Homologous series is a group of organic compounds that have CH2 group and the number of CH2group causes the difference among the homologues. Examples of functional groups in homologous series include, alcohols (-OH), carboxylic acid (-COOH), aldehydes (COH), Ketones (C=O) and amines (N). Alcohols are the most common organic compounds and characterized by one or more –OH groups attached to a carbon atom of any alkali group. Alcohols are colorless liquids and solids at room temperature and those with low molecular weight most soluble in water. As their molecular weight increases the solubility in water decreases, their viscosity, boiling points density and vapor pressure increase. The common names of alcohols combine the alkyl group and the term alcohol. Example, CH3CH2OH (ethanol). Alcohols have higher boiling points than alkanes because alcohols have the ability to form intermolecular hydrogen bonds; the diagram below shows how the hydrogen bonds increase the boiling points.
Organic compound Formula Boiling point
Pentane CH3CH2CH2CH2CH3 36.3oC
Butan-1-ol CH3CH2CH2CH2OH 1170C
2-methylpropan-1-ol CH3CH2(CH3)CH2OH 1080C
Alcohols are commercially important and they include methanol, which mostly used as an industrial solvent and ethanol, which is used as fuel.
BIBLIOGRAPHY l 1033 Bailey, Jane. “Alcohols.” Organic Chemistry (2018).
Murmson, Serm. “What Is a Homologous Series.” Sciencing (2018).