Q.
Decreasing order of reactivity in Williamson ether synthesis of the following is
(I) Me3CCH2Br,
(II) CH3CH2CH2Br,
(III) CH2=CHCH2Cl,
(IV) CH3CH2CH2Cl
Williamsons ether synthesis involves SN2 pathway, ie, involves formation of transition state and back side attack.
Thus, less hindered alkyl halides react readily in Williamsons synthesis.
The order of hindrance is Allyl halide <1∘<2∘<3∘ As the size of halide ion increases, reactivity towards SN2 reaction increases.
Thus, bromides are more reactive than their corresponding chlorides towards Williamsons ether synthesis.
Hence, the decreasing order of reactivity towards Williamsons ether synthesis is IIICH2=CHCH2Cl>IICH2CH2Br<IVCH3CH2CH2Cl>IMe3CCH2Br