Organic Formulae

• Organic Chemistry is the study of the structure, properties, and reactions of organic compounds
• Organic compounds are based on living things
• Organic compounds contain carbon

  • metal carbonates, carbon dioxide and carbon monoxide are not included as organic compounds
  • may contain oxygen, nitrogen and sulfur
• • Hydrocarbon - a compound that contains only hydrogen and carbon atoms
  • Many structures that you will be drawing is hydrocarbons
  • Carbon forms 4 bonds + hydrogen forms 1 bond
  • Comes from dead plants and animals that have been pressurized for over millions of years
• Organic compounds are displayed in a number of ways:

  • displayed formulae
  • general formulae
  • structural formulae
• • Displayed formulae - shows the spatial arrangements of the atoms and bonds in a molecule

  
• Structural formulae - enough information is shown to make the structure clear, but the actual covalent bonds aren’t shown

  • only the important bonds are shown such as double or triple bonds
  • identical groups and side groups (groups that are attached to the main carbon chain) can be bracketed together
• Alkanes - a class of hydrocarbons that consist exclusively of single bonds between carbon atom
• Structural isomers - compounds that have the same molecular formula but different structural formulae

  • molecular formula - the actual number of atoms of each element in a compound
  • compounds with the same molecular formula can have different structural formula because the arrangement of the atoms are different
• Only double and triple bonds are shown in structural formulae
• What do organic compounds always contain? and sometimes include?

  Organic compounds always contain carbon and hydrogen. They sometimes include other elements such as oxygen, nitrogen, and sulfur.
• Define hydrocarbons

  Molecules containing only hydrogen and carbon bonded together covalently
• How is hydrocarbon created?

  Through the decomposition of organic matter that have been pressurised for over millions of years
• All organic compounds are named according to how many carbons they have in the biggest chain, the functional groups and side groups
• Number of carbons in the longest chain and the beginning part of the name:

  • 1 - meth
  • 2 - eth
  • 3 - prop
  • 4 - but
• Functional group gives second part of the organic compound's name

  • Alkanes all end in ‘ane’
  • Alkenes all end in ‘ene’
• Naming Branched Chains

  1. Find the longest carbon chain and name it.
  2. Add on the ending of the functional group.
  3. Name the side group according to how many carbons are in it (same names as longest chain but ending in ‘-yl’; e.g. methyl, ethyl) and state which carbon of the longest chain it is found on.
• Mnemonic: My elephants prefer bananas

  • M - meth
  • E - eth
  • P - prop
  • B - but
• The names of organic compounds have two parts: the prefix (or stem) and the end part (or suffix)

  • 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
• 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
• Naming and draw isomers rules


  1. for isomers of alkanes, you can move one of the carbons to the top or bottom making the moved carbon the side group with '-yl' and the remaining carbons with '-ane' e.g. butane -> methyl propane
  2. for an alkene, the double bond can be first or in the middle e.g. but-1-ene means that the C=C bond is at the start or last while the but-2-ene means that the C=C bond is in the middle