C-H bond distance

Take C—H bond distance and bond strength for example Recalling that an elec tron m a 2s orbital is on average closer to the nucleus and more strongly held than an... 

Structure. Ethylene is a planar molecule with a carbon—carbon bond distance of 0.134 nm, which is shorter than the C—C bond length of 0.153 nm found in ethane. The C—H bond distance is 0.110 nm, and the bond angles are [Pg.432]

Cyclopropane gave photographs showing four rings, with qualitative appearance corresponding closely to the calculated curve of Fig. 4. The s0 and I values given in Table V lead to the radial distribution curve shown in Fig. 3 (curve A), with peaks at 1.12 A. (C-H bond distance), 1.52 A. (C-C bond distance) and 2.2-2.5 A. (larger C-H... 

The intensity curves I, II, III, and IV of Fig. 4 are calculated for coplanar trans models with C-H = 1.06 A., the angle H - C=C = 115°, and the angle H—C—H = 109.5°. Although these hydrogen parameters are so chosen as to agree as well as possible with minor peaks of the radial distribution function, no great reliance can be placed on them, and indeed it is likely that for this molecule the C-H bond distance is 1.09 A. The models have the following additional parameters... 

Indications are that a C—D bond is slightly shorter than a corresponding C—H bond. Thus, electron-diffraction measurements of C2H6 and showed a C—H bond distance of 1.1122 0.0012 A and a C—D distance of 1.1071 0.0012... 

The hard sphere exclusion distances for this system were chosen as follows nonbonded backbone carbons, 4.60 R (twice the C-H bond distance plus van der Waals radius for H) non-neighboring fluorines, 2.70 R (twice van der Waals radius for F) neighboring fluorines, 6.39 R (distance across phenyl ring using dimensions of Table I and van der Waals radius for Hof... 

Still, the reasons for this success were not quite clear for instance, the good performance of the method in reproducing the equilibrium C—H bond distance in methane was thought to depend on fortuitous cancellation of the nuclear repulsion and of the change in... 

Compounds C—H bond distances C=C bond distances ZCCH angles... 

An instructive illustration of the effect of molecular motion in solids is the proton resonance from solid cyclohexane, studied by Andrew and Eades 101). Figure 10 illustrates their results on the variation of the second moment of the resonance with temperature. The second moment below 150°K is consistent with a Dsi molecular symmetry, tetrahedral bond angles, a C—C bond distance of 1.54 A and C—H bond distance of 1.10 A. This is ascertained by application of Van Vleck s formula, Equation (17), to calculate the inter- and intramolecular contribution to the second moment. Calculation of the intermolecular contribution was made on the basis of the x-ray determined structure of the solid. 

For an accurate method of C—H bond distance determination, see Henry Ace. Chem. Res. 1987, 20, 429-435 Bartell Roth Hollowed Kuchitsu Young J. Chem. Phys. 1965, 42. 2683. 

Adamantonium Ions. There exists a single theoretical study for ada-mantonium ions.850 Mota and co-workers have found three isomeric structures (490-492) and two van der Waals complexes (1-adamantyl cation+ H2 and 2-adamantyl cation + H2) [MP2(full)/6-31G level]. The C—H bond lengths in the 3c-2e interactions in ion 490 are 1.276 and 1.266 A and in ion 491 are 1.266 and 1.280 A. The C-adamantonium ion (492) has nonequivalent C—H bond distances (1.191 and 1.294 A) and the C—C bond distance is 2.348 A. Interestingly, the 2-adamantyl cation + H2 complex shows a nonclassical bonding nature similar to the... 

Both Li+ ions Lil and Lila are coordinated identically they are bound side-on to the nitrogen atoms of the hydrazine unit and end-on to the ring nitrogen atom Nl. Their coordination sphere is saturated by two Li-C contacts. Computational positioning of H-atoms with a rigid C—H bond distance of 108 pm and tetrahedral geometry results in Li-H contacts like those cited or evidenced for binding interactions.41 The dimer exists in the gas phase, as well. The mass spectrum shows the molecular ion 76 (Table XI). 

Table 2 The isotropic magnetizability (in ppm cgs) of some polyaromatic hydrocarbons as obtained with Pauling s model [36] and using ab-initio methods. The experimental results given by Pauling are also listed. The numbers in parentheses are obtained by scaling the experimental results by a factor of 1.1 (see Section 8). All calculations were made with idealized C — C bond distances of 1.42A and C — H bond distances of 1.07A.

Uee attanViow to examine transition states for (he readionsnf Br with meUtane, 2-mcthylpropane, and propone. How do the breaking C-H bond distances vaty Account for thta variation using the Hammond poetulatr... 

It is not pertinent here to go into details of 2D NMR spectroscopy such material is adequately covered elsewhere. Suffice it to say that, in this instance, computer simulation of the dipolar coupled sideband patterns allowed estimates to be made of the C-H bond distances and the H-C-H bond angles. Such information is of extreme importance. A great shortcoming of matrix isolation is the lack of Bond Length information. Two techniques have been developed that will give these data one is NMR, the other is extended X-ray absorption fine structure (EXAFS) (see Section 4.6). 

TiChCHa Geometry Optimizations. The results of complete SCF geometry optimizations on TiClsCHs using basis sets I-IV are shown in Table II. As the basis sets are improved, the Ti-C and C-H bond distances show the smallest changes of... 

The corresponding AG(r) is shown in figure 2. A clear peak is observed at 1.1 A which corresponds to the characteristic C-H bond distance and coordination number in the polymer. It is clear that there is no strong structure at larger distances in the first order difference. This is largely due to the fact that the polymeric hydrogen is not at any particular centre of symmetry in relation to the hydrating water. However it is possible to reveal more of the hydration structure after the (known) intermolecular structure of the PEO molecule is subtracted firom the difference function. A detailed analysis of the result after this subtraction. 

From these coordinates the C—C and C-H bond distances can be calculated. When the unit cell is orthorhombic (as it is for crystalline benzene), or tetragonal or cubic, then a = = 7 = 90 , and, as a result. Equation... 

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