JEE Main 2022 · 24 Jun · Shift 1 · Chemistry Q75

ChemistrySingle correct+4 / -1Question 75 of 90

Which of the following is an example of conjugated diketone ?

\mathrm{CH_3COCH_2CH_2CH_2COCH_3}

(heptane-2,6-dione)

\mathrm{CH_3COCH_2}

- attached to a cyclohexanone ring at C-4 (structure shown)

Cyclohexa-2,5-diene-1,4-dione (p-benzoquinone; structure shown)

\mathrm{C_6H_5COCH_2CH_2COCH_3}

(structure shown)

Answer and worked solution

Official answer: C

Conjugation needs the C=O groups linked through alternating single and double bonds.

A, B and D: the carbonyl groups are separated by $sp^3$ $\mathrm{CH_2}$ groups, so they are not conjugated.
C: in p-benzoquinone both C=O groups are joined through ring C=C bonds, a fully conjugated diketone.

(C)

JEE Main 2022 · 24 Jun · Shift 1, Chemistry question 75