organic chemistry Reactions

Alkanes are unreactive except for

Combustion and Substitution with halogens

Alkane combustion

Complete: Alkane + oxygen → carbon dioxide + water

Incomplete: Alkane + oxygen (limited) → carbon monoxide/carbon + water

Alkane substitution with halogens (+ 2example)

Photochemical reaction, requires UV light to provide the activation energy for the reaction . Halogen atom swaps with hydrogen atom and hydrogen halide gas is other product

Alkane + halogen → haloalkane and hydrogen halide

E.g ethane + bromine → bromoethane and hydrogen bromide

E.g methane and chlorine → chloromethane and hydrogen chloride

Cracking of alkanes

Cracking is a thermal decomposition reaction

Catalyst of Alumina or silica (Al2O3 or SiO2)

High temperature 500 degrees Celsius

Alkane Heated until vapour and mixed with catalyst . Cracking produces smaller alkanes and Alkenes

Alkene combustion

Same as alkanes

Why can Alkenes undergo addition reactions

Carbon carbon double bond can be broken and a new single bond is formed from each of the 2 carbon atoms. An addition reaction forms only one product

Addition reaction with Hydrogen (Hydrogenation)

Nickel catalyst, 150 degrees Celsius

H2 adds to alkene molecule to form an alkane

Addition reaction with bromine (Halogenation)

Dihaloalkanes form when halogens attach to the carbons that broke their double bond

E.g ethene + bromine → 1,2 dibromoethane

Doesn’t require sunlight/UV

Test for saturation / Unsaturation

Bromine water (orange-brown) Is used

Alkenes de colourise bromine water (turn colourless) , with alkanes the colour stays the same and no reaction occurs

Alkene addition reaction with Steam(Hydration)

Catalyst of concentrated phosphoric acid (H3PO4) , 300 degrees Celsius, 60atm (60000kPA)

Steam is added to an Alkene molecule forming an alcohol

Production of Ethanol (Natural)

Fermentation of aqueous glucose solution at 25-35 degrees Celsius in the presence of yeast, absence of Oxygen. Yeast is catalyst . At a higher temperature the yeast will die

Production of ethanol (lab)

Hydration of ethene- Catalytic addition of steam- CONC PHOSPHORIC ACID, 60atm (60 000kPa) and 300 degrees Celsius

Dehydration of Alcohols(elimination)

Reversed reaction of alkene + steam

Catalyst is concentrated sulfuric acid or phosphoric acid heating under reflux OR another method is hot aluminium oxide- Ethanol soaked in glass wool and passed over heated Al2O3 catalysing the reaction.Ethene can be collected by the downward displacement of water

Reversible reaction. Dehydration reaction

Production of ethanoic acid

Heat ethanol with oxidising agents like acidified potassium manganate (VII) or acidified potassium dichromate

Under reflux condition (heated with condenser)

OR bacterial oxidation during vinegar production

Combustion of ethanol

Complete: Carbon dioxide + water, burns with a clear blue flame
Incomplete: C or CO formed instead of CO2, yellow sooty flame and less energy released (Less exothermic)

Carboxylic general reactions (As acid)

Under go same reactions as strong acids but at a slower rate.

• metal + acid

• metal oxide/hydroxide + acid

• metal carbonate + acid

• neutralisation

salts - oate

esterfication

carboxylic acids react with alcohols with an acid catalyst to form esters.

catalysed by concentrated sulfuric acid

esterification is a condensation reaction as water is removed. it is a reversible reaction.

addition polymerisation

one monomer(Alkene) joins together forming a polymer

Condensation polymerisation (Polyester)

Dicarboxylic acid + diol/dialcohol

Condensation polymerisation (Polyamide)

Dicarboxylic acid + Diamine