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ChemistryInteger+4 / -1Question 90 of 90

JEE Main 2022 · 24 Jun · Shift 1, Chemistry question 90

The major product 'A' of the following given reaction has ______ sp2sp^2 hybridized carbon atoms.
2,7-Dimethyl-2,6-octadiene→H+AMajor Product\text{2,7-Dimethyl-2,6-octadiene}\xrightarrow{\mathrm{H^+}}\underset{\text{Major Product}}{\mathrm A}

Answer and worked solution

Official answer: 2

Protonation. (CH3)2C=CH-CH2CH2-CH=C(CH3)2\mathrm{(CH_3)_2C=CH\text{-}CH_2CH_2\text{-}CH=C(CH_3)_2} takes H+\mathrm{H^+} at C3 to give a tertiary cation at C2.

Cyclisation. The other C=C (C6=C7) attacks this cation, closing a five-membered ring (C2 to C6) and leaving a tertiary cation on C7.

Loss of H+\mathrm{H^+} from the carbon next to C7 gives one new C=C. The product has a single double bond.

sp2sp^2 carbons: 2.

Answer: 2

Topics:AlkenesReactive intermediates
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