Question

How do you calculate the number of sigma pi bonds in $C{H_3} - CH = CH - C \equiv CH$?

Answer 1

Sigma bonds are formed by the sharing of the bond orbitals between the bonded atoms. Pi bonds are formed by the sideways overlap of the orbitals. A double bond is composed of one sigma and one pi bond.

Complete step by step answer:
Both the sigma and Pi bonds are covalent bonds and are present between the atoms which have no difference in electronegativity or minimal difference of electronegativity. A single bond is composed of a sigma bond. A double bond is composed of one sigma bond and one pi bond. A triple bond is composed of one sigma bond and two pi bonds.
Pi bonds are stronger than sigma bonds, the latter is produced by head-on overlap of atomic orbitals. The former is formed by sideways overlap of the atomic orbitals.
The given compound is pent-$3$-en-$1$-yne. The chemical formula of the compound is ${C_5}{H_6}$ and molecular weight is $66g$. The compound is composed of one double and one triple bond. It contains eight single bonds including the $C - H$ and $C - C$ bond.
Thus two single bonds are equal to two sigma bonds. One double bond is equal to one sigma and one Pi bond. One triple bond is equal to one sigma and two pi bonds.
Hence the given compound contains $10$ sigma bonds and $3$ pi bonds. The $10$ sigma bonds is composed of $6$ $C - H$ bonds and $4$ $C - C$ bonds and the $3$ pi bonds is composed of $1$ pi bond of $C = C$ and $2$ pi bonds of $C \equiv C$.

Note: The triple bonds are stronger than double bonds which are further stronger than single bonds. The sigma and the pi bonds only differ in the overlapping of atomic orbitals. Both the bonds belong to covalent bonds.