Table 3.

Effective N-H and N-D bond lengths of backbone amide groups

	reqa (Å)	Δrstrb (Å)	Δrlibc (Å)	reffd (Å)
N-H	1.008 ± 0.006	0.007e	0.025e	1.040e ± 0.006
N-D	1.008 ± 0.006	0.005	0.017	1.030 ± 0.006

^aEquilibrium bond length determined from RDCs.⁶⁵

^bEffective bond length increase due to zero point bond stretching motion, obtained from B3LYP/6-31G** QM calculations on N-methylacetamide in a water continuum solvent.

^cEffective bond length increase due to zero point bond librational motion, obtained from normal mode analysis.

^dEffective bond length defined as r_eff = r_eq + Δr_str + Δr_lib.

^efrom reference ⁶⁶