What's in a medicine?

Carboxylic acids contain the functional group, O=C-O-H.

Naming

methanoic acid - HCOOH,   propanoic acid - CH3CH2COOH,  benzenecarboxylic acid - C6H5COOH.

Reactions

Being weak acids, carboxylic acids partially dissociate in the aqueous solution to form oxonium ions (H3O-) and carboxylate ions (RCOO-)

HCOOC (aq) +  H2O (l)  <------->  H3O+ (aq) + HCOO- (aq)

Carboxylic acids react with bases to produce salts.

CH3COOH (aq) +  NaOH (aq)  ------> CH3COO-Na+ (aq)   +   H2O 

Carboxylic acids react with alcohols in the presence of a strong acid catalyst (concentrated sulfuric acid) when heated under reflux. This esterification reation is reversible and comes to equilibrium during refluxing.

CH3COOH (aq) + CH3CH2OH (aq)   <----->  CH3COOCH2CH3 (aq) + H2O

Test for carboxylic acids

They will react with some carbonates to produce carbon dioxide. This will fizz and turns lime water milky.

Carboxylic acids are important chemically because many useful derivatives can be made from them.

esters  - COO-    acyl chloride COOCl   amide CONH  acid anhydride cooco

The hydroxyl group, -OH, can occur in three different envirnments in organic molecules, alcohols, phenols and carboxylic acids.

Alcohols contain the hydroxyl functional group (-OH) attached to an aliphatic carbon chain.

Phenols are compounds that have one or more -oh groups attached directly to a benzene ring. Although phenols look simila to alcohols, their chemical reactions are different.

Test for phenols - neutral iron(iii) chloride 

Alcohols, phenols and carboxylic acids are all weak acids.