The effect of the presence of a deuterium (D) or tritium (T) isotope
bonded to the alpha carbon of glycine is determined without the need to
apply external forces e.g. electric fields or using normal mode
analysis. Isotopic effects were accounted for using the mass-dependent
diagonal Born-Oppenheimer energy correction (DBOC) at the CCSD level of
theory. We calculated the stress tensor trajectories of the dominant C-N
bond within next generation quantum theory of atoms in molecules
(NG-QTAIM). S-character chirality was discovered using the stress tensor
trajectories, instead of the Cahn–Ingold–Prelog (CIP) rules, for
ordinary glycine. The S-character chirality was preserved after the
substitution of the H on the alpha carbon for a D isotope but
transformed to R-character chirality after replacement with the T
isotope. This reversal of the chirality depending on the presence of a
single D or T isotope bound to the alpha carbon adds to the debate on
the nature of the extraterrestrial origins of chirality in simple amino
acids. We demonstrate that NG-QTAIM is a promising tool for
understanding isotopic induced electronic charge density changes, useful
in analysis of infrared (IR) or circular dichroism (CD) spectra
explaining changes in mode couplings and bands intensities or sign.