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Study of in situ crystallization method, of liquid compounds and their crystal structures

液体化合物及其晶体结构的原位结晶方法研究

基本信息

批准号：
15550006
负责人：
UEKUSA Hidehiro
金额：
$ 2.43万
依托单位：
TOKYO INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15550006/
关键词：
X-ray Structure Analysis Acetic Esters Low melting point compounds melting point alternation in situ crystallization rapid X-ray measurement X線結晶解析酢酸エステル融点の偶奇性

项目摘要

Low melting point acetic esters are important solvent and also used as industrial materials. Therefore, understanding their physical and chemical properties is essential for utilizing these compounds further. As melting point (m.p.) is one of the fundamental property, explaining m.p.behavior of "m.p.alternation" by structural feature is attracting the interests of crystallographers.Different from n-alkane with two functional group (e.g.alkanedicarboxylic acid and alkanediol), acetic esters (AcO(CH_2)n-1 CH_3) show no m.p.alternation behavior in longer alkyl chain region, however, smaller acetic esters show prominent m.p.alternation (-96,-81,-91,-75,-68,-60℃ for n=1 to 6). In order to investigate this behavior of small acetic esters, crystal structures of methyl acetate (n=1) to amyl acetate (n=5) were investigated by single crystal X-ray structure analysis.As they are liquid in room temperature, single crystals were grown by "in situ crystallization" method on the R-AXIS RAPID diffractometer. The diffraction data were collected at 93K within short measurement time just after a single crystal was obtained. Their crystal structures were determined in good R values (R1=0.039-0.044).Investigation of the crystal structures revealed that both C-H...O type hydrogen bonds between acetic groups and van der Waals interactions between alkyl chains play important role to stabilize the structure. Iwo distinctive H-bond motif recognized were "dimer" (n=2,4,5) and "tetramer" (n=1,3) structures around inversion center. Because of this packing differences, methyl (n=1) and propyl (n=3) acetates have fewer number of H-bond comparing to other acetates. Therefore, lower m.p.of them is caused by this kind of inefficiency of crystal packing

低熔点乙酸酯是重要的溶剂，也是重要的工业原料。因此，了解它们的物理和化学性质对于进一步利用这些化合物至关重要。熔点（m. p.）分子量是其基本性质之一，用结构特征解释分子量的“交替”行为正引起晶体学家的兴趣。（例如链烷二羧酸和链烷二羧酸）、乙酸酯（AcO（CH_2）n-1CH_3）在较长的烷基链区没有熔点变化行为，而较小的乙酸酯则有明显的熔点变化（-96、-81、-91、-75、-68、-60 ℃，n=1至6）。为了研究小分子乙酸酯的这种行为，利用室温下为液态的乙酸甲酯（n=1）和乙酸戊酯（n=5），在R-AXISRAPID衍射仪上用“原位结晶”法生长了单晶，用X射线单晶结构分析法研究了它们的晶体结构。在获得单晶后的短测量时间内在93 K下收集衍射数据。它们的晶体结构具有良好的R值（R_1 =0.039-0.044）。乙酸基团间的O型氢键和烷基链间的货车范德华力对结构的稳定起着重要作用。伊沃的氢键结构是围绕着反转中心的“二聚体”（n= 2，4，5）和“四聚体”（n= 1，3）。由于这种包装差异，与其他乙酸酯相比，乙酸甲酯（n=1）和乙酸丙酯（n=3）具有较少的H-键数。因此，它们的低熔点是由这种晶体堆积的低效率造成的