o-C6H4CH3CN

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Nitrogen


Nuclear Quadrupole Coupling Constants


in ortho-Tolunitrile


 







 

 


 




Nitrogen nqcc's in o-tolunitrile were determined by Hansen et al. [1].
 
Hansen et al. found, for optimization at the MP2/6-311G** level of theory, that the minimum energy with respect to orientation of the methyl hydrogens corresponds to a position of one CH bond (in the Cs plane) pointing away from CN.
 
The nqcc's were calculated here on molecular structures given by B3P86/6-31G(3d,3p) optimization with the CH bond in the Cs plane I) pointing away from CN, and II) pointing toward CN.  These calculated nqcc's are compared with the experimental values in Tables 1 and 2.  Conformer I structure parameters and atomic coordinates are given in Tables 3 and 4.  Rotational constants are given in Table 5.
 
For both the B3P86/6-31G(3d,3p) and the B3PW91/6-311+G(df,pd) models, we find, in agreement with Hansen et al., that EI < EII.
 
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, these are perpendicular to the molecular plane.  Ø (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 o-Tolunitrile, conformer I (MHz).  Calculation was made on the B3P86/6-31G(3d,3p) ropt structure.
 




Calc.
Expt. [1]
   






14N Xaa - 4.096 - 4.094(2)
Xbb 2.170 2.143 *
Xcc 1.926 1.951 *
|Xab| 0.892 0.8(5)
 
RMS 0.022 (0.8 %)
RSD 0.030 (1.3 %)
 
  Xxx 2.295 2.267 **
Xyy 1.926 1.951
Xzz - 4.220 - 4.219
ETA - 0.087 - 0.075
Øz,a 7.94 7.98
Øa,CN 7.63 7.63
Øz,CN 0.31 0.35
 
 
* Calculated here from Xaa and Xbb - Xcc = 0.191(6) [1].
** Calculated here using |Xab| = 0.892 MHz rather than 0.8(5).
 
 
   







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




Calc.
Expt. [1]
   






14N Xaa - 4.064 - 4.094(2)
Xbb 2.183 2.143
Xcc 1.882 1.951
|Xab| 0.930 0.8(5)
 
RMS 0.049 (1.8 %)
RSD 0.030 (1.3 %)
 
 
 
 
Table 3.  o-Tolunitrile, conformer I.  Molecular structure parameters, ropt (Å and degrees).
   
C(1)C(2) 1.4071 C(1)C(2)C(3) 121.18
C(2)C(3) 1.3984 C(2)C(3)C(4) 119.93
C(3)C(4) 1.3857 C(3)C(4)C(5) 119.55
C(4)C(5) 1.3905 C(4)C(5)C(6) 120.34
C(5)C(6) 1.3900 C(5)C(6)C(1) 121.42
C(6)C(1)C(2) 117.58
 
C(3)H(3) 1.0839 C(2)C(3)H(3) 119.19
C(4)H(4) 1.0841 C(3)C(4)H(4) 120.01
C(5)H(5) 1.0848 C(6)C(5)H(5) 119.66
C(6)H(6) 1.0853 C(1)C(6)H(6) 118.88
 
C(1)C(Me) 1.4985 C(2)C(1)C(Me) 120.84
C(Me)H(7) 1.0908 C(1)C(Me)H(7) 111.01
C(Me)H(8) 1.0939 C(1)C(Me)H(8) 111.18
C(Me)H(9) 1.0939 C(1)C(Me)H(9) 111.18
H(7)C(Me)H(8) 108.36
H(7)C(Me)H(9) 108.36
H(8)C(Me)H(9) 106.58
 
C(2)C(cy) 1.4287 C(1)C(2)C(cy) 119.52
C(cy)N 1.1587 C(2)C(cy)N 179.54
 
For comparison, the B3P86/6-31G(3d,3p) optimized molecular structure of benzene is CC = 1.3909 Å and CH = 1.0851 Å.
 
In the structure of conformer II, C(2)C(cy) = 1.4294 Å, and C(cy)N = 1.1587 Å.


 
 
Table 4.  o-Tolunitrile, conformer I.  Atomic coordinates, ropt.
 
 a (Å)  b (Å)  c (Å)
C(1) - 0.0986 0.9417
C(2) 0.4153 - 0.3682
C(3) - 0.4340 - 1.4791
C(4) - 1.8079 - 1.2991
C(5) - 2.3306 - 0.0106
C(6) - 1.4830 1.0910
H(3) - 0.0033 - 2.4738
H(4) - 2.4675 2.1594
H(5) - 3.4051 0.1388
H(6) - 1.9022 2.0921
C(Me) 0.8186 2.1266
H(7) 0.2528 3.0592
H(8,9) 1.4724 2.1204 ± 0.8769
C(cy) 1.8297 - 0.5695
N 2.9781 - 0.7234
 
 
Table 5.  o-Tolunitrile, conformer I.  Rotational Constants (MHz).
 
Calc. ropt    Expt. [1]
A  2906.3 2891.6469(5)
B  1508.1 1499.8809(1)
C    999.0   993.52170(6)
 
 
[1] N.Hansen, H.Mäder, and T.Bruhn, Mol.Phys. 97,587(1999).
 
 

Benzonitrile o-Fluorobenzonitrile

m-Tolunitrile m-Fluorobenzonitrile
p-Tolunitrile p-Fluorobenzonitrile
 
 

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Last Modified 23 Sept 2003