Alkenes

• What type of hydrocarbons are alkenes?

  Unsaturated hydrocarbons
• What is the general formula for alkenes?

  CnH2n
• What structural feature defines alkenes?

  They contain a carbon-carbon double bond

  
• What is the bond angle around the C=C double bond in alkenes?

  120 degrees
• When should numbers be added to the names of alkenes?

  When positional isomers can occur
• What type of bonds does a C=C double bond consist of?

  One sigma bond and one pi bond

  
• Why are π bonds vulnerable to electrophiles?

  They have high electron density
• What are stereoisomers?

  Same structural formulae, different spatial arrangement
• What type of isomerism can alkenes exhibit?

  E-Z stereoisomerism
• What causes E-Z isomers to exist?

  Restricted rotation around the C=C bond
• What is the difference between but-1-ene and but-2-ene regarding E-Z isomerism?

  But-1-ene has no E-Z isomers
• How are E-Z isomers named based on priority groups?

  Priority atom with higher atomic number is first
• What does the label Z indicate in E-Z isomerism?

  Priority atoms on the same side
• What does the label E indicate in E-Z isomerism?

  Priority atoms on opposite sides
• What is the role of electrophiles in alkenes' reactions?

  They are electron pair acceptors
• What happens to the double bond in alkenes during addition reactions?

  It is converted to a single bond
• What is the product of bromine reacting with an alkene?

  Dihalogenoalkane
• What conditions are required for the reaction of bromine with alkenes?

  Room temperature, not in UV light
• What occurs when Br2 approaches an alkene?

  It induces a dipole and becomes electrophilic
• What is a carbocation?

  An intermediate with a positive charge on carbon
• What is the product when hydrogen bromide reacts with an alkene?

  Halogenoalkane
• What is Markownikoff’s Rule?

  Bromine adds to the carbon with fewer hydrogens
• What is the stability order of carbocations?

  Tertiary > secondary > primary
• How does the stability of carbocations affect product formation?

  More stable carbocations lead to major products
• What is the first stage of the reaction of sulfuric acid with alkenes?

  Alkene to alkyl hydrogensulfate
• What is hydrolysis in the context of alkenes?

  Splitting a molecule by adding water
• What is the purpose of bromine water in testing for alkenes?

  It decolourises in the presence of a double bond
• What is the industrial method for converting alkenes to alcohols?

  Direct hydration with water and acid catalyst
• What are the essential conditions for industrial hydration of alkenes?

  High temperature and high pressure
• What is the overall role of sulfuric acid in the hydration of alkenes?

  It acts as a catalyst
• What is addition polymerisation?

  Formation of addition polymers from alkenes
• What is the repeating unit in addition polymers?

  Derived from the monomer structure
• What happens to poly(alkenes) due to strong C-C and C-H bonds?

  They are unreactive
• What effect does adding a plasticiser have on PVC?

  Increases flexibility by weakening intermolecular forces
• What is poly(chloroethene) used for?

  Waterproof and electrical insulation
• How does pure poly(chloroethene) differ from plasticised PVC?

  Pure is rigid, plasticised is flexible
• What are the areas of high electron density in alkenes called?

  Double bonds
• What type of reactions do alkenes undergo?

  Addition reactions
• What is the change in functional group when bromine reacts with alkenes?

  • Alkene to dihalogenoalkane
• What is the reagent used in the reaction of bromine with alkenes?

  Bromine