JEE Main 2015 · 4 Apr · Shift 1 · Chemistry Q53

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ChemistrySingle correct+4 / -1Question 53 of 90

Which compound would give 5 - keto - 2 - methyl hexanal upon ozonolysis ?

1,2-Dimethylcyclopentene

Cyclopentene with methyl groups on both alkene carbons.

1,3-Dimethylcyclopentene

Cyclopentene with a methyl on one alkene carbon and another on the sp³ carbon next to the other alkene carbon.

1,4-Dimethylcyclopentene

Cyclopentene with a methyl on an alkene carbon and another on the ring carbon two bonds away (C4).

1,5-Dimethylcyclopentene

Cyclopentene with a methyl on an alkene carbon and another on the adjacent sp³ carbon (C5).

Answer and worked solution

Official answer: B

5-Keto-2-methylhexanal is $\ce{OHC-CH(CH3)-CH2CH2-CO-CH3}$ . Joining the CHO and C=O carbons back into a double bond gives a ring: 1,3-dimethylcyclopentene. That is the structure with one methyl on an alkene carbon and the other on the sp³ carbon next to the other alkene carbon, (2).

Topics:Alkenes

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JEE Main 2015 · 4 Apr · Shift 1, Chemistry question 53