See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Concept: Acid-catalyzed hydrolysis of a cyclic acetal (1,3-dioxolane) releases the parent carbonyl compound and the diol. However, in this case the acetal is not a simple 1,3-dioxolane derived from an aldehyde or ketone with ethylene glycol; instead, it is a cyclic formal (methylene acetal) where the -O-CH2-O- bridges two adjacent oxygen atoms on the aromatic ring. Step 1: Identify the substrate. The starting material is a compound where the benzene ring bears a free OH at the para position (C4) and at the ortho positions (C1 and C2) the two oxygens are bridged by a -CH2- group forming a five-membered cyclic acetal: -O-CH2-O-. This is a cyclic formal (methylene acetal) of catechol (with an additional para-OH), i.e., it is the methylene acetal of 3,4-dihydroxy phenol (hydroxycatechol / pyrogallol derivative), specifically the 3,4-methylenedioxy-phenol with OH at C1. Step 2: Acid hydrolysis of the cyclic acetal. Under H3O+ conditions, the C-O bonds of the acetal are cleaved. The -O-CH2-O- group hydrolyzes: the CH2 bridging two oxygens is released as formaldehyde (HCHO), and the two oxygens revert to free OH groups. Step 3: Products. After hydrolysis: - The two oxygens that were part of the acetal ring become free OH groups on the ring (C1 and C2 positions), and the para-OH at C4 remains. - This gives 1,2,4-trihydroxybenzene (also called hydroxyhydroquinone or 1,2,4-benzenetriol), which matches option (a). - The CH2 of the -O-CH2-O- is released as formaldehyde (HCHO), which matches option (c). Step 4: Why not (b)? Option (b) shows a non-aromatic (cyclohexane-type) triol, which would require reduction of the ring—this does not occur under simple acid hydrolysis conditions. Acid hydrolysis of an acetal does not reduce the aromatic ring. Step 5: Both (a) and (c) are produced simultaneously in the same hydrolysis reaction. Therefore option (d) is correct. Therefore, the correct answer is D.