Specification Point 4.4:
Understand how to name compounds relevant to this specification using the rules of International union of pure and applied chemistry (IUPAC) nomenclature

Naming Compounds

  • The first part of the name comes from the number of carbon atoms in the hydrocarbon, the second part comes from the functional group present


Further rules

  • When there is more than one carbon a functional group can be located it is important to distinguish which carbon the functional group is on. Each carbon is numbered and these numbers are used to describe where the functional group is
  • When 2 functional groups are present di- is used as a prefix to the second part of the name
  • Branching also needs to be considered, the carbon atoms with the branches are described by their number
  • When the location of functional groups and branches needs to be described the functional group takes precedence so the functional group has the lowest number


Specification Point 4.5:
Understand how to write the possible structural and displayed formulae of an organic molecule given its molecular formula

Displayed & Structured Formulae

Displayed formula: 

A graphic representation that shows the symbols for each atom in a compound, with straight lines joining them to represent the covalent bonds.

Example: Ethene (C2 H4)

From the molecular formula, we know that ethene has 2 carbon atoms and 4 hydrogen atoms:

Carbon atoms will be joined by a double bond as each carbon atom needs 4 bonds in total

Structural Formula:

A condensed representation that shows the symbols for each atom in a compound, with straight lines joining them to represent the covalent bonds.

Example: Ethene

This displayed formula of ethene can be split up into sections and written as a formula:

Other examples:

Specification Point 4.6:
Understand how to classify reactions of organic compounds as substitution, addition and combustion

Classifying Reactions of Organic Compounds

  • Substitution: A reaction where one atom is swapped with another atom
    • Example: Methane reacts with bromine under ultraviolet light

Methane + Bromine   →   Bromomethane + Hydrogen Bromide

CH4    +    Br2       →            CH3Br   +    HBr

  • Addition: A reaction in which one molecule combines with another to form a larger molecule with no other products
    • Example: Bromine will react with ethene and the bromine molecule will react and add across the double bond of the ethene

Ethene   +   Bromine   →   Dibromoethane

C2H4     +       Br2         →         C2H4Br2

  • Combustion: This is the scientific term for burning. In a combustion reaction, a substance reacts with oxygen to form carbon dioxide (or carbon monoxide if incomplete combustion) and water.
    • Example: Alkenes burn when heated in air of oxygen
    • If there is an unlimited supply of air / oxygen, the products are carbon dioxide and water: 

CH4   +   2O2   →   CO2   +   2H2O

C3H8   +   5O2   →   3CO2   +   4H2O

    • This is termed complete combustion     
    • If there is a limited supply of air / oxygen, the products are carbon monoxide and water:

CH4   +   ½O2   →   CO   +   2H2O

    • This is termed incomplete combustion

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Author: Jamie

Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.