Carbon and its Compounds — Part 2: Functional groups, naming and reactions: visual lesson, CBSE Class 10 Science

Lesson

Families, names and reactions

Part 2 — how a functional group decides a compound's family, how families form homologous series, how to name compounds, and four kinds of reactions.

In this lesson you will

Identify halogen, alcohol, aldehyde, ketone and carboxylic acid functional groups
State the features of a homologous series
Name carbon compounds with up to six carbon atoms
Write equations for combustion, oxidation of alcohols, hydrogenation and substitution by chlorine

Concept

Functional groups

A functional group is an atom or group of atoms (a heteroatom such as O, N or Cl) that gives a compound its characteristic properties, whatever the length of the carbon chain.

Table of five functional groups with formula, family and an example of each
Functional group	Formula	Family	Example
Halo (chloro, bromo)	–Cl, –Br	Haloalkane	Chloromethane, CH₃Cl
Alcohol	–OH	Alcohol	Ethanol, CH₃CH₂OH
Aldehyde	–CHO	Aldehyde	Ethanal, CH₃CHO
Ketone	C=O (inside the chain)	Ketone	Propanone, CH₃COCH₃
Carboxylic acid	–COOH	Carboxylic acid	Ethanoic acid, CH₃COOH

Concept

Homologous series

A homologous series is a family of compounds with the same functional group, in which successive members differ by a $\ce{CH2}$ unit (14 u).

Same general formula, e.g. alkanes $C_nH_{2n+2}$ .
Similar chemical properties (same functional group).
Gradation in physical properties: melting point, boiling point and density rise with molecular mass.

Alkanes, methane to hexane

Room temperature is about 298 K: the first four alkanes are gases, pentane and hexane are liquids.

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