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N-Methylpyrrole
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PDF
ac-plane |
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Nitrogen |
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Nuclear
Quadrupole Coupling Constants |
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in N-Methylpyrrole |
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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. |
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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. |
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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. |
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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. |
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Table 1. Nitrogen nqcc's in N-Methylpyrrole (MHz). Calculation was made
on the B3LYP/6-31G(d,p) optimized structure. |
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Calc. |
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Expt. [1-3] |
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14N |
Xaa |
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1.827 |
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1.8261(18) |
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Xbb |
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1.052 |
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1.0629(23) |
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Xcc |
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2.878 |
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2.8889(16) |
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|Xac| |
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0.192 |
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RMS |
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0.009 (0.46 %) |
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RSD |
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0.030 (1.3 %) |
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Xxx |
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1.834 |
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1.834 ** |
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Xyy |
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1.052 |
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1.0629 |
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Xzz |
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2.886 |
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2.897 |
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ETA |
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0.271 |
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0.266 |
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Øx,a |
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2.33 |
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2.33 |
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Øa,NC* |
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2.69 |
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2.69 |
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Øx,NC* |
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0.36 |
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0.36 |
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* Methyl Carbon. |
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** Calculated here from the experimental diagonal
nqcc's and the calculated off-diagonal nqcc. |
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| Table 2. Molecular structure parameters, B3LYP/6-31G(d,p) ropt (Å
and degrees). |
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Pyrole Ring |
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NC(2) |
1.3767 |
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C(2)C(3) |
1.3785 |
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C(3)C(4) |
1.4232 |
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C(2)H(2) |
1.0805 |
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C(3)H(3) |
1.0810 |
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C(5)NC(2) |
108.85 |
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NC(2)C(3) |
108.36 |
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C(2)C(3)C(4) |
107.22 |
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NC(2)H(2) |
120.59 |
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C(2)C(3)H(3) |
125.77 |
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Methyl |
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NC(6) |
1.4503 |
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C(6)Hs |
1.0965 |
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C(6)Ha |
1.0927 |
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NC(6)Hs |
111.91 |
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NC(6)Ha |
109.63 |
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| Table 3. Atomic coordinates, B3LYP/6-31G(d,p) ropt |
| (More figures are shown than are significant.) |
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a (Å) |
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b (Å) |
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c (Å) |
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N |
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0.664250 |
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0.0 |
- |
0.038531 |
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C(2,5) |
- |
0.136288 |
± |
1.119700 |
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0.013330 |
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C(3,4) |
- |
1.452644 |
± |
0.711608 |
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0.016309 |
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H(2,5) |
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0.300168 |
± |
2.108074 |
- |
0.021810 |
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H(3,4) |
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2.315971 |
± |
1.362192 |
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0.021982 |
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C(methyl) |
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2.112914 |
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0.0 |
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0.029668 |
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H(methyl) |
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2.473779 |
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0.0 |
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1.065045 |
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H(methyl) |
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2.504337 |
± |
0.885360 |
- |
0.477098 |
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[1] S.Huber, T.-K. Ha, and A.Bauder, J.Mol.Struct.
413-414, 93(1997). |
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[2] S.Huber, A.Bauder, V.Storm, and H.Dreizler,
Z.Naturforsch. 49a,1063(1994). |
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[3] J.Makarewicz, S.Huber, B.Brupbacher-Gatehouse,
and A.Bauder, J.Mol.Spectrosc. 612,117(2002). |
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Pyrrole |
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Table of Contents |
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Molecules/Nitrogen |
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NMP.html |
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Last
Modified 7 June 2004 |
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