JEE Main 2020 · Chemistry · Carbonyl Compounds, Carboxylic Acids and Amines · medium

The number of structural isomers of C5H10O that are aldehydes or ketones and give a positive iodoform test is

Single correct option

The number of structural isomers of

\mathrm{C_5H_{10}O}

that are aldehydes or ketones and give a positive iodoform test is

A. $1$
B. $2$
C. $3$
D. $4$

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Answer: (B) $2$

Iodoform test needs a

\mathrm{CH_3CO-}

group (an aldehyde qualifies only if it is acetaldehyde). Carbonyl isomers: pentanal, 2-methylbutanal, 3-methylbutanal, 2,2-dimethylpropanal (aldehydes: none positive), pentan-2-one (positive), pentan-3-one (no), 3-methylbutan-2-one (positive). Hence

2

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