For the signal assigned to proton 3 we find even more peaks. We won’t go into details about those in this blog post to keep things relatively easy, but I think this shows that the NMR spectrum of maleic acid is a great example of how NMR spectroscopy is such an information rich analytical technique if you want it to be. The overview spectrum is as easy as a simple singlet, but if you look really closely, there are many more signals, and everyone tells their little story. Theoretical research groups, like the Physical Organic Chemistry Lab around Professor Tormena and Professor Rittner,2 help in rationalizing coupling constants by theoretical calculations, which proves that such signals are not simply some noise or artifact signals but do actually agree with NMR theory.
If you happen to work with maleic acid as an internal calibrant or at all, we hope this blog post helps you in finding an answer to the question why the carbon satellites for this compound look different from what one is used to. If you have any questions on benchtop NMR or interesting signals, please reach out to us, and we will be more than happy to help.