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(CH3)2NC(=O)H
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Nitrogen |
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Nuclear
Quadrupole Coupling Constants |
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in N-Dimethylformamide
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Calculation of 14N
nuclear quadrupole coupling constants in N-dimethylformamide was made here on molecular
structures given by MP2/aug-cc-pVTZ
optimization (assuming Cs symmetry) of each of four conformers, which are shown below along with MP2 relative energy:
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Conformer I 0 kJ/mol
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Conformer II 4.2 kJ/mol |
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Conformer III 9.9 kJ/mol |
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Conformer IV 13.7 kJ/mol |
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Calculated and experimental nqcc's [1] are compared in Tables 1 and 2, rotational constants are compared in Table 3.
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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.
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 B1LYP/TZV(3df,2p) model for calculation of the nqcc's. |
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Table 1. 14N nqcc's in Conformers I and II of N-Dimethylformamide (MHz). Calculation was made
on MP2/aug-cc-pVTZ ropt structures.
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Calc. I
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Calc. II
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Expt. [1]
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Xaa |
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2.020 |
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2.007 |
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2.0614(16)
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Xbb |
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2.195 |
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2.246
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2.303(2)
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Xcc |
-
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4.216 |
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4.253 |
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4.364(2)
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|Xab| |
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0.257 |
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0.350 |
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RMS
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0.108 (3.7 %)
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0.079 (2.7 %)
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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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1.836 |
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1.756 |
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Xyy |
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2.380 |
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2.496 |
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Xzz |
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4.216 |
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4.253 |
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ETA |
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0.129 |
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0.174 |
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Table 2. 14N nqcc's in Conformers III and IV of N-Dimethylformamide (MHz). Calculation was made
on MP2/aug-cc-pVTZ ropt structures.
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Calc. III
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Calc. IV
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Expt. [1]
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Xaa |
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2.075 |
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2.062 |
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2.0614(16)
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Xbb |
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2.312 |
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2.325
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2.303(2)
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Xcc |
-
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4.387 |
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4.387 |
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4.364(2)
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|Xab| |
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0.350 |
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0.441 |
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RMS
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0.016 (0.56 %)
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0.019 (0.64 %)
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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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1.824 |
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1.733 |
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Xyy |
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2.563 |
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2.654 |
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Xzz |
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4.387 |
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4.387 |
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ETA |
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0.168 |
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0.210 |
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| Table 3. Rotational Constants, MP2/aug-cc-pVTZ ropt and experimental (MHz) |
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Conf I
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Conf II |
Conf III |
Conf IV |
Expt. [1]
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A
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8999.9
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8984.5
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8823.4
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8805.8
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8925.516(19)
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B
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4194.0
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4251.1
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4215.8
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4281.4
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4203.8368(57)
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C
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2967.2
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2993.4
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2958.9
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2988.0
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2964.7107(54)
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[1] N.Heineking and Dreizler, Z.Naturforsch. 48a,570(1993).
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Table of Contents |
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Molecules/Nitrogen |
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CH32NCHO.html |
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Last
Modified 15 April 2013 |
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