Theoretical analysis of fluoroglycine conformers

Seven different optimized conformers of alpha-fluoroglycine (H2NCHFCOOH) we re obtained from ab initio calculations. Some of these conformers are excep tionally stable compared to similar conformers of glycine. Conformers in wh ich the lone pair of electrons on the nitrogen atom are antiperiplanar to t he C-F bond are more stable than conformers that do not have such an arrang ement. The stability difference between conformers with such an arrangement and conformers that have the lone pair of electrons synperiplanar to the C -F bond is about 27 kJ/mol (calculated at the MP2/6-31+G* level). Conformer s that have the lone pair of electrons antiperiplanar to the C-F bond posse ss a longer C-F bond, a shorter C-N bond, and sp(2)-like amino bond angles. For some conformers an unusual hydrogen bond involving the acidic carboxyl ic acid hydrogen and the electronegative fluorine atom is observed. (C) 200 0 John Wiley & Sons, Inc.