Aromatic Chemistry
A mindmap of all you need to know for aromatic chemistry A2.
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?- Created by: Phoebe
- Created on: 17-12-12 20:26
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- Aromatic Chemistry
- Benzene
- Structure
- Originally thought to contain alternate single and double bonds
- Kekule Structure
- Double bonds are shorter than single bonds
- All 6 C-C bonds have the same length
- All 6 bonded electrons are delocalised
- The molecule is planar
- Any molecule containing the benzene ring is aromatic
- Originally thought to contain alternate single and double bonds
- Stability
- The delocalization of the electrons in benzene makes the molecule more stable than expected for a molecule with three double bonds
- The enthalpy of hydrogenation of benzene is significantly less than three times the enthalpy of hydrogenation of a typical alkene. This is good evidence that delocalization confers stability to the molecule
- Reactions
- It will not undergo addition reactions
- Delocalised system is stable
- It undergoes substitution reactions
- The delocalized electrons are an electron-rich area, and they are thus susceptible to attack by electrophiles
- Nitration
- H2SO4 + HNO3 <=> H2NO3+ + HSO4- H2NO3+ --> H2O + NO2+
- C6H6
+ HNO3 --> C6H5NO2 + H2O
- Product = nitrobenzene
- sulphuric acid behaves as a catalyst
- Alkylation
- Haloalkanes
- Benzene reacts with chloroalkanes in the presence of anhydrous AlCl3 under reflux at 50oC to form alkylbenzenes
- R-Cl + AlCl3 --> R+ + AlCl4-
- AlCl3 acts as a catalyst
- C6H6 + RCl --> C6H5R + HCl
- Alkenes
- benzene with alkenes
in the presence of HCl and AlCl3, under reflux at temperatures below
50oC
- AlCl3 and the HCl act as catalysts
- C6H6 + R1R2C=CR3R4 --> C6H5CR1R2CR3R4H
- tertiary carbocation more stable than primary so major product
- benzene with alkenes
in the presence of HCl and AlCl3, under reflux at temperatures below
50oC
- Haloalkanes
- Acylation
- Benzene reacts with
acyl chlorides in the presence of anhydrous AlCl3 under reflux at 50oC
- R-COCl + AlCl3 --> R-CO+ + AlCl4-
- C6H6
+ R-COCl --> C6H5COR + HCl
- The AlCl3 is a catalyst
- Benzene reacts with
acyl chlorides in the presence of anhydrous AlCl3 under reflux at 50oC
- Above 55oC further substitution occurs
- It will not undergo addition reactions
- Structure
- Phenylamine
- Properties
- is a much weaker base than aliphatic amines since the lone pair on the nitrogen atom is absorbed into the delocalised system and is thus not available for bonding with a proton
- Preparation
- main use of
nitrobenzene is to make phenylamine
- Nitrobenzene can be
reduced to phenylamine
- Ni catalyst/H2 gas
- and one of the following: Hcl/Fe Sn/Zn SnCl2
- C6H5NO2 + 6[H] --> C6H5NH2 + 2H2O
- Hydrogenation/Reduction
- Nitrobenzene can be
reduced to phenylamine
- main use of
nitrobenzene is to make phenylamine
- Properties
- Uses of Aromatic Compounds
- Explosives
- trinitrotoluene (TNT) is formed by the nitration of methylbenzene
- Dyestuffs
- Phenylamine can be converted into another important compound,
benzenediazonium chloride by reaction with nitrous acid
- Phenylamine + HNO2 +HCl --> benzenediazonium chloride +2H2O
- Benzenediazonium chloride can be used to make a number of different dyes
- Phenylamine can be converted into another important compound,
benzenediazonium chloride by reaction with nitrous acid
- Polystyrene
- Ethylbenzene is manufactured industrially
from benzene and ethene in the presence of AlCl3 and HCl
- Ethylbenzene can be
dehydrogenated to form phenylethene, or “styrene” in the presence of iron oxide
at high temperature
- phenylethene can then be polymerized to form polystyrene (or polyphenylethene)
- Ethylbenzene can be
dehydrogenated to form phenylethene, or “styrene” in the presence of iron oxide
at high temperature
- Ethylbenzene is manufactured industrially
from benzene and ethene in the presence of AlCl3 and HCl
- Explosives
- Benzene
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