Table 3.

Relative Conformational Energies for Alkanes (kcal/mol)

Molecule	Conformers	“Best QM”	OPLS-AA	OPLS/2020
ethane	e - s	2.90a	2.84	2.82
butane	g - a	0.60b	0.80	0.58
butane	120°- a	3.30c	3.23	3.04
butane	cis - a	5.20c	5.18	5.11
pentane	ag - aa	0.61b	0.94	0.52
pentane	gg - aa	0.96b	1.89	1.04
pentane	g+g− - aa	2.81b	3.29	2.51
hexane	aag - aaa	0.60b	0.93	0.51
hexane	aga - aaa	0.60b	1.05	0.60
hexane	agg - aaa	0.93b	1.97	1.10
hexane	gag - aaa	1.18b	1.82	0.97
hexane	ggg-aaa	1.25b	2.09	1.59
2,3-dimethylbutane	g - a	0.05d	−0.23	0.54
methylcyclohexane	ax - eq	1.76e	1.78	0.82
1,2-dimethylcyclohexane	cis - trans	1.81f	1.61	0.68
decalin	cis - trans	3.08g	2.96	1.66
cyclobutane	D4h - D2d	1.46h	1.55	1.63
methylcyclobutane	ax - eq	0.71i	0.54	0.43
cyclohexane	tb - chair	5.98j	7.01	7.02
cycloheptane	b - tc	3.30k	4.75	4.57
cyclooctane	D4d - Cs	2.00k	−1.04	−0.78
octadecane	linear – turn	1.0l	−1.34	0.55

^aRef 33.

^bRef 32.

^cRef 10.

^dRef 34.

^eRef 35.

^fRef 36.

^gRef 37.

^hRef 38.

ⁱRef 39.

^jRef 40.

^kRef 41.

^lRef 42.