HCONHCH2CH3


 








Nitrogen

Nuclear Quadrupole Coupling Constants


in N-Ethylformamide


 







 
 
Nitrogen nqcc's in N-ethylformamide, and a heavy atom substitution structure were determined by Ohba et al. [1].  Calculation of the nqcc's was made here on this structure complemented by MP2/6-311+G(d,p) optimization for the hydrogen structure.  Calculated and experimental nqcc's are compared in Table 1.  Eigenvalues and eigenvectors of the nqcc tensor are given in Table 2.  Structure parameters are given in Table 3, atomic coordinates in Table 4, rotational constants in Table 5.
 
In Table 1, 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.
 
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.
 
 
   






Table 1. Nitrogen nqcc's in N-Ethylformamide (MHz).  Calculation was made on the rs/ropt structure (the derivation of which is briefly discussed below).
   









Calc.
Expt. [1]
   





14N Xaa 1.389 1.3794(13)
Xbb 0.845 0.8171(20)
Xcc - 2.234 - 2.1965(20)
Xab * - 0.735
Xac * - 1.536
Xbc * - 2.318
 
RMS 0.027 (1.9 %)
RSD 0.030 (1.3 %)
 
Xxx 1.896
Xyy 2.117
Xzz - 4.013
ETA 0.055
 
 
* The algebraic signs of the off-diagonal components depend on the orientation of the molecule with respect to a,b,c axes.  Here, the algebraic signs correspond to the atomic a,b,c coordinates given in Table 3.
 
 
 
Table 2.  N-Ethylformamide.  Eigenvalues; Xii, i=x,y,z (MHz) and eigenvectors (direction cosines) of the nitrogen nqcc tensor.
 
  i =     x     y     z
 
Xii 1.896 2.117 - 4.013
 
a 0.8887 0.3464 0.3005
b - 0.4521 0.7717 0.4474
c - 0.0769 - 0.5334 0.8424
 
 
 
Molecular Structure
 
Heavy atom substitution parameters were held fixed, while hydrogen atom parameters were determined by partial optimization at the MP2/6-311+G(d,p) level of theory.
 
Table 3.  Molecular structure parameters, rs/ropt (Å and degrees).
      * rs
Point Group: C1 C(1)O 1.2173(8) *
C(1)H 1.1045
C(1)N 1.3757(32) *
NH 1.0089
NC(4) 1.4390(28) *
C(4)H(8) 1.0943
C(4)H(9) 1.0933
C(4)C(5) 1.5155(6) *
C(5)H(10) 1.0925
C(5)H(11) 1.0944
C(5)H(12) 1.0941
OC(1)N 124.02(6) *
Dihedral angles? See Z-Matrix. C(1)NC(4) 121.27(7) *
NC(4)C(5) 113.20(9) *
C(1)NH 117.88
OC(1)H 123.48
C(1)C(4)H(8) 107.85
C(1)C(4)H(9) 107.39
C(4)C(5)H(10) 110.08
C(4)C(5)H(11) 110.51
C(4)C(5)H(12) 110.84
 
 
Table 3.  N-Ethylformamide.  Atomic coordinates, rs/ropt.
(More figures are shown than are significant.)
 
  a (Å)   b (Å)   c (Å)
C 1.281521 0.280872 - 0.252688
O 1.511462 - 0.835396 0.174971
N 0.078050 0.930079 - 0.101902
C - 1.034828 0.297267 0.555192
C - 1.817173 - 0.628812 - 0.354234
H - 0.037555 1.821794 - 0.559429
H 2.024607 0.889378 - 0.798052
H - 1.680720 1.085157 0.954626
H - 0.636495 - 0.264133 1.404619
H - 1.167410 - 1.422596 - 0.730068
H - 2.646926 - 1.090075 0.190359
H - 2.228511 - 0.080670 - 1.207163
 
 
Table 5. N-Ethylformamide.  Rotational constants (MHz).
 
Calc. rs/ropt     Expt. [1]
A 9873.9 9904.8373(6)
B 3555.3 3521.0995(2)
C 3002.7 2984.9808(2)
 
 
[1] K.Ohba, T.Usami, Y.Kawashima, and E.Hirota, J.Mol.Struct. (2004).

 








 








Formamide Acetamide Dimethylamine
N-Methylacetamide
 

 








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Molecules/Nitrogen
 

 













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Last Modified 27 Nov 2005