Alkenes

• What atoms do alkenes contain?

  C and H atoms only
• What is the minimum number of double bonds in alkenes?

  At least one double bond
• Why are alkenes more reactive than alkanes?

  Due to the presence of a double bond
• What forms a pi (π) bond in a C=C double bond?

  Sideways overlap of p orbitals
• What do electrophiles seek in chemical reactions?

  Electrons to form bonds
• What is the product when ethene reacts with bromine?

  1,2-dibromoethane
• What is the reaction equation for ethene and bromine?

  C₂H₄ + Br₂ → C₂H₄Br₂
• What is the reaction equation for ethene and hydrogen bromide?

  C₂H₄ + HBr → C₂H₅Br
• What is the first step when ethene reacts with sulfuric acid?

  The double bond attacks the H_δ+
• What is formed after ethene reacts with sulfuric acid?

  Ethyl hydrogen sulfate
• What is the reaction equation for ethene and sulfuric acid?

  C₂H₄ + H₂SO₄ → C₂H₅OSO₃H
• What is the bromine water test used for?

  To test for carbon-carbon double bonds
• What happens to bromine water when added to an alkene?

  It decolourises, forming a colourless solution
• What happens to bromine water when added to an alkane?

  It remains orange
• What is formed when the double bond in ethene is broken by H_δ+?

  A carbocation intermediate
• What does the Br^- ion do after the carbocation is formed?

  It attacks the carbocation, donating electrons
• What is the product formed when ethene reacts with HBr?

  Bromoethane
• What is the stability order of carbocations?

  Tertiary > Secondary > Primary
• How do alkyl groups affect carbocation stability?

  More alkyl groups increase stability
• What is the major product formed from propene and HBr?

  2-bromopropane
• What is the minor product formed from propene and HBr?

  1-bromopropane
• What carbocations are formed when 2-methylbut-2-ene reacts with HBr?

  Secondary and tertiary carbocations
• What is the major product formed from 2-methylbut-2-ene and HBr?

  2-bromo-2-methylbutane
• What is the relationship between carbocation stability and product formation?

  More stable carbocations lead to major products
• Who discovered the rule that predicts major products in electrophilic addition?

  Vladimir Markovnikov
• What type of alkene is propene?

  Unsymmetrical alkene
• What can occur due to the lack of symmetry in unsymmetrical alkenes?

  Multiple products in addition reactions
• What is the effect of different groups on the ends of the double bond in unsymmetrical alkenes?

  They can lead to different carbocations
• What happens when the positive charge is on the end carbon atom of propene?

  A primary carbocation forms
• How does the number of alkyl groups affect carbocation stability?

  More alkyl groups increase stability
• What is the trend in stability among primary, secondary, and tertiary carbocations?

  Tertiary > Secondary > Primary
• What is the major product formed from propene and HBr?

  2-bromopropane
• What is the significance of Markovnikov's rule in electrophilic addition reactions?

  It predicts the formation of major products