JEE PYQ: Aldehydes And Ketones Question 5
Question 5 - 2021 (24 Feb Shift 2)
Which one of the following carbonyl compounds cannot be prepared by addition of water on an alkyne in the presence of $\text{HgSO}_4$ and $\text{H}_2\text{SO}_4$?
(1). ($\text{CH}_3\text{CH}_2\text{CHO}$ (Propanal))
(2). (Cyclohexyl methyl ketone)
(3). ($\text{CH}_3\text{CHO}$ (Acetaldehyde))
(4). ($\text{CH}_3\text{COCH}_2\text{CH}_3$ (Methyl ethyl ketone))
Show Answer
Answer: (1)
Solution
Hydration of alkynes with $\text{HgSO}_4/\text{H}_2\text{SO}_4$ follows Markovnikov’s rule. Terminal alkynes give methyl ketones (except acetylene giving acetaldehyde). Propyne gives acetone, not propanal. Hence propanal cannot be prepared this way.
BETA
