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2,6-(CH3)2-C5H3N
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in 2,6-Lutidine |
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The molecular structure of 2,6-lutidine (2,6-dimethylpyridine)
was optimized at the B3P86/6-31G(3d,3p) level of theory. C2V
symmetry was assumed. Within the framework of this symmetry, the
in-plane methyl hydrogen can be cis or trans with respect
to nitrogen. On both these structures, calculation was made of the
nitrogen nqcc's. The results are compared in Tables 1 and 2 with the
experimental nqcc's of Thomsen and Dreizler [1]. |
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Etrans
< Ecis by 0.38 kcal/mol at the B3P86/ 6-31G(3d,3p)
level of theory, and 0.59 kcal/mol at the B3PW91/ 6-311+G(df,pd) level. For the lower energy trans
conformer, structure parameters are given in Table 3, atomic
coordinates in Table 4, and rotational constants in Table 5.
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In Tables 1 and 2, RMS is the root mean square difference between calculated and experimental nqcc's. RSD
is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for
calculation of the nqcc's. |
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Table 1. Nitrogen nqcc's in 2,6-Lutidine, trans (MHz). Calculation
was made on the B3P86/6-31G(3d,3p) ropt structure. |
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Calc. |
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Expt. [1] |
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14N |
Xaa |
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1.657 |
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1.600(5) |
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Xbb |
- |
4.590 |
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4.572(3) |
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Xcc |
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2.933 |
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2.972(5) |
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ETA * |
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0.278 |
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RMS |
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0.041 (1.4 %) |
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RSD |
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0.030 (1.3 %) |
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* ETA = (Xaa
- Xcc)/Xbb = (Xxx - Xyy)/Xzz. |
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Table 2. Nitrogen nqcc's in 2,6-Lutidine, cis (MHz). Calculation
was made on the B3P86/6-31G(3d,3p) ropt structure. |
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Calc. |
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Expt. [1] |
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14N |
Xaa |
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1.603 |
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1.600(5) |
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Xbb |
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4.620 |
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4.572(3) |
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Xcc |
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3.017 |
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2.972(5) |
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ETA * |
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0.306 |
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RMS |
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0.038 (1.3 %) |
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RSD |
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0.030 (1.3 %) |
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* ETA = (Xaa
- Xcc)/Xbb = (Xxx - Xyy)/Xzz. |
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| Table 3. 2,6-Lutidine, trans and Pyridine. Molecular structure parameters, ropt (Å
and degrees). |
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2,6-Lutidine |
Pyridine |
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N(1)C(2) |
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1.3366 |
1.3336 |
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C(2)C(3) |
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1.3949 |
1.3904 |
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C(3)C(4) |
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1.3867 |
1.3885 |
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C(3)H(3) |
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1.0845 |
1.0845 |
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C(4)H(4) |
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1.0853 |
1.0851 |
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C(6)N(1)C(2) |
119.05 |
117.03 |
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N(1)C(2)C(3) |
122.22 |
123.80 |
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C(2)C(3)C(4) |
118.77 |
118.44 |
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C(3)C(4)C(5) |
118.96 |
118.50 |
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C(4)C(3)H(3) |
121.05 |
121.35 |
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C(2)C(7) |
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1.5002 |
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C(7)H(9) |
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1.0914 |
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C(7)H(11,12) |
1.0932 |
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N(1)C(2)C(7) |
116.15 |
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C(2)C(7)H(9) |
111.82 |
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C(2)C(7)H(11,12) |
110.26 |
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| Table 4. 2.6-Lutidine, trans. Atomic coordinates, ropt. |
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a (Å) |
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b (Å) |
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c (Å) |
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N(1) |
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0.0 |
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0.9585 |
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C(2,6) |
± |
1.1520 |
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0.2806 |
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C(3,5) |
± |
1.1946 |
- |
1.1136 |
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C(4) |
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0.0 |
- |
1.8179 |
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H(3,5) |
± |
2.1484 |
- |
1.6298 |
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H(4) |
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0.0 |
- |
2.9032 |
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C(7,8) |
± |
2.4048 |
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1.1059 |
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H(9,10) |
± |
3.3009 |
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0.4828 |
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H(11-14) |
± |
2.4297 |
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1.7562 |
± |
0.8783 |
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| Table 5. 2,6-Lutidine, trans. Rotational Constants
(MHz). |
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Calculated ropt |
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cis |
trans |
Expt. |
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A |
3524.6 |
3551.4 |
3509.7139(84) |
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B |
1921.1 |
1907.4 |
1906.8639(101) |
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C |
1262.7 |
1260.3 |
1254.6215(14) |
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[1] C.Thomsen and H.Dreizler, Z.Naturforsch. 48a,1093(1993). |
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See also ... |
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W.Caminati and S.DiBernardo, Chem.Phys.Lett.
171,39(1990). |
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Pyridine |
2,6-Difluoropyridine |
2,6-Dichloropyridine |
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2-Methylpyridine |
3-Methylpyridine |
2,6-Dicyanopyridine |
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4-Methylpyridine |
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Table of Contents
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Molecules/Nitrogen |
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26LUT.html |
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Last
Modified 22 Nov 2003 |
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