The boiling point of organic compounds can give important information about their physical properties and structural characteristics. Boiling point helps identify and characterise a compound. A liquid boils when its vapour pressure is equal to the atmospheric pressure. Vapour pressure is determined by the kinetic energy of a molecule. The boiling point of a liquid varies with the surrounding atmospheric pressure. A liquid at a higher pressure has a higher boiling point than when that liquid is at lower atmospheric pressure. The boiling point (BP) of an organic molecule is related to the molecular weight of the molecule and the “stickiness” of individual molecules for their neighbors. For molecules with a given functional group, boiling point increases with molecular weight.
This video explains how to determine the boiling point of an organic compound.