Question 20: The treatment of alkyl chlorides with aqueous KOH leads to the formation of alcohols but in the presence of alcoholic KOH, alkenes are major products. Explain.
Answer:
In an aqueous solution, KOH almost completely ionizes to give OH - ions. OH - ion is a strong nucleophile, which leads the alkyl chloride to undergo a substitution reaction to form alcohol.

On the other hand, an alcoholic solution of KOH contains alkoxide (RO - ) ion, which is a strong base. Thus, it can abstract a hydrogen from the β-carbon of the alkyl chloride and form an alkene by eliminating a molecule of HCl.

OH - ion is a much weaker base than RO - ion. Also, OH - ion is highly solvated in an aqueous solution and as a result, the basic character of OH - ion decreases. Therefore, it cannot abstract a hydrogen from the β-carbon.
Comments
Basic medium does not mean RO-. There can be many sources of OH-. Poor explanation..
After searching in diff sites finally find a perfect answer to the question
Thanks for making me understand
Ghosh