Gamma-aminobutyric Acid: A Novel Tetragonal Phase

<div class="line" id="line-5"> In the tetragonal phase of&nbsp; <img src="http://scripts.iucr.org/logos/entities/gamma_rmgif.gif"/> -aminobutyric acid, C <span style="font-size: 9px;"> 4 </span> H <span style="font-size: 9px;"> 9 </span> NO <span style="font-size: 9px;"> 2 </span> , 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&nbsp; <i> gauche </i> &nbsp;conformation with respect to the C2-C3 bond, in this phase the molecules exhibit a&nbsp; <i> trans </i> &nbsp;conformation. The altered pattern of intramolecular N <img src="http://scripts.iucr.org/logos/entities/ctdot_rmgif.gif"/> 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&nbsp; <i> gauche </i> &nbsp;conformation observed in the monoclinic phase.</div><div class="line" id="line-23"> <br/></div>