CHF2CN




 








Nitrogen


Nuclear Quadrupole Coupling Constants


in Difluoroacetonitrile


 







 
 
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.
 
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.
 
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.
 
 
   







Table 1.  Nitrogen nqcc's in CHF2CN (MHz).
   










Calc.
Expt. [1]
   






14N Xaa - 4.418 - 4.3899(33)
Xbb 2.439 2.4017(39)
Xcc 1.978 1.9883(39)
|Xac| 1.260
 
RMS 0.027 (0.9 %)
RSD 0.030 (1.3 %)
 
Xxx 2.218 2.228 *
Xyy 2.439 2.4017(39)
Xzz - 4.657 - 4.630
ETA 0.048 0.038
Øz,a 10.75 10.78
Øa,CN 10.31 10.31
Øz,CN   0.44   0.47
 
   
* Calculated here from the experimental diagonal nqcc's and the calculated off-diagonal nqcc.
 
 
Molecular Structure
 
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].
 
 
Table 2. Molecular structure parameters (Å and degrees).
CF 1.348
CH 1.090
CC 1.474
CN 1.1557
CCF 109.38
CCH 111.22
CCN 178.20
CN tilts away from F's.

 
 
Table 3.  Atomic Coordinates.
(More figures are show than are significant.)
   a (Å)    b (Å)    c (Å)
H 0.580879 1.470616 0.0
F 0.981595 - 0.145645 ± 1.093972
C 0.408260 0.394371 0.0
C - 1.032949 0.085194 0.0
N - 2.169997 - 0.121606 0.0
 
 
[1] J.Spieckermann, M.Andolfatto, and D.H.Sutter, Z.Naturforsch. 42a,167(1987).
[2] W.Kasten, H.Dreizler, B.E.Job, and J.Sheridan, Z.Naturforsch 38a,1015(1983).
[3] J.Demaison, J.Cosléou, R.Bocquet, and A.G.Lesarri, J.Mol.Spectrosc. 167,400(1994).
[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)
[5] J.Demaison and G.Wlodarczak, Structural Chem. 5,57(1994).

 








 







CH2FCN CF3CN CH3CN
 

 








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Molecules/Nitrogen
 

 













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Last Modified 20 Oct 2003