n = 4
glycine (C1-N7 ){ 0.18963[Sσ] ,
-0.33054[Rσ] ,
0.17961[Sσ]}
glycine (C1-C2 ){ 0.05690[Sσ] ,
-0.01130[Rσ] ,
0.00133[Sσ]}
We now present the quantification of the chirality Cσ,
which is defined in terms of the most preferred component,e1σ.dr → bond-twist, for the CCW and CW
torsions. The presence of a positive value for the glycine chirality
Cσ demonstrates that Sσcharacter dominates over Rσ character for the
Tσ(s ) of the dominant torsional C1-N7 BCP ,
see Table 1(a) . This is because the CCW torsion occurs more
readily, which is apparent from thee1σ.dr component being 5.51% larger
than that of the CW torsion, see Table 1(a) . The corresponding
value of the chirality Cσ for the torsional C1-C2BCP also demonstrates Sσ character,
where the CCW e1σ.dr component is 3.16
% larger than the CW e1σ.dr component,
see Table 1(b) . For the glycine torsional C1-C2 BCP the
chirality Cσ = 0.057, bond-flexing Fσ =
-0.011 and the bond-anharmonicity Aσ = 0.0013, seeTable 2(b) . Although these values are small compared to the
Cσ, Fσ and Aσ values of
the stronger torsional bond, i.e. the torsional C1-N7 BCP , they
are more comparable to Cσ = 0.078 and Aσ= 0.003 of the torsional C1-C2 BCP of the S-stereoisomer of
lactic acid and Fσ = -0.030 of the R-stereoisomer of
alanine, compare Table 1(b) with Table 2(b) . For
lactic acid the S-stereoisomer possesses a larger value of
Cσ than the R-stereoisomer, consistent with earlier
work[30], see Table 2(b) . The corresponding
Cσ results for the alanine torsional C1-C2 BCPindicate a preference for the R-stereoisomer, in keeping with
experiment[60].