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Chemical Properties of Alkynes

Acidity of Alkyne

The terminal alkyne is acidic in nature because of its high level of s character. It is SP hybridized. The high S-character causes the overlapping of the sigma bond, causing the hydrogen atom to be more positive and acidic. 

Since alkyne is weakly acidic, they react with the base as an acid-base reaction.

Addition Reaction of Alkyne

  1. Hydrogenation

Alkyne undergoes Hydrogenation reaction stepwise to form alkanes. First, it forms alkene and then forms alkane. The reaction proceeds this way.

2 Halogenation

The halogen is added to the alkyne, in the same manner, it gets added in an alkene. It occurs stepwise, as shown in the reaction below:

3 Hydrohalogenation: Hydrogen Halides react with an alkyne in the same manner as it reacts with alkenes. The reaction is given below:

Addition of Water

Water is added to alkyne by the formation of a carbocation. Dilute mineral acid with mercury ions are necessary for this reaction to happen. The reaction proceeds as:

  1. Ozonolysis Reaction

The organic redox chemical reaction in which ozone is employed to break the bonds of alkenes and alkynes is called ozonolysis.

  • Oxidation with ozone gives alcohols, aldehydes or ketones, and carboxylic acid.
  • Alkynes undergo ozonolysis and give diketones acid anhydrides. The acid anhydride undergoes hydrolysis to give two carboxylic acids if the water is present in the reaction.

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