Question

Give the number of peaks and the relative peak areas that should be observed in the low-resolution proton magnetic resonance spectra of the following molecules:

,$\mathit{C}\mathit{H}\mathbf{3}\mathit{C}\mathit{H}\mathbf{2}\mathit{C}\mathit{H}\mathbf{2}\mathit{C}\mathit{H}\mathbf{3}$,$\mathit{C}\mathit{H}\mathbf{3}\mathit{O}\mathit{C}\mathit{H}\mathbf{3}$.$\mathit{C}\mathit{H}\mathbf{3}\mathit{N}\mathit{H}\mathit{C}\mathit{H}\mathbf{3}$

Short answer

In$CH3CH2CH2CH3$,Number of peaks are 2 and relative peak area is 3:2.

In$CH3OCH3$,Number of peaks are 1 and relative peak area is 1.

In$CH3NHCH3$,Numbers of peaks are 2 and relative area is 1:6.

Step-by-step solution

Homotopic Proton definition 

The word "homotopy" simply means "identical." All of the protons in ethane, for example, are homotopic. Despite the fact that each proton is physically distinct, we refer to them as identical because the rotation around the C-C single bond is so quick that all protons seem in the same environment on average.

Chemically, homotopic protons are the same and produce the same signal.

Diastereotopic Proton definition

Diastereotopic protons are chemically non-equivalent, so give different signal.

Find the peak and relative peak areas 

In,$CH3CH2CH2CH3$there are two distinct types of chemically non-equivalent protons present –$CH3$(a) and –$CH2$(b), so they will show 2 signals, so the number of peaks is 2. (a) type protons are 6 and (b) type protons are 4, so the relative peak area would be 6:4 which becomes 3:2.

In$CH3OCH3$,there is only one type of proton –$CH3$(a), so the number of peak is 1. And relative peak area is 1.

In$CH3NHCH3$,there are two distinct types of chemically non-equivalent protons present –$CH3$(a) and –$NH$(b) , so they will show 2 signals, so the number of peaks is 2. (a) types protons are 6 and (b) type protons are 1, so the relative peak area would be 6:1.

Therefore,In $CH3CH2CH2CH3$, Number of peaks are 2 and relative peak area is 3:2.

In, $CH3OCH3$Number of peaks are 1 and relative peak area is 1.

In $CH3NHCH3$, Numbers of peaks are 2 and relative area is 1:6.