Table 3.

Calculated Dunitz-Winkler distortion parameters and amide bond lengths of planar formamide and 4a–c.

Parametera	Formamide (planar)b	4ac	4b	4c
τ/°	0.0	10.4	5.3	0.6
χC/°	0.0	0.7	3.0	4.5
χN/°	0.0	5.1	1.1	8.9
Bond length/Å C=O	1.193	1.227(17)	1.223(16)	1.223(2)
Bond length/Å N-C(=O)	1.349	1.357(18)	1.355(18)	1.361(3)

^a[25,49–50];

^b[51–53];

^cFor molecule A.