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CH3-NH-C(=O)-CH3
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Nitrogen |
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Nuclear
Quadrupole Coupling Constants |
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in N-Methylacetamide
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Calculation of the
nitrogen nqcc's in N-methylacetamide was made here on the molecular
structures given by HF/6-311++G(3df,3pd) and HF/aug-cc-pVTZ optimizations. These are
compared with the
experimental nqcc's [1] in Table 1. Structure parameters are
given in Table 2, rotational constants in Table 3.
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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.
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 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 nitrogen nqcc's. |
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Table 1. 14N nqcc's in N-Methylacetamide (MHz). Calculation was made
on the (1) HF/6-311++G(3df,3pd) and (2) HF/aug-cc-pVTZ optimized structures. |
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Calc. (1)
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Calc. (2) |
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Expt. [1] |
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Xaa |
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2.212 |
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2.213 |
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2.23660(81) |
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Xbb |
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1.926 |
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1.922 |
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1.9044 * |
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Xcc |
- |
4.138 |
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4.135 |
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4.1410 * |
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|Xab| |
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0.260 |
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0.259 |
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0.1904(28) |
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RMS |
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0.019 (0.70 %) |
0.017 (0.62 %) |
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RSD |
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0.030 (1.3 %) |
0.030 (1.3 %) |
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Xxx |
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1.772 |
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1.770 |
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1.8178 ** |
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Xyy |
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2.366 |
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2.364 |
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2.3232 |
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Xzz |
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4.138 |
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4.135 |
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4.1410 |
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ETA |
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0.143 |
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0.144 |
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0.1220 |
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Øx,a |
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120.62 |
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120.30 |
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114.45 |
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Øa,NH |
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84.66 |
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84.65 --> |
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84.65 |
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Øx,NH |
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35.97 |
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35.65 |
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29.80 |
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* Calculated here from Xaa and Xbb - Xcc = 6.0453(17) MHz [1]. |
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** Calculated here from the experimental nqcc's. |
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| Table 3. Molecular structure parameters (Å
and degrees). |
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ropt (1) = HF/6-311++G(3df,3pd) optimization. |
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ropt (2) = HF/aug-cc-pVTZ(G03) optimization. |
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| Point Group: Cs |
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ropt (1) |
ropt (2) |
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C(1)N |
1.4449 |
1.4454 |
| NC(3) |
1.3467 |
1.3469 |
| C(3)O |
1.1956 |
1.1973 |
| C(3)C(5) |
1.5115 |
1.5115 |
| C(1)H(6) |
1.0810 |
1.0813 |
| C(1)H(7) |
1.0810 |
1.0813 |
| C(1)H(8) |
1.0803 |
1.0806 |
| NH |
0.9880 |
0.9878 |
| C(5)H(10) |
1.0815 |
1.0817 |
| C(5)H(11) |
1.0812 |
1.0815 |
| C(5)H(12) |
1.0812 |
1.0815 |
| C(1)NC(3) |
121.72 |
121.79 |
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NC(3)O |
122.18 |
122.17 |
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NC(3)C(5) |
116.39 |
116.38 |
| Dihedral angles? |
NC(1)H(6) |
111.00 |
111.00 |
| See Z-Matrix |
NC(1)H(7) |
111.00 |
111.00 |
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NC(1)H(8) |
108.64 |
108.61 |
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C(1)NH |
119.12 |
119.09 |
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C(3)C(5)H(10) |
113.50 |
113.48 |
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C(3)C(5)H(11) |
108.37 |
108.39 |
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C(3)C(5)H(12) |
108.37 |
108.39 |
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| Table 4. Rotational Constants (MHz). Normal Species. |
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ropt (1) = HF/6-311++G(3df,3pd) optimization. |
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ropt (2) = HF/aug-cc-pVTZ(G03) optimization. |
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Calc. ropt (1) |
Calc. ropt (2) |
Expt. [1] |
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A |
10454.0 |
10435.9 |
11249.47(43)
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B |
3899.9 |
3897.8 |
3916.5540(73)
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C |
2942.3 |
2939.7 |
2902.7355(51)
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[1] N.Ohashi, J.T.Hougen, R.D.Suenram, F.J.Lovas, Y.Kawashima, M.Fujitake, and J.Pyka, J.Mol.Spectrosc. 227,28(2004). |
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Formamide |
Acetamide |
N-Ethylformamide |
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N-Acetylglycine |
Dimethylamine |
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Table of Contents |
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Molecules/Nitrogen |
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NMA.html |
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Last
Modified 23 Dec 2005 |
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