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2,3-F2-C4N2H2
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in 2,3-Difluoropyrazine |
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The molecular structure of 2,3-difluoropyrazine
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 nqcc's. The results are given in Table 1.
Structure parameters are given in Table 2, atomic coordinates
in Table 3, and rotational constants in Table 4. |
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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-Difluoropyrazine (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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1.459 |
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Xbb |
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4.780 |
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Xcc |
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3.322 |
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Xab |
± |
0.029 |
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RSD |
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0.030 (1.3 %) |
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Xxx |
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1.459 |
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Xyy |
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3.322 |
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Xzz |
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4.780 |
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ETA |
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0.390 |
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Øz,a |
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0.26 |
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Øa,bi |
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0.30 |
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Øz,bi * |
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0.03 |
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* Angle between
the z-axis and the bisector ( 'bi' ) of the CNC angle. |
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| Table 2. Molecular structure parameters, ropt (Å
and degrees). |
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N(1)C(2) |
1.3001 |
C(6)N(1)C(2) |
116.62 |
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C(2)C(3) |
1.4022 |
N(1)C(2)C(3) |
121.99 |
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C(3)C(4) |
1.3001 |
C(2)C(3)N(4) |
121.99 |
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N(4)C(5) |
1.3399
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C(3)N(4)C(5) |
116.62 |
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C(5)C(6) |
1.3838
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N(4)C(5)C(6) |
121.39 |
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C(6)N(1) |
1.3399
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C(5)C(6)N(1) |
121.39 |
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C(2,3)F(2,3) |
1.3246 |
N(1)C(2)Cl(2) |
118.49 |
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C(5,6)H(5,6) |
1.0849
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N(1)C(6)H(6) |
116.96 |
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| Table 3. Atomic coordinates, ropt. Normal species. |
| (More figures are shown than are significant.) |
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a (Å) |
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b (Å) |
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N(1,4) |
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0.694174 |
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1.389854 |
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C(2,3) |
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0.408451 |
± |
0.701115 |
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C(5,6) |
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1.837946 |
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0.691879 |
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F(2,3) |
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1.561060 |
± |
1.353854 |
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H(5,6) |
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2.761526 |
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1.261157 |
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| Table 4. Rotational Constants
(MHz). Normal species. |
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Calc ropt |
Expt. |
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A |
3363.9 |
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B |
2446.9 |
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C |
1416.5 |
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Pyrazine |
Pyridine |
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Pyrimidine |
1,3,5-Triazine |
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Fluoropyrazine |
Chloropyrazine |
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2,6-Difluoropyrazine |
2,6-Dichloropyrazine |
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2,3-Dichloropyrazine |
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Table of Contents
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Molecules/Nitrogen |
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23DFPyrazine.html |
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Last
Modified 22 Feb 2004 |
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