Question

Draw the Lewis structure for the molecule \[C{H_2}CHC{H_3}\] . How many times sigma and pi bonds does it contain?

Answer 1

Hint: A Lewis structure is represented by the valence shell electrons in a molecule. The Lewis structure is used to show how the electrons are arranged around an individual atom in the molecule. Electrons are shown in the form of "dots" or for bonding electrons as a line between the two atoms. The aim is to obtain the "best" electron configuration, i.e., the octet rule and formal charges need to be fulfilled.

Complete step-by-step answer:Propylene is also known as propene or methyl ethylene. It is an unsaturated organic compound which has one double bond and remaining bonds are single-bond. This is the second simplest member of the alkene class of hydrocarbons. It is a colourless gas with a faint petroleum-like smell. Bio-propylene is the bio-based counterpart of propene.

The number of sigma and pi-bonds are eight and one respectively.
Explanation:
Lewis-dot structure: It shows the bonding between the atoms of a molecule as shown in the structure and it also shows the unpaired electrons present in the molecule.
In the Lewis-dot structure the valence electrons are represented by 'dot'.
The given molecule is propylene, \[C{H_2}CHC{H_3}\] .
As we know that carbon has four valence electrons and hydrogen has one valence electron.
Therefore, the total number of valence electrons in propene will be;
\[C{H_2}CHC{H_3}\, = \,3(4)\, + \,6(1)\, = 18\]
According to the Lewis-dot structure, there are \[18\] number of bonding electrons and \[0\] number of nonbonding electrons.
The number of \[8\] \[\sigma \] -bonds and \[1\] \[\pi \] -bond and respectively.

Note: In the propene molecule, \[{H_2}C = CH - C{H_3}\] , there is one \[\pi \] -bond (i.e., \[C = C\] bond), eight \[\sigma \] -bonds (i.e., \[7\;C - H\] and \[C - C\;\sigma \;\] -bonds). There are \[1 \times C - C\] bonds, \[1 \times C = C\;\] bonds, and \[\;6 \times C - H\;\] bonds. The Lewis structure makes it simpler to represent the structure and identify the sigma and pi- bonds.