Aromatic compounds 2 Flashcards
How does bromine react with an alkene?
The pi electron pair in the alkene molecule attacks the slightly positively charged bromine in the bromine molecule. The double bond in the alkene is broken and a new bond is formed between the alkene and the bromine.
Why does benzene not reaction with bromine without a catalyst?
It is due to the delocalised pi electron system in benzene molecules. This lowers the pi electron density and prevents the benzene molecule from being able to polarize the bromine molecule sufficiently to be able to break the br-br bond. This mean no reaction takes place without a catalyst.
What can be used as hydrogen carriers in bromination/chlorination?
Bromination: AlBr3, FeBr3
Chlorination: AlCl3, FeCl3
Bromination of benzene
Halogen carrier AlBr3 is used to produce the bromonium ion, Br(+), which is an electrophile.
The bromonium ion now reacts with benzene in an electrophilic substitution reaction.
The reaction produces H(+) which reacts with the AlBr4(_) to regenerate the AlBr3 catalyst
What is a phenol?
A compound that has a hydroxyl, OH, group attached to a benzene ring. The simplest phenol is benzenol. It dissolves in water to form a very week acid.
