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C8H9NO2
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Nitrogen |
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Nuclear
Quadrupole Coupling Constants |
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in trans-Paracetamol
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Calculation of 14N
nuclear quadrupole coupling constants in trans-paracetamol was made here on molecular
structures given by HF/cc-pVTZ and HF/6-311+G(d,p)
optimization (assuming Cs symmetry) of each of the two conformers shown below:
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trans-E
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trans-Z |
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Calculated
and experimental [1] nqcc's are compared in Tables 1 and 2, rotational
constants are compared in Table 3. Structure parameters are given
here in Z-matrix format.
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In Tables 1 and 2, subscripts a,b,c refer to the
principal axes of the inertia tensor; subscripts x,y,z to the principal axes
of the nqcc tensor.
Ř (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+(df,pd) model for calculation of the nqcc's. |
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Table 1. 14N nqcc's trans-E Paracetamol (MHz). Calculation was made
on (1) HF/cc-pVTZ and (2) HF/6-311+G(d,p) ropt 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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2.058
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2.071
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2.1127(36)
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Xbb |
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1.649
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1.663
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1.7149(44)
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Xcc |
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3.707
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3.734
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3.8276(44)
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|Xab| |
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0.205
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0.203
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RMS
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0.070 (2.7 %)
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0.066 (2.6 %)
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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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2.143
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2.155
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Xyy |
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1.564
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1.579
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Xzz |
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3.707
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3.734
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ETA |
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0.156
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0.154
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Table 2. 14N nqcc's trans-Z Paracetamol (MHz). Calculation was made
on (1) HF/cc-pVTZ and (2) HF/6-311+G(d,p) ropt 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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2.065
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2.078
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2.1176(36)
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Xbb |
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1.655
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1.670
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1.7188(43)
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Xcc |
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3.720
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3.748
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3.8364(43)
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|Xab| |
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0.204
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0.202
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RMS
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0.082 (3.2 %)
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0.063 (2.5 %)
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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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2.149
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2.161
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Xyy |
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1.571
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1.586
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Xzz |
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3.720
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3.748
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ETA |
-
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0.155
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0.153
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| Table 3. Paracetamol, Rotational Constants (MHz). ropt(1) = HF/cc-pVTZ, ropt(2) = HF/6-311+G(d,p) ropt structures. |
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trans-E
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ropt(1) |
ropt(2) |
Expt. [1]
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A
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3724.9
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3710.9
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3668.26678(83)
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B
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550.0
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548.6
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546.763941(89)
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C
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480.7
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479.6
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476.536462(62)
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trans-Z |
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A
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3722.8
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3707.6
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3664.8110(17)
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B
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550.2
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548.8
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546.9009(16)
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C
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480.7
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479.4
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476.61660(51)
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[1] M.Varela, C.Cabezas, J.C.López, and J.L.Alonso, J.Phys.Chem. A 117,13275(2013).
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Acetamide
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N-Methylacetamide
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Formanilide
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N-Acetylglycine
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Table of Contents |
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Molecules/Nitrogen |
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Paracetamol.html |
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Last
Modified 9 June 2013 |
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