CF3(CF2)3CF2CN




 
 
 


Nitrogen


Nuclear Quadrupole Coupling Constants

in n-Perfluoropentyl transoid


 







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





 ropt  ~ re Expt.
   




Xaa - 2.448 - 2.442
Xbb 0.351 0.348
Xcc 2.096 2.094
|Xab| 3.170 * 3.164 *
|Xac| 1.058 1.053
|Xbc| 0.736 0.735
 
RSD 0.030 (1.3 %) 0.030 (1.3 %)
 
Xxx 2.323 2.318
Xyy 2.433 2.428
Xzz - 4.756 - 4.746
ETA 0.0231 0.0231
Øz,CN 0.39 0.37
 

 
* The algebraic sign of the product XabXacXbc is negative.
 
 
Table 2.  n-Perfluoropentyl 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) 1.5469 1.5456
C(2)C(3) 1.5506 1.5491
C(3)C(4) 1.5527 1.5511
C(4)C(5) 1.5519 1.5504
C(5)C(6) 1.4788 1.4805
C(6)N(7) 1.1534 1.1544
C(1)C(2)C(3) 113.91 113.91
C(2)C(3)C(4) 112.79 112.79
C(3)C(4)C(5) 113.76 113.76
C(4)C(5)C(6) 110.10 110.10
C(5)C(6)N(7) 179.48 179.48
C(1)C(2)C(3)C(4) 163.56 163.56
C(2)C(3)C(4)C(5) 162.42 162.42
C(3)C(4)C(5)C(6) 169.07 169.07
C(4)C(5)C(6)N(7)   64.86   64.86

 
 
Table 3.  n-Perfluoropentyl Cyanide, transoid.  Rotational Constants (MHz) and Dipole Moments (D).
 ropt  ~ re  Expt.
A 954.0 950.0
B 278.0 278.1
C 268.9 269.0
 
a| 1.28 1.26
b| 0.74 0.74
c| 0.21 0.21

 
 
Order of the energies of the several conformers of n-perfluoropentyl cyanide is Etransoid(0) < EGA(0.47) < EAA(3.04 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-Perfluoropentyl Cyanide GA n-Perfluorobutyl Cyanide transoid
n-Perfluorohexyl Cyanide transoid n-Perfluoroheptyl Cyanide transoid
 

 








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Last Modified 4 June 2010