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S=C(NH2)2 |
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Nitrogen
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Nuclear
Quadrupole Coupling Constants |
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in
Thiourea |
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Calculation of the nitrogen
nqcc tensor in thiourea was made on the rs/ropt structure
of Lesarri et al. [1], and on the semi-experimental equilibrium
structure of Puzzarini [2].
These are compared in Tables 1 and 2 respectively with the
experimental
nqcc's [1]. Structure parameters are
given in Table 3. Experimental and calculated quartic centrifugal
distortion constants are compared in Table 4. |
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In Tables 1 and 2, RMS is the root
mean square difference between calculated and experimental diagonal
nqcc's (percentage of the average of the magnitudes of the experimental
nqcc's). RSD is the calibration residual standard deviation of
the B3PW91/6-311+G(df,pd) model for calculation of the nitrogen nqcc's. |
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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.
Ø (degrees) is the angle between its subscripted
parameters. ETA = (Xxx - Xyy)/Xzz. |
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Table 1. 14N nqcc's in S=C(14NH2)2
(MHz). Calculation was made on the (1) rs/ropt
structure [1], and (2) the reSE structure [2]. |
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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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1.905 |
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1.933 |
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1.9958(23) |
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Xbb |
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2.077 |
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2.031 |
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2.0726(28) |
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Xcc |
- |
3.982 |
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3.964 |
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4.0684(28) |
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|Xab| |
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0.311 * |
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0.295 * |
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|Xac| |
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1.229 |
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1.178 |
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|Xbc| |
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0.415 |
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0.414 |
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RMS |
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0.072 (2.7 %) |
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0.074 (2.7 %) |
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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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1.737 |
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1.733 |
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Xyy |
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2.510 |
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2.477 |
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Xzz |
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4.247 |
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4.211 |
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ETA |
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0.182 |
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0.176 |
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Øz,a |
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78.87 |
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79.31 |
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Øz,b |
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93.14 |
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93.23 |
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Øz,c |
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11.57 |
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11.18 |
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* The algebraic sign of the
product XabXacXbc is positive. |
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Table 2. 14N nqcc's in S=C(14NH2)(15NH2)
(MHz). Calculation was made on the (1) rs/ropt
structure [1], and (2) the reSE structure [2]. |
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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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1.890 |
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1.920 |
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1.9739(53) |
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Xbb |
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2.092 |
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2.044 |
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2.096(11) |
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Xcc |
- |
3.982 |
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3.964 |
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4.070(11) |
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|Xab| |
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0.305 * |
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0.292 * |
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|Xac| |
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1.216 |
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1.166 |
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|Xbc| |
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0.450 |
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0.447 |
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RMS |
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0.070 (2.6 %) |
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0.074 (2.8 %) |
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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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* The algebraic sign of the
product XabXacXbc is positive. |
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| Table 3. Thiourea.
Molecular structure parameters [1,2] (Å
and degrees). |
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| Point Group: C2 |
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rs/ropt [1] |
reSE [2] |
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S=C |
1.645(4) |
1.65455(18) |
| CN |
1.368(3) |
1.35940(11) |
| NH(5,7) |
1.0075 |
1.00598(46) |
| NH(6,8) |
1.0058 |
1.00308(90) |
| S=CN |
123.0(2) |
122.737(7) |
| CNH(5,7) |
119.20 |
119.40 |
| S=CNH(5,7) |
156.43 |
157.31 |
| CNH(6,8) |
115.33 |
114.934(85) |
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S=CNH(6,8) |
10.35 |
9.99 |
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| Table 4. Thiourea.
Quartic Centrifugal Distortion Constants (kHz): Calculated =
B3LYP/cc-pVTZ and CCSD(T)/cc-pVTZ. |
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B3LYP |
CCSD(T) [2] |
Expt. [1] |
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Delta_J |
1.10 |
1.08 |
1.305(195) |
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Delta_JK |
4.50 |
4.60 |
4.55(43) |
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Delta_K |
4.57 |
4.89 |
4.27(126) |
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delta_J |
0.380 |
0.37 |
0.3938(88) |
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delta_K |
4.53 |
4.56 |
4.34(61) |
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[1] A.Lesarri, S.Mata, S.Blanco,
J.C.López, and J.L.Alonso, J.Chem.Phys. 120,6191(2004). |
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[2] C.Puzzarini, J.Phys.Chem. A
116,4381(2012). |
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Urea |
(NH2)2 |
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Table of Contents |
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Molecules/Nitrogen |
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Thiourea.html |
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Last
Modified 20 April 2012 |
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