N-Methylpyrrole

PDF ab-plane

PDF ac-plane
 


Nitrogen


Nuclear Quadrupole Coupling Constants


in N-Methylpyrrole


 







 

 


 




The molecular structure of N-methylpyrrole was optimized with the B3LYP/6-31G(d,p) model under the constraint that the molecule has a plane of symmetry perpendicular to the plane of the ring.  The optimized structure parameters and atomic coordinates respectively are given in Tables 2 and 3.  Nitrogen nqcc's calculated on this structure are compared with the experimental nqcc's of Huber et al. [1-3] in Table 1.
 
See "Calculation of 14N Quadrupole Coupling Constants on Optimized Molecular Structures of N-Methylpyrrole"  Molecular Quantum Mechanics, An International Conference, University of Washington, July 2001.  Poster PDF.
 
In Table 1, subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  The nqcc y-axis is chosen coincident with the inertia b-axis, these are perpendicular to the molecular symmetry plane.  Ø (degrees) is the angle between its subscripted parameters.  ETA = (Xxx - Xyy)/Xzz.
 
RMS is the root mean square difference between calculated and experimental 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 nitrogen nqcc's.
 
 
   







Table 1.  Nitrogen nqcc's in N-Methylpyrrole (MHz).  Calculation was made on the B3LYP/6-31G(d,p) optimized structure.
   










Calc.
Expt. [1-3]
   






14N Xaa 1.827 1.8261(18)
Xbb 1.052 1.0629(23)
Xcc - 2.878 - 2.8889(16)
|Xac| 0.192
 
RMS 0.009 (0.46 %)  
RSD 0.030 (1.3 %)
 
Xxx 1.834 1.834 **
Xyy 1.052 1.0629
  Xzz - 2.886 - 2.897
  ETA - 0.271 - 0.266
Øx,a 2.33 2.33
Øa,NC* 2.69 2.69
Øx,NC* 0.36 0.36
 
 
* Methyl Carbon.
** Calculated here from the experimental diagonal nqcc's and the calculated off-diagonal nqcc.
 
 
 
Table 2. Molecular structure parameters, B3LYP/6-31G(d,p) ropt  (Å and degrees).
 
Pyrole Ring
NC(2) 1.3767
C(2)C(3) 1.3785
C(3)C(4) 1.4232
C(2)H(2) 1.0805
C(3)H(3) 1.0810
C(5)NC(2) 108.85
NC(2)C(3) 108.36
C(2)C(3)C(4) 107.22
NC(2)H(2) 120.59
C(2)C(3)H(3) 125.77
 
Methyl
NC(6) 1.4503
C(6)Hs 1.0965
C(6)Ha 1.0927
NC(6)Hs 111.91
NC(6)Ha 109.63


 
 
Table 3. Atomic coordinates, B3LYP/6-31G(d,p) ropt 
(More figures are shown than are significant.)
 
 a (Å)  b (Å)  c (Å)
N 0.664250 0.0 - 0.038531
C(2,5) - 0.136288 ± 1.119700 - 0.013330
C(3,4) - 1.452644 ± 0.711608 0.016309
H(2,5) 0.300168 ± 2.108074 - 0.021810
H(3,4) - 2.315971 ± 1.362192 0.021982
C(methyl) 2.112914 0.0 0.029668
H(methyl) 2.473779 0.0 1.065045
H(methyl) 2.504337 ± 0.885360 - 0.477098
 
 

[1] S.Huber, T.-K. Ha, and A.Bauder, J.Mol.Struct. 413-414, 93(1997). 
[2] S.Huber, A.Bauder, V.Storm, and H.Dreizler, Z.Naturforsch. 49a,1063(1994).
[3] J.Makarewicz, S.Huber, B.Brupbacher-Gatehouse, and A.Bauder, J.Mol.Spectrosc. 612,117(2002).

 








 








Pyrrole
 

 








Table of Contents




Molecules/Nitrogen



 

 













NMP.html






Last Modified 7 June 2004