Aromatic Compounds

Question 1

What are arenes?

Answer 1

are hydrocarbons based on benzene

Question 2

What is benzene?

Answer 2

are a 6 member planar ring in a delocalised system of pi electrons above and below the ring

Question 3

What is the electrophilic, bromination & nitration of benzene?

Answer 3

the delocalised system of pi electrons have a high electron density, it is exposed to attack by electrophilic reagents

benzene react with bromine in the presence of a catalyst of iron bromide

benzene reacts with a mixture of concentrated nitric and concentrated sulphuric acid

Question 4

Describe the nitration of methylbenzene

Answer 4

methylbenzene reacts with the same electrophiles as benzene but its slightly less reactive and a mixture of isomers is obtained eg methyl 2 nitrobenzene etc

Question 5

Describe the bromination and nitration of methylbenzene

Answer 5

in the presence of halogens, bromine acts as an electrophilic reagent, a bromine atom is substituted in the position of the 2,4 of the benzene ring, a mixture of isomers is obtained, the methyl group again 2,4 is re directing

Question 6

Describe the bromination and nitration of nitrobenzene

Answer 6

nitrobenzene reacts with the same electrophiles as benzene but its less reactive and a 3 isomer is obtained

Question 7

What is reduced with the reaction of tin and hydrochloric acid of nitrobenzene?

Answer 7

nitrobenzene is reduced to phenyl amine with the reaction of tin and concentrated hydrochloric acid

Question 8

Give an introduction to phenol

Answer 8

C6H5OH has an OH atom attached directly to a benzene ring in place of a hydrogen atom
Phenol is also largely soluble in water because the large aryl group minimises with hydrogen bonding with water

Question 9

What are ways OH group reacts with phenols?

Answer 9

reaction with alkalis & sodium
reaction with acyl halides

Question 10

Describe the reactions

Answer 10

alkalis and sodium- alcohol does not react with sodium but phenol does because of its acidic nature, it reacts with alkalis to form a salt and water
phenol reacts with sodium to form sodium phenoxide and hydrogen

acyl halides- reacts with carboxylic acids with PCL5. Acyl reacts with phenol to form esters. The OH bond is broken, fumes of HCL is released

bromine(substitution reaction)- reacts rapidly with phenol, a white precipitate 2,4 tribromophenol is formed, no halogen carrier is needed

Question 11

Describe diazotisation and coupling reactions

Answer 11

diazotisation- phenalymine C6H5NH2 an aromatic acid reacting with nitric acid in hydrochloric acid to form a diazonium salt, must stay below 10 C to avoid decomposing to nitrogen

coupling- benzenediazonium chloride reacts with phenol to produce an orange colour, it must stay below 10 C to avoid being decomposed to diazonium