Low Temperature Crystal Structure of N-Acetyl-l-Glutamic Acid: Comparison with the DFT Calculated Structure

Abstract

N-acetyl-l-glutamic acid, crystallizes in the orthorhombic space group P212121 with unit cell parameters a = 4.747(3), b = 12.852(7), c = 13.906(7) A, V = 848.5(8) A3, Z = 4, density (calculated) = 1.481 mg/m3, linear absorption coefficient 0.127 mm−1. The crystal structure determination was carried out with MoKα X-ray data measured with liquid nitrogen cooling at 100(2) K temperature. In the final refinement cycle the data/restraints/parameter ratios were 1,691/0/131; goodness-of-fit on F2 = 1.122. Final R indices for [I > 2sigma(I)] were R1 = 0.0430, wR2 = 0.0878 and R indices (all data) R1 = 0.0473, wR2 = 0.0894. The largest electron density difference peak and hole were 0.207 and −0.154 eA−3. Details of the molecular geometry are discussed and compared with a model DFT structure calculated using Gaussian 98. The low temperature X-ray structure of N-acetyl-l-glutamic acid, including absolute configuration, is described. Comparison with the DFT structure is also discussed. Molecular conformation of N-acetyl-l-glutamic acid: (a) drawn with MERCURY [22] and (b) surfaces drawn with VMD [26].