Organic Chemistry: arenes -5
- Created by: Shannon
- Created on: 16-04-15 09:24
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- Arenes
- Reactions of benzene
- Nitration
- Concentrated nitric and sulphuric acid
- HNO3 + H2SO4 -> HSO4- + NO2+ + H2O
- Harsh conditions needed in order to form electrophile
- Concentrated nitric and sulphuric acid
- Bromination
- Br2 + FeBr3
- Chlorination
- Cl2 + FeCl3
- Freidel crafts acylation
- AlCl3 + O=R-Cl
- Freidel crafts akylation
- AlCl3 + R-Cl
- Sulfonation
- Under reflux with "Fuming sulfuric acid"
- H2SO4 + SO3 -> HSO4- + HSO3+
- The ring of delocalised electrons makes addition reactions thermodynamically unfavourable
- Undergoes electrophilic substitution reactions
- This restores aromaticity
- Undergoes electrophilic substitution reactions
- The Wheland intermediate
- Positive charge is not located in one place
- Resonance structures
- Positive charge is not located in one place
- Combustion
- Burns with an extremely smoky flame
- Hydrogenation
- Cycloalkane formed
- Delocalised ring destroyed
- Nitration
- Structure and stability of benzene
- Reactivity
- Theoretical
- Reacts with bromine water
- Actual
- No reaction observed
- Benzene more stable than other alkenes
- Theoretical
- Enthalpy of formation
- Theoretical
- Value of +243 kJmol-1
- Actual
- Value of +49kJmol-1
- More stable than Kekule structure would allow us to believe
- Theoretical
- IR spectra
- Theoretical
- Non-symmetrical
- Actual
- Spectra more symmetrical than predicted
- Theoretical
- Bond lengths
- Theoretical
- Mixture of double bonds and single bonds - 0.134nm & 0.154nm
- Actual
- Bonds lengths are all identical at 0.139nm
- Theoretical
- Thermodynamics
- Theoretical
- 3x that of cyclohexene, around -340 - -360 kJmol-1
- Actual
- It is -208 kJmol-1
- More stable than predicted
- Theoretical
- Thermodynamics
- Theoretical
- Varying electron density dependent on bond type - e.g more dense around C=C
- Actual
- Even distribution throughout molecule
- Theoretical
- Actual structure
- Formation of a ring of delocalised electrons
- Electron density aboive and below the plane of the carbon atoms
- This contributes to the stability of the molecule
- Electron density aboive and below the plane of the carbon atoms
- Formation of a ring of delocalised electrons
- Reactivity
- Phenol v Benzene
- In phenol, the oxygen atom of the -OH has a lone pair of electrons
- This can contribute to the electron density of delocalised ring
- = MESOMERIC EFFECT
- This makes the ring more attractive to electrophiles, making reactions easier to occur
- This can contribute to the electron density of delocalised ring
- In phenol, the oxygen atom of the -OH has a lone pair of electrons
- Reactions of benzene
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