The inversion reaction coordinate of free amino acids (alanine, aspartic acid) have been computationally calculated by semi-empirical methods AM1. A transition state for free alanine and aspartic acid were obtained as a three membered ring in which the α-C-H and α-C-CH3 are slightly elongated, 1.2 and 2.17 Å respectively in the alanine transition state. The activation energy of alanine is 77.52 kcal/mol in the gas phase and 76.66 kcal/mol in aqueous phase, and for aspartic acid is 54.87 kcal/mol in the gas phase and 50.86 kcal/mol in aqueous phase.
International Letters of Chemistry, Physics and Astronomy (Volume 12)
M. E. Mohamed "Theoretical Inversion of Amino Acids (Alanine and Aspartic Acid) by Semi-Empirical Methods", International Letters of Chemistry, Physics and Astronomy, Vol. 12, pp. 37-44, 2013