Oxymercuration works particularly well with alkynes. Here are the conditions, and the product, following the analogy of alkene hydration, should be the compound shown at the right-hand end of the scheme below.
But the product isolated from an alkyne oxymercuration is in fact a ketone. You can see why if you just allow a proton on this initial product to shift from oxygen to carbon—first protonate at C then deprotonate at O. C=O bonds are stronger than C=C bonds, and this simple reaction is very fast.
We now have a ketone, but we also still have the mercury. That is no problem when there is a carbonyl group adjacent because any weak nucleophile can remove mercury in the presence of acid, as shown below. Finally, another proton transfer (from O to C again) gives the real product of the reaction: a ketone.
This is a very useful way of making methyl ketones because terminal alkynes can be made using the methods of Chapter 9 (addition of metallated alkynes to electrophiles).
Anticancer compounds
The anthracyclinone class of anticancer compounds (which includes daunomycin and adriamycin) can be made using a mercury (II)-promoted alkyne hydration. You saw the synthesis of alkynes in this class on Chapter 9, where we discussed additions of metallated alkynes to ketones. Here is the final step in a synthesis of the anticancer compound deoxydauno mycinone: the alkyne is hydrated using Hg2+ in dilute sulfuric acid to give the final product.
