Alkanes Lecture 3

Outline Nomenclature, classification and isomerism Methods of preparation Chemical properties

CnH2n+2 Classification Hydrocarbons: Hydrocarbons: aliphatic saturated alkanes cycloalkanes alkenes cycloalkenes alkynes dienes aromatic (arenes) Hydrocarbons: saturated alkanes cycloalkanes unsaturated alkenes cycloalkenes alkynes dienes arenes Hydrocarbons: cyclic acyclic CnH2n+2

Isomerism Alkanes: normal (linear) branched

Preparation of alkanes

Preparation of alkanes C1 – C4 gas 200C C5 – C9 raw material for organic syntheses 700C C5 – C10 gasoline 1200C C10 – C16 kerosene 1700C C14 – C20 diesel fuel 2700C C20 – C50 oils and waxes C20 - C70 fuel 6000C >C70 tar

Preparation of alkanes 1. Wurtz reaction

Preparation of alkanes 2. Kolbe reaction Mechanism: 1) oxidation of carboxylate ion on the anode cathode process: 2) decarboxylation 3) recombination

Preparation of alkanes 3. Reaction of dialkylcuprates with alkyl halides 4. Hydrogenation of alkenes

Preparation of alkanes 5. Industrial methods 5.1 Coal liquefaction 5.2 From syngas (Fischer–Tropsch process) water-gas shift: steam reforming:

Chemical properties of alkanes 1. Radical reactions 1.1 Chlorination – a photochemical reaction 1) chain initiation 2) chain propagation 3) chain termination

Chemical properties of alkanes 1.1 Chlorination – a photochemical reaction relative activity of secondary C-H relative activity of primary C-H 57 / 2 43 / 6 4 1 =

Chemical properties of alkanes 1.2 Nitration – Konovalov reaction 1.3 Sulfochlorination reaction

Chemical properties of alkanes 2. Oxidation of alkanes complete oxidation: CH4 + 2O2 = CO2 + 2H2O incomplete oxidation: 2CH4 + 3O2 = 2CO + 4H2O CH4 + O2 = C + 2H2O octane rating 100 octane rating 0