CF3(CF2)2CF2CN



 
 
 


Nitrogen


Nuclear Quadrupole Coupling Constants

in n-Perfluorobutyl Cyanide anti-gauche

 







 
 
Calculation of the nitrogen nqcc's in n-perfluorobutyl cyanide 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, AG (MHz).  Calculation was made on ropt and ~ re structures
   




 ropt  ~ re Expt.
   



Xaa - 2.548 - 2.542
Xbb 1.830 1.823
Xcc 0.718 0.719
|Xab| 1.608 * 1.610 *
|Xac| 2.865 2.858
|Xbc| 0.985 0.985
 
RSD 0.030 (1.3 %) 0.030 (1.3 %)
 
Xxx 2.334 2.329
Xyy 2.419 2.413
Xzz - 4.753 - 4.742
ETA 0.0179 0.0177
Øz,CN 0.39 0.37
 

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

  ropt   ~ re
C(1)C(2) 1.5468 1.5455
C(2)C(3) 1.5624 1.5604
C(3)C(4) 1.5504 1.5490
C(4)C(5) 1.4792 1.5808
C(5)N 1.1534 1.1544
C(1)C(2)C(3) 115.02 115.02
C(2)C(3)C(4) 115.00 115.00
C(3)C(4)C(5) 109.94 109.94
C(4)C(5)N 179.72 179.72
C(1)C(2)C(3)C(4) - 98.03 - 98.03
C(2)C(3)C(4)C(5) 172.11 172.11
C(3)C(4)C(5)N   42.62   42.62

 
 
Table 3.  n-Perfluorobutyl Cyanide, AG.  Rotational Constants (MHz) and Dipole Moments (D).
 ropt  ~ re  Expt.
A 1074.1 1070.3
B   470.4   470.2
C   463.0   462.9
 
|µa| 1.24 1.22
|µb| 0.32 0.31
|µc| 0.60 0.59

 
 
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-Butyl Cyanide GA n-Perfluorobutyl Cyanide, GA
n-Butyl Cyanide AA n-Perfluorobutyl Cyanide, transoid
 

 








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Last Modified 3 June 2010