Molecules in which substitution produces diastereomers are called diastereotopic. - Diastereotopic atoms are nonequivalent in all environments so they have different chemical shifts. These differences can lead to complex splitting of the signals of diastereotopic \(\mathrm{H}\) atoms, especially those adjacent to a chiral center.

Question: Explain the relationship between diastereotopic atoms, chemical shifts, and complex splitting patterns in the H NMR spectrum, particularly when adjacent to a chiral center. Answer: Diastereotopic atoms are those that produce diastereomers upon substitution, which are stereoisomers that are not mirror images of each other. These atoms have different chemical environments and thus exhibit different chemical shifts in the H NMR spectrum. When diastereotopic hydrogen atoms are close to a chiral center, their environments are affected by the chiral center's stereochemistry, making the atoms non-equivalent and leading to complex splitting patterns in the spectrum due to the differences in their chemical shifts.