Ozonolysis of alkenes followed by reaction with zinc dust and water yields aldehydes, ketones, or a mixture. Hydration of ethyne in the presence of H₂SO₄ and HgSO₄ produces acetaldehyde, while other alkynes yield ketones in this reaction.
How are aldehydes, ketones, or a mixture of both obtained from alkenes using ozonolysis, and what conditions lead to the formation of acetaldehyde from the hydration of ethyne?
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In ozonolysis of alkenes, the reaction involves the cleavage of the carbon-carbon double bond by ozone (O₃), followed by reductive workup. This process yields either aldehydes or ketones, depending on the substitution pattern of the alkene. Terminal alkenes produce aldehydes, while internal alkenes yield ketones.
For the hydration of ethyne (acetylene), acetaldehyde is formed under specific conditions. The hydration requires a mercuric sulfate (HgSO₄) catalyst and is conducted in the presence of water. This reaction involves the addition of water across the triple bond, leading to the formation of acetaldehyde (ethanal).