Question

A compound ‘A’ having the molecular formula C₅H₁₂O, on
oxidation gives a compound ‘B’ with molecular formula
C₅H₁₀O. Compound ‘B’ gave a 2,4-dinitrophenylhydrazine
derivative but did not answer haloform test or silver mirror
test. The structure of compound ‘A’ is
(a) CH₃ – CH₂ – CH₂ – CH₂ – CH₂– OH
(b) CH₃ – CH₂ – CH₂CH – CH₃
|
OH
(c) CH₃ – CH₂ – CHCH₂ – CH₃
|
OH
(d) CH₃ – CH₂ – CH – CH₂ – OH
|
CH

Answer 1

Explanation:

I think the correct answer is (a)

Answer 2

The structure of Compound A is (c) CH₃ – CH₂ – CHCH₂ – CH₃

|

OH

Given,

The compound A has molecular formula- C₅H₁₂O

The compound B has molecular formula- C₅H₁₀O

• Haloform test- The haloform reaction is the reaction of a methyl ketone with chlorine, bromine, or iodine in the presence of hydroxide ions to give a carboxylate ion and a haloform.
• Silver mirror or Tollen's test- It is a laboratory method used to distinguish between aldehyde and ketones, which involves oxidation of aldehydes by the Tollen's reagent (Ammonical Silver Nitrate) and reduction of the reagent leading to formation of silver mirror on the walls of container.
• It is given that the compound B doesnot give Haloform and Silver mirror test, which means the compound B is not an aldehyde and also doesnot have alpha methyl group.
• But it is given the compound B gives 2,4-dinitrophenylhydrazine  derivative , which means it has a carbonyl group within involved.
• The conclusion leads us compound B as a ketone with no alpha methyl group involved.
• We know B is formed by oxidation of A which means A can be formed by reduction of B.
• This leads us compound A as a reductive product of a ketone (an alcohol) with no alpha-methyl group.
• By seeing the options we may conclude it, the compound A has structure

(c) CH₃ – CH₂ – CHCH₂ – CH₃

|

OH