Alcohols are the organic compounds containing hydroxyl group (-OH) attached to a carbon atom. These are obtained by replacing one or more hydrogen atoms of hydrocarbons by hydroxyl group (– OH).
Alcohols are also known as alkanols. The general formula of alcohol is CnH2n+1OH. Following are the molecular formulae and structural formulae of first five members of homologous series of alcohol.
| Serial No. | Name | Mol. Formula | Structural Formula |
| 1. | Methanol | CH3OH |  |
| 2. | Ethanol | C2H5OH |  |
| 3. | Propanol | C3H7OH |  |
| 4. | Butanol | C4H9OH |  |
| 5. | Pentanol | C5H11OH |  |
Physical Properties of Alcohols
The important physical properties of alcohols are:
- The lower members of alcohols are colourless liquids having a characteristic smell and burning taste. While the higher members are colourless, odourless, wax like solids.
- Alcohols exist as associated molecules having inter molecular hydrogen bonding as shown below:
- The lower members have low boiling points but higher members of alcohol have high melting point.
- The lower members are soluble in water but as the size of alcohol molecule increases solubility in water decreases.
- These are volatile and easily combustible.
- These are bad conductors of electricity.
- These are generally lighter than water.
- Alcohols have intoxicating effect i.e. these are poisonous.
Uses
Alcohols occur widely in nature and have many industrial and pharmaceutical applications. For example, alcohols are widely used as an important component of all alcoholic beverages (beer, wine, and whisky), as an antiseptic in the form of rectified spirit, as a solvent for many chemicals, medicines, lacquers and varnishes. Many other commercially important compounds such as methanal, ethanoic acid, esters, ethers and ethene etc. are also prepared from alcohols.
Test your understanding and answer these questions:
- What are alcohols? give two examples.