Question

The O-O-H bond angle in \(H_2O_2\) is

• A. $106^{\circ}$
• B. $109^{\circ} 28'$
• C. $120^{\circ}$
• D. $97^{\circ}$

Answer 1

The Correct Option is D

Hydrogen peroxide (H_2O_2) is a simple peroxide and involves two hydroxyl groups connected by an oxygen-oxygen single bond. Understanding its structure helps in deducing the bond angles involved. Let's examine the molecular structure and elucidate the O-O-H bond angle.

1. Structure of H_2O_2:

In H_2O_2, each oxygen atom forms a bond with one hydrogen and one oxygen, creating a non-linear structure. The hybridization of the oxygen atoms is sp³ due to the involvement of 2 lone pairs and 2 bonds. The expected bond angle would be close to tetrahedral, approximately 109.5^\circ.

2. Torsional Strain and the ‘Open Book’ structure:

However, due to the presence of lone pairs on the oxygen atoms, the actual molecular geometry is affected by torsional strain, leading to a skewed arrangement. This is often referred to as an 'open book' conformation wherein the O-O-H bond angle is significantly reduced compared to a perfect tetrahedral geometry.

3. Actual O-O-H Bond Angle:

The O-O-H bond angle in H_2O_2 is experimentally determined to be around 97^\circ. This deviation from the ideal tetrahedral angle is primarily due to electron repulsion between the lone pairs of the oxygen atoms which compresses the bond angle.

4. Justification of Options:

• 106^\circ: Close to a tetrahedral angle with some deviation, not applicable here due to greater lone pair repulsion.
• 109^\circ 28': Ideal for tetrahedral (sp³) but not observed in H_2O_2.
• 120^\circ: Suitable for trigonal planar structures, not applicable to H_2O_2.
• 97^\circ: Correct, reflects the observed effect of lone pair interactions.

Thus, the correct bond angle for H_2O_2 due to the influence of lone pairs and molecular shape is 97^\circ.