Two protons are enantiotopic when replacing either two of the protons forms enantiomers. These enantiotopic protons cannot be distinguished using NMR and are considered equivalent. Determine if the two protons at C4 in 4-chlorobut-1-ene are enantiotopic. Use an imaginary replacement method.

For the following structures, identify the compound with enantiotopic hydrogens marked by H_a and H_b.

What is the relationship between the three products obtained when we replace H _a, H_b, and H_cof methylcyclohexane with deuterium? How many signals would you expect the three hydrogens to produce in the ¹H NMR spectrum?

How can ¹H NMR spectroscopy be utilized to distinguish among 1,2-, 1,3-, and 1,4-phthalonitrile?