Thermolysis of Geminal BisAzoalkanes. Stabilization of a Carbon-Centered Radical by the Azo Substituent
摘要:
Two geminal bisazoalkanes (1 and 2) have been employed to generate a radical center next to the azo group. The 8.0 kcal/mol lower Delta G double dagger for thermolysis of 1 and 2 relative to model compounds and 7 is dissected into a 1 kcal/mol contribution from ground state elevation of 1 and 2 and at least 2.6 kcal/mol from phenyl stabilization of radical 3. Any extra stabilization of the aliphatic 2,3-diazaallyl radical (4) relative to alpha,alpha-dimethylallyl amounts to no more than 4.4 kcal/mol. Finally, gamma-phenyl conjugation of the alpha,alpha-dimethylallyl radical stabilizes it by 4.5 kcal/mol.
Thermolysis of Geminal BisAzoalkanes. Stabilization of a Carbon-Centered Radical by the Azo Substituent
摘要:
Two geminal bisazoalkanes (1 and 2) have been employed to generate a radical center next to the azo group. The 8.0 kcal/mol lower Delta G double dagger for thermolysis of 1 and 2 relative to model compounds and 7 is dissected into a 1 kcal/mol contribution from ground state elevation of 1 and 2 and at least 2.6 kcal/mol from phenyl stabilization of radical 3. Any extra stabilization of the aliphatic 2,3-diazaallyl radical (4) relative to alpha,alpha-dimethylallyl amounts to no more than 4.4 kcal/mol. Finally, gamma-phenyl conjugation of the alpha,alpha-dimethylallyl radical stabilizes it by 4.5 kcal/mol.