The number of hydroxyl group(s) in Q is
To determine the number of hydroxyl groups in compound Q, we need to analyze the given reaction sequence step by step.
The starting compound is a cyclic ester (lactone) with the molecular formula C4H4O2. It undergoes hydrolysis with aqueous NaOH, which is a base-catalyzed hydrolysis of an ester.
Hydrolysis of a lactone (cyclic ester) with aqueous NaOH produces the corresponding hydroxycarboxylate salt. For a γ-lactone (5-membered ring), hydrolysis gives a 4-hydroxybutanoate salt.
Reaction:
After acidification, it becomes 4-hydroxybutanoic acid.
When 4-hydroxybutanoic acid is heated, it undergoes intramolecular esterification (lactonization) to reform the original lactone. However, in this case, it is given that heating produces compound Q, which is different. This indicates that the hydroxy acid might be unstable and dehydrates or rearranges.
Actually, 4-hydroxybutanoic acid upon heating readily reforms the lactone. But here, it is specified that Q is formed, which suggests a different behavior. Upon re-examining, the lactone is C4H4O2, which is unsaturated (degree of unsaturation = 3). It is likely an α,β-unsaturated lactone, such as crotonolactone.
The lactone is actually an unsaturated lactone, specifically 2-furanone. Hydrolysis with NaOH gives the sodium salt of 4-hydroxybut-2-enoic acid. Upon acidification, it becomes 4-hydroxybut-2-enoic acid, which upon heating undergoes dehydration to form crotonic acid (but-2-enoic acid) or a similar compound.
However, the product Q is given to have the molecular formula C4H4O2, same as the starting lactone. This indicates that upon heating, it reforms the lactone, not a different compound. But the question says "Q" is formed, which is probably the lactone itself.
Wait, the image shows the reaction: Lactone (C4H4O2) + aq NaOH → then H+ → then heat → Q (C4H4O2). So, after hydrolysis and acidification, we have the hydroxy acid, which upon heating gives back the lactone. Therefore, Q is the same as the starting lactone, which has no free hydroxyl group (it has a carbonyl and an ester oxygen).
But the question asks for the number of hydroxyl groups in Q. Since Q is the lactone, it has zero free -OH groups.
After the sequence, Q is the original lactone, which does not contain any hydroxyl group. It has a carbonyl group and an ester linkage, but no free -OH.
Therefore, the number of hydroxyl groups in Q is 0.
Hydrolysis of Esters: Esters react with base to form carboxylate salts and alcohols. For lactones, it gives hydroxycarboxylates.
Lactonization: Hydroxy acids can cyclize to form lactones, especially for γ and δ positions.
Molecular Formula Analysis: C4H4O2 has degree of unsaturation = 3, indicating possible rings and double bonds.
Key reaction:
The total number of carboxylic acid groups in the product P is
The hottest region of Bunsen flame shown in the figure below is :
The number of hydroxyl group(s) in Q is