Question

Write down the IUPAC name of citric acid. O=C(O)CC(O)(CC(=O)O)C(=O)O (A) 2-Carboxy-2-hydroxy pentandioic acid (B) 2-Carboxy-3-hydroxy propane-1,3-dicarboxylic acid (C) 2 -hydroxy propane- \(1,2,3\)-tricarboxylic acid (D) Propane-1,2,3-tricarboxylic acid

Short answer

The short answer is: \( 2\text{-hydroxy propane-}1,2,3\text{-tricarboxylic acid} \) (option C).

Step-by-step solution

Analyze the molecule structure from SMILES representation

SMILES (Simplified Molecular Input Line Entry System) representation of citric acid is given as: O=C(O)CC(O)(CC(=O)O)C(=O)O. It shows the following functional groups: - 3 carboxylic acid groups (COOH) - 1 hydroxyl group (OH)

Assigning positions to the functional groups

To assign positions to the functional groups, draw the structure of the citric acid molecule. \( O=C(O)CC(O)(CC(=O)O)C(=O)O \) becomes the structure: HOOC-CH2-C(OH)(COOH)-CH2-COOH From this structure, it's clear that the molecule has: - A hydroxyl group at carbon 2 - Carboxylic acid groups attached to carbons 1, 3 and 5.

Match the structure with the correct IUPAC name

Now, let's analyze the options: (A) 2-Carboxy-2-hydroxy pentandioic acid: This option indicates a pentane structure, which is incorrect. (B) 2-Carboxy-3-hydroxy propane-1,3-dicarboxylic acid: This option implies a carboxy group attached to carbon 2, which is incorrect. (C) 2-hydroxy propane-1,2,3-tricarboxylic acid: This option correctly matches our drawn structure for citric acid. It has a hydroxyl group at carbon 2 and carboxylic acid groups at carbons 1, 3, and 5. (D) Propane-1,2,3-tricarboxylic acid: This option is missing the hydroxyl group at carbon 2. The correct IUPAC name for citric acid is: 2-hydroxy propane-1,2,3-tricarboxylic acid (option C).