Alkenes like ethene dissolve in conc. H2SO4 but alkynes like ethyne do not dissolve in conc. H2SO4, whereas but-2-yne dissolves. Explain.
Ethyne (acetylene) readily undergoes hydration reaction when reacted with dilute H2SO4, in the presence of a mercuric sulfate (HgSO4) catalyst. However, in order for this reaction to be facilitated, the reaction medium must contain water (H2O).
In conc. H2SO4, there is very little water available. Since acetylene is a non-polar gas, it readily passes through conc. H2SO4, and remains unreactive. In fact, conc. H2SO4 is a preferred drying medium for obtaining very dry acetylene stream.
The reason acetylene does not react with conc. H2SO4 is because it does not have anything to react with, no nucleophiles available. Especially in the absence of HgSO4 catalyst, the triple bond is not activated sufficiently to undergo any nucleophilic attack. Whereas but-2-yne dissolves.
Ethyne (acetylene) readily undergoes hydration reaction when reacted with dilute H2SO4, in the presence of a mercuric sulfate (HgSO4) catalyst. However, in order for this reaction to be facilitated, the reaction medium must contain water (H2O).
In conc. H2SO4, there is very little water available. Since acetylene is a non-polar gas, it readily passes through conc. H2SO4, and remains unreactive. In fact, conc. H2SO4 is a preferred drying medium for obtaining very dry acetylene stream.
The reason acetylene does not react with conc. H2SO4 is because it does not have anything to react with, no nucleophiles available. Especially in the absence of HgSO4 catalyst, the triple bond is not activated sufficiently to undergo any nucleophilic attack. Whereas but-2-yne dissolves.
