Which compound in each of the following pairs will react faster in SN2 reaction with –OH?

(i) CH3Br or CH3I (ii) (CH3)3CCl or CH3Cl

(i) Since I- ion is a better leaving group than Br- ion, therefore, CH3I reacts faster CH3Br in SN2 reaction with OH- ion.


Note: Better the leaving group, faster is the SN2 reaction.


(ii) On steric grounds, 1◦ alkyl halides are more reactive than tert-alkyl halides in SN2 reactions. Therefore, CH3Cl will react at a faster rate than (CH3)3CCl in a SN2 reaction with OH- ion.(bulkier the g8roup, slower is the SN2 reaction.)


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