Aromatic Compounds

Cindy Lam
Mind Map by , created over 6 years ago

Chemistry Mind Map on Aromatic Compounds, created by Cindy Lam on 04/04/2013.

Cindy Lam
Created by Cindy Lam over 6 years ago
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Aromatic Compounds
1 Benzene
1.1 History
1.1.1 Kekule: Snake - planar, cyclic BUT Thermodynamically more stable than expected Releases 208 kJ per mole when reduced instead of 3*120. Resonance energy = 152 kJ per mole Bond lengths all similar Did not undergo electrophilic addition → no true double bond SO Resonance Hybrid Each bond is between single and double Lower in energy than Kekule → thermochemically stable Delocalised pi orbital system, planar
1.1.2 C6H6 X Aliphatic
1.1.3 First isolated in 1825
1.2 Electrophilic substitution
1.2.1 Does not affect delocalisation
1.2.2 Need stronger electrophiles than those with alkene
1.2.3 Nitration Conc HNO3, conc H2SO4 (catalyst) 55 degrees Electrophile: NO2+ (nitronium) Nitro benzene → Phenylamine → diazonium dyes Not safe, side effects
1.2.4 Halogenation Chlorine, Halogen carrier (catalyst) Reflux
1.2.5 Friedel-Crafts Reaction Acylation Reflux, 50 degrees, dry ether RCOX, anhydrous AlCl3 Electrophile: RC+=O Alkylation RX, anhydrous AlCl3 (catalyst) Electrophile: R+ Room temp, dry ether
1.2.6 Further substitution
1.2.7 Sulfonation + Fuming sulphuric acid → Benzenesulfonic acid Room temp
1.3 Addition
1.3.1 Bromine in UV light Free radical reaction
1.3.2 Hydrogenation with Raney nickel catalyst, 150 degrees C Cyclohexane
1.4 Burns with yellow smoky flame
2 Phenol
2.1 C6H5OH
2.2 Aromatic alcohol
2.3 Preparation
2.3.1 Nitration of benzene Reduction of nitro benzene with Tin, Conc HCl, Reflux Diazotisation of phenyl amine: nitrous acid and hydrochloric acid, below 10 degrees Substitution of diazogroup by OH: water, warm above 10 degrees
2.4 More reactive than benzene as OH group activates benzene ring
2.5 Weak acid
2.6 Electrophilic substitution
2.6.1 Without catalyst
2.6.2 Further Substitution With Bromine water With dilute nitric acid
2.7 Antiseptic, used to make polymers
3 Benzene diazonium chloride
3.1 C6H5N2+Cl-
3.2 Preparation
3.2.1 Phenylamine, nitrous acid (made in situ from sodium nitrite), hydrochloric acid
3.2.2 Kept below 10 degrees to slow down decomposition of salt
3.3 Reactions
3.3.1 Substitution of OH (hydrolysis) → phenol
3.3.2 Substitution with I using KI solution, warm
3.3.3 Coupling + NaOH + Phenol → Azo dye (N=N)
4 Any hydrocarbon system which has a stabilised ring of delocalised electrons

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