The Application of IMOMO Schemes How Stable Are Benzyl and Diphenylmethyl Radicals

With this choice, the lMOMO(G3(MP2)-RAD,ROMP2) radical stabilization energy of radical 12 is calculated as expressed in Equation 5.11. 

We can thus conclude that the use of IMOMO schemes for the calculation of RSE values equates to combining absolute RSE values calculated at a high level of theory for a small core system with changes in RSE values through introduction of new substituents at some lower theoretical level. The results obtained with this strategy for radical 12 are summarized in Table 5.3. The RSE of radical 12 can be determined directly at G3(MP2)-RAD level and amounts to - -85.5kJ/mol. Using the IMOMO approach, the RSE of benzyl radical 11 at G3(MP2)-RAD level of - -61.0kJ/mol is combined with the difference of the RSE values of radicals 12 and 11 at ROMP2 level (79.8 52.5 = 27.3 kJ/mol) to yield RSE(IMOMO, 

12)= - -88.3 kJ/mol. Considering the immense savings in computer time and the challenging nature of the diphenylmethyl radical 12 this is a remarkably good result. 

TABLE 5.3 RSEs at 298.15 K of Benzyl Radical (11) and Diphenylmethyl Radical (12) (in kJ/mol) at Varions Levels of Theory 

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The Application of IMOMO Schemes How Stable Are Benzyl and Diphenylmethyl Radicals ... 

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