CF3(CF2)2CF2CN




 
 


Nitrogen


Nuclear Quadrupole Coupling Constants

in n-Perfluorobutyl Cyanide transoid


 







 
 
Calculation of the nitrogen nqcc's in n-perfluorobutyl cyanide, transoid was made on structures given by B3P86/6-31G(2d) optimization (ropt), and on this same structure but with empirically derived equilibrium CF, C-C, and CN bond lengths (~ re).  These calculated nqcc's are given in Table 1.  Structure parameters are given in Table 2, rotational constants and electric dipole moments in Table 3.
 
In Table 1, subscripts a,b,c refer to principal axes of the inertia tensor; subscripts x,y,z to principal axes of the nqcc tensor.  Øz,CN (degrees) is the angle between the principal z-axis of the nqcc tensor and the CN bond axis.  ETA = (Xxx - Xyy)/Xzz.
RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of the nitrogen nqcc's, which may be taken as an estimate of the uncertainty in the calculated nqcc's (unertainties in the structures not-with-standing).
 
 
 
   





Table 1.  14N nqcc's in n-perfluorobutyl cyanide, transoid (MHz).  Calculation was made on ropt and ~ re structures
   





 ropt  ~ re Expt.
   




Xaa - 1.991 - 1.988
Xbb - 0.295 - 0.295
Xcc 2.286 2.282
|Xab| 3.453 * 3.445 *
|Xac| 0.480 0.477
|Xbc| 0.427 0.426
 
RSD 0.030 (1.3 %) 0.030 (1.3 %)
 
Xxx 2.326 2.321
Xyy 2.432 2.426
Xzz - 4.757 - 4.747
ETA 0.0222 0.0221
Øz,CN 0.44 0.43
 

 
* The algebraic sign of the product XabXacXbc is negative.
 
 
Table 2.  n-Perfluorobutyl Cyanide, transoid.  Selected structure parameters, ropt and ~ re (Å and degrees).   Complete structures are given here in Z-matrix format.
 

  ropt   ~ re
C(1)C(2) 1.5474 1.5461
C(2)C(3) 1.5486 1.5473
C(3)C(4) 1.5513 1.5498
C(4)C(5) 1.4789 1.4806
C(5)N 1.1534 1.1544
C(1)C(2)C(3) 113.82 113.82
C(2)C(3)C(4) 114.00 114.00
C(3)C(4)C(5) 110.08 110.08
C(4)C(5)N 179.39 179.39
C(1)C(2)C(3)C(4) 165.01 165.01
C(2)C(3)C(4)C(5) 169.47 169.47
C(3)C(4)C(5)N   48.70   48.70

 
 
Table 3.  n-Perfluorobutyl Cyanide, transoid.  Rotational Constants (MHz) and Dipole Moments (D).
 ropt  ~ re  Expt.
A 1176.6 1171.6
B   447.8   447.6
C   424.4   424.4
 
a| 1.20 1.18
b| 0.75 0.74
c| 0.15 0.14

 
 
Order of the energies of the several conformers of n-perfluorobutyl cyanide is Etransoid(0) < EGA(0.54) < EAA(0.92) < EAG(6.95 kJ/mol).  These are energies calculated at the B3PW91/6-311+G(df) level of theory on the B3P86/6-31G(2d) optimized structures.
The AA (all trans, Cs) conformer, with one imaginary frequency, is a saddle point connecting two lower energy minima [1].  It is not, itself, a local minimum.
 
 
[1] J.B.Foresman and AE.Frisch, Exploring Chemistry with Electronic Structure Methods, 2nd ed., Gaussian, Inc. Pittsburgh, PA 1995-96.
 
 
n-Butyl Cyanide AG n-Perfluorobutyl Cyanide AG
n-Butyl Cyanide GA n-Perfluorobutyl Cyanide GA
n-Butyl Cyanide AA
 

 








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Last Modified 3 June 2010