Radical Substitution Reactions at the Tetrahedral Carbon Atom

2 Radical Substitution Reactions at the Tetrahedral Carbon Atom 

Among numerous radical substitution reactions [23, 24] those of the Sh2 type at a saturated carbon atom have been studied in the most detailed fashion. The simplest and at the same time most important example is given by the substitution of a hydrogen atom of methane by tritium (or another hydrogen isotope)  

For this value to be correctly reproduced, the use of the minimal or DZ basis set in the HF method is no longer sufficient and the electron correlation needs to be taken into account [25]. Table 8.2 lists data on the dependence of calculated activation energies of Eqs. (8.3) and (8.5) upon computational method. The energetically lowest transition state of the substitution reaction of Eq. (8.5) is the trigonal-bipyramidal structure VIII [25,26]. Such a transition state leads, apparently, to inversion of configuration of the tetrahedral carbon atom in radical substitution reactions. No unambiguous experimental confirmation of this conclusion has been obtained so far, but there is indirect evidence in its favor [24]. 

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