CH bond lengths

Examine the energies of radicals resulting from hydrogen atom abstraction in 3-ethylpentane. Which radical is the lowest energy Is there a relationship between the CH bond lengths in 3-ethylpentane and the stabilities of the radicals resulting from bond dissociation Elaborate. 

A new period in theoretical work on arenediazonium ions began with Vincent and Radom s paper in 1978. This was the first ab initio study of the methane- and benzenediazonium ions, and was carried out with a minimal (STO-3G) basis set, subject only to some (specified) symmetry constraints and a fixed CH bond length (108.3 pm). The optimized structure of the benzenediazonium ion is given in Figure 4-2. 

McKean, D. C., J. E. Boggs, and L. Schafer. 1984. CH Bond Length Variations Due to the Intramolecular Environment a Comparison of the Results Obtained by the Method of Isolated CH Stretching Frequencies and by Ab Initio Gradient Calculations. J. Mol. Struct. 116, 313-330. 

Figure 8 Behavior of the first sharp diffraction peak of PB with experimental scattering lengths for carbon and deuterium. The deuterium atoms are placed at their mechanical equilibrium positions determined by the positions of the united atom centers and the equilibrium CH bond length and HCH and HCC bond angles along a united atom MD trajectory. With increasing pressure (values given in the legend, simulation performed at T = 293 K), the first sharp diffraction peak shifts to larger q as expected but unexpectedly decreases in height.

Crystallographic data giving MH distances less than the sum of the van der Waals radii and some elongation of CH bond lengths. 

LEED-IV structure does not deviate greatly from the theoretically determined structure. The most obvious difference is the tilt of the C-C axis away from parallel to the surface plane (18° 5°) for molecule 1. HC-CH bond lengths of 1.2 0.05 A are deduced from the carbon atom positions. The authors note that within experimental error this distance is identical to the C-C bond length of the free molecule (1.18 A), which is as expected for a physisorbed molecule. Surface Mg and O ions were only displaced by amounts less than the experimental uncertainty. 

CH bond length (A) and isotropic hcc s (G) computed for the methyl radical by different... 

It will be shown that the vibrational frequencies and NMR C-H coupling constants also are related to the CH bond lengths. 

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