naming and isomerism

• Homologous


  Series of organic compounds with the same functional group and similar chemical properties
• Functional group

  Specific group of atoms within a molecule that is responsible for the characteristic chemical reactions of that compound
• Prefix


  Part of a name added to the beginning of a word to modify or change its meaning
• Suffix


  Part of a name added to the end of a word to modify or change its meaning
• Aldehydes


  • -al
  • formyl-
• Ketones


  • -one
  • oxo-
• Carboxylic acids


  • -oic acid
• Nitriles


  • -nitrile
  • cyano-
• Amines


  • -amine
  • amino-
• Esters


  • -yl -oate
• Acyl chlorides


  • -oyl chloride
• Amides


  • -amide
• Acid anhydrides


  • -oic anhydride
• When compounds contain more than one functional group, the order of precedence determines which groups are named with prefix or suffix forms. The highest precedence group takes the suffix (and the lowest number on the carbon chain), with all others taking the prefix form. However, double and triple C-C bonds only take suffix form.
• Order of priority highest first

  • Carboxylic acids>carboxylic acid derivative>nitriles>aldehydes>ketones>alcohols>amines>alkenes>halogenoalkanes
• Amines

  These end in -amine. There is, however, rather confusingly two ways of using this suffix. The exam board tend to use the common version where the name stem ends in -yl propylamine. Another version of the same chemical is propan-1-amine. (This is used in the same way as naming alcohols)
• Amines with another priority functional group

  The prefix amino is used
• Secondary amines with two alkyl groups


  Each chain is named and the smaller alkyl group is preceded by an -N which plays the same role as a number in positioning a side alkyl chain
• Aldehydes


  An aldehyde's name ends in -al. It always has the C=O bond on the first carbon of the chain so it does not need an extra number.
• Ketones


  Ketones end in -one. When ketones have 5C's or more in a chain then it needs a number to show the position of the double bond.
• Carboxylic acids

  These have the ending -oic acid but no number is necessary for the acid group as it must always be at the end of the chain. The numbering always starts from the carboxylic acid end
• Carboxylic acids with two acid groups

  It is called a -dioic acid
• Esters

  Esters have two parts to their names. The bit ending in -yl comes from the alcohol that has formed it and is next to the single bonded oxygen. The bit ending in -anoate comes from the carboxylic acid.
• Acid anhydrides


  This is called ethanoic anhydride. It is ethanoic because it is two ethanoate groups joined together.
• Acyl chlorides

  Add -oyl chloride to the stem name
• Amides


  Add -amide to the stem name
• Secondary and tertiary amides

  The smaller alkyl group is preceded by an -N which plays the same role as a number in positioning a side alkyl chain
• Nitriles

  These end in -nitrile, but the C of the CN group counts as the first carbon of the chain.
• Structural isomers

  Same molecular formula, different structures
• Functional group isomers

  Same molecular formula, different functional groups
• Stereoisomers


  Same structural formulae, different spatial arrangement of atoms
• Geometrical (E-Z) isomerism


  Type of stereoisomerism
• Optical isomerism

  Type of stereoisomerism that occurs in carbon compounds with 4 different groups of atoms attached to a carbon (called an asymmetric carbon)
• Enantiomers


  Two optical isomers that are mirror images and not superimposable
• Racemate


  A 50/50 mixture of two enantiomers
• Dextrorotatory


  An optical isomer that rotates plane-polarised light clockwise
• Laevorotatory


  An optical isomer that rotates plane-polarised light anticlockwise
• Formation of a racemate

  When a reactant or intermediate has a trigonal planar group in the molecule and is approached from both sides by an attacking species, an equal chance of either enantiomer forming leads to a racemate
• Unsymmetrical alkene + HBr


  Can lead to isomeric products and formation of a racemate
• Drug action may be determined by the stereochemistry of the molecule. Different optical isomers may have very different effects.