Anomalous Products Obtained by Nitration of Pentamethylbenzene, Pentaethylbenzene, and Some Mixed Penta-alkylbenzenes

Pentamethylbenzene has been nitrated with fuming nitric acid to give mainly a mixture of nitropentamethylbenzene and 2,3,4,5-tetramethylbenzyl nitrate. Other isomeric nitrates were not formed in any significant amount. 6-Nitro-2,3,4,5-tetramethylbenzyl nitrate, 2,3,4,5-tetramethylbenzyl alcohol, 2,3,4,5-tetramethylbenzaldehyde, 2,2′,3,3′,4,4′,5,5′,6-nonamethyldiphenylmethane, and 2,2′,3,3′,4,4′,5,5′-octamethyl-6-nitroxymethyldiphenylmethane were the minor products. Pentaethylbenzene gave a mixture of nitropentaethylbenzene and α-methyl-2,3,4,5-tetraethylbenzyl nitrate along with some products of oxidation. Preferential side-chain attack occurred at the primary alkyl group ortho to the unsubstituted ring position. Thus, 1-methyl-2,3,4,5-tetraethylbenzene was found to give benzyl nitrate and α-methylbenzyl nitrate nearly in equal amounts, while 3-methyl-1,2,4,5-tetraethylbenzene was found to give them in an approximate ratio of 1 : 3. 1,3,4-Trimethyl-2,5-diisopropylbenzene underwent extensive nitrodealkylation, and 3,4-dimethyl-2,5-diisopropylbenzyl nitrate was the only side-chain substituted product identified.