Consideration of the non-torsional C1-H/D/T BCPs is presented inFigure 3 , Table 2(c) and Table 2(d) . For HD glycine the values of Tσ, Fσ and Aσ are all slightly larger for C1-D3 BCP (the Ra stereoisomer) than for the corresponding Tσ, Fσ and Aσ values of C1-H3 BCP (the Sa stereoisomer), seeTable 2(c) . The same correspondence is found for the C1-D10BCP. This does not hold for the HT glycine where the opposite effect is found for the C1-T10 BCP , where all three of the Tσ, Fσ and Aσ values are smaller for the C1-T10 BCP compared with the C1-H10 BCP . A mixed effect is found for the dominance of the Tσ, Fσ and Aσ values of the C1-T3 BCPcompared with the C1-H3 BCP . Particularly high values of the Fσ and Aσ are observed for the O5-H6BCP and the C2-O5 BCP that reduce significantly with the addition of the T isotope to X3 and X10 sites. Despite the remotely positioned location of the C2-O5 BCP and O5-H6 BCP from the site of the D and T substitutions, the effect of the T isotope in particular is apparent where a significant reduction of the Tσ, Fσ and Aσ values of both the C2-O5 BCP and O5-H6 BCP compared with D and T, see Table 2(d) . These observations are relevant for the interpretation of the vibrational mode coupling, which affects both IR and CD spectra. This is because the high values of Fσ and Aσ of both the C2-O5 BCPand O5-H6 BCP that are consistent with the C2-O5-H6 undergoing a bending vibration which is coupled to the methylene group wagging which is thus expected to be preserved upon deuteration at C1. Thelowering of the corresponding values of Fσ and Aσ for the T isotope indicates that the C2-O5-H6 bending vibration is uncoupled from that of C1-HT wagging.