2,6-F2-C5H3N




 






 








Nitrogen


Nuclear Quadrupole Coupling Constants


in 2,6-Difluoropyridine


 








 








 








Calculation of the nitrogen nqcc's in 2,6-difluoropyridine was made on the substitution structure of  Stiefvater [1], and on a structure obtained by optimization at the B3P86/6-31G(3d,3p) level of theory.  These are compared in Tables 1 and 2 with the experimental nqcc's of Dijk et al. [2].  Structure parameters are compared in Table 3.  Substitution coordinates are given in Table 4.  Rotational constants are compared in Table 5, quartic centrifugal distortion constants in Table 6.


 








Subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  RMS is the root mean square difference between calculated and experimental nqcc's.  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-Difluoropyridine (MHz).  Calculation was made on the substitution structure [1].

 









Calc.
Expt. [2]
   







14N Xaa
1.849
1.8423(11) *



Xbb - 3.965 - 4.1010(11) *



Xcc
2.116
2.2586(11) *



ETA **
0.067



 







RMS
0.114 (4.2 %)




RSD
0.030 (1.3 %)



 







 









* Calculated here from experimental 1.5(Xaa) = 2.7635(16) MHz and 0.25(Xbb - Xcc) = -1.5899(5) MHz using Kisiel's program QDIAG.f.

** ETA = (Xaa - Xcc)/Xbb = (Xxx - Xyy)/Xzz.

 








 








   







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

 









Calc.
Expt. [2]
   







14N Xaa
1.897
1.8423(11) *


Xbb - 4.049 - 4.1010(11) *


Xcc
2.152
2.2586(11) *


ETA **
0.063



 







RMS
0.075 (2.8 %)




RSD
0.030 (1.3 %)



 







 









* Calculated here from experimental 1.5(Xaa) = 2.7635(16) MHz and 0.25(Xbb - Xcc) = -1.5899(5) MHz using Kisiel's program QDIAG.f.

** ETA = (Xaa - Xcc)/Xbb = (Xxx - Xyy)/Xzz.

 







 
 



Table 3.  2,6-Difluoropyridine.  Molecular structure parameters, rs and ropt ( and degrees).
 






 rs [1]   ropt







N(1)C(2) 1.3168(17) 1.3138


C(2)C(3) 1.3767(10) 1.3860


C(3)C(4) 1.3941(5) 1.3887


C(2)F(2) 1.347(1) 1.3315


C(3)H(3) 1.0795(7) 1.0818


C(4)H(4) 1.0822(5) 1.0844


C(6)N(1)C(2) 115.0(3) 115.93


N(1)C(2)C(3) 126.5(1) 125.70


C(2)C(3)C(4) 116.1(1) 116.37


C(3)C(4)C(5) 119.8(1) 119.94


N(1)C(2)F(2) 114.7(1) 115.62


C(2)C(3)H(3) 120.8(1) 120.60


C(3)C(4)H(4) 120.1(1) 120.03



 








 














Table 4.  2,6-Difluoropyridine.  Atomic coordinates, rs [1].
 







 a ()
 b ()







N(1)
0.0 - 0.9437

C(2,6) 1.1100 - 0.2353

C(3,5) 1.2058
1.1376

C(4)
0.0
1.8368

F(2,6) 2.2420 - 0.9659

H(3,5) 2.1690
1.6251

H(4)
0.0
2.9192


 








 













Table 5.  2,6-Difluoropyridine.  Rotational Constants (MHz).
 





Calc ropt Calc rs *     Expt. [2]






A 3770.6 3751.7 3747.68671(7)

B 1911.8 1907.5 1905.82582(5)

C 1268.6 1264.6 1263.24839(5)

 



* Calculated here.



 









 














Table 6.  2,6-Difluoropyridine.  Quartic centrifugal distortion constants (kHz).  Calc = B3LYP/cc-pVTZ opt freq=vibrot
 







  Calc
  Expt [1]
 






Delta_J

0.0673

0.0700(5)

Delta_JK
0.00782

0.0170(10)

Delta_K
0.567

0.5565(22)

delta_j
0.0238

0.02424(14)

delta_k
0.137

0.1406(14)








 









 









[1] O.L.Stiefvater, Z.Naturforsch. 30a,1765(1975).

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

 








S.Doraiswamy and S.D.Sharma, Chem. Phys.Lett. 37,527(1976): Xaa =  1.91(4), Xbb = -4.24(4), and Xcc = 2.33(10) MHz.

O.L.Stiefvater, S.Lui, and J.A.Ladd, Z.Naturforsch. 31a,53(1976): Xaa =  1.82(5), Xbb = -4.16(2), and Xcc = 2.34(5) MHz.

D.Hbner, M.Stolze, and D.H.Sutter, Z.Naturforsch. 36a,332(1981): Xaa =  1.91(4), Xbb = -4.12(6), and Xcc = 2.21(6) MHz.

 









 








Pyridine 2-Fluoropyridine 2,3-Difluoropyridine

3-Fluoropyridine 4-Fluoropyridine 2,4-Difluoropyridine

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

2,6-Dichloropyridine 2,6-Lutidine 2,6-Dicyanopyridine

 








 








Table of Contents





Molecules/Nitrogen




 








 













26DFPYR.html






Last Modified 12 June 2012