Q17-58E - Organic Chemistry (Mcmurry)

Question

Benzoquinone is an excellent dienophile in the Diels – Alder reaction. What product would you expect from reaction of benzoquinone with 1 equivalent of 1,3 butadiene? From reaction with 2 equivalents of 1,3 butadiene?

Step-by-Step Solution

Answer

The answer is 

From 1 equivalent of butadiene,

From 2 equivalent of butadiene,

Step 1: Diels Alder reaction

The Diels Alder reaction is a [4+2] cycloaddition reaction. It takes place in the presence of heat. A diene and a dienophile undergo electron rearrangement in this reaction to give a cyclic product.

Step 2: Explanation

From 1 equivalent of butadiene

                         Formation of 4a,5,8,8a-tetrahydronaphthalene-1,4-dione

In this, 3 double bonds in reactants are converted to 1 double bond and 2 single bonds in the product.

From 2 equivalent of butadiene,

                     Formation of 1,4,4a,5,8,8a,9a,10a-octahydroanthracene-9,10-dione

 

In this, 6 double bonds in reactants are converted to 2 double bond and 4 single bonds in the product.