Functional groups, homologous series

1. Functional Groups

1. Functional groups are specific groups of atoms within a molecule that determine the molecule’s chemical properties and reactivity.
2. They are the reactive part of the molecule responsible for characteristic reactions.
3. Examples of functional groups include:
   • Alcohol (-OH): Found in ethanol, methanol.
   • Carboxylic acid (-COOH): Found in acetic acid, formic acid.
   • Aldehyde (-CHO): Found in formaldehyde, acetaldehyde.
   • Ketone (-C=O): Found in acetone, butanone.
   • Amine (-NH₂): Found in aniline, methylamine.
4. Functional groups are used to classify organic compounds and predict their chemical behavior.

2. Homologous Series

1. A homologous series is a group of organic compounds with the same functional group and similar chemical properties, differing by a CH₂ unit.
2. Members of a homologous series are called homologues.
3. Examples of homologous series include:
   • Alkanes: Methane (CH₄), Ethane (C₂H₆), Propane (C₃H₈).
   • Alkenes: Ethene (C₂H₄), Propene (C₃H₆).
   • Alcohols: Methanol (CH₃OH), Ethanol (C₂H₅OH).
4. Properties of homologous series:
   • They show a gradual change in physical properties like boiling and melting points.
   • Chemical properties remain similar due to the presence of the same functional group.
   • The difference in molecular mass between consecutive members is 14 u (CH₂ group).
5. Homologous series simplifies the study of organic chemistry by grouping compounds with similar properties.

3. Importance of Functional Groups and Homologous Series

1. Functional groups determine the classification and reactivity of organic compounds.
2. They are essential in naming organic compounds according to IUPAC nomenclature.
3. Homologous series provide a systematic way to study organic compounds with similar structures and properties.
4. These concepts are fundamental in understanding reactions like oxidation, reduction, and substitution.
5. Applications include the synthesis of polymers, drugs, and other industrially important compounds.

4. Key Points

1. Functional groups define the chemical properties of organic molecules.
2. Examples of common functional groups include alcohols, aldehydes, carboxylic acids, and amines.
3. A homologous series is a group of compounds differing by a CH₂ unit with similar chemical properties.
4. Homologous series exhibit a gradual change in physical properties.
5. The study of functional groups is essential for IUPAC naming and understanding chemical reactivity.
6. These concepts are widely applied in fields like pharmaceuticals and organic synthesis.