IB DP Chemistry: SL复习笔记10.2.3 Alkenes - Reactivity

Reactivity of Alkenes

  • Alkenes are hydrocarbons containing a carbon-carbon double bond
  • The atoms around the carbon-carbon double bond adopt a planar arrangement and the bond angle is 120o


The bonding arrangement around a carbon-carbon double bond

  • The presence of the C=C bond gives alkenes a number of chemical properties that are not seen in alkanes
  • Since the alkene contains π-bonds, it is possible to break the weaker π-bond and form stronger  σ-bonds with other species without forcing any atoms on the molecule to break off
  • As a result alkenes (unlike alkanes) are capable of undergoing addition reactions


Addition reactions in alkenes

  • Molecules which contain π-bonds and which can hence undergo addition are said to be unsaturated
  • Molecules which do not contain π-bonds and which hence cannot undergo addition are said to be saturated.
  • Alkenes are unsaturated and can hence undergo addition
  • Addition is the combination of two or more molecules to form a single molecule
  • Addition reactions are generally faster than substitution reactions since only weak π-bonds are broken, rather than stronger σ-bonds
  • The ability of alkenes to undergo addition means that they are much more reactive than alkanes