Alkenes

• What is the electronic configuration of carbon?

  1s 2s 2p
• Why do carbon atoms form four covalent bonds?

  To achieve a full outer shell configuration
• What types of bonds are formed when carbon atoms share electrons?

  Sigma bonds (σ) and pi bonds (π)
• What happens when carbon atoms form a σ bond?

  They use three electron pairs and have a p orbital
• How is a π bond formed between carbon atoms?

  By overlapping p orbitals sideways

  
• What is the bond angle in ethene?

  120 degrees
• How many σ bonds does each carbon atom in ethene form?

  Two with hydrogen and one with carbon

  
• What is the result of the overlap of two p orbitals in ethene?

  A π bond is formed

  
• What is a molecular orbital?

  A combined orbital containing two electrons

  
• How are σ bonds formed?

  By end-to-end overlap of atomic orbitals

  
• What is the electron density distribution in a σ bond?

  Symmetrical about the line joining nuclei
• How is a π bond represented?

  As two electron clouds above and below
• What restricts rotation in unsaturated compounds?

  The presence of a π bond
• What types of carbocations exist?

  Primary, secondary, and tertiary

  
• What is the inductive effect in carbocations?

  Electron donation from alkyl groups
• Which carbocation is the most stable?

  Tertiary carbocation

  
• What does Markovnikov's rule predict?

  The halogen bonds to the most substituted carbon
• What is electrophilic addition?

  Addition of an electrophile to a double bond
• What happens to the C=C double bond during electrophilic addition?

  It breaks to form new single bonds
• What is the nature of hydrogen bromide (HBr)?

  It is a polar molecule
• What occurs during the addition reaction of HBr to an alkene?

  The H atom acts as an electrophile

  
• What is formed when HBr reacts with an alkene?

  A highly reactive carbocation intermediate
• How does bromine behave when approaching an alkene?

  It becomes polarized due to electron density

  
• What happens to the Br-Br bond when bromine approaches an alkene?

  The bond breaks heterolytically

  
• What type of molecule is HBr?

  Polar molecule
• In an addition reaction, what role does the H atom play?

  Acts as an electrophile
• What happens to the H-Br bond during the reaction?

  It breaks heterolytically
• What is formed after the H-Br bond breaks?

  A Br^- ion
• What is created as a result of the reaction with the carbocation intermediate?

  A highly reactive carbocation intermediate
• Why is bromine (Br₂) considered a non-polar molecule?

  Atoms share electrons equally
• What happens when a bromine molecule approaches an alkene's double bond?

  Electron density repels Br-Br electron pair

  
• What charge does the closest Br atom acquire when near a double bond?

  Slightly positive charge
• What occurs to Br₂ in an addition reaction with an alkene?

  Closest Br atom acts as an electrophile

  
• What is the result of the Br-Br bond breaking?

  A Br^- ion is formed
• What is the stability order of carbocation intermediates?

  tertiary > secondary > primary

  
• What determines the major product of a reaction with multiple carbocations?

  Most stable carbocation's nucleophilic attack
• What is bromine water used for?

  Test for unsaturation
• What happens to bromine water when shaken with an unsaturated compound?

  It decolourises
• What is addition polymerisation?

  • Reaction of alkenes forming long polymer chains
  • Involves breaking π-bonds in C=C
  • Only one product is formed

  
• What is a polymer?

  A long-chain molecule of repeating units