JEE Main 2017 · Chemistry · General Organic Chemistry and Isomerism · hard

The number of acyclic alkene isomers of C6H12 (counting geometrical and optical isomers separately) that give 3-methylpentane on catalytic…

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The number of acyclic alkene isomers of

\mathrm{C_6H_{12}}

(counting geometrical and optical isomers separately) that give 3-methylpentane on catalytic hydrogenation is

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Answer: (D) 5

3-Methylpentane has the skeleton

\mathrm{CH_3CH_2CH(CH_3)CH_2CH_3}

. Placing a double bond in it: (a) 3-methylpent-1-ene (C-3 is a stereocentre):

2

enantiomers; (b) 3-methylpent-2-ene:

E

and

Z

2

isomers; (c) 2-ethylbut-1-ene (

\mathrm{CH_2=C(C_2H_5)_2}

1

. The double bond at C-4 or C-5 duplicates (b) and (a) by symmetry. Total

=2+2+1=5

(only 3 if stereoisomers were not counted).

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