4. alkenes

• What type of hydrocarbons are alkenes?

  Unsaturated hydrocarbons
• What is the general formula for alkenes?

  C$n$H$2n$
• What do alkenes contain that makes them unsaturated?

  One or more double bonds
• What type of reactions do alkenes undergo?

  Addition reactions
• What is the structural formula for ethene?

  • Ethene: C$2$H$4$
  • Structural formula: H$2$C=CH$2$
• What is the structural formula for buta-1,3-diene?

  • Buta-1,3-diene: C$4$H$6$
  • Structural formula: H$2$C=CH-CH=CH$2$
• Why are alkenes reactive?

  They have high electron density in double bonds
• What are cycloalkenes?

  Cyclic alkenes with two fewer hydrogens
• What is the electrophile in addition reactions of alkenes?

  An electron pair acceptor
• What are examples of electrophiles?

  H+, polar molecules
• What do curly arrows represent in reaction mechanisms?

  The movement of electron pairs
• What happens when bromine water is added to an alkene?

  It decolorizes, indicating an alkene
• What is formed when bromine reacts with an alkene?

  A dibromoalkane
• How does a dipole form in a bromine molecule near an alkene?

  Electrons shift due to electron repulsion
• What is a carbocation intermediate?

  A positively charged carbon species
• What is the role of sulfuric acid in alkene reactions?

  It acts as a catalyst
• What are the types of carbocations based on stability?

  • Primary: One alkyl group
  • Secondary: Two alkyl groups
  • Tertiary: Three alkyl groups
  • Tertiary is the most stable
• What is the product when an unsymmetrical alkene reacts with hydrogen halides?

  Two different halogenoalkanes
• How does the stability of carbocation affect product formation?

  More stable carbocations lead to major products
• What is the mechanism for converting alkenes to alcohols using sulfuric acid?

  1. Alkene reacts with sulfuric acid
  2. Forms alkyl hydrogen sulfate intermediate
  3. Hydrolysis produces alcohol
• What is the product formed when alkenes react with cold concentrated sulfuric acid?

  Alkyl hydrogen sulfates
• What role does sulfuric acid play in the reaction with alkenes?

  It acts as a catalyst
• What is formed from an alkene when sulfuric acid is used?

  An alcohol
• What is the intermediate formed during the reaction of alkenes with sulfuric acid?

  Alkyl hydrogen sulfate
• How does sulfuric acid interact with alkenes in the reaction mechanism?

  It forms a carbocation intermediate
• What is the process called when alkyl hydrogen sulfate is converted to ethanol?

  Hydrolysis
• What does the term "hydrolysis" mean in this context?

  Breaking a bond using water
• What happens when cold water is added to ethyl hydrogen sulfate?

  It forms ethanol and regenerates sulfuric acid
• What is the significance of sulfuric acid being regenerated in the reaction?

  It confirms sulfuric acid is a catalyst
• What type of alkenes can produce two products during the reaction?

  Asymmetric alkenes
• What are alkenes classified as in the context of polymer production?

  Monomers
• What process do monomers undergo to form polymers?

  Addition polymerization
• What are examples of natural and synthetic polymers?

  • Natural: Proteins, natural rubber
  • Synthetic: Polyethylene, polypropylene
• Who discovered vulcanized rubber?

  Charles Goodyear
• What was the purpose of adding chemicals to natural rubber?

  To make it harder wearing
• What are some common uses of synthetic polymers?

  Water bottles, electrical wiring
• What happens to the properties of PVC when plasticizers are added?

  It becomes more flexible
• What is the effect of chain length on the melting point of polymers?

  Longer chains have higher melting points
• What type of intermolecular forces are present in most polyalkene chains?

  Van der Waals forces
• How does branching affect the properties of polymer chains?

  More branching leads to flexibility and weakness