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SiH3-CH2Br |
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Bromine |
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Nuclear
Quadrupole Coupling Constants |
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in Bromomethylsilane |
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Calculation was made of the Br nqcc tensors in SiH3CH2Br and SiD3CH2Br on an ropt
molecular structure given by MP2/aug-cc-pVTZ optimization, and on this same structure but with an empirically corrected CBr bond length, say ropt*. These are compared
with the experimental nqcc's [1] in Tables 1 - 3. Structure
parameters are given in Table 4. |
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In Tables 1 - 3, subscripts a,b,c refer to the
principal axes of the inertia tensor; 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 molecular symmetry plane.
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 (percentage of the
average of the magnitudes of the experimental nqcc's). RSD is the
calibration residual standard deviation for the B1LYP/TZV(3df,3p) model
for calculation of the bromine nqcc's, which may be taken as an estimate of the uncertainty in the calculated nqcc's. |
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Table 1. 79Br nqcc's in SiH3CH2Br (MHz). Calculation was made on ropt and ropt* molecular structures. |
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Calc / ropt |
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Calc / ropt* |
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Expt. [1] |
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Xaa |
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336.16 |
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338.56 |
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339.6(106) |
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Xbb |
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- 44.08 |
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- 45.45 |
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- 47.4 |
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Xcc |
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292.09 |
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293.12 |
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292.2(65) |
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|Xab| |
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383.10 |
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383.99 |
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381.4(106) |
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RMS |
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2.76 (1.22 %) |
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1.38 (0.61 %) |
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RSD |
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1.58 (0.39 %) |
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1.58 (0.39 %) |
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Xxx |
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281.63 |
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282.76 |
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281.6(183) |
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Xyy |
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292.09 |
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293.12 |
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292.2(65) |
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Xzz |
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573.72 |
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575.87 |
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573.7(11) |
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ETA |
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0.0182 |
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0.0180 |
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0.018(43) |
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Øz,a |
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31.80 |
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31.72 |
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31.55(67) |
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Øa,CBr |
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32.48 |
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32.38 |
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Øz,CBr |
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0.68 |
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0.66 |
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Table 2. 81Br nqcc's in SiH3CH2Br (MHz). Calculation was made on ropt and ropt* molecular structures. |
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Calc / ropt |
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Calc / ropt* |
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Expt. [1] |
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Xaa |
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281.35 |
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283.35 |
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283.2(80) |
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Xbb |
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- 37.32 |
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- 38.46 |
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- 39.3 |
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Xcc |
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244.03 |
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244.89 |
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243.9(48) |
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|Xab| |
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319.82 |
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320.56 |
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319.1(101) |
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RMS |
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1.56 (0.83 %) |
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0.75 (0.40 %) |
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RSD |
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1.38 (0.40 %) |
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1.38 (0.40 %) |
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Xxx |
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235.30 |
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236.23 |
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235.6(156) |
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Xyy |
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244.03 |
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244.89 |
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243.9(48) |
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Xzz |
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479.33 |
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481.12 |
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479.5(28) |
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ETA |
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0.0182 |
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0.0180 |
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0.017(43) |
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Øz,a |
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31.76 |
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31.67 |
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31.60(68) |
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Øa,CBr |
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32.44 |
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32.33 |
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Øz,CBr |
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0.68 |
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0.66 |
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Table 3. Bromine nqcc's in SiD3CH2Br (MHz). Calculation was made on ropt and ropt* molecular structures. |
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Calc / ropt |
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Calc / ropt* |
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Expt. [1] |
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Xaa(79Br) |
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327.72 |
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330.08 |
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332.0(176) |
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Xbb |
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- 35.63 |
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- 36.96 |
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- 38.9 |
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Xcc |
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292.09 |
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293.12 |
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293.1(103) |
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|Xab| |
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387.17 |
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388.11 |
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399.1(111) |
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RMS |
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3.16 (1.43 %) |
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1.58 (0.71 %) |
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RSD |
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1.58 (0.39 %) |
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1.58 (0.39 %) |
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Xaa(81Br) |
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274.28 |
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276.25 |
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275.5(133) |
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Xbb |
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- 30.25 |
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- 31.36 |
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- 31.8 |
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Xcc |
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244.03 |
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244.89 |
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243.7(78) |
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|Xab| |
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323.24 |
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324.03 |
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332.6(137) |
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RMS |
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1.15 (0.63 %) |
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0.85 (0.46 %) |
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RSD |
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1.38 (0.40 %) |
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1.38 (0.40 %) |
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| Table 4. SiH3CH2Br. Heavy atom structure parameters, ropt and ropt* (Å and degrees). Complete ropt* structure is given here in Z-matrix format. |
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ropt |
ropt* |
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SiC |
1.8881 |
1.8881 |
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CBr |
1.9381 |
1.9461 |
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SiCBr |
108.71 |
108.71 |
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[1] M.Hayashi and K.Kuwada, Bull.Chem.Soc.Jpn. 46,2691(1973). |
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CH3Br |
CH3CH2Br |
SiH3CH2Cl |
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Table of Contents |
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Molecules/Bromine |
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SiH3CH2Br.html |
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Last
Modified 9 Feb 2009 |
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