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Reaction of benzene confusion

Hi, I am stuck on part c of this question. I have done a and b already, and found that there are 4 isomers. However, for b I get that A is 1,4-dimethylbenzene as this can only direct NO2+ to the second carbon as the 4th carbon is already bonded to a group. However, why can't A be 1,2-dimethylbenzene because this can only form 1 product as well (1,2-dimethyl-4-nitrobenzene)

Thanks

(edited 7 years ago)

Reply 1

coconut64

Why can't this isomer be A? This can only direct the NO2+ electrophile to carbon 4

Reply 2

charco

Study Forum Helper

Original post by coconut64

Why can't this isomer be A? This can only direct the NO2+ electrophile to carbon 4

As the methyl group is 2,4,6 directing, with 1,2-dimethylbenzene there is equal possibility of substitution in the 3 and 4 positions. as both are ortho to a methyl group.

Reply 3

coconut64

Original post by charco

As the methyl group is 2,4,6 directing, with 1,2-dimethylbenzene there is equal possibility of substitution in the 3 and 4 positions. as both are ortho to a methyl group.

Oh okay, I think I get it now. So because
1,2-dimethylbenzene is asymmetrical, ther can be multisubstitution, whereas 1,4-dimethylbenzene is symmetrical. Thanks!