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CBSE Class 12 · 2016 · All India · Aldehydes Ketones and Carboxylic AcidsLong Answer

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(a) Write the structures of A, B, C and D in the sequence shown in the figure.
(b) Distinguish between:
i) C₆H₅–CH=CH–COCH₃ and C₆H₅–CH=CH–COCH₂CH₃
ii) CH₃CH₂COOH and HCOOH
(c) Arrange the following in increasing order of their boiling points: CH₃CH₂OH, CH₃COCH₃, CH₃COOH.
Structure Sequence for A–D
Sequence for A–D

Solution

(a) Follow the printed sequence reagent by reagent; each arrow's standard transformation fixes A → D in turn.
(b)(i) I/NaOH: CHCH=CH–COCH (a methyl ketone) → yellow CHI; the ethyl ketone gives none.
(ii) HCOOH reduces Tollens' (silver mirror) and Fehling's; propanoic acid does neither.
(c) Dipole-only ketone < H-bonded alcohol < dimerising acid:

CBSE Class 12 Board · 2016 · All India · Subjective

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