Nuclear Quadrupole Coupling Constants

in Pyrazine





The molecular structure of pyrazine was optimized at the B3P86/ 6-31G(3d,3p) level of theory.  On this structure, calculation was made of the nitrogen nqcc's.  These are given in Table 1.  Structure parameter are compared in Table 2 with those of Cradock et al. [1] derived by combined analysis of electron diffraction and liquid-crystal NMR.



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


14N Xxx 1.176
Xyy 3.993
Xzz - 5.170
  ETA 0.545
The z-axis is coincident with the CNC bisector, the y-axis is perpendicular to the plane of the molecule.  ETA = (Xxx - Xyy)/Xzz
Table 2. Molecular structure parameters (Å and degrees).
  ropt    r [1]
CH 1.0872 1.0831
CN 1.3317 1.3376
CC 1.3918 1.3968
CNC 115.77 115.65
CCH 120.84 119.96


[1] S.Cradock, P.B.Liescheski, D.W.H.Rankin, and H.E.Robertson, J.Amer.Chem.Soc. 110,2758(1988).



Chloropyrazine 2,6-Dichloropyrazine Pyridine
1,3,5-Triazine 2,3-Dichloropyrazine Pyrimidine


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Last Modified 19 Nov 2003