In this article, the N–H BDE and the IP have been computed both in the gas phase and in solution. In addition, the electronic features such as HOMO orbital distribution and spin density of neutral and radical species have also been presented. As far as the HAT mechanism is concerned, the stability of radicals is enhanced by the possibility that they establish intramolecular H bonds between the radical nitrogen. Solution- and gas-phase BDE values follow o-phenylenediamine > p-phenylenediamine. We notice that para position is more active than ortho position. The dominant antioxidant mechanism of the diaminobenzene should correspond to the HAT.

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