Conjugated π Systems and Aromaticity

________ refers to a group of 3 benzene derivatives which encompasses ortho-, meta-, and para- isomers of dimethyl benzene.

One 1 2 3 4 5 6 7 8 9
Two 10 11 12 13 14
Three 15 16 17 18 19
Four 20 21 22 23 24 25
  
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