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H(O=)C-N(-H)CH3
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Nitrogen |
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Nuclear
Quadrupole Coupling Constants |
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in
N-Methylformamide |
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Nitrogen nqcc's in trans and cis N-methylformamide were determined by Kawashima et al. [1].
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trans |
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cis |
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At MP2/aug-cc-pVTZ level of theory, Etrans < Ecis by 6.0 kJ/mol
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Calculation of the N nqcc
tensor in both trans
and cis N-methylformamide was made here on Cs (assumed) molecular structures given by MP2/aug-cc-pVTZ and HF/6-311++G(3df,3pd) optimization.
Calculated
and
experimental [1] nqcc's are compared 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 principal axes of the inertia tensor, subscripts
x,y,z to principal axes of the nqcc tensor. ETA = (Xxx
-
Xyy)/Xzz. |
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RMS is the root measn square
difference between calculated and experimental diagonal nqcc's (percent
of the average of the absolute experimental nqcc's). RSD is the
residual standard deviation of the calibration of the computional model
for calculation of the nqcc's. |
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Table 1. 14N
nqcc's
in trans
N-Methylformamide, A
(MHz).
Calculation was made on MP2/aug-cc-pVTZ and HF/6-311++G(3df,3pd) optimized structures. |
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Calc /MP2
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Calc /HF
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Expt [1] |
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Xaa |
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1.902 |
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1.897 |
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1.8971(54) |
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Xbb |
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2.159 |
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2.156 |
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2.13865 * |
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Xcc |
- |
4.060 |
- |
4.053 |
- |
4.03575 * |
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|Xab| |
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0.161 |
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0.246
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RMS |
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0.019 (0.69 %) |
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0.014 (0.52 %) |
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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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1.824 |
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1.749 |
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Xyy |
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2.237 |
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2.304 |
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Xzz |
- |
4.060 |
- |
4.053 |
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ETA |
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0.102 |
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0.137 |
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* Derived here from Xaa and
Xbb - Xcc = 6.1744(12) MHz. |
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Table 2. 14N
nqcc's
in cis
N-Methylformamide, E
(MHz).
Calculation was made on MP2/aug-cc-pVTZ and HF/6-311++G(3df,3pd) optimized structures. |
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Calc /MP2
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Calc /HF
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Expt [1] |
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Xaa |
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2.334 |
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2.338 |
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2.3508(29) |
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Xbb |
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1.911 |
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1.892 |
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1.9182 *
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Xcc |
- |
4.245 |
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4.230 |
- |
4.2690 *
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|Xab| |
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0.284 |
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0.309
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RMS |
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0.017 (0.61 %) |
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0.028 (0.97 %) |
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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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1.769 |
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1.733 |
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Xyy |
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2.476 |
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2.497 |
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Xzz |
- |
4.245 |
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4.230 |
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ETA |
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0.167 |
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0.180 |
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* Derived here from Xaa and
Xbb - Xcc = 6.1872(84) MHz. |
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| Table 3. N-Methylformamide. MP2/aug-cc-pVTZ and HF/6-311++G(3df,3pd) selected structure parameters
(Å and degrees). Complete
structures are given here in
Z-matrix format. |
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trans |
MP2 |
HF |
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C(3)O |
1.2213 |
1.1893
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| C(3)N |
1.3574 |
1.3429
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| NC(6) |
1.4484 |
1.4451
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| NH(2) |
1.0055 |
0.9903
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| OC(3)N |
125.24 |
125.83
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| C(6)NC(3) |
122.66 |
123.81
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| C(3)NH(2) |
117.46 |
117.28
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| OC(3)NC(6) |
0. (sym) |
0. (sym) |
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OC(3)NH(2) |
180. (sym) |
180. (sym) |
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cis
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MP2
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HF
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C(3)O |
1.2209
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1.1888
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| C(3)N |
1.3550
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1.3425
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| NC(6) |
1.4512
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1.4447
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| NH(2) |
1.0072
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0.9923
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| OC(3)N |
125.13
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125.15
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| C(3)NH(2) |
116.35
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116.35
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| OC(3)NC(6) |
-180. (sym)
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-180. (sym) |
| OC(3)NH(2) |
0. (sym)
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0. (sym) |
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| Table 3. N-Methylformamide.
Rotational Constants (MHz).
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trans |
Calc /MP2 |
Calc /HF |
Expt. [1] |
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A |
19862.2 |
20726.8 |
19986.8962(30) |
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B |
6154.7 |
6168.1 |
6405.2571(15) |
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C |
4841.8 |
4897.5 |
4902.4309(15) |
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cis
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Calc /MP2
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Calc /HF
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A
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44274.7
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45346.4
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B
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4384.5
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4478.8
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C
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4091.8
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4181.6
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[1] Y.Kawashima, T.Usami,
R.D.Suenram, G.Yu.Golubiatnikov, and E.Hirota, J.Mol.Spectrosc.
263,11(2010). |
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A.C.Fantoni and W.Caminati, J.Chem.Soc. Farad.Trans. 92,343(1996).
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Formamide |
Acetamide |
N-Methylacetamide |
N-Ethylformamide |
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Table of Contents |
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Molecules/Nitrogen |
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NMFA.html |
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Last
Modified 24 May 2015 |
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