GCSE Chemistry C7: Organic Chemistry

Crude Oil (3)

• finite resource found in rocks

• the remains of an ancient biomass consisting of plankto that was buried in mud 

• mixture of hydrocarbons

hydrocarbon definition

• A compound made out of only hydrogen and carbon 

fractional distillation and petrochemicals (5)

• crude oil is heated to about 350 degrees so most of it evaporates

• it is pumped into the fractionating column with a temperature gradient: it is hot at the bottom but cool at the top, the heaviest fraction is removed from the bottom as a liquid

• as the vaporised oil rises, it cools. When it becomes cooler than its boiling point, it condenses and removed

• the crude oil is seperated into fractions collected at different heights of the column 

• used to produce fuels and feedstock for the petrochemical industry such as solvents, lubricants, polymers and detergents

name of the fractions (5)

• petroleum gas (octane)

• gasoline/petrol

• kerosene

• diesel oil 

• residue bitumen

As you go up the fractionating colum (5)

• the shorter the chain (smaller the molecules)

• boiling point decreases

• volatility increases

• viscosity decreases

• flammability increases 

what happens when you burn hydrocarbons (3)

• produce carbon dioxide and water

• the hydrogen and carbon are oxidised in this reaction

• used as fuels since the reaction produces energy and because it has shorter chains making them more flammable

cracking (3)

catalytic cracking: passing the hydrocarbon over a hot catalyst (600-700 degrees) such as bits of ceramic or aluminium oxide

steam cracking: mixing them with steam and heated to a very high temperature so that thermal decomposition reactions can occur

• breaks down alkanes into an alkene and a smaller alkane

Alkenes (3)

• CnH2n+2

• unsaturated because they contain double bond so it has less hydrogens than alkanes 

• produces polymers

bromine water

• alkenes will turn bromine water from orange to colourless as it has a double carbon bond so it is more reactive

Alcohols (6)

• OH functional group 

• ends in anol 

• combusts to make carbon dioxide and water 

• dissolve in water to form neutral solution 

• react with sodium to produce hydrogen and a salt 

• react with oxidising agent (potassium dichromate) to form carboxylic acids

what is a functional group

family of compounds which have the same functional group which determines its chemical properties

uses of metahnol, ethanol

• methanol: chemical feedstock, in antifreeze, biiodiesel

• ethanol: main alcohol in drinks, solvent

• all can be used as fuels 

making ethanol (fermentation) (7)

• using glucose and yeast to turn into ethanol and carbon dioxide 

• temperature of 15-35 degrees

• anaerobic respiration 

• dissolve sugar in water to create an aqueous solution, add yeast 

• create an airtight seal with an airlock so it allows carbon dioxide gas to escape but prevents oxygen from getting in 

• process takes several days or even weeks 

• the water can be seperation using fractional distillation and the yeast dies when the ethanol conc reaches around 15%

disadvantages of fermentation (4)

• less efficient for a large scale

• produces carbon dioxide

• very slow process

• dilute, impure product 

making ethanol (hydration of ethene) (5)

• ethene gas is mixed with steam and passed continiously over the solid phosphoci acid catalyst in a reaction chamber 

• an addition reaction occurs, there the water molecule adds across the carbon to carbon double bond of ethene forming ethanol 

• the ethanol and water is cooled and condenses into a liquid while the unreacted ethene remains a gas as it has a lower boiling point

• the gaseous ethene is seperated and recycled back into the reaction chambre, to enure a high overall yield (95%)

• the liquid ethanol-water mixture is then seperated by factional distillation to obtain pure ethanol

advantages of hydration of ethene (4)

• 100% atom economy

• high rate of reaction

• produces pure ethanol 

• does not produce any other products 

disadvantages of hydration of ethene (2)

• Requires high energy (300 degrees celsius) and pressure which is eexpensive

• Non renewable resources, relying on ethene which is derived from crude oil, a finite

carboxylic acids (6)

• COOH 

• anoic acid

• dissolve in water to produce acidic solutions pH less than 7

• react with metal carbonates to produce carbon dioxide, a salt, and water

• react with alcohols to produce esters

• do not ionise completely so not many H+ ions released making them weak acids

name an esther

ethyl ethanoate

uses of esthers (3)

• perfume 

• solvents

• artificial falvouring

esther equation 

alcohol + carboxylic acid —> ester + water 

how to draw polymer (5)

• the carbon bonds coming out of the brackets 

• brackets

• and the little ‘n’ outside the bracket 

• simplify the things that is not part of the double brackets

• remember that it requires pressure and a catalyst, write it on the arrow from monomer to polymer 

condensation polymerisation (3)

• loses H2O

• Its a polyester, dicarboxylic acid (gives up OH) + diol monomer (gives up O)

• forms 2 molecules of water

why are polyesthers better than polymers

they are biodegradable because the bacteria and microorganisms can break down the esther link

Amino Acids (3)

• amine group + carboxylic acid

• react by condensation polymerisation to produce polypeptides

• different amino acids can be combined in the same chain to produce proteins

naturally occuring polymers (5)

• DNA encodes genetic instructions for the development and functioning of living organisms and viruses

• most molecules are two polymer chains made from four different monomers called nucleotides in the form of a double helix

• proteins (amino acids)

• starch (glucose)

• cellulose (glucose 

homologous series definition

a group of organic compounds with the same functional group and similar chemical properties. Each successive member in the series differs by a CH2 group