4-Br-C5NH4




 






 








Nitrogen and Bromine


Nuclear Quadrupole Coupling Constants


in 4-Bromopyridine


 








 








 


 





Nitrogen and bromine nqcc's in 4-bromopyridine were calculated on a structure given by B3P86/6-31G(3d,3p) optimization.  Calculated and experimental (for Br [1]) nqcc's are shown in Table 1.  Structure parameters are given in Table 2, atomic coordinates in Table 3, and rotational constants in Table 4.

 








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.  RMS is the root mean square difference between calculated and experimental diagonal nqcc's (percent of average absolute experimental nqcc).  RSD is the calibration residual standard deviation of the model for calculation of the nqcc's.


 








 








   







Table 1. Nitrogen and Bromine nqcc's in 4-Bromopyridine (MHz).  Calculation was made on the B3P86/6-31G(3d,3p) ropt structure.
   










Calc.
Expt. [1]
   







14N Xaa - 4.859




Xbb
1.492




Xcc
3.367




ETA *
0.386



 







RSD
0.030 (1.3 %)



 






79Br Xaa
563.79
557.5(13)


Xbb - 304.69 - 300.5(6)


Xcc - 259.10 - 257.0


ETA * - 0.0809



 







RMS
4.5 (1.2 %)




RSD
1.58 (0.39 %)



 






81Br Xaa
471.03
475.4(16)


Xbb - 254.56 - 254.1(6)

  Xcc - 216.47 - 221.3


ETA * - 0.0809



 







RMS
3.8 (1.2 %)




RSD
1.38 (0.40 %)



 







 








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

 







 
   


Table 2.  4-Bromopyridine and Pyridine.  Molecular structure parameters, ropt ( and degrees).

 






Pyridine







N(1)C(2) 1.3321 1.3336


C(2)C(3) 1.3898 1.3904


C(3)C(4) 1.3861 1.3885


C(2)H(2) 1.0875 1.0880


C(3)H(3) 1.0821 1.0845


C(4)Br 1.8724


C(6)N(1)C(2) 116.79 117.03


N(1)C(2)C(3) 124.16 123.80


C(2)C(3)C(4) 117.77 118.44


C(3)C(4)C(5) 119.35 118.50


N(1)C(2)H(2)
115.94


C(2)C(3)H(3)
120.21



 








 














Table 3.  4-Bromopyridine.  Atomic coordinates, ropt.  Normal species.
 







  a ()
  b ()







N(1) - 3.0182
0.0

C(2,6) - 2.3282 1.1345

C(3,5) - 0.9298 1.1965

C(4) - 0.2299
0.0

H(2,6) - 2.8987 2.0541

H(3,5) - 0.4163 2.1490

Br(4)
1.6426
0.0


 








 












Table 4.  4-Bromopyridine.  Rotational Constants (MHz).   Normal species.
 




Calc. ropt     Expt. [1]





A  6084.3 6016.0(12)

B    994.9   986.902(6)

C    855.1   847.769(8)



 









 








[1] W.Caminati and P.Forti, Chem.Phys.Lett. 15,343(1972).

 








 








Pyrimidine Pyridine Pyrazine

2-Bromopyridine 2-Chloropyridine

3-Bromopyridine 3-Chloropyridine

2-Fluoropyridine 4-Fluoropyrimidine

 








 








Table of Contents





Molecules/Nitrogen




Molecules/Bromine




 








 













4MBrP.html






Last Modified 6 Dec 2003