Aromatic Compounds Flashcards
Describe benzene
Six carbon ring
Highly flammable
Component of crude oil and petrol
Carcinogenic
Describe kekules model of benzene
Alternating double bonds
Why was kekules model disproved
The reactivity, bond length and enthalpy of hydrogenation could not be explained
Describe how the reactivity of benzene is not explained by kekules model
Resistance to reaction
Doesn’t undergo electrophillic addition
Doesn’t decolorise bromine water
Describe how the bond lengths in benzene is not explained by kekules model
Bond lengths of benzene are between single and double bonds
All Same length
What is used to measure bond lengths
X Ray diffraction
Describe how the enthalpy change of hydrogenation of benzene is not explained by kekules model
Should be 3x that of cyclo hexene but is not as exothermic
Benzene is more stable
Describe the de localised model of benzene
All bonds are same length between double and single bonds
Pi system because of overlap of p orbitals (de localised ring )
What type of reaction does benzene undergo, why
Electrophillic substitution
Not addition because no double to break
What conditions are required for nitration
50 degrees sulphuric acid catalyst and nitric acid
What conditions are needed for polysubstitution of nitrate
Temp of greater than 50
What are the uses of nitro benzene
Dyes pharmaceuticals and pesticides
Why are arenes less reactive than alkenes
De localised electrons (not localised like in alkenes) means less electron density to un able to polarise
Name the reagents needed for the Halogenation of benzene
Halogen carrier
What are the reagents needed for alkylation of benzene
Haloalkane
Halogen carrier
What is a Halogen carrier
Iron or aluminium chloride or bromide
What is acylation
Formation of aromatic ketone
What is phenol
Benzene with an alcohol group
Compare the acidity and solubility of phenol compared to alcohols
Phenol is less soluble and more acidic
Benzene is non-polar
Is a phenol a weak or strong acid and why
Weak as it partially dissociate to produce a phenoxide ion
How do you distinguish between an alcohol, phenol and a carboxylic acid
Carboxylic acid is the only one to react with sodium carbonate to produce carbon dioxide
Phenol only reacts with sodium hydroxide
Alcohols don’t react with either
What salt is produced when phenol reacts with naoh
Sodium phenoxide
By what mechanism does phenol react with halogens
Electrophillic substitution
Why is phenol more reactive than benzene
OH has a lone pair which is delocalised into the pi system increasing the electro density of it polo rising halogens easier
