Carboxylic acids are molecules with trigonal planar geometry. They have acidic hydrogen in the hydroxyl group and behave like bases on carbonyl oxygen.
![physical properties 01](/images/stories/organica-ii/acidos-carboxilicos/propiedades-fisicas/propiedades-fisicas-01.png)
O : basic oxygen
H : Acidic hydrogen
The melting and boiling points are high since they form dimers, due to hydrogen bonding.
![physical properties 02](/images/stories/organica-ii/acidos-carboxilicos/propiedades-fisicas/propiedades-fisicas-02.png)
Hydrogen bonds ( ------------ )
CH3COOH Boiling point: 118ºC
CH3CH2COOH Boiling point: 141.8ºC
Methanoic acid molecular model
![methanoic acid](/images/stories/organica-ii/acidos-carboxilicos/propiedades-fisicas/acido-metanoico.png)
Ethanoic acid molecular model
![ethanoic acid](/images/stories/organica-ii/acidos-carboxilicos/propiedades-fisicas/acido-etanoico.png)