Aromatic Compounds

What is an arene?

Aromatic hydrocarbon that has 1/more benzene rings

Who originally isolated benzene?

Michael Faraday

What is the molecular formula of benzene?

C6H6

Does benzene undergo addition reactions?

No

What did Kekule suggest for benzene?

cyclic structure

Give the 3 problems of Kekule’s model for benzene

Lack of reactivity, bond length, hydrogenation enthalpy

Does benzene have a higher or lower reactivity than predicted?

Lower

What does benzene having a higher enthalpy of hydrogenation suggest?

More stable than predicted

Why is benzene more stable than cyclohexane?

Has delocalised electrons in the pi system so reactions would need to disrupt the delocalised electron system

When does benzene undergo electrophilic substritution?

When reacted with a powerful electrophile

What does the reaction of benzene and nitric acid form?

Nitrobenzene + water

What is required for chlorination of benzene?

Use of a halogen carrier

What conditions are needed for hydrogenation of benzene?

Heat under pressure & nickel catalyst

What do arenes burn to give?

Sooty flames

What type of reactions are alkylation and acylation?

Friedel-Crafts reactions

Explain why phenol can act as a weak acid

Donates an H into the OH group, phenoxide ion stable as lone pair of electrons delocalised into ring

What is alkylation

Substitution of hydrogen with alkyl group

What is needed along with an acyl chloride for acylation?

AlCl3

What is a phenol?

Hydroxyl group directly attached to aromatic ring

Are phenols more or less soluble than alcohols?

Less

Do phenols fully or partially dissociate?

Partially dissociate

Are phenols more or less acidic than alcohols?

More

Can phenols react with metal carbonates?

No

Are phenols more or less reactive than benzene?

More

What is needed for the reaction of phenols with bromine water?

Halogen carrier

What is an activating group?

Group attached to aromatic ring causing compound to be more susceptible to electrophilic substitution

What is a deactivating group?

Group attached to aromatic ring causing compound to be less susceptible to electrophilic substitution

Explain why methylbenzene is more reactive than benzene (2)

• Alkyl groups donate electrons, increasing electron density

• Benzene more able to attack electrophiles