Question

Draw the major addition product of the acid-catalyzed hydration of 4-ethyl-3,3-dimethyl-1-hexene.

Answer 1

Here we have to draw the major product in the acid catalysed hydration reaction of 4-ethyl-3,3-dimethyl-1-hexene.

The 4-ethyl-3,3-dimethyl-1-hexene converts to 2-hydroxy-4-ethyl-3,3-dimethyl-1-hexane as a major product by acid catalyzed hydration reaction.  

The acid catalyzed hydration of an alkene is the Sn¹ reaction. Where in the first step a carbocation is generated. The stability of the carbocation depends upon the position of the neighboring group having +I inductive effect.

In the next step the water molecule attack the carbocation and the corresponding alcohol is produced.

In 4-ethyl-3,3-dimethyl-1-hexene the carbocation formed in the C₂ position which is more stable than the C₁ position due to presence of the dimethyl and ethyl group in the neighboring position which have strong +I inductive effect. This is absence in C₁ position.

In the next step the water molecule attack the C₂ position to form the alcohol.

4-ethyl-3,3-dimethyl-1-hexene converts to 2-hydroxy-4-ethyl-3,3-dimethyl-1-hexane by acid catalyzed hydration reaction which is the major product along with 1-hydroxy-4-ethyl-3,3-dimethyl-1-hexane as a minor product.

The reaction mechanism is shown in the image.