Question

The number of sigma bonds in \(H_3C-CH=CH-C\equiv CH\) is ________.

Hint:

For any open-chain (acyclic) hydrocarbon, the total number of sigma bonds is always equal to the total number of atoms minus one.

Answer 1

Correct Answer: 10

Step 1: Understanding the Concept:
Every single covalent bond is a sigma (\(\sigma\)) bond.
A double bond contains one sigma bond and one pi (\(\pi\)) bond.
A triple bond contains one sigma bond and two pi bonds.
Step 2: Key Formula or Approach:
Expand the structure to view all \(C-H\) and \(C-C\) bonds.
Sum all single bonds and count one for every double and triple bond.
Step 3: Detailed Explanation:
Structure: Pent-2-en-4-yne.
Let's break it down:
1. \(CH_3\) part: 3 \(\sigma\) bonds from \(C-H\) and 1 \(\sigma\) bond from \(C-C\). (Total: 4)
2. \(CH=CH\) part: 2 \(\sigma\) bonds from \(C-H\) and 1 \(\sigma\) bond from the double bond \(C=C\). (Total: 3)
3. \(C\equiv CH\) part: 1 \(\sigma\) bond from the single bond \(C-C\), 1 \(\sigma\) bond from the triple bond \(C\equiv C\), and 1 \(\sigma\) bond from the final \(C-H\). (Total: 3)
Sum = \(4 + 3 + 3 = 10\).
Alternatively, total atoms in \(C_5H_6\) is 11. For an acyclic structure, \(\text{Sigma bonds} = \text{Total atoms} - 1 = 11 - 1 = 10\).
Step 4: Final Answer:
The number of sigma bonds is 10.