Table 1.

Ranked intrinsic strengths of atom−atom interactions of amide compounds

Interaction Type	Amide atom*		Strength
	i	j	Two-way alpha value (cal⋅mol−1⋅molal−1⋅Å−4)	Relative to sp3C–sp3C
Aliphatic sp3C interactions:	sp3C	sp2C	−0.0103 ± 0.0005	2.6
	sp3C	sp3C	−0.0039 ± 0.0001	1.0
	sp3C	sp2N	−0.0038 ± 0.0002	1.0
	sp3C	sp2O	0.0108 ± 0.0005	(2.8)†
Amide sp2C interactions:	sp2C	sp2O	−0.0139 ± 0.0038	3.6
	sp2C	sp2C	−0.0111 ± 0.0033	2.9
	sp2C	sp3C	−0.0103 ± 0.0005	2.6
	sp2C	sp2N	0.0018 ± 0.0013	(0.5)†
Amide sp2O interactions:	sp2O	sp2C	−0.0139 ± 0.0038	3.6
	sp2O	sp2N	−0.0108 ± 0.0017	2.8
	sp2O	sp3C	0.0108 ± 0.0005	(2.8)†
	sp2O	sp2O	0.0181 ± 0.0051	(4.6)†
Amide sp2N interactions:	sp2N	sp2O	−0.0108 ± 0.0017	2.8
	sp2N	sp3C	−0.0038 ± 0.0002	1.0
	sp2N	sp2C	0.0018 ± 0.0013	(0.5)†
	sp2N	sp2N	0.0034 ± 0.0006	(0.9)†

^*Labels i and j are interchangeable, so only 10 of the 16 two-way alpha values listed are unique.

^†Unfavorable interaction strengths (indicated by parentheses) are expressed relative to the magnitude of the sp³C–sp³C interaction.