AS-Level Halogenoalkanes

  • Halogenoalkanes can be converted to alkenes in an elimination reaction.

  • By reacting halogenoalkanes with hydroxide ions in ethanolic conditions (anhydrous), an alkene and not an alcohol is formed.

  • The reaction is carried out under reflux and the hydroxide ion acts as a base (unlike in the hydrolysis of a halogenoalkane to form an alcohol).


Elimination Reactions of Halogenoalkanes


Halogenoalkanes can be converted into alkenes by an elimination reaction.










A halogenoalkane is reacted with hydroxide ions under reflux in ethanol. Ethanol is used as a solvent to ensure the conditions are anhydrous (no water!).


The hydroxide ion acts as a base and accepts a proton from a C-H bond to form H O.


The important thing to note is that the OH⁻ ion can act as either a nucleophile or as a base depending on the conditions it’s reacting in.