haloalkanes

• reactions with aqueous silver nitrate

  -will result in formation of ppt

  -fluorines - no ppt

  -chlorides - white ppt (silver chloride)

  -bromides - cream ppt (silver bromide)

  -iodides - pale yellow ppt (silver iodide)

  -formation of silver iodide is fastest sub

  -formation of silver fluoride is the slowest

  least reactive fluoroalkanes

  chloroalkanes

  bromoalkanes

  most reactive iodoalkanes
• measuring rate of hydrolysis

  -three test tubes in 50degree water baths with a mixture of ethanol and acidified silver nitrate

  -few drops of a chloro, iodo and bromoalkane to each test tube and start timer

  -time how long it takes for precipitate to form

  -chloro - white

  -bromo- cream

  -iodo - yellow

  -yellow will form fastest, C-I bond is the weakest

  -white will form slowest, C-Cl bond is the strongest
• ozone depletion - fluorohalogenoalkanes

  -most common haloalkane is chlorofluorocarbons (CFCs)

  -contain carbon with Cl and F atoms e. CCl3F, CCl2F2

  -CFCs have many uses due to their chemical inertness as they are non flammable and non toxic

  -refrigerators

  -propellants for aerosols

  -solvent for dry cleaning
• ozone depletion: hydrofluorocarbons

  -HFCs contain a carbon attached to H and F only eg. CH2F-CF3

  -HFCs are also chemically inert and used for a wide range of purposes
• haloalkanes and the ozone layer

  -CFCs absorb lots of UV in the upper atmosphere

  -CFCs are broken down by UV causing formation of chlorine radicals

  -these radicals react with the ozone and break it down

  -HFCs are often used as an alternative to CFCs because they don't contain any chlorine and will not effect ozone