St. Edward's University

Department of Chemistry

Resolution

Effect of OH'''pi Interaction and C-O Rotamer Type on O-H stretch

X	n	Rotamer I	Rotamer II	h-bond
C=C	2
	frequency	3633sh	3642	3598
	Hf(AM1)	-46.62	-45.02	-46.43
	E(6-31G*)	-230.945804	-230.946213	-230.946740
	dipole	1.71	1.72	1.92
	d(H''''C)			2.68, 3.35
	<(OHC)			105, 119

X	n	Rotamer I	Rotamer II	h-bond
C=C	3
	frequency	3634sh	3645	3605
	Hf(AM1)	-53.45	-51.78	-52.69
	E(6-31G*)	-269.978824	-269.978727	-269.978626
	dipole	1.68	1.76	2.20
	d(H''''C)			2.42, 2.80
	<(OHC)			131, 156

X	n	Rotamer I	Rotamer II	h-bond
phenyl	2
	frequency	3634sh	3641	3608
	Hf(AM1)	-38.15	-36.64	-38.24
	E(6-31G*)	-383.613981	-383.614261	-383.614923
	dipole	1.84	1.69	2.06
	d(H''''C)			2.61
	<(OHC)			127

X	n	Rotamer I	Rotamer II	h-bond
phenyl	3
	frequency	3634sh	3645	3608
	Hf(AM1)	-44.92	-43.22	-43.96
	E(6-31G*)	-422.646522	-422.646476	-422.643362
	dipole	1.80	1.77	2.19
	d(H''''C)			2.42
	<(OHC)			140

X	n	Rotamer I	Rotamer II	h-bond
alkyne	2
	frequency	3633sh	36452	3600
	Hf(AM1)	-9.12	-7.65	-9.08
	E(6-31G*)	-229.73973	-229.74028	-229.74064
	dipole	1.61	1.63	1.61
	d(H''''C)			2.70, 3.32
	<(OHC)			102, 121

X	n	Rotamer I	Rotamer II	h-bond
alkyne	3
	frequency	3634sh	3647	3595
	Hf(AM1)	-15.94	-14.25	-15.19
	E(6-31G*)	-268.772200	-268.772276	-268.771744
	dipole	1.52	2.02	2.17
	d(H''''C)			2.47, 2.73
	<(OHC)			131, 155

Summary

X	n	Rotamer I			Rotamer II			h-bond
		Dv	DDHf	DDE	Dv	DDHf	DDE	Dv	DDHf	DDE
C=C	2	35	-0.19	+0.59	44	+1.41	+0.33
C=C	3	29	-0.76	-0.12	39	+0.91	-0.06
Ph	2	26	+0.09	+0.62	33	+1.6	+0.44
Ph	3	26	-0.96	-1.98	37	+0.74	-1.95
alkyne	2	33	-0.04	+0.57	42	+1.43	+0.23
alkyne	3	39	-0.75	-0.29	52	+0.94	-0.33

		Reference	Gauche	Correction
alkyne	E(6-31G*)	-193.103937	193.102492	+0.92
phenyl	E(6-31G*)	-232.135276	-232.130790	+2.80

X	n	H-bond strength
		Dv	DDE(corrected)
C=C	2	35	0.59
C=C	3	29	0.80
Ph	2	26	0.62
Ph	3	26	0.82
alkyne	2	33	0.57
alkyne	3	39	0.63

Predicted	3-21G//3-21G
1.61	1.79

 

PARAXYLENE1

PARAXYLENE2