(CH3)2-N-C6H4CN






















 




 









Nitrogen


Nuclear Quadrupole Coupling Constants


in 4-(Dimethylamino)benzonitrile (DMABN)


 








 








 








Calculation was made of the amine and cyano N nqcc tensors in DMABN (CS*) on an ropt structure given by B3P86/6-31G(3d,3p) optimization.  These are compared with experimental nqcc's [1] in Table 1.  Structure parameters are given in Table 2.  Rotational constants are given in Table 3.

* The symmetry of the molecule as reported by Bird et al. [1] is Cs with a dimethylamine inversion angle of 6o.

 








In Table 1, subscripts a,b,c refer to the principal axes of the inertia tensor.

RMS is the root mean square difference between calculated and experimental diagonal nqcc's (percentage of the average of the magnitudes of the experimental nqcc's).  RSD is the calibration residual standard deviation for the B3PW91/6-311+G(df,pd) model for calculation of the nqcc's, which may be taken as an estimate of the uncertainty in the calculated nqcc's (notwithstanding inaccuracies in the optimized structure).

 








  








   






Table 1.  Nitrogen nqcc tensors in DMABN (MHz).  Calculation was made of the ropt structure.

 









Calc.
Expt. [1]
   






14N (am) Xaa
2.474
2.54(33)


Xbb
2.784
2.80(13)


Xcc - 5.258 - 5.33(13)


|Xac|
0.002



 







RMS
0.06 (1.6 %)




RSD
0.030 (1.3 %)



 






14N (cy) Xaa - 4.081 - 4.11(30)


Xbb
2.473
2.40(13)


Xcc
1.608
1.71(13)


|Xac|
0.001



 







RMS
0.07 (2.7 %)




RSD
0.030 (1.3 %)



 






   








 








 

Table 2.  4-(Dimethylamino)benzonitrile, CS.  Selected structure parameters, ropt (Å and degrees).  Complete structure is given here in Z-matrix (G03 input file) format.
 



Parameter   ropt
 
C(2)C(1) 1.4230
C(1)N 1.1596
 
C(7)N 1.3683
NC(13,17) 1.4442
C(7)NC(13,17) 120.10
C(13)NC(17) 119.80
Inversion Angle *     0.10
 
* Angle between the C(7)N direction and the bisector of the C(13)NC(17) angle.




 








 













Table 3.  4-(Dimethylamino)benzonitrile.  Rotational constants (MHz).  
 



 

 Calc.  Expt. [1]







A 3483.6 3469.2(9)


B   582.3   578.583(2)


C   502.0   499.612(2)


 








 








Benzonitrile (N-Dimethyl)aniline Aniline
(CH3)3N

 








 








[1]  R.G.Bird, J.L.Neill, V.J.Alstadt, J.W.Young, B.H.Pate, and D.W.Pratt, J.Phys.Chem. A 115,9392(2011);    R.G.Bird, V.J.Alstadt, D.W.Pratt, J.L.Neill, and B.H.Pate, Abstract RH05, 65th OSU International Symposium on Molecular Spectroscopy, 2010.

 








 








Table of Contents




Molecules/Nitrogen




 








 













4DMABN.html






Last Modified 12 Sept 2011