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(CH3)2CHCN
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in Isobutylnitrile |
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Calculation of the nitrogen
nqcc's in isobutlynitrile was made on a molecular structure derived
ab initio
as discussed below. These are compared with the experimental
nqcc's of Herberich [1] in Table 1. Structure
parameters are given in Table 2, rotational constants in Table 3.
A link is provided below to the Gaussian input file in Z-Matrix
format. |
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In Table 1, subscripts a,b,c refer to the principal axes of the inertia
tensor, subscripts x,y,z to the principal axes of the nqcc tensor.
The nqcc y-axis is chosen coincident with the inertia b-axis, these
are perpendicular to the symmetry 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 (CH3)2CHCN (MHz). Calculation was
made on the structure given in Table 2. |
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Calc. |
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Expt. [1] |
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14N |
Xaa |
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3.922 |
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3.905(10) |
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Xbb |
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2.094 |
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2.077(20) |
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Xcc |
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1.828 |
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1.828(17) |
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|Xac| |
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1.308 |
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RMS |
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0.014 (0.54 %) |
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RSD |
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0.030 (1.3 %) |
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Xxx |
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2.112 |
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2.112 * |
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Xyy |
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2.094 |
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2.077(20) |
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Xzz |
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4.206 |
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4.189 |
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ETA |
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0.004 |
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0.008 |
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Øz,a |
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12.23 |
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12.26 |
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Øa,CN |
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12.36 |
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12.36 |
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Øz,CN |
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0.13 |
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0.10 |
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* Calculated here from the experimental diagonal nqccc's and the calculated off-diagonal nqcc. |
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Molecular Structure
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The molecular structure was optimized
at the MP2/6-311+G(d,p) level of theory assuming Cs
symmetry. The optimized CN and C-C bond lengths were corrected by
the methods of Ref. [3]. The CH bond lengths were
corrected using r = 1.001 ropt, where ropt is obtained
by MP2/6-31G(d,p) optimization [4]. Interatomic angles used
in the calculation are those given by MP2/6-311+G(d,p) optimization. Structure
parameters thus obtained are shown in Table 2. |
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| Table 2. Molecular structure
parameters (Å and degrees). |
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N(1)C(2) |
1.1567 |
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C(2)C(3) |
1.4650 |
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C(3)H(4) |
1.0940 |
| C(3)C(5) |
1.5264 |
| C(5)H(7) |
1.0904 |
| C(5)H(8) |
1.0893 |
| C(5)H(9) |
1.0900 |
| N(1)C(2)C(3) |
179.15 |
| C(2)C(3)H(4) |
106.71 |
| C(2)C(3)C(5) |
110.18 |
| C(3)C(5)H(7) |
109.54 |
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C(3)C(5)H(8) |
111.20 |
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C(3)C(5)H(9) |
110.26 |
| Dihedral angles? See Z-Matrix |
H(7)C(5)H(8) |
108.73 |
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H(7)C(5)H(9) |
108.56 |
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H(8)C(5)H(9) |
108.49 |
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| Table 3. Rotational Constants
(MHz). |
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Calc. ropt |
Expt. [1] |
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A |
8 050.2 |
7 940.95(4) |
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B |
3 986.9 |
3 968.039(10) |
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C |
2 926.0 |
2 901.030(10) |
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[1] G.E.Herberich, Z.Naturforsch. 22a,543(1967). |
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[2] J.Demaison, J.Cosléou, R.Bocquet,
and A.G.Lesarri, J.Mol.Spectrosc. 167,400(1994). |
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[3] J.Demaison and G.Wlodarczak, Structural
Chem. 5,57(1994). |
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CH3CN
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CH3CH2CN |
(CH3)3CCN |
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Table of Contents |
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Molecules/Nitrogen |
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CH32CHCN.html |
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Last
Modified 16 Nov 2005 |
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