Question

How many σ and π bonds are present in a molecule of cumulene?

Answer 1

Answer: 7σ +3π

Explanation:

Cumulene has its formular to be C4H4. Structurally it is composed of 4 carbon to Hydrogen single bonds and 3 double bonds.

It is worthy of note that in the field of chemistry:

A double bond is made up of 1σ bond and 1π bond.

A single bond is made up of 1σ bond.

Therefore the structure of Cumulene contains:

4 single bonds = 4σ

3 double bonds = 3 (σ + π )

4σ + 3σ +3π = 7σ +3π

Answer 2

A hydrocarbon with three or more consecutive (cumulative) double bonds is known as a cumulene. They are analogous to allenes, only exhibiting a more elongated chain. The basic molecule in this category is butatriene, which is also simply known as cumulene.  

In the structure of a cumulene, there are 3 double bonds and 4 single bonds. The double bond comprises 1 sigma bond, and 1 pi bond and 4 hydrogen bond produces a sigma bond with carbon. Thus, the molecule of cumulene comprises 7 sigma bonds and 3 pi bonds.