Esters and structure of esters

Formation of Esters

• Esters are organic compounds formed through a condensation reaction between an alcohol and a carboxylic acid, a process known as esterification.
• In this reaction, two molecules combine to form a larger molecule, with the elimination of a small molecule, which is water.
• Esters are characterised by their distinct and often pleasant smells, and they are generally insoluble in water.

Ester Structure

• Esters have a specific functional group in their structure: -COO.
• The functional group consists of a hydrocarbon chain (R₁) single-bonded to an oxygen atom, which is then single-bonded to a carbon atom.
• This carbon atom is double-bonded to another oxygen atom and single-bonded to another hydrocarbon chain (R₂).
• This functional group is referred to as the ester link.
• Esters are commonly used in the fragrance and flavour industry and also find applications as solvents in the chemical industry.

Naming Esters

To name an ester, follow these steps:

• Change the name of the parent alcohol to end in '-yl'.
• Change the name of the parent acid to end in '-oate'.
• Place the name of the alcohol in front and the name of the acid at the end.

For example, if you have propanol and ethanoic acid, they can condense to form propyl ethanoate.

Chemical Process of Ester Formation

• To create an ester, a hydrogen atom is removed from the hydroxyl group (-OH) of the alcohol.
• The hydroxyl (-OH) group of the acid's carboxyl group also loses a hydrogen atom.
• These two hydrogen atoms combine to form a water molecule (H₂O).

---

Esters and structure of esters

Structural Formula and Naming

• When examining the structure of an ester, you can easily name it.
• The carbon-oxygen double bond (C=O) part of the molecule comes from the acid.
• In the structural formula, the ester link (-COO) separates the two parts of the molecule.
• The alcohol part of the molecule is named based on the number of carbons in it.
• The acid part of the molecule is named based on the number of carbons in the parent acid.
• For example, ethyl butanoate has 2 carbons in the alcohol part and 4 carbons in the acid part.
• This ester is named ethyl butanoate.
• Other examples include methyl propanoate (CH₃COOC₃H₇), ethyl ethanoate (C₂H₅COOCH₃), and butyl methanoate (C₄H₉COOH).

Conclusion:

• Esters are formed through esterification, a condensation reaction between an alcohol and a carboxylic acid.
• They have a distinct structure with a functional group (-COO) and find applications in the fragrance, flavour, and chemical industries.
• Naming esters is based on the names of their alcohol and acid components, with specific suffixes added.