Return to Contents Chapter 9: Alkynes Ch 9 contents
Hydration of Alkynes
hydration of alkynes
Reaction type: Electrophilic Addition

Summary

Related reactions
MECHANISM FOR REACTION OF ALKYNES WITH H3O+

Step 1:
Simultaneous acid / base reaction and reaction with the nucleophile.
Protonation of the alkyne (the π electrons act pairs as a Lewis base) with Attack of the nucleophilic water molecule on the electrophilic carbocation creates an oxonium ion.

 

Step 2:
An acid / base reaction. Deprotonation by a base generates the alcohol and regenerates the acid catalyst forming an unstable enol.

 

Step 3:
An acid / base reaction. Reprotonation by the acid catalyst occurs on the carbon. The oxygen atom electrons help facilitate this process generating an oxonium ion.

 

Step 4:
Another acid / base reaction. Deprotonation of the oxonium ion creates the ketone. Steps 4 and 5 show the acid catalysed tautomerisation of the enol to the ketone.

addition of H2O to alkynes

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Dr. Ian Hunt, Department of Chemistry, University of Calgary