Q9-5P - Organic Chemistry (Mcmurry)

Question

What alkynes would you start with to prepare the following ketones?

Step-by-Step Solution

Answer

Answer:

a. 

b.

Step1: Hydration of alkynes

Alkyne undergo hydration in the presence of mercury(II) sulfate. The reaction occurs with Markovnikov regiochemistry, so the OH group adds to the more highly substituted carbon and the H attaches to the less highly substituted one.

Enol is an intermediate in the reaction, which rearranges into a ketone by a process called keto–enol tautomerism. The individual keto and enol forms are said to be tautomers.

 

Step 2: Formation of ketone(a) from alkyne

The formation of the single product shows alkyne is symmetrical.

 

The reaction occurs with Markovnikov regiochemistry. Enol is an intermediate in the reaction, which rearranges into a ketone by a process called keto-enol tautomerism.

Step3: Formation of ketone(b) from alkyne

The formation of the two products shows alkyne is unsymmetrical.

 

The reaction occurs with Markovnikov regiochemistry. Enol is an intermediate in the reaction, which rearranges into a ketone by a process called keto-enol tautomerism