Arrange the following compounds in decreasing order of their rate of dehydration when treated with concentrated H ₂ SO ₄ . (P) (Q) (R) (S)

Step-by-step solution

The rate of dehydration of alcohols when treated with concentrated H ₂ SO ₄ depends on the stability of the intermediate carbocation formed during the rate-determining step. Let us analyze the carbocations formed by the protonation and subsequent loss of water from each compound: 1. Compound P: Loss of the - OH group forms a primary ( 1^ ) allylic carbocation. This carbocation is resonance stabilized, with the positive charge delocalizing to a secondary carbon on the ring. Furthermore, its dehydration leads to a hi