C4N2H2F2



 

 








Nitrogen


Nuclear Quadrupole Coupling Constants


in 2,6-Difluoropyrazine


 







 

 


 




The molecular structure of fluoropyrazine was optimized at the B3P86/ 6-31G(3d,3p) level of theory.  C2V symmetry was assumed.  On this structure, calculation was made of the nitrogen nqcc's.  These are given in Table 1.  Structure parameters are given in Table 2, atomic coordinates in Table 3, and rotational constants in Table 4.
 
In Table 1,  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 2,6-Difluoropyrazine (MHz).  Calculation was made on the B3P86/6-31G(3d,3p) ropt structure.
   










Calc.
Expt.
   






14N(2) Xaa 1.652
Xbb - 4.276
Xcc 2.624
ETA * 0.227
 
RSD 0.030 (1.3 %)
 
14N(6) Xaa 1.253
Xbb - 5.369
Xcc 4.116
ETA * 0.533
 
RSD 0.030 (1.3 %)
 
 
* ETA = (Xaa - Xcc)/Xbb = (Xxx - Xyy)/Xzz.
 
 
 
Table 2.  2,6-Difluoropyrazine.  Molecular structure parameters, ropt (Å and degrees).
 
N(1)C(2) 1.3128
C(2)C(3) 1.3910
C(3)N(4) 1.3288
C(2)F(2) 1.3263
C(3)H(3) 1.0843
C(6)N(1)C(2) 114.80
N(1)C(2)C(3) 123.91
C(2)C(3)N(4) 119.79
C(3)N(4)C(5) 117.80
N(1)C(2)F(2) 116.55
C(2)C(3)H(3) 121.32


 
 
Table 3.  2,6-Difluoropyrazine.  Atomic coordinates, ropt.
 
  a (Å)   b (Å)
N(1) 0.0 - 0.9711
C(2,6) ± 1.1060 - 0.2638
C(3,5) ± 1.1378 1.1268
N(4) 0.0 1.8132
F(2,6) ± 2.2447 - 0.9439
H(3,5) ± 2.0767 1.6692
 
 

Table 4.  2,6-Difluoropyrazine.  Rotational Constants (MHz).
 
Calc ropt     Expt.
A 3862.1
B 1939.5
C 1291.1


 
 

Pyrazine Pyridine

Pyrimidine 1,3,5-Triazine
Chloropyrazine 2-Fluoropyridine
2,3-Difluoropyrazine 3-Fluoropyridine
Fluoropyrizine
 
 

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Molecules/Nitrogen



 

 













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Last Modified 21 Feb 2004