Draw structure of the 2,4-dinitrophenylhydrazone derivative of benzaldehyde.
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Solution and Explanation
Answer: Benzaldehyde is C6H5-CHO. Its 2,4-dinitrophenylhydrazone is formed by replacing the =O with =N-NH-(2,4-dinitrophenyl). The product is C6H5-CH=N-NH-C6H3(NO2)2, where the two nitro groups sit at the 2 and 4 positions of the attached benzene ring. The reason: the lone pair on the terminal -NH2 nitrogen of the reagent attacks the carbonyl carbon, water is eliminated, and a stable yellow-orange solid (a >C=N- imine type linkage) results.
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(ii) Secondary and tertiary amines
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(v) Aniline and N-methylanilineAccount for the following:
(i) pKb of aniline is more than that of methylamine.
(ii) Ethylamine is soluble in water whereas aniline is not.
(iii) Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.
(iv) Although amino group is o– and p– directing in aromatic electrophilic substitution reactions, aniline on nitration gives a substantial amount of m-nitroaniline.
(v) Aniline does not undergo Friedel-Crafts reaction.
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