Question

What is the ratio of σ and pi bonds in pyrophosphoric acid ?

Hint:

In polyatomic structures, count sigma and pi bonds systematically by identifying single and double bonds.

Answer 1

The structure of pyrophosphoric acid (H₄P₂O₇) consists of an O=P-O-P=O backbone with terminal hydroxyl groups (OH).

Step 1: Counting Sigma (\( \sigma \)) Bonds: 

• Each single bond (P-O and O-H) is a sigma bond.
• Each double bond (P=O) contains 1 sigma bond.

Total sigma bonds: 12 (8 single P-O and O-H bonds + 4 sigma components from P=O bonds).

Step 2: Counting Pi (\( \pi \)) Bonds:

• Each double bond (P=O) contains 1 pi bond.

Total pi bonds: 2 (from P=O bonds).

Step 3: Ratio of Sigma to Pi Bonds:

\[ \frac{\sigma}{\pi} = \frac{12}{2} = 6 \]

Conclusion:

The ratio of sigma to pi bonds in pyrophosphoric acid is 6:1.