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Pyrimidine
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in Pyrimidine |
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Nitrogen nqcc's in pyrimidine were
determined by Kisiel et al. [1], which authors also determined a heavy
atom substitution structure. A semi-experimental equilibrium
structure, reSE, was derived by Császár et al. [2].
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Calculation of the nitrogen nqcc's in pyrimidine were made on the rs and reSE
structures, as well as an ropt structure given by B3P86/6-31G(3d,3p)
optimization. For the heavy atom substitution structure, the CH
parameters used here are taken from the optimized structure.
These calculated nqcc's are compared with the experimental values [1]
in Table 1. Structure parameters are compared in Table 2.
In Table 3, atomic coordinates are given for the ropt structure. |
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In Table 1, subscripts a,b,c refer to the principal axes of the inertia
tensor, subscripts x,y,z to the principal axes of the nqcc tensor.
The nqcc y-axis is chosen coincident with the inertia c-axis, these
are perpendicular to the plane of the molecule. Ř (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 nqcc's (percentage of
average experimental nqcc). RSD is the residual standard deviation
of calibration of the B3PW91/6-311+G(df,pd) model for calculation of
the nqcc's. |
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Table 1. 14N(1,3)
nqcc's in Pyrimidine (MHz). Calculation was made
on the rs, reSE, and ropt structures. |
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Calc /rs |
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Calc /reSE |
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Calc /ropt |
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Expt. [1] |
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Xaa |
-
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3.070 |
-
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3.109
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- |
3.106 |
- |
3.1004(7) |
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Xbb |
-
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0.286 |
-
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0.255
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- |
0.258 |
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0.2554(7) |
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Xcc |
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3.357 |
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3.364
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3.364 |
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3.3558(7) |
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Xab |
± |
2.739 |
± |
2.721
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± |
2.718 |
± |
2.76(7) |
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RMS |
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0.025 (1.1 %) |
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0.007 (0.3 %)
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0.006 (0.3 %) |
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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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0.030 (1.3 %) |
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Xxx |
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1.394 |
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1.390
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1.386 |
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1.43(6) |
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Xyy |
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3.357 |
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3.364
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3.364 |
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3.3558(7) |
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Xzz |
-
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4.751 |
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4.754
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4.750 |
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4.78(6) |
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ETA |
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0.413 |
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0.415
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0.416 |
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Řz,a |
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31.53 |
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31.16
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31.17 |
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31.4(3) |
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Řa,bi |
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31.5(2) |
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31.54
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31.54 |
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31.5(2) |
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Řz,bi* |
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0 |
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0.38
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0.36 |
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0 |
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* Angle between the z-axis and the bisector ( 'bi' ) of the CNC angle.
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| Table 3. Molecular structure parameters: rs [1], reSE [2], and B3P86/6-31G(3d,3p) ropt (Ĺ and degrees). |
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rs
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reSE
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ropt |
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C(2)N(3) |
1.337(2) |
1.3331(3)
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1.3320 |
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N(3)C(4) |
1.332(3) |
1.3349(6)
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1.3328 |
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C(4)C(5) |
1.393(2) |
1.3874(4)
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1.3877 |
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C(2)H(2) |
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1.0820(23)
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1.0876 |
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C(4)H(4) |
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1.0843(17)
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1.0879 |
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C(5)H(5) |
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1.0799(23)
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1.0835 |
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N(1)C(2)N(3) |
127.2(3) |
127.364(38)
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127.38 |
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C(2)N(3)C(4) |
115.8(3) |
115.712(21)
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115.70 |
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N(3)C(4)C(5) |
122.4(3) |
122.276(19)
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122.40 |
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C(4)C(5)C(6) |
116.4(2) |
116.661(36)
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116.44 |
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C(5)C(4)H(4) |
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121.24(20)
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121.16 |
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| Table 4. Atomic coordinates,
B3P86/6-31G(3d,3p) ropt |
| (More figures are shown
than are significant.) |
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a (Ĺ) |
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b (Ĺ) |
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N(1,3) |
± |
1.193960 |
- |
0.685056 |
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C(2) |
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0.0 |
- |
1.275471 |
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C(4,6) |
± |
1.179635 |
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0.647712 |
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C(5) |
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0.0 |
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1.378622 |
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H(2) |
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0.0 |
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2.363039 |
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H(4,6) |
± |
2.148487 |
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1.142540 |
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H(5) |
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0.0 |
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2.462154 |
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[1] Z.Kisiel, L.Pszczólkowski, J.C.López, J.L.Alonso,
A.Maris, and W.Caminati, J.Mol.Spectrosc. 195,332(1999).
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[2] A.G.Császár, J.Demaison, and H.D.Rudolph, J.Phys.Chem. A, 119(9),1731(2015). |
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G.L.Blackman, R.D.Brown, and F.R.Burden, J.Mol.Spectrosc. 35,444(1970). Xaa = -3.107(14), Xbb = -0.223(16), and Xcc = 3.330(14) MHz. |
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Pyridine |
Pyrazine |
1,3,5-Triazine |
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2-Fluoropyrimidine |
2-Chloropyrimidine |
2-Bromopyrimidine |
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Table of Contents |
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Molecules/Nitrogen |
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Pyrimidine.html |
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Last
Modified 30 Oct 2014 |
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