simple H NMR question

[Amos2014]

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How many peaks does toluene have (H NMR)?
I saw somewhere it has only 2 (one from methyl, the other from benzene), while the other says 4 (one from methyl, the other 3 from benzene). Which one is right?

 

[RCT PC CRN]

4 is correct answer.

 

[lala05]

4 is correct answer.

👍 I agree

 

[UCB05]

One might reasonably conclude that with the addition of a methyl group, it would unequally affect the deshielding of the ortho, meta, and para protons. However, Toluene is one of those special cases in which the addition of substituent does not significantly affect the proton nmr of the benzene protons because the R group does not contribute well to any deshielding on the ring. In this case, all 5 protons on the benzene carbons register as one signal. It's one of the more esoteric exceptions to h nmr theory, and I wouldn't dwell too much on it, so don't read this question and spaz out about how you'll know when you get a question like this. Very likely you won't.

 

[loveoforganic]

It would depend on the strength of the machine. In theory, you'd get 4.

 

[UCB05]

It would depend on the strength of the machine. In theory, you'd get 4.

it would have to be an extremely powerful machine to resolve that minute of a difference 😵