We now consider the chirality Cσ, bond-flexing
Fσ and bond-axiality Aσ values of the
dominant torsional C1-N7 BCP , see Figure 2 andTable 2(b) . The formally achiral HH glycine comprises a
significant degree of chirality Cσ (= 0.18963) for the
torsional C1-N7 BCP with Sσ character,
see Table 2(a-b) . The magnitude of Cσ increases
similarly with the addition of the D isotope for both the
Sa and Ra stereoisomers, where the
Ra stereoisomer possesses the larger value, both
stereoisomers are Sσ character. The
bond-flexing Fσ is more affected by the substitution of
the D isotope to HH glycine than either of the chirality
Cσ or Aσ of the torsional C1-N7BCP , see Table 2(b) .
The substitution of the T isotope onto the alpha carbon of HH glycine to
replace an H significantly changes Cσ,
Fσ and Aσ values. The T isotope changes
the character of the chirality Cσ toRσ character for both the Saand Ra stereoisomers and there is a pronounced
difference in the magnitude of Cσ, that is significantly
lower for the Sa stereoisomer. The bond-flexing
Fσ increases in magnitude from HH glycine through to HD
glycine and HT glycine, again the HD glycine values are similar for the
Sa and Ra stereoisomers with a slight
preference for the Sa stereoisomer. In addition, the
bond-flexing Fσ changes from Sσcharacter, for HH glycine, to Rσ character for
both the Sa and Ra stereoisomers of HD
glycine and HT glycine. The bond-axiality Aσ increases
in magnitude from HH glycine through to HD glycine and
Sa stereoisomer of HT glycine, again the HD glycine
values are similar for the Sa and Rastereoisomers with a slight preference for the Rastereoisomer. The Aσ value of the Rastereoisomer of HT glycine decreases significantly below that of HH
glycine. The Aσ value of HH glycine possessesSσ character that changes toRσ character for both the Saand Ra stereoisomers of HD glycine and HT glycine. The
stereoisomeric excess Xσ values indicate a very slight
preference for the Ra stereoisomer that possesses
chirality Cσ with Sσ character
for HD glycine and a very strong preference for the Rastereoisomer that possesses chirality Cσ withRσ character for HD glycine.
Table 2(c). Values of the bond-twist Tσ =
[(e1σ∙dr)max ]CCW-
[(e1σ∙dr)max ]CW ,
bond-flexing Fσ and the bond-axiality Aσof the C-H/D/T BCP bond-paths corresponding to the torsional
C1-N7 BCP bond-path of the isotopomers of glycine are presented,
see the caption of Table 2(b) for further details.