Zhu Jing, Ren Zhiyong, Zhang Guobao, Guo Xiaozhan, Ma Dezhu
Henan Key Lab of Fine Chemicals, Zhengzhou 450002, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2006 Feb;63(2):449-53. doi: 10.1016/j.saa.2005.05.030. Epub 2005 Aug 19.
In the present paper, the FTIR band and H-bond differences between the two dihydroxy-based carboxyls, 2,2-hydroxymethyl butanoic acid (hereinafter abbreviated to DMBA) and 2,2-hydroxymethyl propionic acid (hereinafter abbreviated to DMPA), were analyzed based on the crystal structure as well as the relation between H-bond and FTIR band of DMPA. In addition, the energy and length of the H-bonds formed between COOH, between OH, between COOH and OH were also calculated via molecular modeling. The results showed that three H-bond types existing in DMPA while only two in DMBA. The COOH pattern and H-bond type in DMBA and DMPA can be preliminarily judged according to the band position and relative strength of the nuOH and nuCOOH in FTIR spectrum. The H atom in COOH is a stronger H-bond donor than that in primary OH, while the O atom in primary OH is a stronger H-bond acceptor than that in COOH. The H-bond formed by two COOH is, therefore, weaker than that formed by COOH (as donor) and OH (as acceptor), which makes nuC=O shift to lower frequency in DMPA than in DMBA.
在本论文中，基于晶体结构以及2,2-羟甲基丙酸（以下简称为DMPA）的氢键与傅里叶变换红外光谱（FTIR）谱带之间的关系，分析了两种基于二羟基的羧基化合物，即2,2-羟甲基丁酸（以下简称为DMBA）和2,2-羟甲基丙酸之间的FTIR谱带和氢键差异。此外，还通过分子建模计算了羧基之间、羟基之间、羧基与羟基之间形成的氢键的能量和长度。结果表明，DMPA中存在三种氢键类型，而DMBA中仅存在两种。根据FTIR光谱中νOH和νCOOH的谱带位置和相对强度，可以初步判断DMBA和DMPA中的羧基模式和氢键类型。羧基中的氢原子作为氢键供体比伯羟基中的氢原子更强，而伯羟基中的氧原子作为氢键受体比羧基中的氧原子更强。因此，由两个羧基形成的氢键比由羧基（作为供体）和羟基（作为受体）形成的氢键弱，这使得DMPA中νC=O的频率比DMBA中的更低。
