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2,6-F2-C5H3N
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in 2,6-Difluoropyridine |
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Calculation of the nitrogen nqcc's in 2,6-difluoropyridine was
made on the substitution structure of Stiefvater [1], and on a
structure obtained by optimization at the B3P86/6-31G(3d,3p) level of theory.
These are compared in Tables 1 and 2 with the experimental nqcc's
of Stiefvater et al. [2]. Structure parameters are compared in Table
3. Substitution coordinates are given in Table 4, rotational constants are compared in Table 5. |
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Subscripts a,b,c
refer to the principal axes of the inertia tensor; x,y,z to the
principal axes of the nqcc tensor. 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-Difluoropyridine (MHz). Calculation
was made on the substitution structure [1]. |
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Calc. |
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Expt. [2] |
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14N |
Xaa |
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1.849 |
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1.82(5) |
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Xbb |
- |
3.965 |
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4.16(2) |
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Xcc |
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2.116 |
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2.34(5) |
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ETA * |
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0.067 |
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RMS |
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0.17 (6.2 %) |
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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-Difluoropyridine (MHz). Calculation
was made on the B3P86/6-31G(3d,3p) ropt structure. |
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Calc. |
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Expt. [2] |
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14N |
Xaa |
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1.897 |
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1.82(5) |
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Xbb |
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4.049 |
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4.16(2) |
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Xcc |
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2.152 |
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2.34(5) |
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ETA * |
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0.063 |
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RMS |
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0.13 (4.8 %) |
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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-Difluoropyridine. Molecular structure parameters, rs and ropt (Å
and degrees). |
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rs [1] |
ropt |
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N(1)C(2) |
1.3168(17) |
1.3138 |
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C(2)C(3) |
1.3767(10) |
1.3860 |
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C(3)C(4) |
1.3941(5) |
1.3887 |
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C(2)F(2) |
1.347(1) |
1.3315 |
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C(3)H(3) |
1.0795(7) |
1.0818 |
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C(4)H(4) |
1.0822(5) |
1.0844 |
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C(6)N(1)C(2) |
115.0(3) |
115.93 |
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N(1)C(2)C(3) |
126.5(1) |
125.70 |
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C(2)C(3)C(4) |
116.1(1) |
116.37 |
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C(3)C(4)C(5) |
119.8(1) |
119.94 |
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N(1)C(2)F(2) |
114.7(1) |
115.62 |
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C(2)C(3)H(3) |
120.8(1) |
120.60 |
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C(3)C(4)H(4) |
120.1(1) |
120.03 |
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| Table 4. 2,6-Difluoropyridine. Atomic coordinates, rs [1]. |
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a (Å) |
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b (Å) |
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N(1) |
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0.0 |
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0.9437 |
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C(2,6) |
± |
1.1100 |
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0.2353 |
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C(3,5) |
± |
1.2058 |
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1.1376 |
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C(4) |
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0.0 |
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1.8368 |
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F(2,6) |
± |
2.2420 |
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0.9659 |
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H(3,5) |
± |
2.1690 |
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1.6251 |
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H(4) |
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0.0 |
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2.9192 |
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| Table 5. 2,6-Difluoropyridine. Rotational Constants
(MHz). |
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Calc ropt |
Calc rs * |
Expt. [1] |
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A |
3770.6 |
3751.7 |
3747.701(24) |
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B |
1911.8 |
1907.5 |
1905.832(12) |
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C |
1268.6 |
1264.6 |
1263.253(11) |
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* Calculated here. |
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[1] O.L.Stiefvater, Z.Naturforsch. 30a,1765(1975). |
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O.L.Stiefvater, S.Lui, and J.A.Ladd, Z.Naturforsch. 31a,53(1976). |
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See also ... |
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S.Doraiswamy and S.D.Sharma, Chem. Phys.Lett. 37,527(1976). These
authors report for nitrogen in 2,6-difluoropyridine the following: Xaa
= 1.91(4), Xbb = -4.24(4), and Xcc = 2.33(10)
MHz. |
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Pyridine |
2-Fluoropyridine |
2,3-Difluoropyridine |
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3-Fluoropyridine |
4-Fluoropyridine |
2,4-Difluoropyridine |
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3,4-Difluoropyridine |
3,5-Difluoropyridine |
2,5-Difluoropyridine |
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2,6-Dichloropyridine |
2,6-Lutidine |
2,6-Dicyanopyridine |
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Table of Contents
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Molecules/Nitrogen |
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26DFP.html |
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Last
Modified 18 Nov 2003 |
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