Which of the following is the correct IUPAC name of the following compound? CH3CH2CH2OH a. hydroxypropylbenzene b. 2-propylphenol c. 2-propyl-1-hydroxybenzene d. 2-propylphenol
The Correct Answer and Explanation is:
The correct answer is b. 2-propylphenol.
Here is a detailed explanation of how to determine the IUPAC name for the given compound.
The process of naming organic compounds using the International Union of Pure and Applied Chemistry (IUPAC) system follows a specific set of rules. For this molecule, we can break down the naming process into several steps.
First, we must identify the parent or base structure. The molecule consists of a benzene ring with two substituents: a hydroxyl group (-OH) and a propyl group (-CH2CH2CH3). According to IUPAC nomenclature, a benzene ring with a hydroxyl group directly attached has a special, accepted parent name, which is phenol. Because the hydroxyl group is a higher priority functional group than the alkyl (propyl) group, we use phenol as the parent name rather than treating it as a substituted benzene.
Second, we need to number the carbon atoms of the parent ring. The rules state that the carbon atom bearing the principal functional group (the hydroxyl group in this case) must be assigned the lowest possible number. Therefore, the carbon attached to the -OH group is designated as carbon-1 (C1).
Third, we number the remaining carbons of the ring to give the other substituent the lowest possible locant. Starting from C1, we can number in the direction that reaches the propyl group first. This places the propyl group on carbon-2 (C2).
Finally, we assemble the complete name. We list the substituent’s name preceded by its locant, followed by the parent name. The substituent is a propyl group at position 2. The parent name is phenol. Combining these parts gives the final IUPAC name: 2-propylphenol.
Let’s review the other options. Option (a) is incorrect because it implies the hydroxyl group is on the propyl chain. Option (c), 2-propyl-1-hydroxybenzene, is a systematic name but not the preferred one, as “phenol” is the accepted IUPAC name for hydroxybenzene. Option (d) is incorrect because the numbering is wrong; the hydroxyl group defines the C1 position in phenol, so the propyl group cannot also be at position 1.
