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Give reasons for any 3 of the following observations:
a. Aniline is acetylated before nitration reaction.
b. pKb of aniline is lower than the m-nitroaniline.
c. Primary amine on treatment with benzenesulphonyl chloride forms a product which is soluble in NaOH however secondary amine gives product which is insoluble in NaOH.
d. Aniline does not react with methyl chloride in the presence of anhydrous AlCl 3 catalyst.
Answer:
a. Aniline is acetylated, before nitration reaction in order to avoid formation of tarry oxidation products and protecting the amino group, so that p -nitro derivative can be obtained as major product.
b.pKb of aniline is lower than the m-nitro aniline.The basic strength of aniline is more that m-nitroaniline . pkb value is inversely proportional to basic strength.
Presence of Electron withdrawing group decrease basic strength.
c. Due to the presence of acidic hydrogen in the N-alkylbenzenesulphonamide formed by the treatment of primary amines.
d. Aniline does not react with methylchloride in the presence of AlCl 3 catalyst ,because aniline is a base and AlCl 3 is Lewis acid which lead to formation of salt.
