HCC-C(H)NH





 


















 









Nitrogen


Nuclear Quadrupole Coupling Constants

in Propargylimine

 








 








The microwave spectra of both Z- and E-isomers of propargylimine were observed and assigned by Sugie et al. [1].  Rotational constants, dipole moments, and 14N  nuclear quadrupole coupling constants were determined.

 








For each conformer, shown below, calculation of the nitrogen nqcc tensor was made on a molecular structures given by MP2/6-311+G(3df,3pd) optimization with empirically corrected approximate equilibrium single and triple CC bond lengths and MP2/aug-cc-pVTZ optimization also with empirically corrected approximate equilibrium single and triple CC bond lengths. These calculated nqcc's are given in Tables 1 and 2.  Structure parameters are given in Z-Matrix format in Table 3, rotational constants and dipole moments in Table 4.

 








Z-Propargylimine

E-Propargylimine


At the


MP2/aug-cc-pVTZ

level of theory,

EZ < EE

by 4.0 kJ/mol















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.  Ø (degrees) is the angle between its subscripted parameters.

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 tensor in Z-Propargylimine (MHz).  Calculation was made on  molecular structures given by (1) MP2/6-311+G(3df,3pd) and (2) MP2/aug-cc-pVTZ optimization each with approximate re single and triple CC bond lengths.
   









Calc (1)
Calc (2)
Expt [1]
   







Xaa -
 4.057
 -
 4.047
 -
 4.1(2)

Xbb
0.691
0.691
1.4(4)

Xcc
3.366
3.357
2.7(3)

Xab
1.166
1.166



 







RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
0.962
0.962



Xyy
3.366
3.357



Xzz -
 4.328
 -
 4.319



ETA
0.555
0.554



Øz,a
13.08
13.11



Øa,bi*
14.87
14.82



Øz,bi
  1.79
  1.72













 








* "bi" is bisector of CNH angle.

 








 








   







Table 2.  14N nqcc tensor in E-Propargylimine (MHz).  Calculation was made on  molecular structures given by (1) MP2/6-311+G(3df,3pd) and (2) MP2/aug-cc-pVTZ optimization, each with approximate re single and triple CC bond lengths.
   









Calc (1)
Calc (2)
Expt [1]
   







Xaa
0.948
0.952
0.1(3)

Xbb -
 4.311
 -
 4.306
 -
 3.8(2)

Xcc
3.363
3.354
3.7(4)

Xab
0.485
0.492



 







RSD
0.030 (1.3 %)
0.030 (1.3 %)



 







Xxx
0.993
0.997



Xyy
3.363
3.354



Xzz -
 4.356
 -
 4.352



ETA
0.544
0.542



Øz,a
95.23
95.30



Øa,bi*
98.25
98.25



Øz,bi
  3.02
  2.95













 








* "bi" is bisector of CNH angle.

 








 








Table 3.  Propargylimine:  MP2/6-311+G(3df,3pd) and MP2/aug-cc-pVTZ optimized structure parameters (Å and degrees).  Approximate re bond lenths are given in parentheses.










Z-Propargylimine
E-Propargylimine

          C
          H,1,B1
          N,1,B2,2,A1
          H,3,B3,1,A2,2,D1,0
          C,1,B4,3,A3,4,D2,0
          C,5,B5,3,A4,1,D3,0
          H,6,B6,3,A5,1,D4,0




____________________ MP2/6-311+G(3df,3pd)____________________











 B1=1.08657074
 B2=1.28264734
 B3=1.02138743
 B4=1.43437427     (1.4365)
 B5=1.21659694     (1.2064)
 B6=1.06227896
 A1=117.8016985
 A2=109.55327158
 A3=125.57321157
 A4=154.54277151
 A5=162.47988488
 D1=180.
 D2=0.
 D3=180.
 D4=180.
 B1=1.09086173
 B2=1.28225496
 B3=1.01991455
 B4=1.43238068     (1.4346)
 B5=1.2156033       (1.2056)
 B6=1.06207224
 A1=123.45952937
 A2=109.08136526
 A3=120.98334695
 A4=155.59596498
 A5=162.26655693
 D1=0.
 D2=180.
 D3=180.
 D4=180.










______________________ MP2/aug-cc-pVTZ______________________











 B1=1.0864415
 B2=1.28409614
 B3=1.02234058
 B4=1.43428466    (1.4361)
 B5=1.21776082    (1.2064)
 B6=1.06245275
 A1=117.70607867
 A2=109.48606543
 A3=125.62617892
 A4=154.31826247
 A5=162.58276506
 D1=180.
 D2=0.
 D3=180.
 D4=180.
 B1=1.0905593
 B2=1.28393075
 B3=1.02091118
 B4=1.43246001    (1.4344)
 B5=1.2167906      (1.2056)
 B6=1.06228171
 A1=123.47663952
 A2=109.07216717
 A3=120.97968429
 A4=155.48010454
 A5=162.32618829
 D1=0.
 D2=180.
 D3=180.
 D4=180.























 




Table 4. Propargylimine: Rotational Constants (MHz) and Dipole Moments (D).  Calc (1)  =  MP2/6-311+G(3df,3pd) and Calc (2) = MP2/aug-cc-pVTZ optimization, each with approximate re single and triple CC bond lengths.








__________Z-Propargylimine__________


Calc (1)
 Calc (2)
  Expt [1,2]







A  54427
  54279
 54640.228(83)  [1]

B    4868
    4868
   4862.4191(59)

C    4469
    4467
   4458.1986(52)

|µa|
    2.40
    2.40
   2.145(2)          [2]

|µb|    0.21
    0.21
   0.182(6)








__________E-Propargylimine__________


Calc (1)
 Calc (2)
  Expt [1]







A
  62765
  62598
 63099.320(79)

B
    4772
    4771
   4766.6104(72)

C
    4435
    4433
   4425.5144(64)

|µa|    0.39
    0.40


|µb|    2.05
    2.05









 








 








[1] M.Sugie, H.Takeo, and C.Matsumura, J.Mol.Spectrosc. 111,83(1985).

[2] D.McNaughton, O.I.Osman, and H.W.Kroto, J.Mol.Struct. 190,195(1988).

 








 








Methylenimine
 EthaniminePropenimine



Difluoromethanimine N-Methylmethanimine










 








 








Table of Contents




Molecules/Nitrogen




 








 













HCCCHNH.html






Last Modified 22 Jan 2014