Organic Chemistry Mechanisms AQA (2016)

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  • Created on: 11-01-18 15:19

Organic Chemistry Review – Mechanisms (AQA)

Nucleophilic Substitution

Nucleophile: ‘Nucleus loving’. Nucleophiles are a species that at strongly attracted to an area of positive charge.            .                         Common nucleophiles include hydroxide(OH-) and cyanide(CN-) ions, water(H2O) and ammonia(NH3).

Halogenoalkanes can undergo Nucleophilic Substitution, because the difference in the electronegativity of the halogen and the carbon, makes the C atom ∂+.

Text Box: Mechanism:


The Nucleophile attacks the ∂+ carbon, and               A halide is produced and a new type of compound                                                                                      the C—X bond breaks heterolytically.                          Is formed.

Nucleophilic Substitution with cyanide ions is special because it increases the length of the carbon chain.

Free Radical Substitution

 Free Radical: A free radical is an atom/ group of atoms with a single unpaired electron. They are formed when a bond breaks homolytically (shared pair of electrons are split evenly. Each atom gets one.)

Free Radical Substitution takes place in three stages; INITIATION, PROPAGATION and TERMINATION. It is an example of a PHOTOCHEMICAL REACTION, as it’s a reaction brought about by (UV) light.

Text Box: Cl2 → 2Cl • Cl—Cl Mechanism: (e.g.  methane and chlorine)

                                                                                INITIATION – The CL2 molecule is split homolytically, to form two chlorine free radicals sdjdjs sjndnsksn     sj             free radicals. This is started by UV light breaking the Cl—Cl bond.

Text Box: CH4 + Cl• → CH3• + HCl CH3• + Cl2 → CH3Cl + Cl•  

                               ,                                       …


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