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Quinoxaline
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in
Quinoxaline |
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Nitrogen nqcc tensors in quinoxaline
were calculated on a molecular structure optimized at the
B3P86/6-31G(3d,3p) level of theory (ropt). These
calculated nqcc's are compared with the experimental values of
McNaughton et al. [1] in Table 1. Structure parameters are
given in Table 2, rotational constants and electric dipole moments in
Table 3. |
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In Table 1, subscripts a,b,c refer to
principal axes of the inertia tensor, subscripts x,y,z to principal
axes of the nqcc tensor. The nqcc y-axis is chosen coincident
with the inertia c-axis, these are perpendicular to the plane of the
molecule. Ø (degrees) is the angle between its subscripted
parameters. ETA = (Xxx - Xyy)/Xzz. |
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RMS is the root mean square
difference between calculated and experimental nqcc's (percentage of
average experimental nqcc). RSD is the residual stand deviation
of calibration of the B3PW91/6-311+G(df,pd) model for calculation of
the nqcc's. |
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Table 1. Nitrogen
nqcc's in Quinoxaline (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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14N(1,2) |
Xaa |
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1.203 |
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1.2123(61) |
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Xbb |
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4.973 |
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4.9402 * |
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Xcc |
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3.770 |
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3.7279 * |
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Xab |
± |
0.272 |
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RMS |
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0.032 (0.96 %) |
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RSD |
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0.030 (1.3 %) |
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Xxx |
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1.215 |
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Xyy |
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3.770 |
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Xzz |
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4.985 |
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ETA |
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0.512 |
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Øz,b |
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2.51 |
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Øb,bi |
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0.75
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Øz,bi** |
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3.27
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* Calculated here from experimental Xaa and
Xbb - Xcc = -8.6681(64) MHz. |
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** The z-axis makes an angle of
3.27
with the external bisector ('bi') of the CNC angle and tilts toward
C(3,4). See Table 2 for atomic numbering. |
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| Table 2. Quinoxaline and
Pyrazine. Selected molecular structure parameters,
B3P86/6-31G(3d,3p) ropt (Å and degrees).
The complete structure of quinoxaline is given here in Z-matrix format. |
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Quinoxaline |
Pyrazine |
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C(4)N |
1.3592 |
1.3317 |
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NC(11) |
1.3099 |
1.3317 |
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C(4)NC(11) |
116.14 |
115.77 |
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| Table 3.
Quinoxaline, ropt.
Rotational constants (MHz) and B3PW91/6-311+G(df,pd) calculated
dipole moments (D). |
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Calc. |
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Expt. [1] |
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A |
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3187.98 |
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3165.90728(64) |
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B |
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1319.30 |
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1310.636904(72) |
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C |
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933.14 |
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927.130503(46) |
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µa |
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0.56 |
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[1] D.McNaughton, P.D.Godfrey,
M.K.Jahn, D.A.Dewald, and J.-U.Grabow, J.Chem.Phys. 134,154305(2011). |
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Pyrazine |
Quinazoline |
Phthalazine |
1,10-Phenanthroline |
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Acridine |
Quinoline |
Isoquinoline |
Phenanthridine |
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Table of Contents |
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Molecules/Nitrogen |
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Quinoxaline.html |
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Last
Modified 20 April 2011 |
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