PREPARATION, C-13 NMR DFT/IGLO STUDY OF BENZYLIC MONOCATIONS AND DICATIONS, AND ATTEMPTED PREPARATION OF A TRICATION/

Substituted benzylic mono- and dications were prepared and investigate d by H-1 and C-13 NMR spectroscopy and DFT/IGLO calculations. Combined experimental and theoretical study suggest that the structure la is t he major resonance contributor to the 2,4,6-trimethylbenzyl cation 1. Similar results were also found for the 2,4,6-dimethyl-4-tert-butylben zyl 2 and 2,3,4,5,6-pentamethyIbenzyl cation 3. It was found that the structure 4a is the predominant resonance contributor to the overall s tructure of 2,6-dimethylmesityldiyl dication 4 wherein the dienyl and allylic cation units are insulated from each other. Similar studies in dicate structure 5a as the predominant canonical structure for 5-metho xy-2,6-dimethyl-m-xylyldiyl dication 5 wherein the dienyl and oxoallyl ic cation units are insulated from each ether. Attempts to generate th e 2,3,5,6-tetramethyl-1,4-dimethylbenzenediyl dication 8 was, however, not successful as were the generation of the 2,4,6-trimethylmesityltr iyl trication 10 by ionization of 2,4,6-bis(chloromethyl)mesitylene. T he resulting ion was characterized as a chloromethyl substituted dicat ion 9.