Tautomeric Equilibria in Solutions of 2-Phenacylbenzimidazoles

Table 3

Optimized (MP2/6-311+G(d,p)) bond lengths [Å] and dihedral angles [deg] for 2-phenacylbenzimidazoles and their tautomers.

Comp.	Taut.	R =	N1–H1 O12–H12 N3–H3	O12…H1; or; N1…H12	H10…H18	Ψ (C14–C13–C11–O12); Ψ (C18–C13–C11–O12)
2a	K	p-OCH3	1.01	2.70	2.22,	12.25
			-		3.70	-165.66
			-
2a	O	p-OCH3	-	1.74	2.29	-29.75
			0.99			150.23
			1.01
2a	E	p-OCH3	1.03	1.82	2.25	-28.71
			-			150.53
			1.01
2d	K	H	1.01	2.69	2.25,	-15.81
			-		3.70	162.48
			-
2d	O	H	-	1.74	2.31	-31.42
			0.99			148.46
			1.01
2d	E	H	1.03	1.82	2.28	-30.93
			-			148.00
			1.01
2i	K	p-NO2	1.01	2.82	2.27,	14.17
			-		3.71	-164.73
			-
2i	O	p-NO2	-	1.73	2.26	-28.20
			1.00			151.17
			1.01
2i	E	p-NO2	1.03	1.82	2.26	-29.30
			-			149.28
			1.01

Distances to H18 from two distinct H10.