CHF2-CH2NH2















 








 









Nitrogen


Nuclear Quadrupole Coupling Constants

in 2,2-Difluoroethylamine

 








 








 

 





The microwave spectrum of 2,2-difluoroethylamine has been investigated by Marstokk and Møllendal [1].

Calculation of the 14N nuclear quadrupole coupling constant tensor in each of the following rotamers of the title molecule was made here on ropt molecular structures given by MP2/6-311+G(3df,3pd) and MP2/aug-cc-pVTZ optimization.

 








Conformer I

Conformer III


EIII < EI


 by 0.90 kJ/mole

at MP2/aug-cc-pVTZ

level of theory.









 








 








Calculated and experimental nitrogen nqcc's are compared in Tables 1 and 2.  Rotational constants and electric dipole moments are compared in Table 3.  Structure parameters are given here in Z-matrix format.

In Tables 1 and 2, subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  ETA = (Xxx - Xyy)/Xzz.  RMS is the root mean square difference between calculated and experiment diagonal nqcc's (percent of average magnitude of experimental nqcc's).  RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of the efg's/nqcc's. 


 








 








   







Table 1.  14N nqcc's in 2,2-Difluoroethylamine, conformer I (MHz).  Calculation was made on (1) MP2/6-311+G(3df,3pd) and (2) MP2/aug-cc-pVTZ ropt structures.
   









Calc (1)
Calc (2)
Expt [1]
   







Xaa
2.698
2.702
3.1(10)

Xbb
2.055
2.054
2.5(6)

Xcc -
 4.754
 -
 4.756
 -
 5.6

Xab
0.462
0.465



Xac
0.395
0.386



Xbc -
 0.425
-
 0.405


 







RMS
0.599 (16.0 %)
0.597 (16.0 %)



RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
2.943
2.948



Xyy
1.861
1.855



Xzz -
 4.804
 -
 4.803



ETA
 -
 0.225
 -
 0.228



 








 








 








   







Table 2.  14N nqcc's in 2,2-Difluoroethylamine, conformer III (MHz).  Calculation was made on (1) MP2/6-311+G(3df,3pd) and (2) MP2/aug-cc-pVTZ ropt structures.
   









Calc (1)
Calc (2)
Expt [1]
   







Xaa -
 4.032
 -
 4.017
 -
 3.77(17)

Xbb
1.780
1.772
2.78(17)

Xcc
2.252
2.245
0.99

Xac
2.161
2.182



 







RMS
0.942 (37.5 %)
0.940 (37.4 %)



RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
2.923
2.930



Xyy
1.780
1.772



Xzz -
 4.704
 -
 4.702



ETA
 -
 0.243
 -
 0.246



 








 








 







 





Table 3.  2,2-Difluoroethylamine. Rotational Constants (MHz) and Dipole Moments * (D).  ropt(1) = MP2/6-311+G(3df,3pd), ropt(2) = MP2/aug-cc-pVTZ.

 



Conf I
 ropt(1) ropt(2)      Expt [1]

 



A
 9043.1
 9003.1
 8987.2718(51)

B
 3738.9
 3727.3
 3699.8821(19)

C
 2855.7
 2845.8
 2828.9179(18)

µa
 2.13
 2.15
 2.042(15)

µb 1.04
 1.06
 1.101(29)

µc 0.46
 0.45
  ~ 0

µtot 2.41
 2.44
 2.320(27)

 



Conf III



 



A
 7141.0
 7116.0
 7125.170(12)

B
 4236.3
 4216.0
 4185.890(13)

C
 3474.6
 3457.7
 3441.172(13)

µa 0.02
 0.003
 0.090(28)

µb 0 (symm)
 0 (symm) 0 (symm)

µc 1.36
 1.38
 1.427(28)

µtot 1.36
 1.38
 1.430(30)

 



* Calculated by B3PW91/6-311+G(df,pd) method on MP2 ropt structures.



 








 








[1] K.-M.Marstokk and H.Møllendal, Acta Chem.Scand. A 36,517(1982).


 








 








CH3NH2 CH3CH2NH2 CH2FCH2NH2


 








 








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Last Modified 2 Jan 2014