Organic Compounds

  • Organic chemistry is the study of the structure, properties, and reactions of organic compounds. 
  • Organic compounds are those which contain carbon
  • For conventional reasons metal carbonates, carbon dioxide and carbon monoxide are not included in organic compounds.
  • The names of organic compounds have two parts: the prefix or stem and the suffix or end part.
  • The prefix tells you how many carbon atoms are present in the longest continuous chain in the compound.
  • The suffix tells you what functional group is on the compound.

Organic compounds naming table, Edexcel GCSE Chemistry

Further Rules for Naming Compounds

  • When there is more than one carbon atom where a functional group can be located it is important to distinguish exactly which carbon the functional group is on. 
  • Each carbon is numbered and these numbers are used to describe where the functional group is.
  • Numbering begins at the end of the molecule that produces the smallest number in the name.
  • E.g. below are two molecules of butene with the C=C bond at different ends of either chain.
  • Numbering assigns the double bond to the carbon atom that produces the lowest number, hence both molecules are named but-1-ene.

But-1-ene (a), Edexcel GCSE Chemistry

Numbering begins on the left of this molecule

Numbering begins on the right of this molecule

  • 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 9.10C:
  • Recall the formulae of molecules of the alkanes, methane, ethane, propane and butane, and draw the structures of these molecules, showing all covalent bonds
  • Alkanes are a homologous series of hydrocarbon compounds with the general formula:


  • E.g. an alkane with 6 carbon atoms therefore has (6 x 2) + 2 = 14 hydrogen atoms.
  • They can be represented by their molecular formula or displayed formula.
  • The lines in between the atoms in displayed formulae represent covalent bonds.
  • They are colourless compounds which have a gradual change in their physical properties as the number of carbon atoms in the chain increases.
  • Alkanes are generally unreactive compounds but they do undergo combustion reactions, can be cracked into smaller molecules and react with halogens in the presence of light.

Alkane formulae & covalent bond table, Edexcel GCSE Chemistry

Saturation in Hydrocarbons

Specification Point 9.11C:
  • Explain why the alkanes are saturated hydrocarbons
  • Alkanes contain only single bonds between the carbon atoms, there is no carbon carbon (C=C) double bond present.
  • This means that alkanes form bonds with as many atoms as they can, hence the term saturated, since no more atoms can be added to an alkane.

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Edexcel GCSE Chemistry Notes

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Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.