What is the number of pi bonds in the molecule below?

enter image source here

2 Answers
May 26, 2017



Most of the carbon-carbon bonds in this molecule (which appears to be a 1,5-hexadiyne) are single and contain only sigma bonds. Each of the carbon-carbon triple bonds involves three pi bonds. There are two triple carbon-carbon bonds in the molecule and therefore we have four pi bonds in the molecule.

(Since the photo was a little bit shaky, here's another condensed structure formula for your reference)
1,5-hexadiyne, ChemSpider, Royal Society of Chemistry

May 26, 2017

There are 4 pi bonds in the molecule shown.


Pi bonds are present in double or triple bonds.

A single bond contains #1sigma# bond and #0 pi# bond.
A double bond contains #1sigma# and #1pi# bond.
A triple bond contains #1sigma# and #2pi# bonds.

There are 2 triple bonds in the molecule, therefore, #2xx2=4pi# bonds.

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