Hydrogen bonding occurs when a molecule has a hydrogen atom bonded to a highly electronegative atom like N, O, or F - and there is a lone pair on another N,O, or F atom that can participate in bonding. 1. Ethanol (CH3CH2OH) Has an - OH group Can form hydrogen bonds ( O−H⋯O ) 2. Acetic acid (CH3COOH) Has both C=O and - OH groups Forms strong hydrogen bonds (dimers, intramolecular and intermolecular H-bonding possible) 3. Ethylamine (CH3CH2NH2) Has an −NH2 group Can form hydrogen bonds ( N−H⋯N or N−H⋯O with other molecules) 4. Trimethylamine ((CH3)3N) Has nitrogen with a lone pair but no N−H bond Cannot form H-bonds as donor, though it can accept them - but "having H-bonding" typically means being capable of intermolecular H -bonding as both donor and acceptor. Since it cannot donate an H , we generally do not count it as hydrogen-bonding on its own. 5. Salicylic acid (o-hydroxybenzoic acid) Has both - OH and - COOH groups; strong intramolecular hydrogen bond and intermolecular as well. H-bonding present 6. Ethanal ( CH3CHO ) Has a C=O group only, no - OH or −NH− Cannot form hydrogen bonds with itself (can accept H bonds but not donate). Substances with H-bonding: Ethanol Acetic acid Ethylamine Salicylic acid Total =4
