Phenols Flashcards
What is a phenol?
A class of aromatic compounds with a hydroxyl group directly bonded to a benzene ring.
What is the simplest phenol?
C6H5OH (phenol itself)
Why are phenols weakly acidic?
They are slightly soluble in water and partially dissociate.
C6H5OH <—> C6H5O- + H+
We are left with a phenoxide compund
What is phenols acidity in comparison to ethanol and carboxylic acids?
More acidic than ethanol but less acidic than carboxylic acids.
So, ethanol does not react with strong or weak bases (NaOH vs Na2CO3).
Phenol reacts with strong bases but not with weak bases.
Carboxylic acids will react with strong bases AND weak bases
What is the reaction of phenols with sodium hydroxide?
Salt and water, neutralisation reaction
How do phenols react with bromine?
Reacts with aqueous bromine in an electrophilic substitution reaction to form a white precipitate of 2,4,6-tribromophenol and Hydrogen bromide.
How do phenols react with Nitric acid?
Reacts with DILUTE HNO3 at ROOM TEMP to form a mixture of 2-nitrophenol and 4-nitrophenol.
What is the difference for when benzene vs phenol react with nitric acid?
For benzene nitric acid must be concentration and concentrated sulphuric acid catalyst is needed and a temp of 50-55 degrees is needed.
With phenol we only need dilute nitric acid and room temperature
Why is phenol more reactive than benzene?
Due to the presence of a lone pair of e- in the oxygen p orbital of the hydroxyl group. This becomes delocalised into the delocalised ring of pi electrons, increasing the e- density of the ring. It is able to polarise/attract electrophiles more easily than benzene.
