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Chemistry

  • IGCSE Edexcel
  • Revision Notes

4. Organic Chemistry

4.1 Introduction>4.2 Crude Oil>4.3 Alkanes>4.4 Alkenes>4.5 Alcohols>4.6 Carboxylic Acids>4.7 Esters>4.8 Synthetic Polymers>

1.2 Elements, Compounds & Mixtures >1.3 Atomic Structure >1.4 The Periodic Table >1.5 Chemical Formulae, Equations and Calculations >1.6 Ionic Bonding >1.7 Covalent Bonding >1.8 Metallic Bonding >1.9 Electrolysis >

2.1 Group 1 (Alkali Metals) – Lithium, Sodium and Potassium >2.2 Group 7 (Halogens) – Chlorine, Bromine and Iodine >2.3 Gases in the Atmosphere >2.4 Reactivity Series >2.5 Extraction and Uses of Metals >2.6 Acids, Alkalis and Titrations >2.7 Acids, Bases and Salt Preparations >2.8 Chemical Tests >

3.1 Energetics >3.2 Rates of Reaction >3.3 Reversible Reactions and Equilibria >

4.3 Alkanes

4.3.1 Know the general formula for alkanes

General formula for alkanes:

CnH2n+2

EXAMPLE

Ethane is a type of alkane with the formula C2H6

4.3.2 Explain why alkanes are classified as saturated hydrocarbons

ALKANES

  • Contain only single bonds (C–C and C–H)
  • Each carbon has 4 single bonds around it, which is the maximum number of bonds it can form
  • Therefore, the carbons are saturated

4.3.3 Understand how to draw the structural and displayed formulae for alkanes with up to five carbon atoms in the molecule, and to name the unbranched-chain isomers

4.3.4 Describe the reactions of alkanes with halogens in the presence of ultraviolet radiation, limited to mono-substitution

knowledge of reaction mechanisms is not required

Reaction of Alkanes with Halogens

UV

alkane + halogen → halogenoalkane + hydrogen halide

  • As alkanes are saturated, they undergo substitution reaction
  • The reaction only happens in presence of ultraviolet (UV) radiation
  • It is a mono-substitution reaction:
    • One of the hydrogen is substituted by the halogen
Product names:
fluoro / chloro / bromo / iodo [alkane name]
+ hydrogen fluoride / chloride / bromide / iodide

 UV

C2H6 + Br2 → C2H5Br + HBr

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