What are X and Z in the following sequence of reactions?
Show Hint
To find the components of an aldol condensation product, mentally "cleave" the double bond \(\text{C}=\text{C}\):
- Change the \(\text{C}\) on the side without the carbonyl back to a carbonyl (\(\text{C}=\text{O}\)), which gives \(\text{PhCHO}\).
- Add two hydrogens to the other \(\text{C}\) to get the original ketone, \(\text{CH}_3\text{COCH}_3\).
To identify the compounds X and Z in the sequence, let's examine the sequence of reactions provided:
The first reaction involves an alkyne reacting with mercuric sulfate (\( \text{HgSO}_4 \)) in the presence of dilute sulfuric acid (\( \text{H}_2\text{SO}_4 \)) and water. This is a hydration reaction of an alkyne which typically results in the formation of a ketone or aldehyde. For non-terminal alkynes, a ketone is formed, while for terminal alkynes, an aldehyde is formed.
Given the need for the final product, the intermediate (Y) must have a ketone functional group. This suggests that X should be a terminal alkyne, most likely acetylene or a methyl-substituted acetylene like propyne (\( \text{H}_3\text{C}-\text{C}\equiv\text{CH} \)).
In the second reaction, the compound Y undergoes an aldol condensation, often requiring sodium hydroxide (\( \text{NaOH} \)) and heat. The condensation would lead to a product with the structure of an α,β-unsaturated carbonyl compound.
The final product suggests that Z must be an aldehyde involved in the aldol condensation. Given the structure of the final product, benzaldehyde (\( \text{PhCHO} \)) appears to be a fitting choice.
After evaluating the reactions, the correct choice for X and Z is:
