Carboxylic Acids

Carboxylic acids are a homologous series of compounds. Each member differs from the next by one -CH2 group in the molecular formulae. All carboxylic acids share similar chemical properties, but there is a gradual variation in their physical properties. For example:

  • Boiling points – Increase as the carbon chain length increases
  • Viscosity – Increases as the carbon chain length increases

One easy way to identify a carboxylic acid is through the ‘-oic acid’ ending in the name. The functional group responsible for the chemical behaviour of carboxylic acids is the carboxyl group, represented as ‘-COOH’.

The general formula for carboxylic acids is:

A chemical formula enclosed in a rectangular border. The formula reads "CnH2n+1COOH", representing the general structure of a carboxylic acid.

In terms of the carboxylic acid structure – their molecular formula, structural formula and ball-and-stick model can be seen below:

The molecular formula, structural formula and ball-and-stick model of the first four carboxylic acids can be seen in the table below:

Carboxylic acidNo. of carbon atomsFormulaStructural formulaBall + stick diagram
Methanoic acid1HCOOHThis image has an empty alt attribute; its file name is image-65.pngThis image has an empty alt attribute; its file name is image-55.png
Ethanoic acid2CH3COOHThis image has an empty alt attribute; its file name is image-67.pngThis image has an empty alt attribute; its file name is image-56.png
Propanoic acid3C2H5COOHThis image has an empty alt attribute; its file name is image-68.pngThis image has an empty alt attribute; its file name is image-57.png
Butanoic acid4C3H7COOHThis image has an empty alt attribute; its file name is image-69.pngThis image has an empty alt attribute; its file name is image-59.png

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