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p-C6H4CH3CN
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in para-Tolunitrile |
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Nitrogen nqcc's in p-tolunitrile were determined by Andersen
et al. [1,2]. |
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Calculation of the nqcc's was made here
on molecular structures given by B3P86/6-31G(3d,3p) optimization assuming
Cs symmetry with the plane of symmetry I) perpendicular to the plane of the ring, and II) coincident
with the plane of the ring. These calculated nqcc's are compared
with the experimental values in Tables 1 and 2. Structure parameters
and atomic coordinates for conformer I are given in Tables 3 and 4. Rotational
constants are given in Table 5. |
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At the B3P86/6-31G(3d,3p) level
of theory, EI < EII by 48 cal/mol. At the B3PW91/6-311+G(df,pd)
level of theory, EI < EII by 17 cal/mol. |
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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. Ø (degrees) is the angle between its
subscripted parameters. ETA = (Xxx - Xyy)/Xzz.
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RMS is the root mean square differene between calculated and
experimental nqcc's (percent of average of the magnitudes of the experimental nqcc). RSD
is the calibration residual standard deviation 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 p-Tolunitrile, conformer I (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 |
Xaa |
- |
4.207 |
- |
4.212(1) |
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Xbb |
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2.337 |
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2.310 |
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Xcc |
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1.870 |
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1.902 |
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|Xac| |
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0.018 |
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RMS |
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0.024 (0.9 %) |
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RSD |
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0.030 (1.3 %) |
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Xxx |
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2.337 |
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2.310 |
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Xyy |
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1.870 |
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1.902 |
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Xzz |
- |
4.207 |
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4.212 |
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ETA |
- |
0.111 |
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0.097 |
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Øz,a |
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0.16 |
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Øa,CN |
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0.18 |
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Øz,CN |
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0.02 |
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Table 2. Nitrogen nqcc's in p-Tolunitrile, conformer II (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 |
Xaa |
- |
4.207 |
- |
4.212(2) |
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Xbb |
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2.337 |
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2.310 |
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Xcc |
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1.870 |
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1.902 |
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|Xab| |
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0.010 |
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RMS |
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0.024 (0.9 %) |
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RSD |
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0.030 (1.3 %) |
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| Table 3. p-Tolunitrile, conformer I. Molecular structure parameters, ropt (Å
and degrees). |
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C(1)C(2) |
1.3968 |
C(1)C(2)C(3) |
121.22 |
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C(2)C(3) |
1.3852 |
C(2)C(3)C(4) |
119.83 |
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C(3)C(4) |
1.3984 |
C(3)C(4)C(5) |
119.58 |
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C(6)C(1)C(2) |
118.32 |
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C(2)H(2) |
1.0856 |
C(1)C(2)H(2) |
119.42 |
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C(3)H(3) |
1.0838 |
C(4)C(3)H(3) |
119.54 |
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C(1)C(Me) |
1.5003 |
C(2)C(1)C(Me) |
120.84 |
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C(Me)H(7) |
1.0953 |
C(1)C(Me)H(7) |
110.75 |
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C(Me)H(8) |
1.0922 |
C(1)C(Me)H(8) |
111.42 |
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C(Me)H(9) |
1.0922 |
C(1)C(Me)H(9) |
111.42 |
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H(7)C(Me)H(8) |
107.35 |
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H(7)C(Me)H(9) |
107.35 |
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H(8)C(Me)H(9) |
108.36 |
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C(4)C(cy) |
1.4275 |
C(5)C(4)C(cy) |
120.21 |
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C(cy)N |
1.1584 |
C(4)C(cy)N |
179.88 |
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| For comparison, the B3P86/6-31G(3d,3p) optimized molecular
structure of benzene is CC = 1.3909 Å and CH = 1.0851 Å. |
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| Table 4. p-Tolunitrile, conformer I. Atomic coordinates, ropt. |
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a (Å) |
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b (Å) |
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c (Å) |
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C(1) |
- |
1.7898 |
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0.0000 |
- |
0.0088 |
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C(2,6) |
- |
1.0737 |
± |
1.1993 |
- |
0.0089 |
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C(3,5) |
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0.3114 |
± |
1.2084 |
- |
0.0032 |
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C(4) |
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1.0150 |
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0.0000 |
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0.0007 |
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H(2,6) |
- |
1.6122 |
± |
2.1420 |
- |
0.0156 |
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H(3,5) |
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0.8574 |
± |
2.1446 |
- |
0.0051 |
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C(Me) |
- |
3.2900 |
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0.0000 |
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0.0158 |
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H(7) |
- |
3.6612 |
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0.0000 |
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1.0462 |
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H(8,9) |
- |
3.6970 |
± |
0.8856 |
- |
0.4771 |
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C(cy) |
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2.4425 |
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0.0000 |
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0.0037 |
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N |
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3.6009 |
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0.0000 |
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0.0074 |
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| Table 5. p-Tolunitrile, conformer I. Rotational Constants (MHz). |
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Calc. ropt |
Expt. [1] |
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A |
5539.2 |
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B |
984.8 |
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C |
840.5 |
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[1] U.Andresen, T.Bruhn, M.Gnida, and H.Mäder, unpublished, cited in [2]. |
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[2] N.Hansen, H.Mäder, and T.Bruhn,
Mol.Phys. 97,587(1999). |
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Benzonitrile |
o-Fluorobenzonitrile |
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o-Tolunitrile |
m-Fluorobenzonitrile |
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m-Tolunitrile |
p-Fluorobenzonitrile |
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Table of Contents
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Molecules/Nitrogen |
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p_TolNit.html |
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Last
Modified 23 Sept 2003 |
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