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CH3-C(=O)-NH-CH2C(=O)OH
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Nitrogen |
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Nuclear
Quadrupole Coupling Constants |
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in N-Acetylglycine
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Nitrogen nqcc's in N-acetylglycine were determined by Lovas et al [1]. |
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Lovas et al. identified four conformations of N-acetylglycine. Calculation of the
nitrogen nqcc's was made here on the two lowest energy conformers (AGI and AGII) on molecular
structures given by HF/6-311+G(d,p) and MP2/6-311++G(d,p) optimizations. Calculated nqcc's for AGI are
compared with the
experimental values [1] in Table 1. Calculated nqcc's for AGII are given in Table 2. Rotational constants are compared in Table 3.
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AGI (CS) |
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AGII (C1) |
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In Tables 1 and 2, 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. |
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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-Acetylglycine, AGI (MHz). Calculation was made
on the (1) HF/6-311+G(d,p) and (2) MP2/6-311++G(d,p) 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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2.215 |
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2.212 |
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2.232(12) |
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Xbb |
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1.977 |
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2.022 |
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1.952(12) |
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Xcc |
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4.193 |
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4.234 |
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4.184(12) |
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|Xab| |
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0.562 |
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0.495 |
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RMS |
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0.018 (0.65 %) |
0.051 (1.8 %) |
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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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1.522 |
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1.612 |
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Xyy |
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2.671 |
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2.622 |
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Xzz |
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4.193 |
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4.234 |
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ETA |
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0.274 |
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0.238 |
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Table 2. 14N nqcc's in N-Acetylglycine, AGII (MHz). Calculation was made
on the (1) HF/6-311+G(d,p) and (2) MP2/6-311++G(d,p) optimized structures. |
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Calc. (1)
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Calc. (2) |
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Expt. |
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Xaa |
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1.363 |
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1.261 |
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Xbb |
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0.883 |
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1.068 |
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Xcc |
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2.246 |
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2.329 |
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|Xab| |
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0.762 |
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0.724 |
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|Xac| |
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2.206 |
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2.208 |
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1.802 |
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1.688 |
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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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1.647 |
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1.719 |
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Xyy |
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2.416 |
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2.319 |
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Xzz |
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4.064 |
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4.039 |
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ETA |
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0.189 |
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0.148 |
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Molecular Structures: See Z-Matrix, AGI and Z-Matrix, AGII
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| Table 3. Rotational Constants (MHz). Normal Species. |
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Calc (1) HF/6-311+G(d,p) structure. |
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Calc (2) MP2/6-311++G(d,p) structure. |
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Calc (1) |
Calc (2) |
Expt. [1] |
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| AGI |
A |
5497.6 |
5289.8 |
5318.3033(47)
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B |
1003.5 |
998.3 |
1000.6984(31)
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C |
857.4 |
848.6 |
852.6391(13)
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| AGII |
A |
4770.2 |
4647.1 |
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B |
1237.6 |
1246.7 |
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C |
1089.0 |
1090.8 |
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[1] F.J.Lovas, R.J.Lavrich, and D.F.Plusquellic, J.Mol.Spectrosc. 228,251(2004). |
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Formamide |
Acetamide |
N-Ethylformamide |
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N-Methylacetamide |
2-Chloroethyl ethyl sulfide |
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Dimethylamine |
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Table of Contents |
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Molecules/Nitrogen |
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NAG.html |
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Last
Modified 11 Jan 2006 |
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