Alcohols

Alcohols belong to a homologous series derived from hydrocarbons. We can identify these compounds by the ‘ol’ at the end of their name (e.g. ethanol).

The functional group that defines alcohols is hydroxyl (OH), which determines how alcohols react. Although, alcohols can have more than one hydroxyl group.

  • Alcohols with two hydroxyl groups are called diols
  • Alcohols with three hydroxyl groups are called triols

The general formula for alcohols is:

"CnH2n+1OH"

‘n’ is the number of carbon atoms in the molecule. So if there are four carbon atoms, the formula will be C4H9OH, which represents butanol.

Alcohols can also be represented by the formula R−OH, where R is a hydrocarbon chain. The number of carbon atoms in this chain can vary, which results in differences in the physical properties of alcohols. However, they share similar chemical properties.

Let’s take a look at the molecular formulae and structures of the first three alcohols:

AlcoholNo. of carbon atomsMolecular formulaStructural formulaBall + stick diagram
Methanol1CH3OHThis image has an empty alt attribute; its file name is image-33.pngThis image has an empty alt attribute; its file name is image-38.png
Ethanol2C2H5OHThis image has an empty alt attribute; its file name is image-34.pngThis image has an empty alt attribute; its file name is image-39.png
Propanol3C3H7OHThis image has an empty alt attribute; its file name is image-35.pngThis image has an empty alt attribute; its file name is image-40.png

These alcohols differ from each other in the number of CH2 units in their molecular formulaestructures, which leads to variations in their physical properties. Nonetheless, they share the same functional group (hydroxyl) and exhibit similar chemical behaviours.

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