Question

The sum of sigma (σ) and pi (π) bonds in Hex-1,3-dien-5-yne is:

Answer 1

Correct Answer: 15

To solve this problem, we need to determine the number of sigma ($\sigma$) and pi ($\pi$) bonds in the given structure of Hex-1,3-dien-5-yne, which is $CH_2=CH-CH=CH-CH_2-C \equiv CH$.

1. Analyzing the Structure:
We need to count each $\sigma$ and $\pi$ bond in the molecule.

2. Counting Sigma Bonds:

• C1=C2: 1 $\sigma$ bond
• C2-C3: 1 $\sigma$ bond
• C3=C4: 1 $\sigma$ bond
• C4-C5: 1 $\sigma$ bond
• C5≡C6: 1 $\sigma$ bond
• C1-H (2): 2 $\sigma$ bonds
• C2-H (1): 1 $\sigma$ bond
• C3-H (1): 1 $\sigma$ bond
• C4-H (2): 2 $\sigma$ bonds
• C6-H (1): 1 $\sigma$ bond

Total $\sigma$ bonds = 1 + 1 + 1 + 1 + 2 + 1 + 1 + 2 + 1 = 11

3. Counting Pi Bonds:

• C1=C2: 1 $\pi$ bond
• C3=C4: 1 $\pi$ bond
• C5≡C6: 2 $\pi$ bonds

Total $\pi$ bonds = 1 + 1 + 2 = 4

4. Calculating the Sum:
Sum of $\sigma$ and $\pi$ bonds = 11 + 4 = 15

Final Answer:
The sum of sigma ($\sigma$) and pi ($\pi$) bonds is 15.

Answer 2

Step 1: Understand the Structure of Hex-1,3-dien-5-yne

Hex-1,3-dien-5-yne is a hydrocarbon with 6 carbon atoms (hex- means 6). The name gives us key information:

• "dien" means two double bonds at positions 1 and 3.
• "yne" means one triple bond at position 5.

The carbon chain is linear with the following bonds:

• C1=C2: Double bond
• C2-C3: Single bond
• C3=C4: Double bond
• C4-C5: Single bond
• C5≡C6: Triple bond

The structural formula is: H₂C=CH-CH=CH-C≡CH.

Step 2: Count the Sigma (σ) Bonds

Sigma (σ) bonds are the single covalent bonds between atoms. In organic molecules:

• Every single bond is 1 σ bond.
• A double bond has 1 σ bond and 1 π bond.
• A triple bond has 1 σ bond and 2 π bonds.

Let’s count the σ bonds in H₂C=CH-CH=CH-C≡CH:

Carbon-carbon bonds:

• C1=C2 (double bond): 1 σ bond
• C2-C3 (single bond): 1 σ bond
• C3=C4 (double bond): 1 σ bond
• C4-C5 (single bond): 1 σ bond
• C5≡C6 (triple bond): 1 σ bond

Total C-C σ bonds = 5.

Carbon-hydrogen bonds:

• C1: 2 H atoms (2 σ bonds)
• C2: 1 H atom (1 σ bond)
• C3: 1 H atom (1 σ bond)
• C4: 1 H atom (1 σ bond)
• C6: 1 H atom (1 σ bond)

Total C-H σ bonds = 2 + 1 + 1 + 1 + 1 = 6.

Total σ bonds = 5 (C-C) + 6 (C-H) = 11.

Step 3: Count the Pi (π) Bonds

Pi (π) bonds are the additional bonds in double and triple bonds:

• A double bond has 1 π bond.
• A triple bond has 2 π bonds.

Let’s count the π bonds in the molecule:

• C1=C2 (double bond): 1 π bond
• C3=C4 (double bond): 1 π bond
• C5≡C6 (triple bond): 2 π bonds

Total π bonds = 1 + 1 + 2 = 4.

Step 4: Calculate the Sum of Sigma and Pi Bonds

Now, add the number of σ Favored and π bonds:

σ bonds = 11

π bonds = 4

Sum = 11 + 4 = 15.

Final Answer

The sum of sigma (σ) and pi (π) bonds in hex-1,3-dien-5-yne is 15