ORGANIC CHEMISTRY Flashcards
What is a hydrocarbon?
Any compound that contains only hyrdogen and carbon atoms.
What is the formula for an alkane?
2n+2
What type of bonds do alkanes have?
Single bonds.
Why do alkanes have single bonds?
Because they are saturated.
How many bond does a carbon atom have to have in an alkane?
4 single bonds.
What are the first four alkanes?
Methane
Ethane
Propane
Butane
What happens when the length of a carbon chain is short?
The hydrocarbon is runny (less viscous)
Lower boiling point
More flammable
What is the equation for complete combustion with hydrocarbons?
hydrocarbon + oxygen –> carbon dioxide + water
What happens during combustion?
Both carbon and hydrogen from the hydrocarbon are oxidised.
Why are hydrocarbons used as fuels?
Because they release large amounts of energy when combusted completely.
Why are alkanes saturated?
Because they contain single bonds so they cannot hold anymore hydrogen atoms.
What do you use to test whether something is an alkane or alkene?
Bromine water.
How do you know if something is an alkane?
When added to bromine water, the solution stays orange
How do you know if something is an alkene?
When added to bromine water, the solution turns colourless.
Why does bromine water stay the same colour (orange) when added to an alkane?
When an alkane added to bromine water, there is no spare bonds so the bromine water is unable to bond so no reaction occurs therefore it stays orange.
Why does bromine water change colour (to colourless) when added to an alkene?
Because bromine reacts with the alkene as it is unsaturated (has a spare bond)
What type of bonds does carbon have in alkenes?
Double bond.
What is the formulae for alkenes?
CnH2n
Why do alkenes have double bonds?
Because they are unsaturated.
Why are alkenes unsaturated?
The double bond between the carbon atoms can open up to make two single bonds allowing the two carbon atoms to bond with other atoms.
Why are alkenes reactive?
Because they have double bonds that can be split open to react with other atoms.
What are the first four alkenes?
Ethene
Propene
Butene
Pentene
Why is there no methene?
Because you have to have at least two carbons because there needs to be a double bond in between then.
Why can alkenes not combust completely in the air?
Because there is not enough oxygen so therefore they undergo incomplete combustion.
What is the equation for incomplete combustion with alkenes?
alkene + oxygen –> carbon + carbon monoxide + carbon dioxide + water
What flame does incomplete combustion result in?
A yellow smoky flame.
What happens when alkenes are reacted with steam?
Water is added and an alcohol is formed.
What can alkenes react with apart from steam?
Halogens such as bromine, chlorine and iodine.
What are alcohols (symbol wise)?
-OH
What is a homologous series?
A family of organic compounds with the same functional group
What is a hydroxyl group?
-OH (alcohols)
What are the first four alcohols?
Methanol
Ethanol
Propanol
Butanol
What is the formula for alcohols?
2n+1 + OH
How do alcohols undergo complete combustion (word equation)?
alcohol + air —> carbon dioxide + water
What happens when you mix alcohols with water?
They become neutral (pH 7).
What happens when alcohols are oxidised?
They become carboxylic acids.
What happens when methanol is oxidised?
It turns into methanoic acid (a carboxylic acid).
Why are alcohols used as solvents in industry?
Because they can dissolve most things water can and can’t dissolve.
What alcohol is found in alcoholic drinks?
Ethanol
How is alcohol in drinks made?
Fermentation
How does fermentation work?
Fermentation uses an enzyme in yeast to convert sugars into ethanol. Carbon dioxide is also produced.
What is the fermentation word equation?
sugar —> ethanol + carbon dioxide
What temp does fermentation happen faster at?
37 degrees
(as well as in anaerobic conditions in a slightly acidic solution)
What are the first carboxylic acids?
Methanoic acid
Ethanoic acid
Propanic acid
Butanoic acid
What are carboxylic acids functional group?
-COOH
What is the formula for carboxylic acids and their group ?
n-1 2n-1 + COOH
How many bonds does oxygen have to have to have a complete outer shell?
2
How many bonds does hydrogen need to have?
1
Acids + metals
Salt + hydrogen
Acids + alkalis/base
Salt + water
Acids + carbonates
Salt + carbon dioxide + water
What are the salts called when you react carboxylic acids and carbonates?
ends in ‘anoate’ e.g. methanoate
What does ethanoic acid + sodium carbonate produce?
sodium ethanoate + carbon dioxide + water
What happens when carboxylic acids dissolve in water?
They ionise and release H+ ions resulting in an acidic solution. They don’t ionise completely so the are weak acidic solution.
What are esters functional group?
-COO-
What are esters formed from?
They are formed from an alcohol and carboxylic acid.
What is the word equation for the production of an ester?
alcohol + carboxylic acid —> ester + water
What is an example of an ester (eth)?
ethyl ethanoate
How are the different hydrocarbons in crude oil seperated?
Fractional distillation.
What can crude oil be used for?
Fuel
What is crude oil?
It is a fossil fuel formed from the remains of plants and animals that died millions of years ago. It is a mixture of lots of different hydrocarbons.
How does fractional distillation work?
Oil is heated till it is a gas and enters a fractionating column
Temp gradient inside (hot at bottom and cold at top)
Longer hydrocarbons have high boiling points so condense back into liquids early on
Shorter hydrocarbons have low boiling points so condense much later on
This ends up with crude oil mixture separated out into different fractions
What is cracking?
The splitting up of long-chain hydrocarbons to more useful hydrocarbons (short-chain ones which are good fuels).
What does cracking produce (word equation)?
Long-chain hydrocarbon —> shorter alkane + alkene
What type of reaction is cracking?
Thermal decomposition reaction.
How does catalytic cracking occur?
Heat long-chain hydrocarbon into a gas
Gas is passed over hot powedered aluminium oxide catalyst
Long-chain molecules split apart on the surface of the catalyst
What processes are used in fractional distillation?
Evaporation and condensation
How does steam cracking occur?
Vaporise long-chain hydrocarbon
Mix it with steam
Heat to very high temperature
What are polymers?
Long molecules formed when lots of small molecules (monomers) join together.
What is the reaction that joins monomers to become a polymer?
Polymerisation.
What is an example of something made out of polymers?
Plastics.
What bonds do addition polymers have?
Double covalent bonds.
What is addition polymerisation?
When lots pf unsaturated monomers (alkenes) open up their double bonds and join together to form polymer chains.
What are the two types of polymers?
Addition and condensation.
What is condensation polymerisation?
When monomers react together and bonds form between them making polymer chains. For each new bond that forms, a small molecule (e.g. water) is lost.
What is different about condensation polymerisation?
The monomers involved contain different functional groups.
How many products are formed from addition polymerisation?
1 (the polymer)
How many products are formed from condensation polymerisation?
2 (the polymer and the small molecule)
What two functional groups do amino acids contain?
A basic amino group and an acidic carboxyl group.
What polymers can amino acids form?
Polypetitides (via condensation polymerisation).
How do amino acids form proteins?
The amino group reacts with the acid group and produces polypetides (one or more long-chains are proteins) and a molecule of water is lost.
What is DNA made of?
Two polymer chains of monomers called nucleotides.
What does each nucleotides in DNA contain?
A base (A,T,C,G,)
What do the bases do in DNA?
They form cross links between each other to keep the two strands of nucleotides together (double helix structure).
What elements do sugars contain?
Carbon, oxygen and hydrogen.
What do sugars form through polymerisation?
Larger carbohydrate polymers (e.g. starch to store energy and make cellulose).
What is a monomer?
A small unit which can be joined together by a chemical reaction to make a long chain called a polymer.
