Question

Calculate the number of o and a bonds in 2-n-propylpent-1-ene.

• A. 22 σ bonds, 2π bonds
• B. 23 σ bonds, 1π bonds
• C. 21 σ bonds, 1π bonds
• D. 23 σ bonds, 2π bonds
• E. 20 σ bonds, 1π bonds

Answer 1

The Correct Option is B

2-n-Propylpent-1-ene is a hydrocarbon with the following structure:  
- There are 5 carbon atoms in the main chain and 3 more in the propyl group, totaling 8 carbon atoms.
- The bonds are single bonds (sigma) between all atoms except for the double bond between C1 and C2, which contains one \(\sigma\) bond and one \(\pi\) bond.

The number of \(\sigma\) bonds is calculated as follows:
- 8 C-C single bonds (each contributing one \(\sigma\) bond)
- 9 C-H bonds (each contributing one \(\sigma\) bond)
- 1 C=C double bond (which contributes 1 \(\sigma\) bond)
Thus, the total number of \(\sigma\) bonds = 23.

The number of \(\pi\) bonds is calculated as:
- 1 \(\pi\) bond in the C=C double bond.

Therefore, the number of \(\sigma\) bonds is 23 and the number of \(\pi\) bonds is 1.

The correct option is (B) : 23 σ bonds, 1π bonds

Answer 2

23 σ bonds, 1π bond 

Explanation:

Let's first draw the structure of 2-n-propylpent-1-ene:

The compound consists of a pentane chain with a double bond at the first position and a propyl group attached to the second carbon. The structure is:

CH2=CH-CH2-CH2-CH3   |  CH2-CH3 (propyl group)

To determine the number of sigma (σ) and pi (π) bonds:

• Each single bond (C–C or C–H) is a sigma (σ) bond.
• Each double bond consists of one sigma (σ) bond and one pi (π) bond.

Now, count the bonds:

• In the pentane chain (C–C and C–H), there are 6 C–C single bonds and 12 C–H single bonds, contributing 18 sigma bonds.
• The double bond between C1 and C2 contributes 1 sigma bond and 1 pi bond.
• The propyl group at C2 contributes 4 sigma bonds (C–C and C–H).

Thus, the total number of sigma (σ) bonds is: 18 (from pentane chain) + 1 (from the double bond) + 4 (from propyl group) = 23 sigma bonds.

The total number of pi (π) bonds is 1 (from the double bond). So, the correct answer is 23 sigma bonds, 1 pi bond.