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2,3-Cl2-C4N2H2
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Nitrogen and Chlorine
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Nuclear
Quadrupole Coupling Constants |
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in 2,3-Dichloropyrazine |
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The molecular structure of 2,3-dichloropyrazine
was optimized at the B3P86/6-31G(3d,3p) level of theory. C2V
symmetry was assumed. On this structure, calculation was
made of the nitrogen and chlorine nqcc's. The results are given in
Tables 1 and 2. Structure parameters are given in Table 3, atomic
coordinates in Table 4, and rotational constants in Table 5. |
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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. Ø (degrees) is the angle between its
subscripted parameters. ETA = (Xxx - Xyy)/Xzz. RSD
is the calibration residual standard deviation of the model for
calculation of the nqcc's.
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Table 1. Nitrogen nqcc's in 2,3-Dichloropyrazine (MHz). Calculation
was made on the B3P86/6-31G(3d,3p) ropt structure. |
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Calc. |
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Expt. |
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14N(1,4) |
Xaa |
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1.492 |
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Xbb |
- |
4.996 |
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Xcc |
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3.505 |
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Xab |
± |
0.121 |
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RSD |
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0.030 (1.3 %) |
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Xxx |
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1.494 |
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Xyy |
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3.505 |
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Xzz |
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4.999 |
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ETA |
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0.402 |
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Øz,a |
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1.06 |
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Øa,bi |
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0.04 |
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Øz,bi * |
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1.10 |
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* Angle between
the z-axis and the bisector ( 'bi' ) of the CNC angle. |
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Table 2. Chlorine nqcc's in 2,3-Dichloropyrazine (MHz). Calculation
was made on the B3P86/6-31G(3d,3p) ropt structure. |
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Calc. |
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Expt. |
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35Cl(2,3) |
Xaa |
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39.36 |
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Xbb |
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9.64 |
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Xcc |
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29.72 |
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Xab |
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53.51 |
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RSD |
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0.49 (1.1 %) |
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Xxx |
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44.00 |
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Xyy |
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29.72 |
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Xzz |
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73.71 |
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ETA |
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0.194 |
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Øz,a |
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32.70 |
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Øa,CCl |
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31.27 |
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Øz,CCl |
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1.43 |
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37Cl(2,3) |
Xaa |
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31.02 |
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Xbb |
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7.60 |
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Xcc |
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23.42 |
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Xab |
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42.17 |
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RSD |
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0.44 (1.1 %) |
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| Table 3. Molecular structure parameters, ropt (Å
and degrees). |
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C(2,3)Cl(2,3) |
1.7208 * |
N(1)C(2)C(3) |
121.17 |
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N(1)C(2) |
1.3144 |
C(2)C(3)N(4) |
121.17 |
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C(2)C(3) |
1.4086 |
C(3)N(4)C(5) |
117.59 |
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C(3)N(4) |
1.3144 |
N(4)C(5)C(6) |
121.24 |
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N(4)C(5) |
1.3326 |
C(5)C(6)N(1) |
121.24 |
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C(5)C(6) |
1.3869 |
C(6)N(1)C(2) |
117.59 |
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C(6)N(1) |
1.3326 |
N(1)C(2)Cl(2) |
117.56 |
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C(5,6)H(5,6) |
1.0856 |
N(1)C(6)H(6) |
116.96 |
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* In
chloropyrazine, CCl = 1.7327 Å. |
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| Table 4. Atomic coordinates, ropt. Normal species. |
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a (Å) |
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b (Å) |
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N(1,4) |
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1.196362
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± |
1.384584 |
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C(2,3) |
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0.071702
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± |
0.704322 |
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C(5,6) |
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2.335717
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0.693454 |
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Cl(2,3) |
- |
1.399122
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± |
1.597577 |
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H(5,6) |
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3.258434
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± |
1.265421 |
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| Table 5. Rotational Constants
(MHz). Normal species. |
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Calc ropt |
Expt. |
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A |
1952.3 |
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B |
1534.0 |
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C |
859.0 |
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Pyrazine |
Pyridine |
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Pyrimidine |
1,3,5-Triazine |
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Chloropyrazine |
2,3-Difluoropyrazine |
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2,6-Dichloropyrazine |
2,6-Difluoropyrazine |
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Table of Contents
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Molecules/Nitrogen |
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Molecules/Chlorine |
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23DCPyrazine.html |
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Last
Modified 22 June 2004 |
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