CF3N=C=O































 









Nitrogen


Nuclear Quadrupole Coupling Constants


in Trifluoromethyl Isocyanate


 








 








Calculation was made of the 14N nqcc tensor in trifluoromethyl isocyanate on ropt structures given by B3LYP/6-311+G(3df,3pd) and MP2/6-311+G(3df,3pd) optimization. 


 








In Table 1, these calculated nqcc's are compared with the experimental values of Koput et al. [1].  Subscripts a,b,c refer to the principal axes of the inertia tensor.  Subscripts x,y,z refer to the principal axes of the nqcc tensor.  ETA = (Xxx - Xyy)/Xzz.  Ø (degrees) is the angle between its subscripted parameters.  RMS is the root mean square difference between calculated and experimental nqcc's (percentage of average experimental nqcc).  RSD is the residual standard deviation of calibration of the B3PW91/6-311+G(df,pd) model for calculation of the efg's/nqcc's.

Structure parameters are given in Z-matrix format in Table 2, rotational constants are given in Table 3.

 








 








   







Table 1.  14N nqcc's in CF3N=C=O (MHz).  Calculation was made on ropt molecular structures given by B3LYP/6-311+G(3df,3pd) and MP2/6-311+G(3df,3pd) optimization.  NOTE: Calculated Xbb and Xcc have been reversed (see below).
   









Calc. B3LYP
Calc. MP2
Expt. [1]
   







Xaa
3.309
3.249
3.2977(8)

Xbb - 2.079 - 2.118 -
 2.1313(40)

Xcc - 1.230 - 1.132
 -
 1.1664(40)

|Xac|
0.258
0.209
0.227(19)

 







RMS
0.048 (2.2 %)
0.035 (1.6 %)



RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx - 2.079 - 2.118
 -
 2.1313

Xyy - 1.245
 - 1.142 -
 1.1779

Xzz
3.324
3.259
3.3092

ETA
0.251
0.299



Øz,a
  3.25
  2.73
2.90

Øa,N=C







Øz,N=C







 








 

















 
 






Table 2.  CF3N=C=O.  Structure parameters, B3LYP/6-311+G(3df,3pd) and MP2/6-311+G(3df,3pd) (Å and degrees).
 







 F
 C,1,B1
 N,2,B2,1,A1
 C,3,B3,2,A2,1,D1,0
 O,4,B4,3,A3,2,D2,0
 F,2,B5,3,A4,4,D3,0
 F,2,B6,3,A5,4,D4,0










   B3LYP
    MP2

 B1=1.33036372
 B2=1.40287148
 B3=1.21304848
 B4=1.15563981
 B5=1.34339482
 B6=1.34339482
 A1=109.56903999
 A2=130.97237598
 A3=173.3896775
 A4=111.94970035
 A5=111.94970035
 D1=180.
 D2=180.
 D3=-60.23444432
 D4=60.23444432
  B1=1.32292923
 B2=1.40462186
 B3=1.22216511
 B4=1.16338695
 B5=1.33485641
 B6=1.33485641
 A1=109.21817901
 A2=127.75175369
 A3=172.70146532
 A4=111.76568662
 A5=111.76568662
 D1=180.
 D2=180.
 D3=-60.27908605
 D4=60.27908605



 








 








NOTE:  As can be seen in Table 1, good agreement between calculated and experimental inertial axes nqcc's is obtained if calculated Xbb and Xcc are reversed.  As can be seen in Table 3, there is little difference between B and C rotational constants.  Calculated rotational constants are rigid molecule values, whereas the experimental values are measured in the ground vibrational state of the molecule.  So, I assume that consideration of zero point vibrational effects could easily reverse the nearly equal Be and Ce, and thus Xbb and Xcc.  Alternatively, small changes in some optimized structural parameters could accomplish this same reversal.

 








 




Table 3.  CF3N=C=O.  Rotational Constants (MHz).








B3LYP
 MP2
   Expt [1]







Ae
  5637
 5685
 Ao 5675 (fixed)

Be
  1719
 1744
 Bo 1752.5237(20)

Ce
  1715
 1739
 Co 1746.1322(20)



 








 








[1] J.Koput, W.Stahl, N.Heineking, G.Pawelke, B.Steger, and D.Christen, J.Mol.Spectrosc. 168,323(1994).

 








 








HNCO
 CH2C(H)NCO (CH3)3CNCO
 CH3CH2NCO

CH3NCO







 


















Table of Contents




Molecules/Nitrogen




 








 













CF3NCO.html






Last Modified 27 March 2015