Question

The number of sigma $(\sigma)$ and pi $(\pi)$ bonds present in 1, 3, 5, 7-octatetraene are _________ respectively.
A.14 and 3
B.17 and 4
C.16 and 5
D.15 and 4
E.16 and 3

Answer 1

Hint:
Sigma bonds can be used to identify the type of bonds present between two atoms in a molecule. These bonds in which the sigma and pi bonds produce a single bond, double bond, and triple bond.

Complete step by step answer:
Sigma bonds are the strongest type of covalent chemical bond and are formed due to the head-on overlapping between the atomic orbitals. pi bonds are the covalent chemical bonds where two lobes of an orbital on an atom overlap the two lobes on the other atom. This overlap occurs laterally. They identify the type of bond present between the atoms in a molecule.
In a single bond, there is only one sigma bond and no pi bond present.
In a double bond, there are one sigma and one pi bond present.
In a triple bond, there are one sigma and two pi bonds present.
Now, let us look at the given compound 1, 3, 5, 7-octatetraene. The chemical formula of this compound is ${C}_{8}{H}_{10}$. The structure of the same is shown below.
Thus, by looking at the structure we can see that it has 13 single bonds and 4 double bonds. Therefore, according to the above-mentioned points, we can say that 1, 3, 5, 7-octatetraene has 17 sigma bonds and 4 pi bonds.
Hence, option (b) is the correct option.

Note:
By looking at the structure it seems like the double bonds or the triple bonds contain only pi bonds but it's a wrong assumption. The double bond and the triple bonds have one sigma bond each. Take care of this while calculating the no. of sigma and pi bonds in a compound.