Dobson A J, Gerkin R E
Department of Chemistry, Ohio State University, Columbus 43210, USA.
Acta Crystallogr C. 1996 Dec 15;52 ( Pt 12):3075-8. doi: 10.1107/s0108270196010001.
In the tetragonal phase of gamma-aminobutyric acid, C4H9NO2, the single type of molecule adopts a partially folded zwitterionic form. Whereas in the previously characterized monoclinic phase the partially folded zwitterionic molecules exhibit a gauche conformation with respect to the C2-C3 bond, in this phase the molecules exhibit a trans conformation. The altered pattern of intramolecular N...O distances may be of significance with respect to the neurotransmission behavior of this substance. In addition to three strong hydrogen bonds involving the three H atoms bound to the N atom, as in the monoclinic phase, there is a fourth weaker one which results in a two-center bifurcated bond. There is also evidence suggestive of an intramolecular bridging hydrogen bond involving the N atom, an O atom and a methylene H atom, as previously proposed as a stabilizing factor for the gauche conformation observed in the monoclinic phase.
在γ-氨基丁酸（C4H9NO2）的四方相中，单一类型的分子呈现出部分折叠的两性离子形式。而在先前表征的单斜相中，部分折叠的两性离子分子相对于C2-C3键呈现出 gauche 构象，在该相中分子呈现出反式构象。分子内N...O距离的改变模式可能与该物质的神经传递行为有关。与单斜相一样，除了涉及与N原子相连的三个H原子的三个强氢键外，还有第四个较弱的氢键，这导致了一个双中心分叉键。也有证据表明存在一个涉及N原子、一个O原子和一个亚甲基H原子的分子内桥连氢键，如先前提出的作为在单斜相中观察到的gauche构象的稳定因素。
