Question

Name the reagent used to detect the carbonyl group in a given compound

Answer 1

The reagent used to detect the carbonyl group in a given compound is 2,4 _dinitrophenylhydrazine

Answer 2

2,4-dinitrophenylhydrazine ( Brady’s reagent) is used to identify carbonyl group from other functional groups.

• 2,4-DNP derivatives help us identify and separate the components of a mixture of aldehydes and ketones.
• They react to form orange yellow derivative.
• Hydrolysis of the separated derivatives will then regenerate the original carbonyl compounds.
• The reagent is prepared by reacting hydrazine with 2,4-dinitrochlorobenzene.
• Due to the electron-accepting effect of the two nitro groups present makes chloride easy to displace.
• The aqueous solution of 2,4-dinitrophenyl hydrazine (DNP) is usually known as Brady’s reagent.
• It reacts with carbonyl compounds to give a coloured precipitate.
• These coloured derivative precipitate formed have fixed melting point.
• The derivatives which are orange coloured crystalline solids are called 2,4-dinitrophenylhydrazones.
• A carbonyl group consists of a double bond linking a carbonyl carbon atom and a carbonyl oxygen atom.

• The carbonyl oxygen atom shares two of its six valence electrons with the carbonyl carbon atom.

• Its remaining four valence electrons remain as two sets of electron lone pairs.

• When the carbonyl group is linked to one alkyl or aryl group and one hydrogen atom, the resulting carbonyl compound is called an aldehyde.
• Ketone is an organic compound with highly electronegative atoms and no hydrogen atom.

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