Question

4-(2-Aminoethyl)benzene-1,2-diol is commonly known as ________.

• A. catechol
• B. dopamine
• C. hydroquinone
• D. resorcinol

Hint:

Master the three primary catecholamines and their side chains: - Dopamine: Catechol + standard ethylamine chain. - Norepinephrine: Catechol + ethylamine chain with an extra hydroxyl group on the beta-carbon. - Epinephrine: Catechol + ethylamine chain with a beta-hydroxyl AND a methyl group on the amine nitrogen.

Answer 1

The Correct Option is B

Understanding the Concept: This question requires translating a formal, systematic IUPAC chemical name into its widely recognized common or generic pharmacological name. Let us deconstruct the IUPAC name 4-(2-Aminoethyl)benzene-1,2-diol piece by piece to build the chemical structure, and then match it to the given options.

Step 1: Deconstructing the IUPAC Name.

• benzene-1,2-diol: This indicates the core framework of the molecule is a benzene ring with two hydroxyl (\(-\text{OH}\)) groups attached to adjacent carbons (positions 1 and 2). This specific adjacent di-hydroxy benzene ring is classically known as a catechol nucleus.
• 4-(2-Aminoethyl): This describes the substituent attached to carbon 4 of the benzene ring. The substituent is an "ethyl" chain (two carbon atoms: \(-\text{CH}_2-\text{CH}_2-\)). On the 2nd carbon of this ethyl chain, there is an "amino" group (\(-\text{NH}_2\)). Therefore, the entire side chain is \(-\text{CH}_2-\text{CH}_2-\text{NH}_2\). Combining these, the structure is a catechol ring with an aminoethyl chain attached. Molecules that possess a catechol ring and an amine side chain are broadly categorized biologically as catecholamines.

Step 2: Evaluating the Options against our derived structure.

• Option (A) catechol: Catechol is simply benzene-1,2-diol. It completely lacks the 2-aminoethyl side chain. Therefore, it is incorrect.
• Option (B) dopamine: Dopamine is the most fundamental biological catecholamine. Its structure perfectly matches the description: a catechol ring (benzene-1,2-diol) with an ethylamine side chain at the para position to one of the hydroxyls (position 4). Therefore, dopamine is definitively the correct answer.
• Option (C) hydroquinone: Hydroquinone is benzene-1,4-diol (the hydroxyl groups are opposite each other). It lacks the aminoethyl chain entirely and has the wrong hydroxyl positioning. Therefore, it is incorrect.
• Option (D) resorcinol: Resorcinol is benzene-1,3-diol (the hydroxyl groups are separated by one carbon). It also entirely lacks the side chain. Therefore, it is incorrect. Conclusion: The systematic nomenclature distinctly defines the exact structural map of the vital neurotransmitter dopamine.