General Organic Chemistry

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 $( CH _3 CH _2 OH )$Has an - OH groupCan form hydrogen bonds ( $O - H ⋯ O$ )2. Acetic acid $( CH _3 C O O H )$Has both $C = O$ and - OH groupsForms strong hydrogen bonds (dimers, intramolecular and intermolecular H-bonding possible)3. Ethylamine $( C H _{ 3 } C H _{ 2 } N H _{ 2 })$Has an $- NH _2$ groupCan form hydrogen bonds ( $N - H ⋯ N$ or $N - H ⋯ O$ with other molecules)4. Trimethylamine $( ( CH _3) _3 N)$Has nitrogen with a lone pair but no $N - H$ bondCannot 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 present6. Ethanal ( $C H _{ 3 } C H O$ )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:EthanolAcetic acidEthylamineSalicylic acidTotal $= 4$