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CHF2CN
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in Difluoroacetonitrile |
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Calculation of the nitrogen nqcc's was made
here on a molecular structure derived ab initio
(see below). These are compared with the experimental nqcc's [1,2] in
Table 1. Structure parameters and atomic coordinates respectively
are given in Tables 2 and 3. |
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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 CHF2CN (MHz). |
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Calc. |
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Expt. [1] |
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14N |
Xaa |
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4.418 |
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4.3899(33) |
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Xbb |
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2.439 |
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2.4017(39) |
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Xcc |
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1.978 |
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1.9883(39) |
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|Xac| |
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1.260 |
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RMS |
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0.027 (0.9 %) |
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RSD |
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0.030 (1.3 %) |
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Xxx |
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2.218 |
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2.228 * |
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Xyy |
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2.439 |
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2.4017(39) |
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Xzz |
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4.657 |
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4.630 |
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ETA |
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0.048 |
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0.038 |
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Øz,a |
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10.75 |
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10.78 |
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Øa,CN |
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10.31 |
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10.31 |
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Øz,CN |
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0.44 |
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0.47 |
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* Calculated here from the experimental
diagonal nqcc's and the calculated off-diagonal nqcc. |
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Molecular Structure
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The molecular structure was optimized
at the MP2/6-311G(d,p) level of theory assuming Cs symmetry.
The optimized CC and CN bond lengths were then corrected using
equations obtained from linear regression analysis of the data given
in reference [3]. Likewise, the optimized CF bond lengths were corrected
by regression analysis of the data given in reference [4]. The
CH bond lengths were corrected using r = 1.001 ropt, where
ropt is obtained by MP2/6-31G(d,p) optimization [5]. |
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| Table 2. Molecular structure
parameters (Å and degrees). |
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CF |
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1.348 |
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CH |
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1.090 |
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CC |
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1.474 |
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CN |
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1.1557 |
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CCF |
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109.38 |
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CCH |
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111.22 |
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CCN |
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178.20 |
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CN tilts away from F's. |
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| Table 3. Atomic Coordinates. |
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show than are significant.) |
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a (Å) |
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b (Å) |
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c (Å) |
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H |
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0.580879 |
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1.470616 |
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0.0 |
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F |
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0.981595 |
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0.145645 |
± |
1.093972 |
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C |
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0.408260 |
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0.394371 |
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0.0 |
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C |
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1.032949 |
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0.085194 |
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0.0 |
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N |
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2.169997 |
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0.121606 |
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0.0 |
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[1] J.Spieckermann, M.Andolfatto, and D.H.Sutter, Z.Naturforsch.
42a,167(1987). |
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[2] W.Kasten, H.Dreizler, B.E.Job, and
J.Sheridan, Z.Naturforsch 38a,1015(1983). |
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[3] J.Demaison, J.Cosléou, R.Bocquet,
and A.G.Lesarri, J.Mol.Spectrosc. 167,400(1994). |
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[4] R.M.Villamañan, W.D.Chen, G.Wlodarczak,
J.Demaison, A.G.Lesarri, J.C.López, and J.L.Alonso, J.Mol.Spectrosc.
171,223(1995) |
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[5] J.Demaison and G.Wlodarczak, Structural
Chem. 5,57(1994). |
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CH2FCN |
CF3CN |
CH3CN |
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Table of Contents |
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Molecules/Nitrogen |
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CHF2CN.html |
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Last
Modified 20 Oct 2003 |
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