Question

How many $\sigma$ and $\pi$ bonds are present in the following molecule?
(𝑎) $HC\equiv CCH=CHC{H}_3$
(𝑏) $C{H}_2=C=CHC{H}_3$

Answer 1

(a) $HC\equiv CCH=CHC{H}_3$

Step 1: Lewis’s structure:

Draw the Lewis structure of given compound to visualize the number and types of bonds. Lewis’s structure of given molecular formula can be drawn as:


Step 2: Identification $\sigma \&\pi$ bonds:

Identify $\sigma \&\pi$ bonds then mark it.

Step 3: Count the number of $\sigma \&\pi$ bond:

${\sigma }_{C-H}=6$
${\sigma }_{C-C}=4$

$\text{Total number of sigma}\left(\sigma \right)\text{bonds}=10$

${\pi }_{C=C}=1$
${\pi }_{C\equiv C}=2$

$\text{Total number of pi}\left(\pi \right)\text{bonds}=3$

Final Answer: In given compound $10$ sigma $\left(\sigma \right)$ and $3$ pi $\left(\pi \right)$ bonds are present.


(b) $C{H}_2=C=CHC{H}_3$

Step 1: Lewis’s structure:

Draw the Lewis structure of given compound to visualize the number and types of bonds. Lewis’s structure of given molecular formula can be drawn as:



Step 2: Identification $\sigma \&\pi$ bonds:

Identify $\sigma \&\pi$ bonds then mark it.

Step 3: Count the number of $\sigma \&\pi$ bond:

${\sigma }_{C-H}=6$
${\sigma }_{C-C}=3$

$\text{Total number of sigma}\left(\sigma \right)\text{bonds}=9$

${\pi }_{C=C}=2$

$\text{Total number of pi}\left(\pi \right)\text{bonds}=2$

Final Answer: In given compound $9$ sigma $\left(\sigma \right)$ and $2$ pi $\left(\pi \right)$ bonds are present.