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C4N2H3Cl
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Nitrogen and Chlorine
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Nuclear
Quadrupole Coupling Constants |
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in Chloropyrazine |
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The molecular structure of chloropyrazine 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 and chlorine nqcc's. The nitrogen nqcc's are given
in Tables 1 and 2. The calculated chlorine nqcc's are compared with the experimental
values of Akavipa, Su, and Cook [1] in Table 3. Structure parameters
are given in Table 4, atomic coordinates in Table 5, and rotational
constants in Table 6. |
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In Tables 1 - 3, 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.
RMS is the root mean square differene between calculated and
experimental nqcc's (percent of average experimental nqcc). 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 2-35Cl-Pyrazine (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 |
- |
0.285 |
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Xbb |
- |
3.211 |
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Xcc |
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3.497 |
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|Xab| |
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2.860 |
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RSD |
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0.030 (1.3 %) |
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Xxx |
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1.464 |
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Xyy |
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3.497 |
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Xzz |
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4.961 |
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ETA |
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0.410 |
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Øz,a |
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58.54 |
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Øa,bi |
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58.33 |
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Øz,bi * |
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0.21 |
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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 2-35Cl-Pyrazine (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 |
- |
0.476 |
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Xbb |
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3.524 |
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Xcc |
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4.000 |
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|Xab| |
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2.809 |
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RSD |
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0.030 (1.3 %) |
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Xxx |
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1.196 |
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Xyy |
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4.000 |
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Xzz |
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5.196 |
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ETA |
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0.540 |
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Øz,a |
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59.24 |
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Øa,bi |
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58.47 |
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Øz,bi * |
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0.77 |
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Table 3. Chlorine nqcc's in Chloropyrazine (MHz). Calculation
was made on the B3P86/6-31G(3d,3p) ropt structure. |
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Calc. |
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Expt. [1] |
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35Cl |
Xaa |
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71.65 |
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71.64 |
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Xbb |
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40.88 |
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40.48 |
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Xcc |
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30.76 |
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31.16 |
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|Xab| |
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2.33 |
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RMS |
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0.33 (0.69 %) |
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RSD |
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0.49 (1.1 %) |
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Xxx |
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40.93 |
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40.53 * |
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Xyy |
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30.76 |
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31.16 |
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Xzz |
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71.70 |
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71.69 |
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ETA |
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0.142 |
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0.131 |
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Øz,a |
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1.18 |
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1.19 |
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Øa,CCl |
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1.53 |
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1.53 |
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Øz,CCl |
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0.35 |
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0.34 |
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37Cl |
Xaa |
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56.47 |
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56.67(32) |
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Xbb |
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32.22 |
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Xcc |
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24.24 |
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|Xab| |
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1.80 |
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* Calculated
here from the experimental diagonal elements and the calculated Xab. |
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| Table 4. Molecular structure parameters, ropt (Å
and degrees). |
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C(2)Cl(2) |
1.7327 |
N(1)C(2)C(3) |
123.14 |
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N(1)C(2) |
1.3160 |
C(2)C(3)N(4) |
120.74 |
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C(2)C(3) |
1.3966 |
C(3)N(4)C(5) |
116.72 |
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C(3)N(4) |
1.3265 |
N(4)C(5)C(6) |
121.75 |
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N(4)C(5) |
1.3335 |
C(5)C(6)N(1) |
121.84 |
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C(5)C(6) |
1.3888 |
C(6)N(1)C(2) |
115.82 |
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C(6)N(1) |
1.3339 |
N(1)C(2)Cl(2) |
117.77 |
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C(3)H(3) |
1.0856 |
C(2)C(3)H(3) |
121.04 |
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C(5)H(5) |
1.0863 |
C(4)C(5)H(5) |
117.13 |
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C(6)H(6) |
1.0864 |
C(5)C(6)H(6) |
121.39 |
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| Table 5. Atomic coordinates, ropt. Normal species. |
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a (Å) |
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b (Å) |
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Cl(2) |
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2.132996
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0.024124
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N(1) |
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0.180986
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1.202678
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C(2) |
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0.400891
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0.022265
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C(3) |
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0.310507
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1.179610
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N(4) |
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1.636971
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1.182247
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C(5) |
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2.238839
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0.007719
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C(6) |
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1.514860
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1.192922
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H(3) |
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0.204817
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2.135077
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H(5) |
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3.325098
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0.013411
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H(6) |
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2.011229
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2.159312
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| Table 6. Rotational Constants
(MHz). Normal species. |
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Calc ropt |
Expt. [1] |
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A |
6094.6 |
6024.281(115) |
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B |
1667.3 |
1664.099(3) |
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C |
1309.2 |
1304.622(3) |
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[1] S.Akavipa, C.F.Su, and R.L.Cook, J.Mol.Spectrosc. 111,209(1985). |
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Pyrazine |
Pyridine |
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Pyrimidine |
1,3,5-Triazine |
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2-Chloropyridine |
3-Chloropyridine |
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2,6-Dichloropyrazine |
2,3-Dichloropyrazine |
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Table of Contents
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Molecules/Nitrogen |
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Molecules/Chlorine |
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ClPyrazine.html |
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Last
Modified 19 Nov 2003 |
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