Question

Rank the alkyl halides in order of increasing E2 reactivity. Then do the same for E1 reactivity

Short answer

The given alkyl halides are ranked for E2 reactivity as shown:

The same trend is followed for E1 too.

Step-by-step solution

Identification of the type of alkyl halide

Structure A and C are tertiary halides, whereas B is a secondary halide.

Representation of different types of alkyl halide

Stability based on more substituted product

Tertiary halides give a trisubstituted product, whereas secondary halides give a disubstituted product. With the increase of substitution of the alkyl, the +I effect of the alkyl groups increases the stability of the system.

As a result, tertiary halides are found to be more reactive towards elimination(E1 and E2) than secondary halides.

Hence, structures C and A are found to be more reactive than B.

Reactivity based on the leaving group

Bromine has a large size and more conjugate basicity than that of chloride. Hence bromide is considered to be a better leaving group than chloride. Hence, structure C is found to be more reactive than A.

The reactivity order will be the same for both E1 and E2 as both carry a similar explanation. The alkyl halides are ranked in the following based on E2 reactivity:-

Representation of the E2 reactivity order

The same trend is followed for E1 too.

Representation of the E1 reactivity order