Theoretical analysis of fluoroglycine conformers

Seven different optimized conformers of α-fluoroglycine (H2NCHFCOOH) were obtained from ab initio calculations. Some of these conformers are exceptionally stable compared to similar conformers of glycine. Conformers in which the lone pair of electrons on the nitrogen atom are antiperiplanar to the CF bond are more stable than conformers that do not have such an arrangement. The stability difference between conformers with such an arrangement and conformers that have the lone pair of electrons synperiplanar to the CF bond is about 27 kJ/mol (calculated at the MP2/6-31+G* level). Conformers that have the lone pair of electrons antiperiplanar to the CF bond possess a longer CF bond, a shorter CN bond, and sp2-like amino bond angles. For some conformers an unusual hydrogen bond involving the acidic carboxylic acid hydrogen and the electronegative fluorine atom is observed. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 426–431, 2000