What is ester?
Ester is an organic compound derived from an acid in which one hydroxyl group is replaced by alkyl group. The hydroxyl group is replaced by substitutions reaction. These esters on hydrolysis yield water and organic/inorganic acid. In this blog we going to study ester synthesis.
General structure of ester:
Glycerides are esters that are produced as a result of the reaction between glycerol and fatty-acid.
Some physical uses of ester:
- Easters give fruits aroma including apple, pear, banana.
- The sweet smell is used in essential oils.
- Low molecular weight ones are used in fragrance.
- Form high-grade solvents such as resin.
- Polyester is also made by esters which is a well-known polymer.
Process of ester synthesis
Basically, esterification is a process that is used for esters synthesis. Esterification is a chemical process in which two reactants generally acids and alcohols react to form esters. There are different processes by which we can synthesis esters. These processes are discussed in detail below:
By esterification of carboxylic acids with alcohols:
It is classic method of esterification in which carboxylic acid are heated in the presence of suitable dehydrating agent with alcohol to produced esters.
RCO2H + R′OH ⇌ RCO2R′ + H2O
This process is quiet slow without a catalyst. Sulfuric acid is a usual catalyst used for this reaction.
By the esterification of carboxylic acid with epoxides:
Carboxylic acids can also be esterified with epoxides which yield β-hydroxyester.
RCO2H + RCHCH2O → RCO2CH2CH(OH)R
This reaction is used to produce vinyl ester resins.
Ester synthesis by Trans-esterification
Trans-esterification, it is a process which includes transferring one ester into another one. This method is broadly adept.
RCO2R′ + CH3OH → RCO2CH3 + R′OH
Trans-esterification use acids and bases as catalyst.
By reaction of alcohol with acid anhydrides and acyl chlorides:
The reaction to form ester is following:
RCOCl + R′OH → RCO2R′ + HCl
(RCO)2O + R′OH → RCO2R′ + RCO2H
Mostly this process is used for laboratory-scale procedures, as it is an expensive method.
Ester synthesis by Carbonylation:
Alkenes go through the process of hydro-esterification which use metal carbonyl as a catalysts. Propionic acid produced their esters commercially by this process:
C2H4 + ROH + CO → C2H5CO2R
The process of preparation of methyl propionate is shown below:
C2H4+ CO + MeOH →MeO2CCH2CH3
These are some useful methods for ester synthesis.