Lately, we have been studying electrophilic aromatic substitution reactions. We have studied several examples, learned several mechanisms, and performed brominations in lab. After we have understood and mastered the basics, it is important to make connections from these concepts to the world around us. Therefore, listed below are several examples of electrophilic aromatic substitution reactions which occur biologically and are relevant to our everyday lives.
The first example is of the synthesis of Thyroxine, which occurs within the thyroid:
In these reactions, hydrogen ions in the initial reactant are electrophilically substituted by Iodine. The esterifcation of the alcohol also occurs.
A second example is the drug Prontosil, which is converted by intestinal enzymes into sulfanilamide:
In these reactions, a hydrogen atom attached to the aromatic ring was replaced by a ClSO_2 ion.
A third example of electrophilic aromatic substitution is the biosynthesis of vitamin K, an essential vitamin:
As is observed in the figure, the biosynthesis of vitamin K includes the substitution of an R group for a hydrogen atom.
In conclusion, electrophilic aromatic substitution can be expanded beyond what we have learned in class. In many biologically relevant instances, including the three examples listed, these types of reactions become relevant and important to our everyday life.
Each example and its corresponding figure can be found at the following source:
The Department of Chemistry Turk Group. Electrophilic Aromatic Substitution. http://www.drtchemistry.com/CHM_224_files/Chapter%2016.pdf
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