Organic Chemistry

• Isomers are a molecule with the same molecular formula but a different structural formula
• Carbon-carbon double bonds are unable to rotate freely like single bonds do – they have restricted rotation.
• Groups or atoms bonded to carbon atoms in a double bond are ‘locked’ into position, and there are two possible ways they can be arranged.
• • Stereoisomerism occurs when two molecules have the same molecular and structural formula, but atoms within the molecules are arranged in space differently.
  • Z and E notation is used to name alkene based stereoisomers.
• • In Z isomers, the highest priority groups bonded to each carbon in the double bond are pointing in the same direction.
• • In E isomers, the highest priority groups bonded to each carbon in the double bond are pointing in opposite directions.
• • Cis and trans isomers are forms of Z and E isomers (respectively), but both carbons in the double bond are bonded to the same type of groups.

  
• Chain isomer – these have changed carbon chains. For example, one might be pentane, the other 2-methylbutane.

  
• Functional group isomers – these have the exact same atoms but these are sorted into a changed functional group. For example but-1-ene and cyclobutane.

  
• Positional isomers – The carbon chain and attached atoms are the same. However, the functional group is attached to a changed carbon. For example, 1-fluoropropane and 2-fluoropropane.

  
• Structural isomers are molecules with the same molecular formula but differing structural formulas. (i.e chain isomerism, functional group isomerism and positional isomerism)