How do you calculate the number of sigma pi bonds in #"H"_3"C-CH=CH-C≡CH"#?

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Answer 1 · 2016-04-08T22:07:06

Here's how you do it.

Every bond between two atoms contains 1 σ bond.

Every bond after the first bond is a π bond.

The expanded structural formula of #"H"_3"C-CH=CH-C≡CH"# is

pent-3-en-1-yne

We count #"6 C-H"# bonds and #"4 C-C"# bonds, for a total of #"10 σ"# bonds.

The bond between #"C1"# and #"C2"# is a triple bond, so the two "extra" bonds are π bonds.

The bond between #"C3"# and #"C4"# is a double bond, so the "extra" bond is a π bond.

Hence, pent-3-en-1-yne contains #"10 σ bonds"# and #"3 π bonds"#.