2,3-Cl2-C4N2H2

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Nitrogen and Chlorine


Nuclear Quadrupole Coupling Constants


in 2,3-Dichloropyrazine


 







 

 


 




The molecular structure of 2,3-dichloropyrazine 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 and chlorine nqcc's. The results 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 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.  RSD is the calibration residual standard deviation of the model for calculation of the nqcc's.
 

 







   







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










Calc.
Expt.
   






14N(1,4) Xaa 1.492
Xbb - 4.996
Xcc 3.505
Xab ± 0.121
 
RSD 0.030 (1.3 %)
 
  Xxx 1.494
Xyy 3.505
Xzz - 4.999
ETA 0.402
Øz,a   1.06
Øa,bi   0.04
Øz,bi *   1.10
 
 
* Angle between the z-axis and the bisector ( 'bi' ) of the CNC angle.
 
 
   







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










Calc.
Expt.
   






35Cl(2,3) Xaa - 39.36
Xbb   9.64
Xcc 29.72
Xab ± 53.51
 
RSD 0.49 (1.1 %)
 
  Xxx 44.00
Xyy 29.72
Xzz - 73.71
ETA - 0.194
Øz,a 32.70
Øa,CCl 31.27
Øz,CCl   1.43
 
37Cl(2,3) Xaa - 31.02
Xbb   7.60
Xcc 23.42
Xab ± 42.17
 
RSD 0.44 (1.1 %)
 
 
 
 
Table 3. Molecular structure parameters, ropt (Å and degrees).
 
C(2,3)Cl(2,3) 1.7208 * N(1)C(2)C(3) 121.17
N(1)C(2) 1.3144 C(2)C(3)N(4) 121.17
C(2)C(3) 1.4086 C(3)N(4)C(5) 117.59
C(3)N(4) 1.3144 N(4)C(5)C(6) 121.24
N(4)C(5) 1.3326 C(5)C(6)N(1) 121.24
C(5)C(6) 1.3869 C(6)N(1)C(2) 117.59
C(6)N(1) 1.3326 N(1)C(2)Cl(2) 117.56
C(5,6)H(5,6) 1.0856 N(1)C(6)H(6) 116.96
 
* In chloropyrazine, CCl = 1.7327 Å.


 
 
Table 4. Atomic coordinates, ropt.  Normal species.
(More figures are shown than are significant.) 
 
  a (Å)   b (Å)
N(1,4) 1.196362
± 1.384584
C(2,3) 0.071702
± 0.704322
C(5,6) 2.335717
± 0.693454
Cl(2,3) - 1.399122
± 1.597577
H(5,6) 3.258434
± 1.265421
 
 

Table 5.  Rotational Constants (MHz).   Normal species.
 
Calc ropt     Expt.
A 1952.3
B 1534.0
C   859.0


 
 

Pyrazine Pyridine

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

Table of Contents





Molecules/Nitrogen




Molecules/Chlorine



 

 













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Last Modified 22 June 2004