2,4-F2-C5H3N




 






 








Nitrogen


Nuclear Quadrupole Coupling Constants


in 2,4-Difluoropyridine


 








 








 


 





Calculation of the nitrogen nqcc's in 2,4-difluoropyridine was made here on a molecular structure given by B3P86/6-31G(3d,3p) optimization.  These are compared with experimental values [1] in Table 1.  Structure parameters are given in Table 2, atomic coordinates in Table 3, rotational constants in Table 4, and quartic centrifugal distortion constants in Table 5.


 








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.


RMS is the root mean square difference between calculated and experimental diagonal coupling constants.  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 2,4-Difluoropyridine (MHz).  Calculation was made on the B3P86/6-31G(3d,3p) ropt structure.

 









Calc.
Expt. [1]

   







14N Xaa - 2.977 -
2.9921(11) *



Xbb
0.486
0.4445(11) *



Xcc
2.491
2.5477(11) *



|Xab|
2.524
2.55(6)



 






  RMS

0.041 (2.1 %)





RSD
0.030 (1.3 %)



 






  Xxx
1.815
1.801(50) *



Xyy
2.491
2.5477(11) *



Xzz - 4.306 -
4.349(50) *



ETA
0.157
0.172(12) *



Øz,a
27.78
28.0(3) *



Øa,bi
27.30




Øz,bi **
  0.48



 







 









* Calculated here from experimental 1.5(Xaa) = -4.4882(16) MHz and 0.25(Xbb - Xcc) = -0.5258(5) MHz using Kisiel's program QDIAG.f.

** The z-axis makes an angle of 0.48o with the external bisector ( 'bi' ) of the C(6)N(1)C(2) angle, and tilts toward C(6).

 







 
 


Table 2.  2,4-Difluoropyridine.  Molecular structure parameters, ropt and rs [1] (Å and degrees).
 


  ropt    rs


N(1)C(2) 1.3092 1.299(6)


C(2)C(3) 1.3893 1.389(12)


C(3)C(4) 1.3805 1.389(12)


C(4)C(5) 1.3879 1.378(7)


C(5)C(6) 1.3851 1.38(2)


C(6)N(1) 1.3374 1.358(19)


C(2)F(2) 1.3329


C(3)H(3) 1.0816


C(4)F(4) 1.3329


C(5)H(5) 1.0821


C(6)H(6) 1.0863


C(6)N(1)C(2) 116.38 115.7(17)


N(1)C(2)C(3) 126.40 127.5(14)


C(2)C(3)C(4) 115.14 114.0(11)


C(3)C(4)C(5) 121.39 122.1(12)


C(4)C(5)C(6) 116.65 116.8(17)


C(5)C(6)N(1) 124.04 124.(2)


N(1)C(2)F(2) 116.09


C(2)C(3)H(3) 122.33


C(3)C(4)F(4) 119.11


C(4)C(5)H(5) 120.97


C(5)C(6)H(6) 120.13



 








 














Table 3.  2,4-Difluoropyridine.  Atomic coordinates, ropt.
 







 a (Å)
 b (Å)







N(1) - 1.2444 - 1.0504

C(2) - 1.1413
0.2547

C(3)
0.0383
0.9885

C(4)
1.1964
0.2371

C(5)
1.1580 - 1.1502

C(6) - 0.0966 - 1.7370

F(2) - 2.2886
0.9333

H(3)
0.0467
2.0701

F(4)
2.3743
0.8612

H(5)
2.0701 - 1.7325

H(6) - 0.1925 - 2.8191


 








 












Table 4.  2,4-Difluoropyridine.  Rotational Constants (MHz).
 




Calc ropt     Expt. [1]





A 3988.6 3965.04713(16)

B 1794.2 1787.44610(5)

C 1237.5 1231.91930(4)



 









 















Table 5.  2,4-Difluoropyridine.  Quartic centrifugal distortion constants (kHz).  Calc = B3LYP/cc-pVTZ opt freq=vibrot
 







  Calc
  Expt [1]
 






Delta_J

0.0639

0.0656(4)

Delta_JK -
0.0165
-
0.0102(22)

Delta_K
0.707

0.712(9)

delta_j
0.0218

0.02232(26)

delta_k
0.139

0.148(5)








 









 









[1] C.W. van Dijk, M.Sun, and J. van Wijngaarden, J.Mol.Spectrosc. 280,34(2012).

 








 









Pyridine 2-Fluoropyridine 2,3-Difluoropyridine

3-Fluoropyridine 4-Fluoropyridine 2,5-Difluoropyridine

2,6-Difluoropyridine 3,4-Difluoropyridine 3,5-Difluoropyridine

 








 








Table of Contents





Molecules/Nitrogen




 








 













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Last Modified 12 June 2012