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C4N2H3F
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in Fluoropyrazine |
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The molecular structure of fluoropyrazine was
optimized at the B3P86/ 6-31G(3d,3p) level of theory. Cs
symmetry was assumed. On this structure, calculation was made
of the nitrogen nqcc's. These 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 - 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-Fluoropyrazine (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) |
Xaa |
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0.339 |
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Xbb |
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2.940 |
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Xcc |
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3.279 |
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|Xab| |
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2.774 |
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RSD |
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0.030 (1.3 %) |
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Xxx |
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1.424 |
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Xyy |
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3.279 |
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Xzz |
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4.703 |
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ETA |
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0.394 |
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Øz,a |
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57.56 |
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Øa,bi |
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56.88 |
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Øz,bi * |
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0.67 |
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* Angle between
the z-axis and the bisector ( 'bi' ) of the CNC angle. |
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Table 2. Nitrogen nqcc's in 2-Fluoropyrazine (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(4) |
Xaa |
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0.608 |
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Xbb |
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3.452 |
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Xcc |
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4.060 |
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|Xab| |
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2.927 |
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RSD |
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0.030 (1.3 %) |
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Xxx |
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1.224 |
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Xyy |
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4.060 |
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Xzz |
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5.284 |
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ETA |
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0.537 |
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Øz,a |
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57.96 |
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Øa,bi |
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57.26 |
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Øz,bi * |
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0.70 |
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* Angle between
the z-axis and the bisector ( 'bi' ) of the CNC angle. |
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| Table 3. Fluoropyrazine. Molecular structure parameters, ropt (Å
and degrees). |
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C(2)F(2) |
1.3311 |
N(1)C(2)C(3) |
124.27 |
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N(1)C(2) |
1.3069 |
C(2)C(3)N(4) |
120.12 |
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C(2)C(3) |
1.3944 |
C(3)N(4)C(5) |
116.73 |
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C(3)N(4) |
1.3255 |
N(4)C(5)C(6) |
121.81 |
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N(4)C(5) |
1.3354 |
C(5)C(6)N(1) |
121.82 |
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C(5)C(6) |
1.3875 |
C(6)N(1)C(2) |
115.25 |
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C(6)N(1) |
1.3367 |
N(1)C(2)F(2) |
116.93 |
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C(3)H(3) |
1.0859 |
C(2)C(3)H(3) |
121.05 |
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C(5)H(5) |
1.0857 |
C(4)C(5)H(5) |
117.10 |
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C(6)H(6) |
1.0863 |
C(5)C(6)H(6) |
121.40 |
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| Table 4. Fluoropyrazine. Atomic coordinates, ropt. |
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a (Å) |
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b (Å) |
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F(2) |
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2.1467
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0.0557
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N(1) |
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0.2746
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1.1896
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C(2) |
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0.8167
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0.0005
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C(3) |
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0.0940
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1.1920
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N(4) |
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1.2313
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1.1664
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C(5) |
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1.8089
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0.0376
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C(6) |
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1.0620
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1.2070
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H(3) |
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0.5992
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2.1532
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H(5) |
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2.8943
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0.0655
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H(6) |
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1.5388
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2.1831
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| Table 5. Fluoropyrazine. Rotational Constants
(MHz). |
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Calc ropt |
Expt. |
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A |
6092.0 |
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B |
2777.8 |
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C |
1907.8 |
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Pyrazine |
Pyridine |
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Pyrimidine |
1,3,5-Triazine |
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Chloropyrazine |
2-Fluoropyridine |
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2,3-Difluoropyrazine |
3-Fluoropyridine |
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2,6-Difluoropyrazine |
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Table of Contents
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Molecules/Nitrogen |
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FPyrazine.html |
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Last
Modified 21 Feb 2004 |
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