Isonicotinic Acid

























 






 






 








Nitrogen


Nuclear Quadrupole Coupling Constants

in Isonicotinic Acid


(Pyridine-4-Carboxylic Acid)

 








 








 








Calculation of the N nqcc's in isonicotinic acid was made here on molecular structures derived by B3P86/6-31G(d,p) and B3P86/6-31G(3d,3p) optimizations.  Calculated and experimental nqcc's [1] are compared in Table 1.  Structure parameters are given in Table 2, rotational constants in Table 3.

 








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.  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 nqcc's (percent of the average of the absolute experimental nqcc's).  RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of nitrogen efg's/nqcc's, which may be taken as an estimate of the uncertainty in the calculated nqcc's.

 








 








   








Table 1.  14N nqcc's in Isonicotinic Acid (MHz).  Calculation was made on (1) B3P86/6-31G(d,p) and (2) B3P86/6-31G(3d,3p) optimized structures.
   










Calc. (1)

Calc. (2)
Expt. [1]
   








Xaa -
5.081 -
5.090 -
5.0395(46)

Xbb
1.364
1.355
1.3574(44)

Xcc
3.717
3.735
3.6822(44)

|Xab|
0.086
0.095



 







RMS
0.032 (1.0 %)
0.042 (1.3 %)



RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
1.365
1.356



Xyy
3.717
3.735



Xzz - 5.083 - 5.091



ETA
0.463
0.467



Øz,a
0.77
0.84



Øa,bi *
0.75
0.86



Øz,bi 
0.02
0.02



 








 








* "bi" is the bisector of the CNC angle.

 








 



Table 2.  Isonicotinic Acid.  Selected structure parameters (Å and degrees).  Complete structures are given here in Z-matrix format.
 




ropt (1) = B3P86/6-31G(d,p) optimization.

ropt (2) = B3P86/6-31G(3d,3p) optimization.
 





ropt (1) ropt (2)
 

N(1)C(2) 1.3351 1.3328
C(2)C(3) 1.3918 1.3898
C(3)C(4) 1.3942 1.3919
C(4)C(5) 1.3938
1.3915
C(5)C(6) 1.3899
1.3880
C(6)N(1) 1.3361
1.3342
C(6)N(1)C(2)
117.28
117.32
N(1)C(2)C(3) 123.86
123.81
 
C(2)C(3)C(4) 118.09
118.14


C(3)C(4)C(5) 118.74
118.74


C(4)C(5)C(6) 118.30
118.29


C(5)C(6)N(1) 123.72
123.71


C(4)C
1.4866
1.4857


C=O
1.2111
1.2063


C--O
1.3467
1.3455


O--H
0.9699
0.9679


 








 



Table 3.  Isonicotinic Acid.  Rotational Constants (MHz).
 




ropt (1) = B3P86/6-31G(d,p) optimization.

ropt (2) = B3P86/6-31G(3d,3p) optimization.
 





  Calc. ropt (1) Calc. ropt (2)    Expt. [1]






A    4045.8
   4059.2
4027.83775(63)

B    1223.8
   1227.1
1219.95126(12)

C      939.6
     942.3
  937.018821(90)
 





 








 








[1] I.Peña, M.Varela, V.G.Franco, J.C.López, C.Cabezas, and J.L.Alonso, J.Phys.Chem. A, 118,11373(2014).


 








 








Pyridine Nicotinic Acid
Picolinic Acid




 








 








Table of Contents




Molecules/Nitrogen




 








 













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Last Modified 11 Nov 2014