Formulae, Functional Groups and Naming

• Hydrocarbon


  A compound made up of C and H atoms only

  
• Alkanes


  Simple hydrocarbons with no functional group
• The compounds in the table on page 26 and 27 contain a functional group which dictates their physical and chemical properties

  
• Interpreting and using formulae

  1. General

  2. Structural

  3. Displayed

  4. Skeletal
• Systematic nomenclature


  Used to name organic compounds, makes it easier to refer to them
• Naming organic compounds


  1. Alkanes provide the basis

  2. Stem indicates number of C atoms in longest chain

  3. Position of side-chains/functional groups indicated by numbering C atoms

  4. Hydrocarbon side-chains shown in brackets in structural formula

  5. Alkyl groups named by adding '-yl'

  6. Prefixes used for multiple side-chains/functional groups

  
• Carbon forms a vast number of compounds because it can form strong covalent bonds with itself
• Carbon always forms four covalent bonds which can be single, double or triple bonds

  
• There is an almost infinite variety of chains, branches and rings able to form
• Functional group


  A specific atom or group of atoms which confer certain physical and chemical properties onto the molecule
• Organic molecules


  Classified by the dominant functional group on the molecule
• Homologous series


  Organic compounds with the same functional group, but with each successive member different by CH2
• Every time a carbon atom is added to the chain, two hydrogen atoms are also added, which is why the successive members differ by CH2

  
• Formulae of organic compounds


  • General formula
  • Structural formula
  • Displayed formula
  • Skeletal formula
• Alkanes


  Provide the basis of the naming system and the stem of each name indicates how many carbon atoms are in the longest chain in one molecule of the compound

  
• Nomenclature of organic compounds

  • If there are any side-chains or functional groups present, then the position of these groups are indicated by numbering the carbon atoms in the longest chain starting at the end that gives the lowest possible numbers in the name
  • The hydrocarbon side-chain is shown in brackets in the structural formula

  
• Alkyl group


  A side-chain named by adding '-yl' to the normal alkane stem
• Prefixes for multiple alkyl side-chains or functional groups

  di- (for two), tri- (for three) or tetra- (for four)

  
• Numbering of side-chains/functional groups

  • Adjacent numbers have a comma between them
  • Numbers are separated from words by a hyphen
• Order of listing multiple side-chains/functional groups

  They are listed in alphabetic order
• Functional groups & their nomenclature


  • See table
• An aliphatic compound is straight or branched-chain and also includes cyclic organic compounds that do not contain a benzene ring

  
• Molecular formula


  Shows the number and type of each atom in a molecule

  
• Empirical formula


  Shows the simplest whole number ratio of the elements present in one molecule of the compound