HC(=O)-N(H)-C6H5


 
 
 


Nitrogen


Nuclear Quadrupole Coupling Constants

in cis-Formanilide


 







 

 


 




Calculation of the nitrogen nqcc's in formanilide was made here on molecular structures given by MP2/6-311++G(d,p) and B3LYP/6-311++G(d,p) optimizations.  These are compared with the experimental nqcc's [1] in Table 1.  Structure parameters in Z-matrix format are given here.  Rotational constants and dipole moments are given in Table 2.
 
Note:  The MP2 and B3LYP angles between the pseudo-peptidic group and the benzene ring are respectively ±44.3o and ±32.5o.
 
In Table 1, 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.  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 B3PW91/6-311+G(df,pd) model for calculation of the nitrogen nqcc's.
 
 
   







Table 1.  14N nqcc's in cis-Formanilide (MHz).  Calculation was made on the (1) MP2/6-311+G(d,p) and (2) B3LYP/6-311++G(d,p) optimized structures.
   








Calc. (1)

Calc. (2)
Expt. [1]
   






Xaa 2.136 2.111 2.17 *
Xbb - 0.048 0.700 0.59 *
Xcc - 2.088 - 2.811 - 2.77 *
Xab 0.249 - 0.224
Xac 0.136 0.141
Xbc - 2.651 2.141
 
RMS 0.54 (29. %) 0.08 (4.1 %)
RSD 0.030 (1.3 %) 0.030 (1.3 %)
 
Xxx 1.733 1.669
Xyy 2.186 2.164
Xzz - 3.919 - 3.833
ETA 0.116 0.129
 
 
* Derived here from (3/2)Xaa = 3.26(2) and (1/4)(Xbb - Xcc) = 0.84(3) MHz.
 
 
Table 2.  cis-Formanilide.  Rotational constants (MHz) and B3PW91/6-311+G(df,pd) calculated dipole moments (D).
 
ropt (1) = MP2/6-311++G(d,p) optimization.
ropt (2) = B3LYP/6-311++G(d,p) optimization.
 
  Calc. ropt (1) Calc. ropt (2)  Expt. [1]
A 4982.4 5106.7 5061.76(5)
B   926.4   922.2   929.1786(2)
C   796.0   789.0   794.6967(2)
a|   3.90   3.77
b|   0.34   0.25
c|   0.22   0.10
 
 

[1] S.Blanco, J.C.López, A.Lesarri, W.Caminati, and J.L.Alonso, Mol.Phys. 103,1473(2005).


 








 







Formamide Acetamide N-Ethylformamide
N-Acetylglycine Dimethylamine
N-Methylacetamide Propionamide
trans-Formanilide
 

 








Table of Contents




Molecules/Nitrogen



 

 













Formanilide_cis.html






Last Modified 10 Jan 2011