Question

Propose the mechanism of formation of the products in the following reaction explaining indicated relative proportions:

is structure:

Answer 1

In presence of phosphoric acid, a molecule of water is added. This is followed by dehydrtaion to obtain the isomers alkene.
2,3-dimethylbut-2-ene is tetra substituted alkene. It is obtained in maximum proportion as it is most stable. The proportion of 3,3-dimethylbut-1-ene is minimum as its formation involves rearrangement of more stable tertiary carbocation to less stable secondary carbocation.