How many ¹³C signals would 1,4-dimethylbenzene give?

Question

Quizplus · Accepted Answer

1,4-dimethylbenzene has two substituents on the benzene ring, namely two methyl groups. Each methyl group has three possible positions to attach to the ring, namely ortho (o), meta (m), and para (p) positions. Therefore, there are six possible isomers of dimethylbenzene: 1,2-dimethylbenzene (ortho), 1,3-dimethylbenzene (meta), 1,4-dimethylbenzene (para), 2,3-dimethylbenzene (meta), 2,4-dimethylbenzene (ortho), and 3,4-dimethylbenzene (meta). 
Out of these six isomers, only 1,4-dimethylbenzene has two para-substituents, which means that it can give a total of three S1U1P113S1S1P0C signals: two equivalent signals for the para-substituents (S1U1P113S1), and one singlet signal for the other hydrogens on the ring (S1P0C). Therefore, the answer is C) 3.

How Many 13C Signals Would 1,4-Dimethylbenzene Give

How Many ¹³C Signals Would 1,4-Dimethylbenzene Give