CFCs & OTHER USES OF HALOgenoALKANES

Starter Gethin produces chloroethane, bromoethane and iodoethane in an experiment but forgot to label his test tubes. Typical Gethin. Devise a method for identifying the correct test tubes. Include any results you would expect to find.

Helping out Gethin Steps: Add sodium hydroxide (NaOH) to perform a nucleophilic substitution reaction. Add dilute nitric acid (HNO3) to neutralise the mixture Add silver nitrate (AgNO3) to create a precipitate A further test can be done with ammonia (NH3) to be completely sure. Halogen in halogenoalkane Addition of Ag+(aq) Addition of NH3 (aq) to precipitate formed Chlorine White precipitate Dissolves in dilute NH3 Bromine Cream precipitate Dissolves in conc NH3 Iodine Yellow precipitate Does not dissolve in NH3

Uses of Halogenoalkanes Solvents - Halogenoalkanes contain a polar section (carbon halogen bond) and non-polar region (presence of alkyl chain). Can mix with polar and non-polar organic substances so therefore useful as solvents. Non-flammable – dry cleaning and other processes involving degreasing. Examples include tetrachloromethane CCl4 and tetrachloroethene, CCl2=CCl2

Uses of halogenoalkanes Anaesthetics – halogenoalkanes are often used before surgical procedures as ‘knock out’ drugs. Trichloromethane CHCl3 (chloroform). ‘Mickey Finn’ – 2,2,2-trichloroethane-1,1-diol, CCl3CH(OH)2 (choral hydrate). Halothane, CF3CHBrCl still used.

USES of halogenoalkanes Task: Highlight any key points Create paragraph headings Answer the knowledge check questions at the bottom.