Problem 104 - General Chemistry

Question

Describe the formation of hydrogen bonds in hydrogen peroxide, \(\mathrm{H}_{2} \mathrm{O}_{2}\). Represent possible hydrogen bonding structures in hydrogen peroxide by using structural formulas and the conventional notation for a hydrogen bond.

Step-by-Step Solution

Answer

Hydrogen bonds in hydrogen peroxide form between an oxygen atom of one molecule and a hydrogen atom of another, depicted by dashed lines in structural formulas.

Step 1: Understanding Hydrogen Bonds

Hydrogen bonds are a type of attractive force that occurs when a hydrogen atom, which is covalently bonded to a highly electronegative atom (like oxygen), experiences an attractive interaction with another electronegative atom nearby. In the case of hydrogen peroxide, the electronegative atoms are the oxygen atoms.

Step 2: Structure of Hydrogen Peroxide

Hydrogen peroxide has the molecular formula \(\mathrm{H}_{2}\mathrm{O}_{2}\). It consists of two oxygen atoms bonded by a single bond and each oxygen also bonded to a hydrogen atom. The structural formula can be represented as: \( \text{H-O-O-H} \).

Step 3: Identify Hydrogen Bond Donor and Acceptor

For hydrogen bonding, one oxygen atom in \(\mathrm{H}_{2}\mathrm{O}_{2}\) will act as a hydrogen bond donor and another can act as a hydrogen bond acceptor. The hydrogen bonded to one oxygen can form a hydrogen bond with the lone pairs on the oxygen from another molecule of \(\mathrm{H}_{2}\mathrm{O}_{2}\).

Step 4: Drawing Hydrogen Bond Formation

In hydrogen peroxide, hydrogen bonds can form between the hydrogen atom of one \(\mathrm{H}_{2}\mathrm{O}_{2}\) molecule and the oxygen atom of another. The conventional notation for hydrogen bonding involves dashed lines to indicate this intermolecular force: \( \text{H-O-O-H} \,\, \cdots \text{H-O-O-H} \), where the dashed line represents the hydrogen bond between the lone pair on oxygen and the hydrogen atom from the adjacent molecule.

Key Concepts

Hydrogen Peroxide

Hydrogen peroxide (\(\text{H}_2\mathrm{O}_2\)) is a chemical compound known for its strong oxidizing properties. It is used in various applications such as disinfectant and bleaching agent.
The bond structure of hydrogen peroxide consists of two hydrogen atoms and two oxygen atoms, represented as \(\text{H-O-O-H}\). This structural formula shows that the two oxygen atoms are linked by a single bond, and each oxygen also forms a single bond with a hydrogen atom.
Understanding the structure of hydrogen peroxide is crucial for explaining how hydrogen bonds can form within and between molecules, which affects its chemical behavior and physical properties.

Intermolecular Forces

Intermolecular forces are the forces of attraction or repulsion between neighboring molecules. They play a vital role in determining the physical properties of substances such as boiling and melting points, solubility, and viscosity.
One type of intermolecular force is hydrogen bonding, which occurs when a hydrogen atom covalently bonded to an electronegative atom is attracted to another electronegative atom nearby. In hydrogen peroxide, the electronegative oxygen atoms facilitate hydrogen bonding with other \(\mathrm{H}_2\mathrm{O}_2\) molecules.
The hydrogen bonds between hydrogen peroxide molecules significantly impact its physical properties, like its relatively high boiling point compared to water, despite having fewer hydrogen bonds.

Structural Formulas

Structural formulas are representations that show the arrangement of atoms within a molecule and how they are bonded together. In hydrogen peroxide, the structural formula is depicted as \(\text{H-O-O-H}\), highlighting the single bonds connecting the atoms in the molecule.
These formulas are essential for visualizing potential sites for hydrogen bonding. In the case of hydrogen peroxide, the structural formula helps identify where the hydrogen bonds can form.

• The oxygen atoms each have lone pairs that can act as hydrogen bond acceptors.
• The hydrogen atoms attached to oxygens can serve as hydrogen bond donors.

The use of dashed lines is conventional in depicting hydrogen bonds, emphasizing the connections between molecules beyond the primary covalent structure.