Condensation reaction

Esterification (Fischer-Speier esterification) is a reflux reaction producing an ester from a carboxylic acid and alcohol in the presence of an acid catalyst (H₂SO₄ or HCl).

Keys:

1. increasing [reactant] can shift the equilibrium to product formation, either the carboxylic acid or alcohol.

2. removing water using a drying agent (anhydrous Na₂SO₄ or MgSO₄) can shift equilibrium to product formation

3. the carbonyl donates the -OH and the hydroxyl donates the -H (evidence by ¹⁸O labeled reactions-see here)

4. steric hindrance can affect the reaction rate--highly substituted alcohols or carboxylic acids reduce reaction rates.

    -3^o alcohols can lead to acid-catalyzed elimination reactions.  

Mechanism:

-The mechanism is described as an acid-catalyzed nucleophilic addition-elimination reaction at the acyl carbon.

 - the forward reaction is described as an acid-catalyzed esterification of an acid, controlled by increasing [alcohol] and removing H₂O

- the reverse rection is an acid-catalyzed hydrolysis of an ester, controlled by increasing [H₂O] (i.e. diluting the acid).

Video- Fischer esterification mechanism

Video: Esterification lab- UGA

Uses of esters

1. Esters that are have fragrant odors are used as a constituent of perfumes, essential oils, food flavorings, cosmetics, etc - Table-- Lab

2. Esters are used as an organic solvent (eg. ethyl acetate/ethyl ethanoate). See carbonate esters

3. Natural esters are found in pheromones (insect pheromones)

4. Naturally occurring fats and oils are fatty acid esters of glycerol

5. Phosphodiesters form the backbone of DNA molecules

6. Nitrate esters, such as nitroglycerin, are known for their explosive properties

7. Polyesters are used to make plastics

8. Esters are used to make surfactants E.g. soap, detergents (eg. sodium lauryl sulfate)