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I am searching the web for the number of 1H NMR signals of toluene and I find two different results. Some say there are two signals while others say there are four (According to me, it should be 4). For the two signals, it suggests that all five aromatic hydrogens are taken as equivalent. A similar problem arises for compounds like ethylbenzene, benzyl alcohol, and anisole. How can I reconcile these different results?

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In general, the aromatic region of any $\ce{^1H-NMR}$ spectrum would display a complex coupling pattern even if for mono substituted nucleus such as toluene. However, your $\ce{^1H-NMR}$ spectrum is taken by using a low field NMR instruments such as 60 MHz, you'd not able to get one with good resolution to show these patterns (other factors involve in having broad multiplets instead of resolved peaks are low quality calibration, RF instability, etc.). The following spectrum is taken using a high resolution NMR instrument. The $\delta~7.70-7.70$ region was expanded to show the coupling pattern of 5 aromatic hydrogens. In a low-field instrument, those peaks would overlap to give you a broad multiplet. Read this article to learn about basic principles of coupling patterns.

Toluene proton NMR

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  • $\begingroup$ Thanks for answering my query, but then what should I answer for a question when asked me about number of signal should I consider it as a high resolution ? $\endgroup$
    – Kartikey Pandey
    May 4, 2018 at 2:27
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    $\begingroup$ The phrase, "number of signals" has a broad meaning, and it is based on the person who asking the question in this case. For example, there are signals for three magnetically different hydrogens in this spectrum. But, your teacher may consider a doublet as 'two signals.' $\endgroup$
    – Mathew Mahindaratne
    May 4, 2018 at 3:20
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    $\begingroup$ A lot of times in answering questions like this it is best to state your assumptions. So when answering the question -- "Assuming that the number of signals means the number of peaks, then..." $\endgroup$
    – MaxW
    May 4, 2018 at 5:54
  • $\begingroup$ @ MaxW: Thank you for your valuable instructions. $\endgroup$
    – Mathew Mahindaratne
    May 4, 2018 at 6:38
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    $\begingroup$ Question should ask for the number of non equivalent protons rather than for a variable depending on experimentals. Or both the asker and whom is asked should be open for circumstances $\endgroup$
    – Alchimista
    May 4, 2018 at 7:31

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