1973, Vol.46, No.7


The structure of γ-aminobutyric acid (GABA), C4H9NO2, was determined by single-crystal X-ray diffraction analysis using the data collected on a four-circle diffractometer. The compound was crystallized from an aqueous ethanol solution as needles of the monoclinic space group P21/c with four molecules in the following unit cell; a=7.193, b=10.120, c=8.260 Å and β=111.05°. The structure was solved directly by a symbolic addition method and refined by a least-squares procedure. The final R is 9.3%. The molecular geometry is not a planar trans-zigzag configuration as found in γ-guanidinobutyric acid hydrochloride or homotaurine, but a gauche configuration with respect to Cα–Cβ bond. The expected zwitterionic structure is evident from the locations of the hydrogen atoms in a difference Fourier map, each molecule being connected with three N–H···O hydrogen bonds to form a three-dimensional network.