Addition Reactions | Chemistry for Grade 11 (IGCSE) PDF Download

Addition Reactions

• Alkenes engage in addition reactions where atoms from a basic molecule add across the C=C double bond.
• An instance of such an addition reaction is observed in the interaction between bromine and ethene.
  
• Alkenes can also participate in addition reactions with hydrogen, resulting in the formation of an alkane.
• These reactions, known as hydrogenation reactions, typically take place at around 150ºC and employ a nickel catalyst.
• Hydrogenation reactions are utilized in the production of margarine from vegetable oils.
• Vegetable oils, being polyunsaturated molecules, are partially hydrogenated through these reactions to raise their molecular weight (M_r) and transform them into solid fats.
  
• Alkenes can undergo addition reactions with steam, leading to the formation of alcohols.
• This process, often referred to as hydration reaction, involves the addition of water molecules to the alkene.
• Industrially, this reaction holds significant importance for the production of alcohols.
• The reaction typically occurs under specific conditions: a temperature of approximately 300ºC, a pressure range of 60 to 70 atm, and the presence of a concentrated phosphoric acid catalyst.