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(CH3)2CHCN |
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in
Isobutyronitrile (Isopropyl Cyanide) |
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Calculation of the nitrogen nqcc's in
isobutyronitrile was made on an approximate equilibrium molecular
structure derived ab initio by MP2/aug-cc-pVTZ
optimization with empirically corrected C-C and CN bond lengths.
These are compared with the experimental
nqcc's [1,2] in Table 1. Structure
parameters are given in Table 2, rotational constants in Table 3. |
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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. 14N nqcc's
in (CH3)2CHCN (MHz). Calculation was
made on the MP2 structure given in Table 2. |
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Calc. |
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Expt. [1] |
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Expt. [2] |
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Xaa |
- |
3.916 |
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3.93838(23) |
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3.905(10) |
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Xbb |
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2.090 |
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2.11117(30) |
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2.077(20) |
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Xcc |
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1.825 |
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1.82721(24) |
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1.828(17) |
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|Xac| |
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1.325 |
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1.278 * |
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1.325(30) ** |
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RMS |
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0.018 (0.68 %) |
0.009 (0.36 %) |
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RSD |
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0.030 (1.3 %) |
0.030 (1.3 %) |
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Xxx |
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2.116 |
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2.119(20) *** |
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Xyy |
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2.090 |
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2.077(20) |
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Xzz |
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4.206 |
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4.209 |
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4.196(16) |
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ETA |
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0.006 |
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0.003 |
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0.010(7) |
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Øz,a |
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12.39 |
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12.40(25) |
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Øa,CN |
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12.54 |
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12.54 |
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Øz,CN |
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0.15 |
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0.14 |
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* Scaled ab initio value, see Ref. [1]. |
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** Calculated value. Assumed
uncertainity is 1*RSD. |
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*** Calculated here using Kisiel's
QDIAG.f program. |
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| Table 2. (CH3)2CHCN
Heavy atom
structure parameters (Å and degrees). Complete structure is
given here in Z-matrix format. |
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N(1)C(2) |
1.1566 |
| C(2)C(3) |
1.4645 |
| C(3)C(5,6) |
1.5273 |
| N(1)C(2)C(3) |
179.05 |
| C(2)C(3)C(5,6) |
110.03 |
| N(1)C(2)C(3)C(5,6) |
±61.73 |
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| Table 3. (CH3)2CHCN
Rotational
Constants (MHz). |
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Calc. |
Expt. [1] |
Expt. [2] |
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A |
8 047.8 |
7940.877174(31) |
7940.95(4) |
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B |
3 992.7 |
3968.087775(27) |
3968.039(10) |
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C |
2 930.7 |
2901.053223(22) |
2901.030(10) |
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[1] H.S.P.Müller, A.Coutens,
A.Walters, J.-U.Grabow, and S.Schlemmer, J.Mol.Spectrosc. 267,100(2011). |
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[2] G.E.Herberich, Z.Naturforsch.
22a,543(1967). |
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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 28 Feb 2011 |
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