• 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 120^o

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