Chapter 12, Problem 12.8YT

Interpretation Introduction

Interpretation:

Equations 12-27 and 12-28 show the overall products of hydration of the alkynes. For each reaction, the enol that is produced prior to tautomerization to the more stable keto form is to be drawn.

Concept introduction:

Alkynes can undergo Markovnikov addition of water via oxymercuration. Hydration of an alkyne leads to an initial enol, which tautomerizes into the more stable keto form. A $\text{δ}$ charge on the first structure would be better accommodated by the benzylic carbon. This is the $\text{C}$ atom that the ${\text{H}}_{\text{2}}\text{O}$ attacks and is the site of the enol- a species in which $\text{OH}$ (characteristic of an alcohol) is attached to a $\text{C=C}$ bond (characteristic of an alkene). A charge on the second structure would be better accommodated by C2 because it is more highly substituted. This is the carbon that the ${\text{H}}_{\text{2}}\text{O}$ attacks and is the site of the enol.