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Isonicotinic
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in Isonicotinic
Acid
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(Pyridine-4-Carboxylic
Acid) |
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Calculation of the N nqcc's in isonicotinic acid was made here on molecular structures derived by
B3P86/6-31G(d,p) and B3P86/6-31G(3d,3p)
optimizations. Calculated and experimental nqcc's [1] are
compared in
Table 1. Structure parameters are given in Table 2,
rotational constants 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; 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 (percent
of the average of the absolute 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,
which may be taken as an estimate of the uncertainty in the
calculated nqcc's. |
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Table 1. 14N nqcc's in Isonicotinic Acid (MHz). Calculation was made on (1)
B3P86/6-31G(d,p) and (2) B3P86/6-31G(3d,3p) 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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5.081 |
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5.090 |
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5.0395(46) |
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Xbb |
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1.364 |
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1.355 |
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1.3574(44) |
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Xcc |
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3.717 |
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3.735 |
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3.6822(44) |
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|Xab| |
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0.086 |
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0.095 |
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RMS |
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0.032 (1.0 %) |
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0.042 (1.3 %) |
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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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1.365 |
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1.356 |
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Xyy |
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3.717 |
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3.735 |
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Xzz |
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5.083 |
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5.091 |
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ETA |
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0.463 |
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0.467 |
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Øz,a |
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0.77 |
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0.84 |
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Øa,bi * |
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0.75 |
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0.86 |
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Øz,bi |
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0.02 |
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0.02 |
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* "bi" is the bisector of the CNC
angle. |
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| Table 2. Isonicotinic Acid. Selected structure parameters (Å
and degrees). Complete structures are given here in Z-matrix format. |
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ropt (1) =
B3P86/6-31G(d,p) optimization. |
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ropt (2) =
B3P86/6-31G(3d,3p) optimization. |
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ropt (1) |
ropt (2) |
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| N(1)C(2) |
1.3351 |
1.3328
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| C(2)C(3) |
1.3918 |
1.3898
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| C(3)C(4) |
1.3942 |
1.3919
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| C(4)C(5) |
1.3938
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1.3915
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| C(5)C(6) |
1.3899
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1.3880
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| C(6)N(1) |
1.3361
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1.3342
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C(6)N(1)C(2)
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117.28
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117.32
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| N(1)C(2)C(3) |
123.86
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123.81
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C(2)C(3)C(4) |
118.09
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118.14
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C(3)C(4)C(5) |
118.74
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118.74
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C(4)C(5)C(6) |
118.30
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118.29
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C(5)C(6)N(1) |
123.72
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123.71
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C(4)C
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1.4866
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1.4857
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C=O
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1.2111
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1.2063
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C--O
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1.3467
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1.3455
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O--H
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0.9699
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0.9679
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Table 3. Isonicotinic
Acid. Rotational Constants (MHz).
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ropt (1) =
B3P86/6-31G(d,p) optimization. |
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ropt (2) =
B3P86/6-31G(3d,3p) optimization. |
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Calc. ropt (1) |
Calc. ropt (2) |
Expt. [1] |
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A |
4045.8
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4059.2
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4027.83775(63)
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B |
1223.8
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1227.1
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1219.95126(12)
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C |
939.6
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942.3
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937.018821(90)
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[1] I.Peña, M.Varela, V.G.Franco, J.C.López, C.Cabezas, and J.L.Alonso, J.Phys.Chem. A, 118,11373(2014).
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Pyridine |
Nicotinic Acid
| Picolinic Acid
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Table of Contents |
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Molecules/Nitrogen |
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isonicotinic_acid.html |
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Last
Modified 11 Nov 2014 |
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