Photochimie de Dérivés Aromatiques: III [1] Propriétés Acido-Basiques de Dérivés Aromatiques non Substitués dans les États Électroniques Excités Singulet et Triplet
The acidity constants of protonated naphthalene, anthracene, phenanthrene, chrysene, triphenylene and 1,2,5,6-dibenzanthracene in their lowest singlet and triplet excited states have been estimated by application of the Forster cycle to the electronic spectra of the neutral and protonated species prepared in 96% sulfuric acid or in trifluoroactic-boron trifluoride mixtures.



With the exception of 1,2,5,6-dibenzanthracene, the basicity of these hydrocarbons is increased in the S1 state compared to the ground state. Except chrysene and 1,2,5,6-dibenzanthracene, a similar trend is observed for the lowest triplet state although the ΔpK(T1-So) values are smaller than the ΔpK(S1-So) values. Solutions of naphtalene, anthracene and phenanthrene in CH3COOD were irradiated. It is shown that the positions of H/D exchange are the same for naphthalene in the ground state and in the excited state (position 1 or equivalent). Phenanthrene is photodeuterated essentially on positions 4,5, although in dark condition, deuteration occurs on positions 9, 10.