Nuclear Quadrupole Coupling Constants

in Chlorotrifluoroethylene


Calculation of the chlorine nqcc's in chlorotrifluoroethylene was made on a structure derived ab initio, as described below.  These are compared with the experimental nqcc's of Hillig et al. [1] in Table 1.  Structure parameters are given in Table 2.
In Table 1, RMS is the root mean square difference between calculated and experimental diagonal nqcc's (percentage of the average of the magnitudes of the experimental nqcc's).  RSD is the calibration residual standard deviation for the B1LYP/TZV(3df,2p) model for calculation of the chlorine nqcc's. 
Subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  The nqcc y-axis is chosen coincident with the inertia c-axis, these are perpendicular to the molecular symmetry plane.  Ø (degrees) is the angle between its subscripted parameters.  ETA = (Xxx - Xyy)/Xzz.



Table 1. Chlorine nqcc's in F2C=CFCl (MHz).  Calculation was made on the ab initio ropt structure.

Expt. [1]

35Cl Xaa - 49.66 - 49.84817(83)
Xbb 11.54 11.2341 *
Xcc 38.12 38.6140 *
|Xab| 49.25 49.489(34)
RMS 0.35 (1.1 %)
RSD 0.49 (1.1 %)
Xxx 38.93 38.85(10)
Xyy 38.12 38.614(3)
Xzz - 77.05 - 77.46(10)
ETA - 0.010
Øz,a 29.07 29.16(3)
Øa,CCl 29.95
Øz,CCl   0.87
37Cl Xaa - 40.17
Xbb 10.13
Xcc 30.04
|Xab| 38.16
RSD 0.44 (1.1 %)
* Calculated here from Xaa and Xbb - Xcc = -27.3799(17) MHz [1].
Ab Initio Molecular Structure
The molecular structure was optimized at the MP2/6-311+G(d,p) level of theory assuming Cs symmetry.  The optimized C=C bond length was then corrected using the equation obtained from linear regression analysis of the data given in Table IX of Ref. [4].  Likewise, the optimized CF bond lengths were corrected by regression analysis of the data given in Table VI of Ref. [3].  For the CCl bond, the structure was optimized at the MP2/6-311+G(2d,p) level and corrected by linear regression analysis of the data given in Table 4 of Ref. [2].  Interatomic angles are those given by MP2/6-311+G(2d,p) optimization.
Table 2.  Molecular structure parameters, ropt (Å and degrees).
C(1)Cl 1.6896
C(1)F 1.3271
C=C 1.3256

C(2)Fc 1.3094
C(2)Ft 1.3100
C=CCl 124.09
ClCF 116.13
C=CFc 123.87
C=CFt 123.24

[1] K.W.Hillig II, E.R.Bittner, R.L.Kuczkowski, W.Lewis-Bevan, and M.C.L.Gerry, J.Mol.Spectrosc. 132,369(1988).
[2] I.Merke, L.Poteau, G.Wlodarczak, A.Bouddou, and J.Demaison, J.Mol.Spectrosc. 177,232(1996).
[3] 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).
[4] J.Demaison, J.Cosléou, R.Bocquet, and A.G.Lesarri, J.Mol.Spectrosc. 167,400(1994).


R.G.Stone and W.H.Flygare, J.Mol.Spectrosc. 32,233(1969).  Xaa = -50.10(10), Xbb = 11.36(10), and Xcc = 38.74(20) MHz for 35Cl.




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Last Modified 14 Feb 2006