1- Nitro-2,3,6-trimethylbenzene

Given this behavior (little selectivity in distinguishing between different substrate molecules), the selectivity relationship would predict that positional selectivity should also be very small. However, it is not. For example, under conditions where nitration of p-xylene and 1,2,4-trimethylbenzene takes place at about equal rates, there was no corresponding lack of selectivity at positions within the latter.83 Though steric effects are about the same at both positions, more than 10 times as much 5-nitro product was formed as 6-nitro product. 

Polymethylbenzenes undergo nitration more readily as illustrated by the conversion of sym-trimethylbenzene (mesitylene) to nitromesitylene (76%). Durene (sym-tetramethylbenzene) gives dinitrodurene (94%) no mononitrodurene is ever obtained. In the nitration of other polysub-stituted benzenes, certain anomalous reactions occur. Thus nitration of p-cymene (p-isopropyltoluene) and p-diisopropylbenzene gives in part p-nitrotoluene (8%) and p-nitroisopropylbenzene (50%), respectively, each resulting from the replacement of an isopropyl group by the nitro group. 

Draw the major product when 4-nitro-l,2,3-trimethylbenzene reacts with a mixture of nitric acid and sulfuric acid. 

The solvent effect on the aromatization of the cis- and /rans-isomers of 4-nitro-3,4,5-trimethylcyclohexa-2,5-dienyl acetate (43) (prepared from acetyl nitrate and 1,2,3-trimethylbenzene) has been reported and two major pathways of solvolytic aromatization have been identified. In 50% H2SO4, loss of acetate yields the ipso-ion (44), which is then partitioned along two paths, one leading to oxidation (to 5-hydroxy-l,2,3-trimethylbenzene), the other to migration of the NO2 group, eventually giving 4-nitro-l,2,3-trimethylbenzene. Aromatization in weakly acidic systems leads to loss of nitrite ion, formation of ion (45), and subsequent proton loss to yield 5-acetoxy-l,2,3-trimethylbenzene. ° ... 

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