Carbon and Its Compounds is one of the most important chapters in SSLC Science. In this chapter, students learn about covalent bonding, versatile nature of carbon, hydrocarbons, functional groups, homologous series, ethanol, ethanoic acid, soaps and detergents. This article is prepared based on the uploaded LBA document.
Learning Points
This chapter mainly includes:
- Covalent bonding in carbon
- Versatile nature of carbon
- Saturated and unsaturated compounds
- Chains, branches and rings
- Functional groups
- Homologous series
- Nomenclature of carbon compounds
- Combustion and oxidation
- Addition and substitution reactions
- Properties of ethanol and ethanoic acid
- Soaps and detergents
Carbon and Covalent Bonding
Carbon has four valence electrons and forms covalent bonds by sharing electrons.
C:2,4
Carbon does not easily form ions because gaining or losing four electrons requires a large amount of energy.
Covalent Bond
A chemical bond formed by sharing of electrons between atoms is called a covalent bond.
Example – Methane
$\ce{CH4}$
Methane is the simplest hydrocarbon.
Versatile Nature of Carbon
Carbon forms large number of compounds because of:
- Catenation property
- Tetravalency
Catenation
The property of carbon atoms linking with one another is called catenation.
Carbon can form:
- Straight chains
- Branched chains
- Ring structures
Saturated and Unsaturated Hydrocarbons
Saturated Hydrocarbons
Hydrocarbons containing only single bonds are called saturated hydrocarbons.
Example
$\ce{C2H6}$
These are called alkanes.
Unsaturated Hydrocarbons
Hydrocarbons containing double or triple bonds are called unsaturated hydrocarbons.
Alkene Example
$\ce{C2H4}$
Alkyne Example
$\ce{C2H2}$
Homologous Series
A series of compounds with the same functional group and similar chemical properties is called the homologous series.
Important Feature
Successive compounds differ by:
$\ce{CH2}$
Functional Groups
Atoms or groups of atoms that determine the chemical properties of organic compounds are called functional groups.
Important Functional Groups
| Functional Group | Representation |
| Alcohol | –OH |
| Aldehyde | –CHO |
| Carboxylic acid | –COOH |
| Halo group | –Cl / –Br |
Questions related to haloalkanes and alcohol are frequently asked in exams.
Ethanol
Molecular Formula
$\ce{C2H5OH}$
Properties of Ethanol
- Colourless liquid
- Used as solvent
- Used in medicines and perfumes
- Reacts with sodium to release hydrogen gas
Reaction with Sodium
$\ce{2C2H5OH + 2Na -> 2C2H5ONa + H2}$
Ethanoic Acid
Molecular Formula
$\ce{CH3COOH}$
Ethanoic acid is also called acetic acid.
Properties
- Sour smell
- Turns blue litmus red
- Used in vinegar
- Pure ethanoic acid is called glacial acetic acid
Esterification Reaction
The reaction between carboxylic acid and alcohol to form ester is called esterification.
$\ce{CH3COOH + C2H5OH -> CH3COOC2H5 + H2O}$
Esters have a pleasant smell and are used in perfumes and flavouring agents.
Saponification Reaction
The reaction in which ester reacts with sodium hydroxide to form soap is called saponification.
$\ce{CH3COOC2H5 + NaOH -> CH3COONa + C2H5OH}$
Addition Reaction
Unsaturated compounds react with hydrogen in the presence of a catalyst to form saturated compounds.
$\ce{C2H4 + H2 ->[\text{Ni}] C2H6}$
This reaction is used in hydrogenation of vegetable oils.
Substitution Reaction
In saturated hydrocarbons, one atom is replaced by another atom.
$\ce{CH4 + Cl2 ->[\text{Sunlight}] CH3Cl + HCl}$
Soaps and Detergents
Soap
Soap molecules form micelles that trap dirt and grease.
Detergents
Detergents work even in hard water.
Hard water contains salts of calcium and magnesium.
Important Exam Questions
One Mark Questions
- What is catenation?
- What is a homologous series?
- What are esters?
- Write a molecular formula of ethanol.
Two Mark Questions
- Write properties of covalent compounds.
- Explain additional reactions.
- Differentiate soaps and detergents.
Three and Four Mark Questions
- Explain esterification reaction.
- Explain cleaning action of soaps.
- Explain formation of covalent bond.
- Differentiate saturated and unsaturated compounds.
These questions are repeatedly asked in examinations.
Preparation Tips for Students
- Learn all functional groups carefully
- Practice chemical equations regularly
- Study homologous series properly
- Learn differences between saturated and unsaturated compounds
- Revise reactions of ethanol and ethanoic acid
