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(CH2CH3)2N-C(=O)CH3 |
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Nitrogen |
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Nuclear
Quadrupole Coupling Constants |
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in
N,N-Diethylacetamide
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The
microwave spectrum of each of the following conformers of
N,N-diethylacetamide was observed and assigned by Kannengiesser et al.
[1].
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Conformer I
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Conformer II
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EI < EII
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Calculation of the
nitrogen nqcc tensor in each conformer was made here on ropt
molecular
structure given by B3P86/6-31G(3d,3p) and HF/6-311++G(3df,3pd) optimization. These are
compared with the
experimental nqcc's [1] in Tables 1 and 2. Structure parameters are
given in Table 3, rotational constants in Table 4.
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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.
Ø (degrees) is the angle between its subscripted
parameters.
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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 efg's/nqcc's. |
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Table 1. 14N
nqcc's in
N,N-Diethylacetamide, conformer I (MHz). Calculation was made on
(1) B3P86/6-31G(3d,3p) and (2) HF/6-311++G(3df,3pd) 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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1.101
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1.144
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1.06868(58)
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Xbb - Xcc |
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5.055
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5.065
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5.07830(82)
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Xbb
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1.977
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1.961
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2.00483 *
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Xcc |
-
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3.078
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3.105
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3.07351 *
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Xab |
-
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0.119
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-
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0.018
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Xac |
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2.675
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2.712
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Xbc |
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0.121
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-
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0.053
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RMS |
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0.025 (1.2 %)
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0.054 (2.6 %)
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RSD |
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0.030 (1.3 %) |
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0.030 (1.3 %) |
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Xxx |
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1.975
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1.958 |
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Xyy |
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2.412
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2.468 |
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Xzz |
-
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4.387
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- |
4.426 |
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ETA |
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0.100
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0.115 |
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Øz,n** |
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0.70
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0.65 |
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* Calculated here from experimental Xaa and Xbb - Xcc
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** Angle between normal to C(2)C(5)C(7) plane (see below) and z-principal axis of the nqcc tensor.
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Table 2. 14N
nqcc's in
N,N-Diethylacetamide, conformer II (MHz). Calculation was made on
(1) B3P86/6-31G(3d,3p) and (2) HF/6-311++G(3df,3pd) 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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1.486
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1.444
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1.49797(61)
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Xbb - Xcc |
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6.145
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6.280
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6.2522(11)
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Xbb
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2.329
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2.418
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2.3771 *
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Xcc |
-
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3.815
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3.862
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3.8751 *
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Xab |
-
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0.233
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0.187
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Xac |
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1.720
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1.732
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Xbc |
-
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0.396
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-
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0.319
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RMS |
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0.045 (1.7 %)
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0.039 (1.5 %)
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RSD |
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0.030 (1.3 %) |
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0.030 (1.3 %) |
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Xxx |
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1.964
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1.944
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Xyy |
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2.391
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2.452
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Xzz |
-
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4.355
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-
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4.396
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ETA |
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0.0980
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0.116
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Øz,n** |
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0.19
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0.34
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* Calculated here from experimental Xaa and Xbb - Xcc |
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** Angle between normal to C(2)C(5)C(7) plane (see below) and z-principal axis of the nqcc tensor. |
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| Table 3.
N,N-Diethyacetamide. Selected structure parameters, ropt (Å and degrees). Optimized structures (1) B3P86/6-31G(3d,3p) and (2) HF/6-311++G(3df,3pd). Complete structures are given here is Z-matrix format.
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Conformer I |
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ropt (1) |
ropt (2) |
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C(2)N |
1.3637 |
1.3528 |
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C(5)N |
1.4520 |
1.4511 |
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C(7)N |
1.4571 |
1.4568 |
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C(2)NC(5) |
124.53 |
124.49 |
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C(5)NC(7) |
117.52 |
117.24 |
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C(7)NC(2) |
117.94 |
118.25 |
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Conformer II |
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ropt (1) |
ropt (2) |
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C(2)N |
1.3643
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1.3537
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C(5)N |
1.4516
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1.4512
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C(7)N |
1.4599
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1.4595
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C(2)NC(5) |
124.57
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124.35
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C(5)NC(7) |
118.18
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117.92
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C(7)NC(2) |
117.20
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117.59
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Note: The extent to which the three CNC angles sum to 360o is the extent to which the N atom is co-planar with C(2)C(5)C(7).
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| Table 4.
N,N-Diethyacetamide. Rotational Constants (MHz).
Calculation was made on the (1) B3P86/6-31G(3d,3p) and (2)
HF/6-311++G(3df,3pd) optimized structures. |
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Calc (1)
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Calc (2) |
Expt [1]
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Conf. I
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A
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2056
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2083
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2065.94325(15)
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B
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1963
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1960
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1946.434197(70)
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C
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1159
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1163
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1157.141719(42)
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| Conf. II |
A
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2212
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2196
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2181.25231(20)
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B
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1917
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1938
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1933.673393(99)
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C
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1186
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1187
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1191.944060(91)
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[1] R.Kannengiesser, S.Klahm,
H.V.L.Nguyen, A.Lüchow, and W.Stahl, J.Chem.Phys. 141,204308(2014).
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| R.Kannengiesser,
H.V.L.Nguyen, and W.Stahl, Abstract WD02, The 23rd International
Conference on High Resolution Molecular Spectroscopy, Bologna, Italy,
Sept. 2-6, 2014.
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Acetamide |
N-Methylacetamide |
N,N-Dimethylacetamide
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Table of Contents |
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Molecules/Nitrogen |
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NNDEA.html |
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Last
Modified 26 Nov 2014 |
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