Author: J R Reid Organics: Continued from Level 2…. Alcohols Haloalkanes

Alcohols - Oxidation Back in Level 2 organic chemistry we learnt that alcohols come in three main forms: Primary Secondary Tertiary We also found out that primary alcohols can be oxidised to form carboxylic acids Later we will discover that primary alcohols can be partially oxidised to form a group called aldehydes. Then the aldehydes can be oxidised further to form carboxylic acids: This year we will also discover that secondary alcohols can be oxidised to form ketones:

Alcohols - Substitution This year we are introduced to a new set of chemicals that add chlorine to organic chemicals. Two of these are: PCl 5 – phosphorus pentachloride SOCl 2 – thionyl chloride These can be used to substitute the –OH group in an alcohol with a –Cl: CH 3 OH + PCl 5  CH 3 Cl + POCl 3 + HCl CH 3 OH + SOCl 2  CH 3 Cl + SO 2 + HCl

Haloalkanes Last year we also discovered a few things about haloalkanes, like the facts that: They are made by halogenating unsaturated hydrocarbons We can also use hydrogen halides to create halo alkanes from unsaturated hydrocarbons When hydrohalogenation occurs, we must work out where the H and the halogen get placed. To do this we follow Markovnikov’s rule (Birds of a feather flock together – in this case, the hydrogen will ‘flock’ closest to the most hydrogens that it can) Major product Minor product

Haloalkanes – Substitution Some chemicals have the ability to remove the halogens from a haloalkane. These chemicals have a strong attraction to positive nuclei, we therefore call them nucleophiles (nucleus friend) Three good nucleophilic substituters are: Hydroxide Water Ammonia (dissolved in alcohol – not water)

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 (just like the NH 3 in the substitution section) We have a similar rule (to the Markovnikov rule) to follow so that we can determine where the double bond goes: The hydrogens still like to ‘flock’ together in the largest amount possible: