18-18-6P-b - Organic Chemistry (Mcmurry)

Question

Rank the following halides in order of their reactivity in Williamson synthesis:

1. Bromoethane, 2-bromopropane, bromobenzene
2. Chloroethane, bromoethane, 1-iodopropene

Step-by-Step Solution

Answer

b) The rank of given halides in order of their reactivity is,

Williamson synthesis

The ethers are synthesized by the best method known as Williamson synthesis, in which alkoxide and alkyl halide react together by an S_N2 reaction. The aryl halides are not reactive in Williamson synthesis because they have a double-bond character and are involved in resonance.

Order of reactivity of halides in Williamson synthesis

b) 

From the given alkyl halides, bromoethane and chloroethane are primary halides. But Br is a better leaving group, and Cl is a poorer leaving group. Thus, the reactivity of bromoethane is more than chloroethane. In the case of 1-iodopropene (vinylic), there is a double bond that is more difficult to break than a single bond. So, it is not reactive. Thus, bromoethane is the most reactive, and 1-iodopropene is the least reactive.

                The rank of halides in order of their reactivity