# Why are Terminal Alkynes less reactive than internal alkynes?

I got in Paula Bruice under the section Mechanism for Mercuric ion catalysed Hydration of Alkyne

Terminal alkynes are less reactive than internal alkynes towards addition of water. Hydration will take place if Hg²+ is added to acidic mixture.

Why are Terminal Alkynes less reactive than internal alkynes?

This support is taken away in case of terminal alkynes as their is no alpha-carbon. Now terminal alkynes can still be hydrated but only in presence of $$\ce{Hg^2+}$$ ion in acidic medium because of $$\ce{Hg^2+}$$'s high polarizing power(because it has a pseudo inert configuration). This polarization succeeds in catalyzing the reaction.