Reactions

• What is meant by a functional group?

  The part of a molecule that determines how it reacts
• What is a homologous series?

  A series of compounds with the same functional group and a gradual change in physical properties
• What is a homologous series in chemistry?

  A series of compounds with the same functional group
• What is the functional group of alkenes?

  The double bond
• What do all alkenes have in common?

  They all have a carbon to carbon double bond
• How do all alkenes react?

  They react in the same way due to having the same functional group
• How does the structure of members of a homologous series change?

  Each molecule has an extra carbon atom and two extra hydrogen atoms
• What reaction of alkenes was discussed in the last video?

  The combustion of alkenes
• What is the process of combustion?

  Burning
• What is the term used for the reaction of alkenes with water?

  Hydration
• What products are formed when alkenes are combusted?

  Carbon dioxide and water, along with unburned carbon particles
• What product is formed when ethene reacts with water?

  Ethanol
• What form must water be in for the hydration of alkenes?

  Steam
• What is incomplete combustion?

  A process that produces unburned carbon particles along with carbon dioxide and water
• What are the conditions required for the hydration of ethene?

  Temperature around 300 degrees Celsius and pressure around 70 atmospheres
• What catalyst is used in the hydration of alkenes?

  Phosphoric acid
• Why is the hydration reaction of alkenes considered reversible?


  Unreacted ethene and steam can be passed back through the catalyst
• How do alkenes burn in air?

  They burn with a smokey flame due to incomplete combustion
• What is the second key reaction of alkenes?

  The reaction of alkenes with hydrogen, known as hydrogenation
• What temperature is required for the hydrogenation of alkenes?

  A temperature of around 150° C
• What happens to the double bond in alkenes during hydration?

  The double bond turns into a single bond
• What is the reaction of alkenes with halogens called?

  Halogenation
• What catalyst is used in the hydrogenation of alkenes?

  A nickel catalyst
• What product is formed when ethene reacts with chlorine gas?

  Dichloroethane
• How do halogens react with alkenes?

  They react rapidly with alkenes
• What happens to the double bond during the hydrogenation of alkenes?

  The carbon to carbon double bond is converted into a carbon to carbon single bond
• What is formed when ethene reacts with bromine?

  Dibromoethane
• What alkane is produced when ethene reacts with hydrogen?

  Ethane
• What is formed when ethene reacts with iodine?

  Diiodoethane
• What are the key reactions of alkenes that students should learn for exams?

  • Reaction with water (hydration)
  • Reaction with halogens (halogenation)
• What are the key reactions and conditions for alkenes that students should learn for their exams?

  • Combustion of alkenes produces carbon dioxide, water, and unburned carbon particles (incomplete combustion).
  • Hydrogenation of alkenes requires:
  • Temperature: ~150° C
  • Catalyst: Nickel
  • Converts double bond to single bond, producing alkanes.
• What are the conditions for the hydration of alkenes?

  • Water must be in the form of steam
  • Temperature around 300 degrees Celsius
  • Pressure around 70 atmospheres
  • Phosphoric acid as a catalyst
• What is the significance of the double bond in alkenes during reactions?

  • The double bond allows for addition reactions
  • It is converted to a single bond during hydration and halogenation