3.3.4.2 Addition reactions of alkenes

• Name all the addition reactions of alkenes

  Combustion, hydrogen, halogen, halides, steam, potassium mangante
• Why will akenes burn with a smokier flame than an alkane

  Higher percentage of carbon, more incomplete combustion
• Which addition reaction is reversible

  Steam
• Addition reaction of hydrogen

  Reagent hydrogen, conditions nickel catalyst, temperature 150, product alkanes
• Addition reaction of halogen

  Reagent bromine, room temperature, product is dihaloalkanes, colour change orange to colourless
• For the addition reaction of halogens, bromine needs to be

  Dissolved in organic solvent
• Addition reaction of hydrogen halides

  Reagent HCl, HBr, HI, room temperature, product halogenalkane
• Alkenes can be converted to

  Alcohol
• Addition of steam

  Reagent steam, conditions acid catalyst concentration H3PO4, temperature 300-600, pressure 70atm, product alcohols, reaction is reversible
• Alkenes can be oxidisied by potassium manganate to form

  Diols
• Bromination of alkenes

  Aqueous Br dissolved in organic solvent, room temperature, orange to colourless
• Why do akenes undergo addition reactions?

  Unsaturated HC, contain C=C double bond which has a high electron density, so more susceptible to attack by electrophiles
• Define an electrophile

  Accepts lone pairs
• Why are electrophiles attracted to alkenes

  C=C double bond has a high electron density causing attration
• Define a carbocation

  Carbon that carries a positive charge
• What is an intermediate

  A molecule that forms in the middle of a step-wise reaction mechanism
• What is an alkyl group

  Group or chain of carbon atoms