Alkanes

Summary

Alkanes are saturated hydrocarbons with only single covalent bonds, making them generally unreactive except in combustion and substitution reactions. They are used as fuels and can undergo cracking to produce smaller alkanes and alkenes. Structural isomerism in alkanes includes chain, positional, and functional group isomerism, affecting their physical and chemical properties.

• Saturated compound — a compound with only single carbon-carbon bonds. Example: Methane (CH4) is a saturated compound.
• Unsaturated compound — a compound with one or more double or triple carbon-carbon bonds. Example: Ethene (C2H4) is an unsaturated compound.
• Chain isomerism — occurs when compounds have the same molecular formula but different carbon chain arrangements. Example: Butane (C4H10) and isobutane (C4H10) are chain isomers.
• Positional isomerism — occurs when the position of a functional group or atom differs in compounds with the same molecular formula. Example: 1-propanol (C3H8O) and 2-propanol (C3H8O) are positional isomers.
• Functional group isomerism — occurs when compounds have the same molecular formula but different functional groups. Example: Ethanol (C2H6O) and dimethyl ether (C2H6O) are functional group isomers.

Exam Tips

Key Definitions to Remember

• Saturated compound
• Unsaturated compound
• Chain isomerism
• Positional isomerism
• Functional group isomerism

Common Confusions

• Confusing saturated and unsaturated compounds
• Misidentifying types of structural isomerism

Typical Exam Questions

• What is a saturated compound? A compound with only single carbon-carbon bonds.
• What is chain isomerism? Isomerism where compounds have the same molecular formula but different carbon chain arrangements.
• How does cracking benefit fuel production? It produces smaller, more useful alkanes and alkenes.

What Examiners Usually Test

• Understanding of structural isomerism
• Differences between saturated and unsaturated compounds
• Applications and reactions of alkanes