellvolumes for the three compounds are bigger with the increasing of the carbon chain length ofthe ester in the three compounds. The growth cell suffers the bigger diffusion resistance to enterthe lattice position. The relevant growth rates are decreased with the increasing of long carbonchains. The kinetics experiments had used the method of dynamic loop, measuring the growthrate of（031—）and （111—）. The results showed that the growth rates reduced with the longer carbon chains by the comparative of THM, HHM and OHM. The growth rate of a and c-axisdirections are faster than that on b-axis direction. The theory of crystal growth in the aqueoussolution preliminarily explains the phenomena existing in the process of crystal growth. Theseries of work has instructed the research of X-ray dispersing crystal of maleate acid. Thesethree title esters should be a good candidate for homologous X-ray analyzer crystals.