C4N2H3F



 

 








Nitrogen


Nuclear Quadrupole Coupling Constants


in Fluoropyrazine


 







 

 


 




The molecular structure of fluoropyrazine was optimized at the B3P86/ 6-31G(3d,3p) level of theory.  Cs symmetry was assumed.  On this structure, calculation was made of the nitrogen nqcc's.  These are given in Tables 1 and 2.  Structure parameters are given in Table 3, atomic coordinates in Table 4, and rotational constants in Table 5.
 
In Tables 1 - 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.  RSD is the calibration residual standard deviation of the model for calculation of the nqcc's.
 

 







   







Table 1. Nitrogen nqcc's in 2-Fluoropyrazine (MHz).  Calculation was made on the B3P86/6-31G(3d,3p) ropt structure.
   










Calc.
Expt.
   






14N(1) Xaa - 0.339
Xbb - 2.940
Xcc 3.279
|Xab| 2.774
 
RSD 0.030 (1.3 %)
 
  Xxx 1.424
Xyy 3.279
Xzz - 4.703
ETA 0.394
Øz,a 57.56
Øa,bi 56.88
Øz,bi *   0.67
 
 
* Angle between the z-axis and the bisector ( 'bi' ) of the CNC angle.
 
 
   







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










Calc.
Expt.
   






14N(4) Xaa - 0.608
Xbb - 3.452
Xcc 4.060
|Xab| - 2.927
 
RSD 0.030 (1.3 %)
 
  Xxx 1.224
Xyy 4.060
Xzz - 5.284
ETA 0.537
Øz,a 57.96
Øa,bi 57.26
Øz,bi *   0.70
 
 
* Angle between the z-axis and the bisector ( 'bi' ) of the CNC angle.
 
 
 
Table 3. Fluoropyrazine.  Molecular structure parameters, ropt (Å and degrees).
 
C(2)F(2) 1.3311 N(1)C(2)C(3) 124.27
N(1)C(2) 1.3069 C(2)C(3)N(4) 120.12
C(2)C(3) 1.3944 C(3)N(4)C(5) 116.73
C(3)N(4) 1.3255 N(4)C(5)C(6) 121.81
N(4)C(5) 1.3354 C(5)C(6)N(1) 121.82
C(5)C(6) 1.3875 C(6)N(1)C(2) 115.25
C(6)N(1) 1.3367 N(1)C(2)F(2) 116.93
C(3)H(3) 1.0859 C(2)C(3)H(3) 121.05
C(5)H(5) 1.0857 C(4)C(5)H(5) 117.10
C(6)H(6) 1.0863 C(5)C(6)H(6) 121.40


 
 
Table 4.  Fluoropyrazine.  Atomic coordinates, ropt.
 
  a (Å)   b (Å)
F(2) 2.1467
- 0.0557
N(1) 0.2746
1.1896
C(2) 0.8167
0.0005
C(3) 0.0940
- 1.1920
N(4) - 1.2313
- 1.1664
C(5) - 1.8089
0.0376
C(6) - 1.0620
1.2070
H(3) 0.5992
- 2.1532
H(5) - 2.8943
0.0655
H(6) - 1.5388
2.1831
 
 

Table 5.  Fluoropyrazine.  Rotational Constants (MHz).
 
Calc ropt     Expt.
A 6092.0
B 2777.8
C 1907.8


 
 

Pyrazine Pyridine

Pyrimidine 1,3,5-Triazine
Chloropyrazine 2-Fluoropyridine
2,3-Difluoropyrazine 3-Fluoropyridine
2,6-Difluoropyrazine
 
 

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Molecules/Nitrogen



 

 













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Last Modified 21 Feb 2004