(a) Write the chemical reaction involved in the Etard reaction.
(b) Arrange the following in increasing order of reactivity towards nucleophilic addition: CH₃CHO, C₆H₅COCH₃, HCHO.
(c) Why is the pKₐ of Cl–CH₂–COOH lower than the pKₐ of CH₃COOH?
(d) Write the product of the following reaction:
(e) A and B are two functional isomers of C₃H₆O. On heating with NaOH and I₂, isomer A forms a yellow precipitate of iodoform whereas B does not. Write the formulae of A and B.
(b) Arrange the following in increasing order of reactivity towards nucleophilic addition: CH₃CHO, C₆H₅COCH₃, HCHO.
(c) Why is the pKₐ of Cl–CH₂–COOH lower than the pKₐ of CH₃COOH?
(d) Write the product of the following reaction:
(e) A and B are two functional isomers of C₃H₆O. On heating with NaOH and I₂, isomer A forms a yellow precipitate of iodoform whereas B does not. Write the formulae of A and B.
Solution
(a) Etard:
(b) Reactivity falls with +I groups and conjugation/steric bulk:
(c) The −I chlorine disperses the negative charge of the carboxylate, so ClCHCOOH ionises more — stronger acid, \textbf{lower pK}.
(d) DIBAL-H half-reduces only the –CN:
(e) CHO isomers: \textbf{A = propanone} (CHCOCH, iodoform-positive), \textbf{B = propanal} (CHCHCHO, negative).
(b) Reactivity falls with +I groups and conjugation/steric bulk:
(c) The −I chlorine disperses the negative charge of the carboxylate, so ClCHCOOH ionises more — stronger acid, \textbf{lower pK}.
(d) DIBAL-H half-reduces only the –CN:
(e) CHO isomers: \textbf{A = propanone} (CHCOCH, iodoform-positive), \textbf{B = propanal} (CHCHCHO, negative).
CBSE Class 12 Board · 2016 · All India · Subjective