See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

Step 1 – Identify the substrate and reaction type. Resorcinol is 1,3-dihydroxybenzene. Treatment with I2/NaOH is the iodoform reaction, which cleaves methyl ketone (or equivalent CH3CO–) groups, but here it is applied to an aromatic ring system bearing two hydroxyl groups in the meta arrangement. Step 2 – Understand how resorcinol reacts with I2/NaOH. Resorcinol, like other phenols activated toward electrophilic substitution, undergoes extensive iodination at the ring. Under alkaline conditions (NaOH), the ring is cleaved oxidatively. Resorcinol (1,3-diol on benzene) reacts with I2/NaOH to give iodoform (CHI3) plus the sodium salt of a carboxylate fragment. The ring-opening of the aromatic system under these conditions yields a small molecule carboxylate salt as the co-product. Step 3 – Determine the carbon skeleton of compound (A). The six-carbon benzene ring, after losing the CHI3 unit (one carbon), leaves a five-carbon fragment. However, the specific oxidative cleavage of resorcinol with alkaline hypoiodite (NaOI, formed from I2 + NaOH) is known to produce iodoform and the disodium salt of an organic diacid or a sodium salt fragment. The product depicted in option (a) shows a sodium enedioate / unsaturated dicarboxylate sodium salt structure consistent with incomplete oxidation of the ring and retention of the conjugated carbon skeleton from resorcinol after CHI3 loss. Step 4 – Match with option (a). Option (a) depicts the sodium salt of an alpha,beta-unsaturated carboxylate with an additional CH2CO2Na group — this is consistent with the known cleavage product retaining the C5 framework as a sodium carboxylate/enedioate after one carbon is removed as CHI3 from the resorcinol ring system under iodoform conditions. Step 5 – Eliminate other options. Option (b) succinic acid is a free diacid, not a sodium salt, and does not match the expected product under NaOH conditions. Option (c) pentanoic acid is a free acid, inconsistent with basic conditions and the carbon framework. Option (d) sodium pentanoate is a saturated salt and does not arise from aromatic ring opening of resorcinol. Therefore, the correct answer is A.