Unit 4: Module 1 - Rings, Acids and Amines

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Chemistry (Unit 4) Mind Map on Unit 4: Module 1 - Rings, Acids and Amines, created by tommyshellerpaulson on 11/12/2014.

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Unit 4: Module 1 - Rings, Acids and Amines
1 BENZENE: Structure
1.1 Formula: C6H6
1.2 Cyclic
1.2.1 Two ways of representing it...
1.2.1.1 Kekule's
1.2.1.1.1 If it was correct..
1.2.1.1.1.1 3 x length of C-C bonds (147pm)
1.2.1.1.1.2 3 x length of C=C bonds (135pm)
1.2.1.1.1.3 HOWEVER
1.2.1.1.1.3.1 X-ray diffraction have shown all the bond lengths have the same value (140pm)
1.2.1.1.1.4 Hydrogenation Enthalpy Change of C=C bond is -120 Kj/mol
1.2.1.1.1.4.1 so with 3 C=C bonds, enthalpy change should be -360 Kj/mol
1.2.1.1.1.4.1.1 HOWEVER
1.2.1.1.1.4.1.1.1 Experimental enthalpy change is -208 Kj/mol...... Far less exothermic than expected
1.2.1.1.1.4.1.1.1.1 Indicates that Benzene is more stable than the Kekule structure would be. This is thought to be due to the delocalised electrons.
1.2.1.2 Delocalised Model
1.2.1.2.1 P-Orbitals of all 6 Carbon atoms overlap to create Pi Bonds
1.2.1.2.1.1 3 Electrons in the top ring, 3 in the bottom ring (due to the repulsion of negative charges)
2 BENZENE: Aromatic Compounds
2.1 Compounds containing a benzene ring are called arenes or 'aromatic compounds'
2.1.1 Chlorobenzene
2.1.2 Nitrobenzene
2.1.3 1,3-dimethylbenzene
2.2 Others are named as compounds with a phenyl group (C6H5) attached
2.2.1 Phenol
2.2.2 2-methylphenol
2.2.3 phenylamine
3 Reactions with Benzene
3.1 Alkenes react easily with Bromine water (the famous experiment where Br water decolourises)
3.1.1 If the Kekule model was correct, Benzene would be expected to react similarly (due to the C=C bonds)
3.1.1.1 Because of the electron rings above and below the carbon atoms, it makes the benzene ring VERY staable, and spreads out the negative charge.
3.1.1.1.1 This means Benzene is very unwilling to undergo addition reactions which would destroy the stable ring
3.1.1.1.1.1 Instead, benzene prefers to react by electrophilic substitution
3.1.1.1.1.1.1 Electrophile: Positively charged ions or polar molecules that are attracted to ares of high electron density
3.1.1.1.1.1.2 Arenes undergo Electrophilic Substitution with....
3.1.1.1.1.1.2.1 With Nitric Acid and a Catalyst (this catalyst is Sulfuric acid)
3.1.1.1.1.1.2.1.1 Sulfuric acid (how to make the NO2+)
3.1.1.1.1.1.2.2 HALOGENS using a HALOGEN CARRIER
3.1.1.1.1.1.2.2.1 PICTURE OF BROMINE OR CHLORINE REACTING WITH BENZENE IS TOO BLOODY HARD TO FIND - JUST LEARN IT
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