Reactions, Reagents, and Conditions

• Alkanes do not react with:

  • Acids
  • Bases
  • Oxidising or reducing agents
• Cracking involves breaking a long chain hydrocarbon into shorter chain hydrocarbons
• In cracking, the chain is split into an alkene and alkane
• Thermal cracking needs a temperature between 700-1200K and 700kPn
• Hydrogenation

  • Needs a nickel catalyst
  • 150C
  • Used to manufacture magarine
• Halogenation:

  • Room temperature
  • Room pressure
  • Can also be called chlorination or bromination
• Hydration:

  • Phosphoric acid catalyst
  • Heated so water becomes steam (usually 300C)
  • Products are ethanol and propanol
• Addition of hydrogen halides:

  • Room temperature
  • Room pressure
• Oxidation to diols:

  • Potassium manganate oxidising agent
  • Acidic conditions (usually sulfuric)
• Chlorination:

  • Posphorus (IV) chloride is used
  • Done at room temperature
  • Creates a haloalkane, HCl and phosphorusoxychloride
• Bromination:

  • Mixture of bromide with concentrated sulfuric acid
  • Needs to be warmed
• Iodination:

  • Phosphorus and iodine are used
  • Heated with alchohol under reflux
  • Forms a haloalkane and H3PO3
• Sulfur and oxygen makes sulfur dioxide and sulfur trioxide
• Sulfur dioxide and water make sulfuric acid
• When alkanes are combusted at very high temperatures, this can cause reactions with nitrogen in the air
• Nitrogen dioxide and water make nitric acid
• Oxidation to diols needs potassium manganate as an oxidising agent
• During the reaction of oxidation to diols, the colour changes from purple to colourless
• Haloalkanes are reactive due to the polarity of the halogen-carbon bond
• In hydrolysis, water is added to a haloalkane. The polarity of the water is attracted to the carbon-halogen bond.
• Homolytic fission is when a covalent bond breaks, 1 electron goes to each atom, forming 2 free radicals
• Heterolytic fission is when a covalent bond is broken and electrons are shared unevenly, forming 2 ions
• Initiation is a photochemical reaction
• In free radical subsitution reactions, halogenoalkanes can react further to produce di, tri and tetrahalogenoalkanes
• If you add more alkane to free radical substitution reactions, you reduce the chance of getting, di, tri, and tetra halogenoalkanes
• Catalytic cracking mainly produces aromatics
• Reforming needs a straight chain alkane and a platinum catalyst
• Alkenes to alchohols is addition with steam
• Alkenes to diols is oxidation using cold, acidified potassium manganate
• Haloalkanes to alcohols is nucleophilic substitution with aqueous alkali
• Haloalkanes to alkenes is elimination with ethanolic potassium hydroxide]
• Haloalkanes to amines is nucleophilic substitution with alcoholic ammonia
• Haloalkanes to nitriles is nucleophilic substitution with alcoholic potassium cyanide
• Alkenes to alcohols is hydration with phosphoric acid at 300C
• Halogenoalkanes with concentrated ammonia in ethanol in a seal tube make amines
• Halogenoalkanes heated under reflux in ethanol with potassium cyanide give nitriles
• Halogenoalkanes and water make alcohols
• Primary alcohols in dilute sulfuric acid and sodium dichromate make aldehydes
• Aldehydes heated under reflux in dilute sulfuric acid with potassium dichromate make carboxylic acids
• Secondary alcohols with potassium dichromate make ketones