Table 2.

Geometric properties of minimum energy rotamers of the alkene model compounds from QM calculations, the Drude polarizable force field and the C36 additive force field, along with data collected from the Cambridge Structural Database (CSD).⁶² For the CSD data, averaged structural properties are reported. Crystal structures with alkenes in ring systems or that contain ions were omitted. A threshold of the crystallographic R-factor was set to <= 0.05. For dihedral angles, median values were used instead of averaged properties. Bonds, angles, and dihedrals are defined as shown in Figure 1.

Method	Dihedrals			Angles				Bonds (Å)
	Ψ1	Ψ2	Ψ3	Θ1	Θ2	Θ3	Θ4	r1	r2	r3	r4	r5
2-butene
QM	180.0	-	-	124.7	124.7	-	-	1.50	1.34	1.50	-	-
Drude	180.0	-	-	125.4	125.1	-	-	1.50	1.34	1.50	-	-
C36	180.0	-	-	124.0	124.1	-	-	1.51	1.34	1.51	-	-
CSD	−178.2	-	-	124.7	124.7	-	-	1.50	1.32	1.49	-	-
2-pentene
QM	−178.9	116.9	-	124.7	124.8	111.9	-	1.50	1.34	1.50	1.53	-
Drude	−179.7	116.9	-	125.1	124.0	110.1	-	1.50	1.34	1.50	1.53	-
C36	−179.8	116.0	-	124.0	124.8	111.0	-	1.51	1.34	1.51	1.54	-
CSD	48.7	149.7	-	126.0	126.2	112.9	-	1.49	1.32	1.49	1.53	-
2-hexene
QM	179.4	116.8	−65.0	124.6	125.0	112.4	112.5	1.53	1.50	1.34	1.50	1.53
Drude	179.4	116.8	−65.0	124.6	125.0	112.4	112.5	1.52	1.50	1.34	1.50	1.52
C36	179.7	118.6	−65.8	124.0	124.8	112.7	114.2	1.53	1.51	1.34	1.51	1.53
CSD	165.1	−133.5	177.8	126.9	127.0	112.6	114.0	1.53	1.49	1.32	1.49	1.53
3-hexene
QM	116.6	180.0	−116.5	111.8	124.9	124.9	111.8	1.53	1.50	1.34	1.50	1.53
Drude	116.6	180.0	−116.6	111.9	124.9	124.9	111.8	1.53	1.50	1.34	1.50	1.53