[C(=O)H]2NH




 









Nitrogen


Nuclear Quadrupole Coupling Constants

in Formimide

(Diformamide, N-Formylformamide)

 








 








Possible planar conformers of formimide, and MP2/aug-cc-pVTZ energies, are shown below:


 








cis-cis
cis-trans
trans-trans
























0
3.1 kJ/mol
26.4 kJ/mol











The microwave spectrum of the cis-trans conformer was investigated by Steinmetz [1],  Nitrogen nqcc's were determined.











Calculation was made here of the 14N nqcc tensors on ropt molecular structures given by MP2/aug-cc-pVTZ and HF/aug-cc-pVTZ optimizations.  These calculated nqcc's are given in Tables 1 and 2.  Structure parameters, along with corresponding rotational constants and dipole moments, are given in Table 3.  Centrifugal distortion constants are given in Table 4.

 








In Table 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 root mean square difference between calculated and experimental nqcc's.  RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of the nitrogen efg's/nqcc's.

 







 
   







Table 1.  14N nqcc's in cis-cis Formimide (MHz).  Calculation was made on MP2 and HF ropt  molecular structures.
   









Calc /MP2
Calc /HF
Expt.
   







Xaa
1.367
1.300



Xbb
1.464
1.496



Xcc -
 2.830
 -
 2.796












RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
1.367
1.300



Xyy
1.464
1.496



Xzz -
 2.830
 -
 2.796



ETA
0.034
0.070



 








 








 








   







Table 2.  14N nqcc's in cis-trans Formimide (MHz).  Calculation was made on MP2 and HF ropt  molecular structures.
   









Calc /MP2
Calc /HF
Expt [1]
   







Xaa
1.437
1.372
1.88 (11)

Xbb
1.580
1.594
1.53(7)

Xcc -
 3.018
 -
 2.966
 -
 3.41(7)

Xab
0.064
0.056



 







RMS
0.343 (15. %)
0.391 (17. %)



RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
1.413
1.359



Xyy
1.605
1.607



Xzz -
 3.018
 -
 2.966



ETA
0.063
0.084



 








 








 













Table 3.  Formimide, ropt structure parameters (Å and degrees), rotational constants (MH), and electric dipole moments (D).






_________cis-cis__________
 ________cis-trans_________

MP2 HF
 MP2 HF





NH
 1.0126
 0.9969
 1.0102
 0.9942
NC(1)
 1.3818
 1.3691
 1.3899
 1.3797
C(1)Oc 1.2113
 1.1802
 1.2124
 1.1811
C(1)Hc 1.0983
 1.0890
 1.0932
 1.0832
NC(2)
 1.3818
 1.3691 1.3847
 1.3700
C(2)Ot 1.2113
 1.1802 1.2119
 1.1817
C(2)Ht
 1.0983
 1.0890 1.0984
 1.0889
HNC(1)
 118.13
 117.83
 116.63
 116.42
NC(1)Oc 123.75
 123.72
 123.37
 122.25
NC(1)Hc 112.69
 113.41
 112.80
 113.49
HNC(2) 118.13
 117.83 119.23
 119.10
NC(2)Ot 123.75
 123.72 124.59
 124.82
NC(2)Ht 112.69
 113.41 112.12
 112.40





A
 43229.
 44472.
 21650.
 22512.
B
   2460.
   2534.
   3009.
   3087.
C
   2327.
   2397.
   2642.
   2715.
Expt A,B, and C are respectively 21490.671(18), 3029.943(2), and 2655.748(2) MHz [1]





|µa|
     0
     0
   1.12
   1.02
|µb|   1.58
   1.52
   2.73
   2.58
 





 








 













Table 4.  Formimide.  Centrifugal Distortion Constants (kHz).  Calc = B3LYP/cc-pVTZ.






_________cis-cis__________
 ________cis-trans_________

Calc Expt
 Calc Expt





Delta_J
 0.199
0.743
Delta_JK - 3.56
- 11.6
Delta_K 357.
149.
delta_J 0.0143
0.144
delta_K 1.08
3.17





D_J
 0.198
0.720
D_IK
 - 3.55
- 11.5
D_K
 357.
149.
d_1
 - 0.0143
- 0.144
d_2
 - 0.00044
- 0.00738
 





 








 








[1] W.E.Steinmetz, JACS 95(9),2777(1973),

 








 








Formamide
 Acetamide
 see Amides


 








 








Table of Contents




Molecules/Nitrogen




 








 













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Last Modified 20 April 2015