Aromaticity and conformational deformability of some environmental pollutants - methylated anthracenes

Abstract

There is little information on methylated anthracenes which are constituents of diesel fuel. In this paper, a theoretical investigation of some molecular properties of methyl-anthracenes (MAs), 1-MA and 2-MA, and all dimethylanthracene isomers (DMAs), 1,2-DMA, 1,3-DMA, 1,4-DMA, 1,5-DMA, 1,6-DMA, 1,7-DMA, 1,8-DMA, 1,9-DMA, 1,10-DMA, 2,3-DMA, 2,6-DMA, 2,7-DMA, 2,9-DMA, 2,10-DMA, and 9,10-DMA, are presented. The aromaticity indices, based on nucleus-independent chemical shifts (NICS), indicate the aromatic character of methylated anthracenes. The lowest frequencies associated with the out-of-plane deformations of the anthracene (ANTH) aromatic system decrease in the order ANTH > MAs > DMAs. They are related to an increase in conformational non-rigidity of the aromatic system in these molecules, and indicate that they can change their conformation easily through intermolecular interactions, such as interactions with the enzymes of bacteria that catalyze the dioxygenation of these molecules.