AS Mechanisms

Carbocation:

A reaction intermediate containing a positively charged carbon

Alkanes Write a mechanism to show the formation of 1-chloropropane from propane (use structural formulae).

Initiation: Cl2 —> 2Cl∙ Propagation x2: CH3CH2CH3 + Cl∙ —> ∙CH2CH2CH3 + HCl ∙CH2CH2CH3 + Cl2 —> CH2ClCH2CH3 + Cl∙ Termination (include carbon radical(s)): ∙CH2CH2CH3 + ∙Cl —> CH2ClCH2CH3 Name the mechanism and each step: Free radical substitution State the essential condition required: UV light Write an overall equation to represent the formation of tribromomethane from methane: CH4 + 3Br2 —> CHBr3 + 3HBr

Curly Arrows:

Movement of a pair of e− There are two places a curly arrow can start from: 1) Lone pair 2) Covalent bond

Halogenoalkanes Part 2 Draw a mechanism to show the reaction of 1-chloropropane with ethanolic NaOH.

Name the mechanism. Elimination What is the hydroxide acting as? Base Overall equation: CH3CH2CH2Cl+NaOH—>CH3CH=CH2+NaCl+ H2O

Alkenes Draw a mechanism to show the reaction of but-2-ene with H2SO4.

Name the mechanism: Electrophilic Addition What is the sulfuric acid acting as? Electrophile How could we convert the product to an alcohol? Add water and heat State the role of the sulfuric acid considering both steps? Catalyst

Halogenoalkanes Part 1 Draw a mechanism to show the reaction of 1-chlorobutane with aqueous NaOH.

Name the mechanism: Nucleophilic Substitution What is the hydroxide acting as? Nucleophile Overall equation: CH3CH2CH2CH2Cl + NaOH —> CH3CH2CH2CH2OH + NaCl

Alcohols Part 1: Direct Hydration Mechanism Industrial production of ethanol:

Reagents: H2O with conc. phosphoric acid catalyst Conditions: 6000 kPa, 300 °C Uses of ethanol produced: solvent, chemical feedstock, fuel Advantages: High yield and atom economy.

Alcohols Part 2: Elimination Mechanism

Reagents: conc. sulfuric acid catalyst Conditions: heat Uses of alkene produced: make polymers, chemical feedstock Advantages: can reduce the reliance on crude oil for the production of alkenes and polymers.

Unsymmetric alkenes Draw the two possible products formedfrom the reaction of prop-1-ene with HBr. Label the two products as major or minor with a reason.

The major product (2-bromopropane) is formed from the most stable 2° carbocation intermediate compared to the minor product (1-bromopropane) which is formed from the less stable 1° carbocation intermediate.

Reaction Mechanisms:

break reactions down into a series of steps.

Electrophiles:

lone pair acceptor Three examples: Br2, HBr, H2SO4

Nucleophiles:

lone pair donor Three examples: :CN−, :OH−, :NH3

Free radicals:

species with an unpaired e− Two examples: Cl∙, Br∙