MCQ Detailed View

Hydrogen bonding is a type of strong dipole-dipole interaction that occurs when a hydrogen atom is covalently bonded to a highly electronegative atom such as oxygen (O), nitrogen (N), or fluorine (F), and this hydrogen is also attracted to another electronegative atom nearby. This interaction is responsible for many physical properties of substances, such as boiling point, solubility, and viscosity.

In water (H₂O), hydrogen bonding occurs extensively. Each water molecule can form up to four hydrogen bonds—two through its hydrogen atoms and two through lone pairs on the oxygen atom. This network of hydrogen bonds gives water its high boiling point, high specific heat capacity, and unusual density behavior in its solid state (ice).

Ethyl alcohol (C₂H₅OH), also known as ethanol, contains an –OH (hydroxyl) group. The hydrogen atom attached to oxygen participates in hydrogen bonding with another oxygen atom of a neighboring ethanol or water molecule. This makes ethanol miscible with water and elevates its boiling point compared to hydrocarbons of similar molecular weight.

Phenol (C₆H₅OH) also contains a hydroxyl group directly attached to an aromatic ring. It exhibits both intramolecular and intermolecular hydrogen bonding. The hydroxyl group can donate and accept hydrogen bonds, affecting solubility and boiling point.

All three compounds listed—water, ethyl alcohol, and phenol—have hydrogen atoms bonded to oxygen, enabling hydrogen bonding. This property influences their chemical behavior, solubility in polar solvents, and physical characteristics such as melting and boiling points.

Hydrogen bonding is an essential concept in physical chemistry, impacting the structure and interaction of molecules in liquids and biological systems.