# Role of Hg2+ as catalyst

in the reaction of addition of hydrogen halides to alkynes $\ce{Hg^2+}$ can be used as a catalyst. But what is its role? How does it increase the rate of reaction.

I think that the vacant orbitals in Hg would help in the process of ionisation of hydrogen halides. Is this concept correct? please help

The main use of $\ce{Hg}$$^{\text{2+}}$ is to polarize the electron cloud of the alkyne. Else the attacking specie wont be able to approach the bond
• @QuarkyLittleThing you mean that cyclic intermediate that $\ce{Hg^2+}$ forms with triple bond – Ankit Agrawal Mar 19 '17 at 17:00