Haloalkanes Revision Cards (AQA Module 2)

To convert an Alkane into a Haloalkane, it must be reacted with Cl radicals.

It has a three step process

1. Initiation- making radicals (by reacting chlorine molecules with UV light)

2. Propagation- Making products (by reacting haloalkane with Cl radicals)

3. Termination- Getting rid of radicals (by reacting hydrogen radicals (extra product of initiation) with chlorine radicals)

This is a free radical mechanism.

To convert an Alkene into and Alkane, simply hydrogen must be added and it must react with a Nickel catalyst.

This process is called hydrogenation (and/or reduction)

To convert a haloalkane into an alcohol, you must react your haloalkane with aqueous sodium hydroxide.

The mechanism of Nucleophilic substition takes place, as the OH^-acts as a nucleophile (an ion or group of atoms with a negative charge that takes part in an organic reaction by attacking an electron deficient area in another reactant)

E.g. R-X + OH^- -> ROH + X^-

This is another nucleophilic substitution and the reactant used is CN ion (a.k.a Cyanide)

The CN attacks the carbon atom, causing the bond to break between it and the halogen. This halogen is kicked off of the molecule and is replaced by the CN ion.

This nitrile has one more carbon atom that the starting haloalkane.

Ammonia is used for this nucleophilic substitution as the nucleophile.

It is carried out under pressure and the ammonia is in ethanol.

Ammonia is a nucleophile because it has a lone pair of electrons that it can donate (although it has no negative charge) and the nitrogen atom has a δ- charge.

The only reaction that has a mechanism called elimination in the AQA module. It is called this because a hydrogen halide is eliminated from the molecule, leaving a double bond in its place so that an Alkene is formed.

KOH in ethanol is used. The OH ion acts as a base, which removes a H+ ion from the haloalkane.

To test that an alkene is made from an elimination reaction, add a few drops of bromine to the product. You should find that if a successful reaction has occured the bromine decolourises.

[These aren't specifically on the syllabus, however AQA sometimes ask questions on them in the exams, so it would be a good idea to read further into these reactions]

Nitriles to carboxylic acid (Hydrolysis): Water or hydrogen ions are reacted with nitriles to form carboxylic acid. This is hydrolysis due to the use of hydrogen.

Nitriles to amine (Reduction): Hydrogen molecules and a nickel catalyst are reacted with the nitrile to form amines. This is reduction because the atoms gain electrons.