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Aromatic Chemistry
AQA A Level Chemistry
Question | Answer |
---|---|
Draw the structure that Kekule proposed for Benzene | |
What chemical test shows that Benzene molecules do not contain any double bonds? | It does not decolourise bromine water. |
Describe the shape and structure of a Benzene molecule in full | hexagon, planar, all carbon carbon bonds the same length. |
How do the carbon carbon bond lengths in a benzene molecule prove it cannot be made up of alternate double and single carbon carbon bonds. | All the carbon carbon bonds are the same length. |
The enthalpy of hydrogenation of cyclohexene is -120KJ/Mol, The enthalpy of hydrogenation of benzene is -208KJ/Mol. By how many KJ/Mol is Benzene more stable than you would expect | 152KJ/mol |
" What word describes how the electrons are delocalized (spread) across the whole Benzene molecule? | " Conjugation. |
How does valence bond theory describe the bonding in Benzene? | "unhybridized p-orbitals which overlap forming a cloud of electron density above and below the molecule. |
Give four pieces of evidence that Benzene does not contain the Kekule structure? | The carbon -carbon bond lengths are all the same, Benzene does not undergo electrophilic addition reactions, Benzene molecules are 152KJ/Mol more stable than the Kekule structure. |
What are the conditions required to convert Benzene to Cyclohexane by reaction with Hydrogen | Rayney Nickel Catalyst at 150oC |
Why do electrophiles that react with benzene have to be stronger than those that react with alkenes | "Because the mechanism involves an initial disruption to the ring. The delocalized electrons in the benzene ring make it more stable. |
What are the required reagents and conditions for the nitration of benzene. | "conc. nitric acid and conc. sulphuric acid (catalyst), reflux at 55°C |
Draw out the mechanism for the nitration of benzene | |
Write the equation for the formation of the nitrate electrophile when nitric acid reacts with concentrated sulfuric acid. | "2H2SO4 + HNO3 <----> 2HSO4¯ + H3O+ + NO2+ |
What are the reagents for the Friedel Crafts Alkylation of benzene | Reagents a halogenoalkane (RX) and anhydrous aluminium chloride AlCl3 |
What are the conditions for the Friedel Crafts Alkylation of benzene | "Conditions reflux ; dry inert solvent (ether) |
Write an equation for the Friedel Crafts Alkylation of benzene with chloroethane. | "C6H6 + C2H5Cl ———> C6H5C2H5 + HCl |
Draw out the mechanism for the Friedel Crafts alklyation by chloroethane. | |
What are the reagents for the Friedel Crafts Acylation of benzene | "Reagents an acyl chloride (RCOX) and anhydrous aluminium chloride AlCl3 |
What are the conditions for the Friedel Crafts Acylation of benzene | "Conditions reflux 50°C; dry inert solvent (ether) |
Write an equation for the Friedel Crafts Acylation of benzene by ethanoyl chloride | "C6H6 + CH3COCl ———> C6H5COCH3 + HCl |
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