# Naming the spin system present in ethyl butanoate

I am to identify the spin system of ethyl butanoate, but I am confused as to how I should start.

I know that chemically equivalent but magnetically inequivalent nuclei should be denoted as $$\ce{AA'A''}$$ or $$\ce{BB'B''B'''}$$, etc., whereas magnetically equivalent nuclei are denoted as $$\ce{A3}$$, etc.

But there seem to be many chemically nonequivalent protons in this molecule. Should I just put down this: $$\ce{A3B2C2D2E3}$$? How can I determine if the $$\ce{CH2}$$ protons are not magnetically equivalent, i.e. couple differently to neighboring protons?

• The geminal protons in the methylene groups are magnetically inequivalent in $\ce{H3C-\color{red}{CH2}-\color{blue}{CH2}-CO2Et}$, I think? (Merry Christmas!) – orthocresol Dec 25 '18 at 16:20