(a) What atoms must a molecule contain to participate in hydrogen bonding with other molecules of the same kind? (b) Which of the following molecules can form hydrogen bonds with other molecules of the same kind: CH₃F, CH₃NH₂, CH₃OH, CH₃Br?

Verified step by step guidance

1. Identify the functional groups in each molecule: CH3F (fluoromethane) has a fluorine atom, CH3NH2 (methylamine) has an amino group, CH3OH (methanol) has a hydroxyl group, and CH3Br (bromomethane) has a bromine atom.
2. Recall the requirement for hydrogen bonding: a molecule must contain a hydrogen atom attached to a highly electronegative atom (N, O, or F) which can act as a hydrogen bond donor, and a lone pair on a highly electronegative atom which can act as a hydrogen bond acceptor.
3. Analyze CH3F: Although fluorine is highly electronegative, the molecule lacks a hydrogen atom bonded to it, thus it cannot form hydrogen bonds with other CH3F molecules.
4. Analyze CH3NH2: The nitrogen atom is both bonded to a hydrogen (making it a hydrogen bond donor) and has a lone pair (making it a hydrogen bond acceptor), allowing CH3NH2 to form hydrogen bonds with other CH3NH2 molecules.
5. Analyze CH3OH: The oxygen atom is bonded to a hydrogen (making it a hydrogen bond donor) and has two lone pairs (making it a hydrogen bond acceptor), allowing CH3OH to form hydrogen bonds with other CH3OH molecules.

Key Concepts

Hydrogen Bonding

Hydrogen bonding is a type of intermolecular force that occurs when a hydrogen atom covalently bonded to a highly electronegative atom, such as nitrogen, oxygen, or fluorine, experiences an attraction to another electronegative atom. This interaction is crucial for the properties of many substances, including water and biological molecules.

Electronegativity

Electronegativity is the tendency of an atom to attract electrons in a chemical bond. Atoms with high electronegativity, like nitrogen, oxygen, and fluorine, can create polar bonds with hydrogen, enabling the formation of hydrogen bonds. Understanding electronegativity helps predict which molecules can engage in hydrogen bonding.

Molecular Structure and Polarity

The molecular structure and polarity of a compound determine its ability to form hydrogen bonds. Molecules with polar bonds and a suitable geometry can interact through hydrogen bonding. For example, molecules like CH3OH (methanol) have a hydroxyl group (-OH) that allows for hydrogen bonding, while others may not.