128270-91-7Relevant academic research and scientific papers
Carbon-carbon bond cleavage in radical anions of strained diphenylethane derivatives
Maslak,Narvaez,Vollombroso Jr.
, p. 12373 - 12379 (2007/10/03)
Fragmentation reactions of radical anions (mesolytic cleavages) of 1,1,2,2-tetraalkyl-1-(4'-nitrophenyl)-2-phenylethanes with varying degrees of steric strain have been studied in polar solvents. The rates and activation parameters obtained were compared to the corresponding values obtained for homolytic bond scissions in the neutrals. The free energies of activations for both types of reactions strongly depend on the strain present in the molecule. With the exception of the most crowded members of the series, nearly all of the strain is released in the transition state of homolytic reactions, and ca. 77% of it is relieved in the transition states of mesolysis. The mesolytic fragmentations have activation energies that are on average ca. 12.5 kcal/mol lower than the homolytic processes. The observed redox activation is shown to have thermodynamic origins.
Transition-State Polarization in Cleavage of C-C Bonds in Radical Anions
Maslak, Przemyslaw,Narvaez, Javier N.,Kula, Jozef,Malinski, David S.
, p. 4550 - 4559 (2007/10/02)
The substituent effect on the rate of C-C bond cleavage in radical anions of 1-(4-nitrophenyl)-2-(substituted-phenyl)-1,1,2,2-tetraethylethanes has been explored.The data provide evidence for two distinctive modes of bond scission.One mode is characterized by a significant negative charge transfer across the scissile bond in the transition state.Such polarization of the transition state is in contradiction to the prediction based on the fragments' stability.The second mode, dominant in cases where the charge shift leads to negative charge accumulation on an already electron-rich fragment, involves a ?* radical anion.Both modes point to a general kinetic preference for a cleavage of radical anions that allows for charge delocalization across the scissile bond.
