Final answer:
Enantiotopic protons are protons that are related by symmetry and lead to enantiomers when substituted, while diastereotopic protons are not related by symmetry and their substitution leads to diastereomers with different properties. Stereochemistry is important in biological processes as it affects the activity of molecules in organisms.
Step-by-step explanation:
To distinguish between enantiotopic and diastereotopic protons, we must first understand that they are terms used to describe types of hydrogens in molecules that have stereocenters or chiral centers. Enantiotopic protons are two hydrogen atoms that are interconverted by the reflection in a mirror plane within the molecule, leading to enantiomers if replaced by a different substituent. Enantiomers have identical physical and chemical properties except in their interaction with chiral objects or reagents. Diastereotopic protons, on the other hand, are not related by any symmetry elements and their substitution results in diastereomers, which have different physical and chemical properties, as noted in Table 1.
An example of enantiotopic protons can be seen in a molecule like 1,2-dichloroethane, where the two protons on the same carbon are equivalent in the achiral environment but become non-equivalent in a chiral environment and would give rise to different enantiomers if replaced. Diastereotopic protons are present in molecules with more than one stereocenter, such as 1,3-dichloro-2-butanol, where the protons of the methylene (CH2) group adjacent to the stereocenters are not equivalent and their replacement leads to diastereomers.
Stereochemistry plays a crucial role in biological processes as many organisms prefer one enantiomeric form of a molecule over another, affecting nutrients and pharmaceuticals. The different tastes of L and D-enantiomers of aspartame and the distinct pharmacologic effects of dextromethorphan and levomethorphan are examples of how these subtle differences can have significant real-world consequences.