JEE Main 2025 Jan 29 Shift 2, Chemistry Q13: Naming of Alkenes

JEE Main2025Jan 29, Shift 2Chemistry

Total number of sigma ( $σ$ ) ______ and pi ( $π$ ) ______ bonds respectively present in hex-1-en-4-yne are :

Solution

Hex-1-en-4-yne has the structure $C H_{2} = C H - C H_{2} - C \equiv C - C H_{3}$ .

Count $σ$ bonds (every single bond counts once, and each multiple bond contributes exactly one $σ$ ):

C–H bonds: $2 + 1 + 2 + 0 + 0 + 3 = 8$ . C–C framework $σ$ bonds: $5$ (five C–C linkages along the chain).

Total $σ$ bonds $= 8 + 5 = 13$ .

$π$ bonds: the $C = C$ contributes $1$ and the $C \equiv C$ contributes $2$ , giving $3$ in total.

$∴$ The molecule has $13$ $σ$ and $3$ $π$ bonds.

Concept behind this question

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