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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Hydrogen bonding

An especially strong dipole–dipole attraction between an H atom bonded to N, O or F and a lone pair on an N, O or F atom of another molecule (or another part of the same molecule). A C–H bond is not polar enough to hydrogen-bond.

Hydrogen bond between two water moleculesAn O–H hydrogen on one water molecule (partial positive) is attracted to a lone pair on the oxygen of a neighbouring water molecule (partial negative). The dotted line is the hydrogen bond; the solid lines are covalent O–H bonds.OHHOHHδ+δ−hydrogen bondH on N, O or F ··· lone pair on N, O or Fstrongest intermolecular force between neutral molecules

The dotted O–H···O contact between two water molecules.

Example

Methanol (CHX3OH\ce{CH3OH}, 32.0 g/mol) boils at 337.8 K, while ethane (CX2HX6\ce{C2H6}, 30.1 g/mol), with no O–H group, boils at 184.6 K.

See alsoDipole–dipole forcesLone pairElectronegativityIntermolecular forces