For the reaction sequence given below, the correct statement(s) is(are) [figure]
- P is optically active.
- S gives Bayer’s test.
- Q gives effervescence with aq. NaHCO3.
- R is an alkyne.
Answer
(2) S gives Bayer’s test., (3) Q gives effervescence with aq. NaHCO3.
Solution
The lactone is (R)-4-benzyltetrahydropyran-2-one.
LiAlH4 reduces the lactone (ester) to a diol, P:
[figure] LiAlH4 [figure] (P)
In P, C-3 carries two identical –CH2CH2OH arms → not a stereocentre; P is optically inactive. (A) false.
Jones reagent oxidises both 1° alcohols to –COOH, Q:
[figure] CrO3-H2SO4 [figure] (Q)
Q (a dicarboxylic acid) gives CO2 effervescence with aq. NaHCO3. (C) true.
Soda-lime removes both –COOH groups as CO2 (decarboxylation), R:
[figure] NaOH and CaO, [figure] (R)
R is isobutylbenzene, not an alkyne. (D) false.
Conc. H2SO4 at 443 K dehydrates both alcohol groups of P, S:
[figure] H2SO4, 443 K [figure] (S)
S has C=C bonds → decolourises cold dilute alkaline KMnO4 (Baeyer’s test). (B) true.
Answer: (B), (C)