p-C6H4CH3CN

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Nitrogen


Nuclear Quadrupole Coupling Constants


in para-Tolunitrile


 








 








 


 





Nitrogen nqcc's in p-tolunitrile were determined by Andersen et al. [1,2].

 








Calculation of the nqcc's was made here on molecular structures given by B3P86/6-31G(3d,3p) optimization assuming Cs symmetry with the plane of symmetry I) perpendicular to the plane of the ring, and II) coincident with the plane of the ring.  These calculated nqcc's are compared with the experimental values in Tables 1 and 2.  Structure parameters and atomic coordinates for conformer I are given in Tables 3 and 4.  Rotational constants are given in Table 5.

 








At the B3P86/6-31G(3d,3p) level of theory, EI < EII by 48 cal/mol. At the B3PW91/6-311+G(df,pd) level of theory, EI < EII by 17 cal/mol.

 








In Tables 1 and 2, subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  The nqcc y-axis is chosen coincident with the inertia c-axis.  (degrees) is the angle between its subscripted parameters.  ETA = (Xxx - Xyy)/Xzz.


RMS is the root mean square differene between calculated and experimental nqcc's (percent of average of the magnitudes of the experimental nqcc).  RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of the nqcc's.

 








 








   







Table 1. Nitrogen nqcc's in p-Tolunitrile, conformer I (MHz).  Calculation was made on the B3P86/6-31G(3d,3p) ropt structure.

 









Calc.
Expt. [1]
   







14N Xaa - 4.207 - 4.212(1)


Xbb
2.337
2.310


Xcc
1.870
1.902


|Xac|
0.018



 







RMS
0.024 (0.9 %)




RSD
0.030 (1.3 %)



 






  Xxx
2.337
2.310


Xyy
1.870
1.902


Xzz - 4.207 - 4.212


ETA - 0.111 - 0.097


z,a
0.16




a,CN
0.18




z,CN
0.02



 







 








 








   







Table 2. Nitrogen nqcc's in p-Tolunitrile, conformer II (MHz).  Calculation was made on the B3P86/6-31G(3d,3p) ropt structure.

 









Calc.
Expt. [1]
   







14N Xaa - 4.207 - 4.212(2)


Xbb
2.337
2.310


Xcc
1.870
1.902


|Xab|
0.010



 







RMS
0.024 (0.9 %)




RSD
0.030 (1.3 %)



 







 







 
 



Table 3.  p-Tolunitrile, conformer I.  Molecular structure parameters, ropt ( and degrees).
   



C(1)C(2) 1.3968 C(1)C(2)C(3) 121.22

C(2)C(3) 1.3852 C(2)C(3)C(4) 119.83

C(3)C(4) 1.3984 C(3)C(4)C(5) 119.58



C(6)C(1)C(2) 118.32

 



C(2)H(2) 1.0856 C(1)C(2)H(2) 119.42

C(3)H(3) 1.0838 C(4)C(3)H(3) 119.54

 



C(1)C(Me) 1.5003 C(2)C(1)C(Me) 120.84

C(Me)H(7) 1.0953 C(1)C(Me)H(7) 110.75

C(Me)H(8) 1.0922 C(1)C(Me)H(8) 111.42

C(Me)H(9) 1.0922 C(1)C(Me)H(9) 111.42



H(7)C(Me)H(8) 107.35



H(7)C(Me)H(9) 107.35



H(8)C(Me)H(9) 108.36

 



C(4)C(cy) 1.4275 C(5)C(4)C(cy) 120.21

C(cy)N 1.1584 C(4)C(cy)N 179.88

 


For comparison, the B3P86/6-31G(3d,3p) optimized molecular structure of benzene is CC = 1.3909 and CH = 1.0851 .



 








 
















Table 4.  p-Tolunitrile, conformer I.  Atomic coordinates, ropt.

 









 a ()
 b ()
 c ()









C(1) - 1.7898
0.0000 - 0.0088

C(2,6) - 1.0737 1.1993 - 0.0089

C(3,5)
0.3114 1.2084 - 0.0032

C(4)
1.0150
0.0000
0.0007

H(2,6) - 1.6122 2.1420 - 0.0156

H(3,5)
0.8574 2.1446 - 0.0051

C(Me) - 3.2900
0.0000
0.0158

H(7) - 3.6612
0.0000
1.0462

H(8,9) - 3.6970 0.8856 - 0.4771

C(cy)
2.4425
0.0000
0.0037

N
3.6009
0.0000
0.0074


 








 












Table 5.  p-Tolunitrile, conformer I.  Rotational Constants (MHz).
 




Calc. ropt    Expt. [1]





A  5539.2

B    984.8

C    840.5


 








 









[1] U.Andresen, T.Bruhn, M.Gnida, and H.Mder, unpublished, cited in [2].

[2] N.Hansen, H.Mder, and T.Bruhn, Mol.Phys. 97,587(1999).

 









 








Benzonitrile o-Fluorobenzonitrile

o-Tolunitrile m-Fluorobenzonitrile

m-Tolunitrile p-Fluorobenzonitrile

 








 








Table of Contents





Molecules/Nitrogen




 








 













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Last Modified 23 Sept 2003