alkenes

• What type of hydrocarbons are alkenes?

  Unsaturated hydrocarbons
• What does the presence of a carbon-carbon double bond in alkenes indicate?


  It indicates high electron density, making it susceptible to electrophilic attack
• What is the role of bromine water in identifying alkenes?

  It turns the solution from orange-brown to colourless if a double bond is present
• What is electrophilic addition in relation to alkenes?

  It is the reaction mechanism where electrophiles attack the double bond in alkenes
• What are electrophiles?


  Electron acceptors attracted to areas of high electron density
• Name three common electrophiles.


  HBr, Br₂, H₂SO₄
• What happens when the double bond in alkenes is broken during electrophilic addition?


  A carbocation forms, which is a carbon atom with only three bonds and a positive charge
• How does the stability of carbocations affect the products formed in an addition reaction?


  The more stable the carbocation, the more likely it is to form, leading to the major product being the most stable possible
• What is the mechanism for the formation of halogenoalkanes from alkenes?


  The π bond causes the bromine molecule to gain a temporary dipole, allowing electron transfer
• What product is formed when an alkene reacts with sulphuric acid?


  Ethyl hydrogensulphate
• What are addition polymers produced from?


  Alkenes where the double bond is broken to form a repeating unit
• How should the repeating unit of an addition polymer be represented?


  With extended bonds through brackets showing it bonds to other repeating units on both sides
• How do reaction conditions affect the properties of addition polymers?


  High pressures and temperatures produce branched chain polymers, while lower conditions produce straight chain polymers
• Why are addition polymers useful for manufacturing plastic products?


  They are unreactive hydrocarbon chains with multiple strong, non-polar covalent bonds
• What is an example of a product made from addition polymers?


  Shopping bags (poly(ethene))
• What is a significant environmental concern regarding addition polymers?


  They are not biodegradable and cannot be broken down by species in nature
• What is PVC more commonly known as?


  Poly(chloroethene)
• How does PVC gain waterproof properties?


  By the addition of plasticisers during the reaction