Proton induced structural reorganization of a few carbonyl molecules in the ground and excited states

Quantum chemical valence parameters have been used to analyze the structura l reorganization of carbonyl molecules like acrolein, glyoxal, propynal, an d formamide after protonation. The effect of proton at the carbonyl oxygen is countable in the electronic configuration of the molecule as a whole. St ructures in different electronic states are analyzed with respect to calcul ated values of bond orders and net charge densities on the atoms. Correlati on has been made between the extent of structural changes in the protonated molecules and proton affinities of the molecules. Prominent structural reo rganizations have been observed after protonation of the carbonyl molecules in comparison to the changes in the free molecules. The directionality of protonation and the pi polarization of the C = O bond is also observed to b e dependent on the type of substituents attached to the carbonyl group.