Alkenes

• What type of hydrocarbons are alkenes?

  Unsaturated hydrocarbons
• What is the significance of the carbon-carbon double bond in alkenes?

  It creates an area of high electron density that is susceptible to electrophilic attack
• What is used to identify the presence of a double bond in alkenes?

  Bromine water
• What color change occurs when bromine water reacts with an alkene?

  It turns from orange-brown to colourless
• What type of reaction do alkenes undergo at the double bond?

  Electrophilic addition
• What are electrophiles?

  Electron acceptors attracted to areas of high electron density
• Name three common electrophiles that react with alkenes.

  HBr, Br₂, H₂SO₄
• What products can be formed from the electrophilic addition of alkenes?

  Alkyl hydrogensulphates or halogenoalkanes
• What happens to the double bond during electrophilic addition?

  The double bond is broken, forming a carbocation
• What is a carbocation?

  A carbon atom with only three bonds and a positive charge
• How does the stability of carbocations vary?

  Tertiary carbocations are the most stable, while primary are the least stable
• What determines the major product in an addition reaction involving alkenes?

  The stability of the carbocation formed during the reaction
• What effect does the π bond have on a bromine molecule during the reaction?

  It causes the bromine molecule to gain a temporary dipole
• What is produced when an alkene reacts with sulphuric acid?

  Ethyl hydrogensulphate
• What are addition polymers produced from?

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

  With extended bonds through brackets showing it bonds to other units
• How do reaction conditions affect the properties of produced polymers?

  High pressures and temperatures produce branched polymers, while lower conditions produce straight-chain polymers
• What type of forces do branched chain polymers have?

  Weak intermolecular forces
• What type of forces do straight-chain polymers have?

  Strong intermolecular forces
• Why are addition polymers useful for manufacturing plastic products?

  They are unreactive hydrocarbon chains with strong, non-polar covalent bonds
• What is a common example of an addition polymer used in everyday products?

  Poly(ethene), used for shopping bags
• What is a major environmental concern regarding addition polymers?

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

  Poly(chloroethene)
• What property does PVC gain from the addition of plasticisers?

  Waterproof properties