Nicotine (N-Methylpyrrolidine-Pyridine)
	Nitrogen
	Nuclear Quadrupole Coupling Constants
		in Nicotine
	Rotational spectra of two conformers of nicotine, trans-a and trans-b, have been investigated first by Lavrich et al. [1] and revisited by Grabow, et al. [2].  The latter determined the nitrogen nqcc's.
	Calculation of the N nqcc tensors was made here on molecular structures optimized at the B3P86/6-31G(d,p) and B3P86/6-31G(3d,3p) levels of theory.  These structures are shown below.  Calculation of the PE at the B3PW91/6-311+G(df,pd) level of theory on optimized structures gives Etrans-a < Etrans-b by about 2.2 kJ/mol.  Calculated and experimental nqcc's are compared in Tables 1 and 2.  Rotational constants and dipole moments are given in Table 3.
		trans-a				trans-b
	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.
	RMS is the root mean square difference between calculated and experimental diagonal nqcc's (percent of the average of the magnitudes of experimental nqcc's).  RSD is the residual standard deviation of the model for calculation of the nqcc's, which may be taken as an estimate of uncertainty in the calculated nqcc's (not taking into account inaccuracies in the structure parameters).
	Table 1. 14N nqcc's in trans-a Nicotine (MHz).  N(5) is pyrrolidinic nitrogen, N(20) is pyridinic.  Calc (1) was made on the B3P86/6-31G(d,p) opt structure, Calc (2) on the B3P86/6-31G(3d,3p) opt structure.     Calc (1) Calc (2)   Expt [2]     Xaa  N(5) 2.140 2.116 2.1311(91) Xbb 2.572 2.608 2.572(38) Xcc - 4.713 - 4.724 - 4.703(38) Xab - 0.262 - 0.195 Xac - 1.930 - 2.015 Xbc - 0.589 - 0.311   RMS 0.008 (0.25 %) 0.025 (0.81 %) RSD 0.030 (1.3 %) 0.030 (1.3 %)   Xxx 2.531 2.536 Xyy 2.739 2.753 Xzz - 5.270 - 5.290 ETA 0.039 0.041            --------------------------------------------------------------------------------------------------------   Xaa  N(20) - 1.224 - 1.246 - 1.1509(95) Xbb 2.911 3.149 3.3292(56) Xcc - 1.687 - 1.903 - 2.1784(56) Xab 0.948 0.706 Xac 2.980 3.045 Xbc - 1.645 - 1.281   RMS 0.370 (17 %) 0.198 (8.9 %) RSD 0.030 (1.3 %) 0.030 (1.3 %)   Xxx 1.446 1.435 Xyy 3.440 3.456 Xzz - 4.886 - 4.891 ETA 0.408 0.413
	Table 2. 14N nqcc's in trans-b Nicotine (MHz).  N(5) is pyrrolidinic nitrogen, N(20) is pyridinic.  Calc (1) was made on the B3P86/6-31G(d,p) opt structure, Calc (2) on the B3P86/6-31G(3d,3p) opt structure.     Calc (1) Calc (2)   Expt [2]     Xaa  N(5) 2.060 2.058 2.0431(98) Xbb 2.549 2.570 2.574(19) Xcc - 4.609 - 4.627 - 4.617(19) Xab 0.338 0.314 Xac - 2.084 - 2.119 Xbc 0.779 0.683   RMS 0.018 (0.58 %) 0.011 (0.34 %) RSD 0.030 (1.3 %) 0.030 (1.3 %)   Xxx 2.539 2.545 Xyy 2.758 2.768 Xzz - 5.298 - 5.313 ETA 0.041 0.042            --------------------------------------------------------------------------------------------------------   Xaa  N(20) 0.886 0.871 0.8559(97) Xbb 2.434 2.608 3.188(18) Xcc - 3.320 - 3.479 - 4.044(18) Xab 0.655 0.615 Xac - 1.653 - 1.676 Xbc 2.680 2.506   RMS 0.604 (22 %) 0.468 (17 %) RSD 0.030 (1.3 %) 0.030 (1.3 %)   Xxx 1.430 1.421 Xyy 3.489 3.507 Xzz - 4.919 - 4.928 ETA 0.418 0.423
	The B3P86/6-31G(d,p) and B3P86/6-31G(3d,3p) optimized structures of these conformers are given in Z-matrix format here: trans-a and trans-b.
	Table 3.  Nicotine.  Rotational constants (MHz) and dipole moments (D).  Calc (1) was made on the B3P86/6-31G(d,p) opt structure, Calc (2) on the B3P86/6-31G(3d,3p) opt structure.     ________trans-a_________    Calc (1) Calc (2)   Expt. [2]   A 2059.6 2056.5 2059.56318(65) B   582.9   583.6   579.87099(12) C   549.0   551.7   549.32304(11)   |µa|   2.32   2.33 |µb|   0.37   0.25 |µc|   1.20   1.24      _________trans-b_________   A 2045.8 2049.5 2045.68314(49) B   586.9   587.4   583.257764(87) C   552.2   553.6   552.824597(97)   |µa|   1.53   1.53 |µb|   0.94   0.88 |µc|   2.38   2.40
	Pyridine		Pyrrolidine		N-Me-Pyrrolidine
	[1] R.J.Lavrich, R.D.Suenram, D.F.Plusquellic, and S.Davis, 58th International Symposium on Molecular Spectroscopy, 2003; Abstract RH13.
	[2] J.-U.Grabow, S.Mata, J.L.Alonso, I.Peńa, S.Blanco, J.C.López, C.Cabezas, PCCP 13,21063(2011);  J.-U.Grabow, S.Mata, J.C.López, I.Peńa, C.Cabezas, S.Blanco, and J.L.Alonso,  65th International Symposium on Molecular Spectroscopy, 2010; Abstract WH06.
	Table of Contents
	Molecules/Nitrogen
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						Last Modified 24 Oct 2011