Organics: Level 3 Haloalkanes

Name used in Haloalkane Haloalkanes –yr12 recap Also called ALKYL HALIDES one hydrogen atom replaced with a halogen (substitution reaction) Named the same way as alkanes with a prefix for the halogen The position on the parent chain Names in alphabetical Order if more than one type of halogen Use prefixes di, tri if more than one halogen Atom Name used in Haloalkane bromine bromo chlorine chloro fluorine fluoro iodine iodo

Draw and Name: CH3CBr(CH3)CHBrCH3 Parent chain Halogen atoms Side chain

Haloalkanes- yr12 recap

Haloalkane properties Slightly polar molecules Low polarity slightly soluble in water MP and BP depend on molar mass and shape of the molecule as these affect the strength of intermolecular bonding Chloromethane and chloroethane are gases Most of the other up to C6 are liquid

Haloalkane - uses Uses Solvents eg tetrachloromethane for drycleaning, 1,1,1 trichloroethane is twink Chloroform is an anaesthetic Used as monomers ie chloroethene for PVC, teflon from tetrafluromethane CFC’s as aerosol propellants but now banned.

Haloalkane - preparation FAST:- Alkene + HX ----> haloalkane (Addition ) Requires heat/Pt   SLOW: Alkane + Halogen( X2) --- haloalkane + HX ( substitution) requires UV light Alcohol + Lucas Reagent -- haloalkane + H2O zinc chloride catalyst Alcohol with PCl3, PCl5 SOCl2

Haloalkanes- preparation Also addition reaction When hydrohalogenation rxn with an alkene occurs, Remember Markovnikov’s rule Minor product Major product

Haloalkanes - Elimination Major product Minor product

Haloalkanes - Elimination The halogen can also be removed (eliminated) from the haloalkane leaving an alkene behind The reagent used in this process is KOH or NaOH dissolved in alcohol (not dilute which is used for substitution -> alcohol)

Haloalkanes- Substitution Substitution and elimination are due to the C-X bond that gives the carbon atom in a haloalkane has a slight positive charge, which attracts nucleophiles These are molecules or ions characterised by having a lone pair of electrons and which seeks a positive centre

Haloalkanes – Substitution Halogen is replaced by a group that is negatively charged or carries a lone pair nucleophile Hydroxide ion replaces a halogen forming an alcohol (dilute KOH is used)

Haloalkanes – Substitution Using conc ammonia forms an aminoalkane (amine) –NH2 replaces the halogen, require high pressure and conc ammonia to be dissolved in ethanol 1o amine formed can further react with chloroalkane to form 2o aminoalkane