2-F-C4N2H3




 







 


Nitrogen


Nuclear Quadrupole Coupling Constants


in 2-Fluoropyrimidine


 








 

 




The asymmetry in the quadrupole tensor (Xbb  -  Xcc) for nitrogen in 2-fluoropyrimidine was determined by Chen et al. [1].  "Xaa is very small", and was not determined.
 
Nitrogen nqcc's in 2-fluoropyrimidine were calculated on a structure given by B3P86/6-31G(3d,3p) optimization.  These nqcc's are given in Table 1.  Structure parameters are given in Table 2, atomic coordinates in Table 3, rotational constants in Table 4.
 
  In Table 1, 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 B3PW91/6-311+G(df,pd) model for calculation of the nqcc's.
 
   








 







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










Calc.
Expt. [1]
 







14N(1,3) Xaa - 0.063
Xbb  -  Xcc - 5.257 - 5.206(57)


Xbb -
 2.597



Xcc 2.660


Xab ± 2.806


 








RSD 0.030 (1.3 %)
 








Xxx 1.749


Xyy 2.660


Xzz -
 4.409



ETA
0.207



Øz,a
57.15



Øa,bi
57.89



Øz,bi*
  0.74

   







 








* The z-axis makes an angle of 0.74o with the external bisector ( 'bi' ) of the C(6)N(1)C(2) angle, and tilts toward C(2).

 







 
Table 2.  2-Fluoropyrimidine and Pyrimidine.  Structure parameters ropt (Å and degrees).
 
X = F X = H
C(2)N(3) 1.3178 1.3320
N(3)C(4) 1.3337 1.3328
C(4)C(5) 1.3877 1.3877
C(2)X(2) 1.3231 1.0876
C(4)H(4) 1.0871 1.0879
C(5)H(5) 1.0823 1.0835
N(1)C(2)N(3) 129.61 127.38
C(2)N(3)C(4) 114.60 115.70
N(3)C(4)C(5) 122.46 122.40
C(4)C(5)C(6) 116.28 116.44
C(5)C(4)H(4) 121.47 121.16
 
 
Table 3.  2-Fluoropyrimidine.  Atomic coordinates, ropt.
 
 a (Å)  b (Å)
N(1,3) 0.2154 ± 1.1925
C(2) 0.7764 0.0
C(4,6) - 1.1182 ± 1.1786
C(5) - 1.8507 0.0
F(2) 2.0995 0.0
H(4,6) - 1.6061 ± 2.1501
H(5) - 2.9330 0.0
 
 
Table 4.  2-Fluoropyrimidine.  Rotational Constants (MHz).
 
Calc. ropt Expt. [1]
A  6127.9 6081.7252(11)
B  2851.0 2837.80277(27)
C  1945.7 1934.83496(30)
 
 
[1] J.Chen, C.D.Paulse, R.W.Davis, J.Mol.Spectrosc. 143,258(1990).
 

 







Pyrimidine 2-Chloropyrimidine
4-Fluoropyrimidine 2-Bromopyrimidine
5-Fluoropyrimidine 2-Cyanopyrimidine

 








 








Table of Contents




Molecules/Nitrogen




 








 













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Last Modified 2 Aug 2006