Reactions of Alkenes (T)

• What is meant by a functional group in chemistry?

  It is the part of a molecule that determines how it reacts.
• What is a homologous series?

  A series of molecules that all have the same functional group.
• What is the functional group of alkenes?

  A carbon to carbon double bond.
• What characterizes members of a homologous series?

  • Same functional group
  • Each molecule has an extra carbon atom and two extra hydrogen atoms
• Why do alkenes react in a similar way?

  Because they all contain a carbon to carbon double bond.
• What is combustion in the context of alkenes?

  Combustion means burning.
• What products are formed when alkenes are combusted?

  Carbon dioxide and water, along with unburned carbon particles.
• What is incomplete combustion?

  It is when alkenes burn in air with a smoky flame due to insufficient oxygen.
• What is the second key reaction of alkenes?

  Reaction with hydrogen, known as hydrogenation.
• What conditions are required for the hydrogenation of alkenes?

  A temperature of around 150°C and a nickel catalyst.
• What happens to the double bond during the hydrogenation of an alkene?

  • The carbon to carbon double bond is converted into a carbon to carbon single bond.
  • Two hydrogen atoms add across the double bond.
• What is produced when an alkene reacts with hydrogen?

  An alkane.
• How does the reaction of ethene with hydrogen change its structure?

  It converts ethene into ethane by changing the double bond to a single bond.
• What is the functional group of alkenes?

  Double bond
• What is the significance of the functional group in a homologous series?

  • Determines the chemical properties
  • All molecules in the series react similarly
• What is the reaction of alkenes with water called?

  Hydration
• What are the conditions required for the hydration of ethene?

  Steam, 300 degrees Celsius, 70 atmospheres, and phosphoric acid as a catalyst
• Why is the hydration reaction of ethene considered reversible?

  Because unreacted ethene and steam can be passed back through the catalyst
• What happens to the double bond in alkenes during the reaction with halogens?

  • The double bond turns into a single bond
  • Halogen atoms add across the double bond
• What are the halogens that react with alkenes?

  Chlorine, bromine, and iodine
• What is the product formed when ethene reacts with chlorine gas?

  Dichloroethane
• What is the product formed when ethene reacts with bromine?

  Dibromoethane
• What is the product formed when ethene reacts with iodine?

  Diiodoethane
• What are the general characteristics of the reaction between alkenes and halogens?

  • No special conditions required
  • Alkenes react rapidly with halogens
  • Halogens add across the double bond