(CH3)2NC(=O)H















 








 









Nitrogen


Nuclear Quadrupole Coupling Constants

in N-Dimethylformamide


 








 








 


 





Calculation of 14N nuclear quadrupole coupling constants in N-dimethylformamide was made here on molecular structures given by MP2/aug-cc-pVTZ optimization (assuming Cs symmetry) of each of four conformers, which are shown below along with MP2 relative energy:


 








Conformer I     0 kJ/mol


Conformer II     4.2 kJ/mol



























 









Conformer III     9.9 kJ/mol

Conformer IV     13.7 kJ/mol



























 









Calculated and experimental nqcc's [1] are compared in Tables 1 and 2, rotational constants are compared in Table 3. 


 









In Tables 1 and 2, subscripts a,b,c refer to the principal axes of the inertia tensor; subscripts x,y,z to the principal axes of the nqcc tensor.  Ø (degrees) is the angle between its subscripted parameters.  ETA = (Xxx - Xyy)/Xzz.

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 of the B1LYP/TZV(3df,2p) model for calculation of the nqcc's.

 








 








   








Table 1.  14N nqcc's in Conformers I and II of N-Dimethylformamide (MHz).  Calculation was made on  MP2/aug-cc-pVTZ ropt structures.

   










Calc. I

Calc. II

Expt. [1]

   








Xaa
2.020
2.007
2.0614(16)


Xbb
2.195
2.246

2.303(2)


Xcc -
4.216 -
4.253 -
4.364(2)


|Xab|
0.257
0.350



 







RMS

0.108 (3.7 %)

0.079 (2.7 %)




RSD
0.030 (1.3 %) 0.030 (1.3 %)


 







Xxx
1.836
1.756



Xyy
2.380
2.496



Xzz - 4.216 - 4.253



ETA
0.129
0.174



 








 








 









   








Table 2.  14N nqcc's in Conformers III and IV of N-Dimethylformamide (MHz).  Calculation was made on  MP2/aug-cc-pVTZ ropt structures.

   










Calc. III

Calc. IV

Expt. [1]

   








Xaa
2.075
2.062
2.0614(16)


Xbb
2.312
2.325

2.303(2)


Xcc -
4.387 -
4.387 -
4.364(2)


|Xab|
0.350
0.441



 







RMS

0.016 (0.56 %)

0.019 (0.64 %)




RSD
0.030 (1.3 %) 0.030 (1.3 %)


 







Xxx
1.824
1.733



Xyy
2.563
2.654



Xzz - 4.387 - 4.387



ETA
0.168
0.210



 








 









 








 







Table 3.  Rotational Constants, MP2/aug-cc-pVTZ ropt and experimental (MHz)









Conf I
Conf II Conf III Conf IV Expt. [1]








A
8999.9
8984.5
8823.4
8805.8
8925.516(19)

B
4194.0
4251.1
4215.8
4281.4
4203.8368(57)

C
2967.2
2993.4
2958.9
2988.0
2964.7107(54)



 








 









[1] N.Heineking and Dreizler, Z.Naturforsch. 48a,570(1993).


 









 








Table of Contents




Molecules/Nitrogen




 








 













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Last Modified 15 April 2013