ORGANIC CHEMISTRY
Crude oil and hydrocarbons
Crude oil: finite source, formed from sea creatures, mixture of hydrocarbons
Combustion of hydrocarbons
Hydrocarbon fuels release energy when they combust
Carbon and hydrogen reacts with oxygen, causing them to be oxidised
Complete combustion: unlimited oxygen
Incomplete combustion: limited oxygen
Fractional distillation of crude oil
The crude oil is separated into fractions which each have hydrocarbons with a similar number of carbon atoms
The crude oil is first boiled, then evaporate and turn into a gas. The vapours rise up the column and condense when they reach their boiling point. These hydrocarbons are collected as fractions. The rest of them rise up and do the same.
Some fractions are used as fuels.
Cracking
Long hydrocarbon chains are not flammable so they require a lot of energy to break so CRACKING is used.
Smaller and more useful hydrocarbons are made and alkenes are also produced.
Alkenes
Have a double carbon bond, CnH2n
Can be tested for using bromine water
Reactions of alkenes
Functional group-tells us the part of the molecule that determines how it reacts. An alkenes functional group is the carbon double bond
Molecules like alkenes are part of a group called the homologous series. Members of the homologous series all have the same functional group.
Combustion - when we combust alkanes we produce carbon dioxide and water.
-Combusting alkenes produces unburnt carbon particles due to incomplete combustion
In hydration, the water must be in the form of steam, temp around 300 and pressure around 70 atmospheres. We use a catalyst in the process (phosphoric acid). To increase the yield of the product (ethanol), any unreacted product (ethene) and steam are passed back through the catalyst.
Alcohols
Uses-fuels, solvents, alcoholic drinks.
Same functional group which is OH
Alcohols
Hydration of ethene:
The reaction requires a lot of energy. So, the ethene comes from crude oil.
Fermentation of sugar:
We start with a sugar solution and mix it with yeast. The yeast then converts the sugar solution into ethanol+CO2.
Reactions of alcohols
Reaction with sodium: bubbles of hydrogen gas produced.
Oxidising agent: carboxylic acids and water
Combustion: Alcohols release energy when they combust. Produce carbon dioxide and water.
Carboxylic acids
Functional group-COOH
Weak acids in water
With metal carbonate: salt+carbon dioxide+water
Addition polymers
Polymers are made up of small molecules called monomers
Alkanes: saturated hydrocarbons as carbons are fully bonded to hydrogen, CnH2n+1
In addition polymers, monomers are always alkenes. The monomer has a double carbon bond, but its polymer has a single bond.
Condensation polymers
monomers are not alkene and when monomers react, small molecules such as water are lost
2 different monomers are used of the same functional group.
Amino acids
Have 2 different functional groups: H2N and COOH
DNA
Polymers made from one type of amino acid are called polypeptides and polymers made from different amino acids are called proteins.
Found in all living organisms.
Consist of 2 polymer chains made from monomers called nucleotides.
4 different monomers : G, A, T, C
Forms a double helix