1 eq. of H2O and an acid catalyst (alkyne)
Has two steps. The first step uses the eq. of H2O and makes an enol, adding an OH to the most subst. and an H to the least subst. and reducing the alkyne to an alkene. The second step is spontaneous and adds a H to the least subst. side, reduces the alkene to an alkane, and makes the bond to an O a double bond and takes away the H connected to the O.