cyclic-C5H5-CN
	Nitrogen
	Nuclear Quadrupole Coupling Constants
		in Cyclopentadiene-1-carbonitrile
	The microwave spectrum of cyclopentadiene-1-carbonitrile was observed by Ford and Seitzman [1], by Sakaizuma et al. [2,3].  1,3- and 1,4- conformers, as shown below, have been identified:
	1,3-Cyclopentadiene-1-carbonitrile				1,4-Cyclopentadiene-1-carbonitrile
		At the MP2/6-311+G(d,p) opt level of theory, E1,3 < E1,4 by 6.1 kJ/mol.
	Calculation of the nitrogen nqcc tensor in each conformer was made here on molecular structures given by B3P86/6-31G(3d,3p) and MP2/6-311+G(d,p) optimization, the latter with correction for the CN bond length.  These calculated nqcc's are given in Tables 1 and 2, rotational constants and dipole moments in Table 3.  Structure parameters are given here in Z-matrix format.
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	In Tables 1 and 2, subscripts a,b,c refer to the principal axes of the inertia tensor, subscripts x,y,z to the principal axes of the nqcc tensor.  ETA = (Xxx - Xyy)/Xzz.  Ø (degrees) is the angle between its subscripted parameters.
	RSD is the residual standard deviation of calibration of the B3PW91/6-311+G(df,pd) model for calculation of the efg's/nqcc's.
	Table 1.  14N nqcc tensor in 1,3-Cyclopentadiene-1-carbonitrile (MHz).  Calculation was made here on the B3P86 and MP2 molecular structures (as discussed above).   Calc /B3P86 Calc /MP2 Expt   Xaa - 4.156 - 4.171 Xbb 2.352 2.357 Xcc 1.804 1.814 |Xab| 0.189 0.192 RSD 0.030 (1.3 %) 0.030 (1.3 %) Xxx 2.358 2.363 Xyy 1.804 1.814 Xzz - 4.162 - 4.177 ETA - 0.133 - 0.131 Øz,a 1.66 1.68 Øa,CN 2.17 2.13 Øz,CN 0.50 0.45
	Table 2.  14N nqcc tensor in 1,4-Cyclopentadiene-1-carbonitrile (MHz).  Calculation was made here on the B3P86 and MP2 molecular structures (as discussed above).   Calc /B3P86 Calc /MP2 Expt   Xaa - 4.245 - 4.247 Xbb 2.256 2.257 Xcc 1.989 1.990 |Xab| 0.142 0.146 RSD 0.030 (1.3 %) 0.030 (1.3 %) Xxx 2.259 2.260 Xyy 1.989 1.990 Xzz - 4.248 - 4.251 ETA - 0.0638 - 0.0635 Øz,a 1.25 1.29 Øa,CN 1.63 1.68 Øz,CN 0.38 0.39
	Table 3.  Cyclopentadiene-1-carbonitrile.  Rotational Constants (MHz) and Dipole Moments (D). Calc /B3P86 Calc /MP2  Expt [2] 1,3- A  8426  8336 8353.7(9) B  1914  1899 1904.24(1) C  1575  1561 1565.38(1) |µa|  4.70  4.69 4.15(15) |µb|  0.35  0.33 0.27(3) 1,4- A  8382  8222 8235.0(13) B  1913  1897 1902.07(2) C  1569  1556 1559.67(2) |µa|  5.03  5.02 4.36(25) |µb|  0.58  0.56 0.77(10)
	[1] R.G.Ford and H.A.Seitzman, J.Mol.Spectrosc. 69,326(1978).
	[2] T.Sakaizuma, H.Kikuchi, O.Ohashi, and I.Yamaguchi, Bull.Chem.Soc.Jpn. 60,3903(1987).
	[3] T.Sakaizuma and H.Ishii, J.Mol.Spectrosc. 162,458(1993).
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						Last Modified 15 Feb 2014