JEE Main · 2019 · 09 Jan 2019 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

The tests performed on compound

X

and their inferences are:

\begin{tabular}{lcl}
& \multicolumn{1}{c}{ Test } & \multicolumn{1}{c}{ Interference } \\
(a) & 2, 4-DNP test & Colorued precipitate \\
(b) & Iodoform test & Yellow precipitate \\
(c) & Azo-dye test & No dye formation \\
Compound ' X ' is &
\end{tabular}

(A)(see structure)
(B)(see structure)
✓ Correct
(C)(see structure)
(D)(see structure)

Answer: (B)

Solution

Work through the three tests. A positive

2, 4

-DNP test says a carbonyl group is present. A positive iodoform test narrows that to a methyl ketone,

- COCH X_{3}

(or a group that oxidises to one). The failed azo-dye test says no free primary aromatic amine is available to couple. The compound that satisfies all three is

p

-dimethylaminoacetophenone: it carries the

- COCH X_{3}

group, while its nitrogen is tertiary as

- N (CH X_{3}) X_{2}

-- with its lone pair tied up it gives no diazo coupling.

JEE Main · 2019 · 09 Jan 2019 · Shift 2 · Single correct option

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JEE Main · 2019 · 09 Jan 2019 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

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