CHEM 281 Study Guide - Midterm Guide: Allyl Group, Methine Group, Alkyne
13 Nov 2017
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In order to determine the number of chemically equivalent protons, we need to find all possible mirror planes in a molecule. Consider a mirror plane as an imaginary line through which all atoms/bonds on either side of the line are identical. As an analogy, your body would have one mirror plane. For the two examples below the mirror planes are identified and equivalent protons are labelled with the same letter subscript (e. g. ha). Recall that the methyl protons on a single carbon are always. Equivalent to one another (this does not mean that the methyl protons on different methyl groups in a molecule are necessarily equivalent). Ha two mirror planes one from top, one from side - 3 inequivalent protons, therefore three signals in 1h nmr spectrum. Hb from side also one from side that is difficult to draw (if you want to visualize it make a model)
