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o-C6H4CH3CN
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in ortho-Tolunitrile |
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Nitrogen nqcc's in o-tolunitrile were determined by Hansen
et al. [1]. |
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Hansen et al. found, for optimization at the MP2/6-311G**
level of theory, that the minimum energy with respect to orientation
of the methyl hydrogens corresponds to a position of one CH bond (in the Cs
plane) pointing away from CN. |
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The nqcc's were calculated here on molecular
structures given by B3P86/6-31G(3d,3p) optimization with the CH bond
in the Cs plane I) pointing away from CN, and II) pointing toward CN.
These calculated nqcc's are compared with the experimental values in
Tables 1 and 2. Conformer I structure parameters and atomic coordinates
are given in Tables 3 and 4. Rotational constants are given in Table
5. |
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For both the B3P86/6-31G(3d,3p) and the B3PW91/6-311+G(df,pd)
models, we find, in agreement with Hansen et al., that EI <
EII. |
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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.
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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 o-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 |
- |
4.096 |
- |
4.094(2) |
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Xbb |
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2.170 |
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2.143 * |
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Xcc |
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1.926 |
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1.951 * |
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|Xab| |
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0.892 |
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0.8(5) |
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RMS |
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0.022 (0.8 %) |
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RSD |
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0.030 (1.3 %) |
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Xxx |
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2.295 |
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2.267 ** |
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Xyy |
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1.926 |
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1.951 |
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Xzz |
- |
4.220 |
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4.219 |
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ETA |
- |
0.087 |
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0.075 |
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Øz,a |
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7.94 |
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7.98 |
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Øa,CN |
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7.63 |
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7.63 |
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Øz,CN |
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0.31 |
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0.35 |
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* Calculated here from Xaa and Xbb - Xcc = 0.191(6) [1]. |
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** Calculated here using |Xab|
= 0.892 MHz rather than 0.8(5). |
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Table 2. Nitrogen nqcc's in o-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 |
- |
4.064 |
- |
4.094(2) |
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Xbb |
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2.183 |
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2.143 |
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Xcc |
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1.882 |
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1.951 |
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|Xab| |
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0.930 |
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0.8(5) |
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RMS |
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0.049 (1.8 %) |
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RSD |
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0.030 (1.3 %) |
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| Table 3. o-Tolunitrile, conformer I. Molecular structure parameters, ropt (Å
and degrees). |
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C(1)C(2) |
1.4071 |
C(1)C(2)C(3) |
121.18 |
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C(2)C(3) |
1.3984 |
C(2)C(3)C(4) |
119.93 |
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C(3)C(4) |
1.3857 |
C(3)C(4)C(5) |
119.55 |
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C(4)C(5) |
1.3905 |
C(4)C(5)C(6) |
120.34 |
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C(5)C(6) |
1.3900 |
C(5)C(6)C(1) |
121.42 |
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C(6)C(1)C(2) |
117.58 |
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C(3)H(3) |
1.0839 |
C(2)C(3)H(3) |
119.19 |
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C(4)H(4) |
1.0841 |
C(3)C(4)H(4) |
120.01 |
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C(5)H(5) |
1.0848 |
C(6)C(5)H(5) |
119.66 |
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C(6)H(6) |
1.0853 |
C(1)C(6)H(6) |
118.88 |
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C(1)C(Me) |
1.4985 |
C(2)C(1)C(Me) |
120.84 |
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C(Me)H(7) |
1.0908 |
C(1)C(Me)H(7) |
111.01 |
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C(Me)H(8) |
1.0939 |
C(1)C(Me)H(8) |
111.18 |
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C(Me)H(9) |
1.0939 |
C(1)C(Me)H(9) |
111.18 |
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H(7)C(Me)H(8) |
108.36 |
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H(7)C(Me)H(9) |
108.36 |
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H(8)C(Me)H(9) |
106.58 |
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C(2)C(cy) |
1.4287 |
C(1)C(2)C(cy) |
119.52 |
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C(cy)N |
1.1587 |
C(2)C(cy)N |
179.54 |
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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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| In the structure of conformer II, C(2)C(cy) = 1.4294 Å, and C(cy)N = 1.1587
Å. |
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| Table 4. o-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) |
- |
0.0986 |
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0.9417 |
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C(2) |
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0.4153 |
- |
0.3682 |
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C(3) |
- |
0.4340 |
- |
1.4791 |
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C(4) |
- |
1.8079 |
- |
1.2991 |
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C(5) |
- |
2.3306 |
- |
0.0106 |
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C(6) |
- |
1.4830 |
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1.0910 |
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H(3) |
- |
0.0033 |
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2.4738 |
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H(4) |
- |
2.4675 |
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2.1594 |
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H(5) |
- |
3.4051 |
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0.1388 |
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H(6) |
- |
1.9022 |
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2.0921 |
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C(Me) |
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0.8186 |
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2.1266 |
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H(7) |
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0.2528 |
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3.0592 |
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H(8,9) |
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1.4724 |
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2.1204 |
± |
0.8769 |
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C(cy) |
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1.8297 |
- |
0.5695 |
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N |
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2.9781 |
- |
0.7234 |
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| Table 5. o-Tolunitrile, conformer I. Rotational Constants (MHz). |
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Calc. ropt |
Expt. [1] |
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A |
2906.3 |
2891.6469(5) |
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B |
1508.1 |
1499.8809(1) |
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C |
999.0 |
993.52170(6) |
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[1] N.Hansen, H.Mäder, and T.Bruhn, Mol.Phys. 97,587(1999). |
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Benzonitrile |
o-Fluorobenzonitrile |
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m-Tolunitrile |
m-Fluorobenzonitrile |
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p-Tolunitrile |
p-Fluorobenzonitrile |
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Table of Contents
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Molecules/Nitrogen |
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o_TolNit.html |
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Last
Modified 23 Sept 2003 |
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