Organic Chemistry Flashcards
2
What is a hydrocarbon?
it is a compound made up of only hydrogen and carbon atoms
What is the alkane formula?
CnH2n+2
What is a homologous series?
a group of organic compounds that react in similar ways
What are alkanes?
they are fully saturated hydrocarbons that are a homologous series.
What is a saturated compound/hydrocarbon?
it has the maximum amount of single bonds (carbon is fully saturated in a hydrocarbon when it makes 4 bonds, ie max amount of bonds)
What are the first 5 alkanes called?
Methane, Ethane, Propane, Butane, Pentane
Draw methane and propane as displayed formula.
Methane: CC - H - C CPropane: C C C C - H - H - H - C C C C
How do the properties of Hydrocarbons change as the length of the carbon chain changes?
The longer the chain, the more viscous it isThe longer the chain, the less volatile it is (higher boiling points as length continues)The longer the chain, the less flammable it isAffects how they are used for fuels.
How does the length of a hydrocarbon affect how they are used in fuels?
Short hydrocarbons with lower boiling points are used as ‘bottled gases’, stored under pressure as liquid in bottles.
What is the equation for complete combustion?
Hydrocarbon + oxygen -> carbon dioxide + water (+ energy)
What is oxidation?
the gain of oxygen, loss of electrons
During complete combustion what happens to the hydrocarbon?
Both the hydrogen and carbon from the hydrocarbon are oxidised
Why are hydrocarbons used/good as fuels?
Due to the high amount of energy they release when they completely combust
Write the balanced equation for the complete combustion of methane (CH4)
CH4 + 2O2 -> CO2 + 2H2O
What is fractional distillation?
it is a process which can be used to seperate Hydrocarbon fractions.
What is crude oil?definition
It is a fossil fuel, formed over millions of years due to high temp and pressure.
Are fossil fuels renewable/ infinite resources?
No. Fuels like coal, oil and gas are are non-renewable fuels which are non-finite
What is crude oil?in terms of hydrocarbons
It is a mixture of lots of different hydrocarbons, which are mainly alkanes.
What is the process of fractional distillation?
- The oil is heated until most of it has evaporated into gas- the gases enter the fractioning column- In the column there is a temperature gradient (hot at the bottom, colder as you go up)-Longer hydrocarbons have higher boiling points, so as the gases rise up the column, they condense back to a liquid at a lower point than shorter hydrocarbons, which condense at the top of the column- the crude oil is now separated into different fractions, which all have a similar amount of carbon atoms thus why they have a similar boiling point.
Why do some hydrocarbons condense earlier in the fractioning column?
they have higher boiling points, so they condense when the temperature becomes too low as they rise up as a gas. This is because of the high amount of carbon atoms they have, giving them a higher boiling point.
What are some uses of crude oil?
- oil for fuel for transport- lubricants, polymers, solvents
What is cracking?
Its the splitting up of long hydrocarbon chains to make them into shorter, more valuable chains.
Why are short hydrocarbon chains good fuels?
They are flammable so combust fully more easily, therefore are also in high demand.
What are some benefits to cracking?
- create more in demand, valuable short hydrocarbon chains- use up the less useful long chain hydrocarbons
What is the cracking equation?
Long chain hydrocarbon -> shorter chain hydrocarbon (alkAne) + an alkEne
What type of reaction is cracking?
it is a thermal decomposition reaction, which breaks down molecules by heating them up
What are the types of cracking?
Steam cracking and catalytic cracking
What is catalytic cracking?
- heat long chain hydrocarbons to vaporise them (turn to gas)- pass the vapour over a hot powdered aluminium oxide catalyst- the long chain hydrocarbon splits on the catalyst
What is steam cracking?
-vaporise the hydrocarbons, mis them with steam- heat them to a very high temperature
What are alkenes?
They are unsaturated hydrocarbons in a homologous series. They have 2 less hydrogens than a alkane due to their double bond ( C=C)
What does unsaturated mean?
a not fully bonded molecule as it doesnt have the maximum amount of single bonds (double bonds instead)
What is the alkene formula?
CnH2n
Why are alkenes more reactive than alkanes?
The alkene C=C double bond can open up, creating a single bond, which allows them to bond with other atoms.
What are the first 4 alkenes?
Ethene, Propene, Butene, Pentene
What is incomplete combustion?
When there isn’t enough oxygen for a complete combustion reaction, creating carbon monoxide as an extra product
What is the incomplete combustion formula?
Alkene + oxygen -> carbon + carbon monoxide + carbon dioxide + water
What is the result of Incomplete combustion?
- Smoky yellow flame
- less energy (than complete combustion of the same compound)
What is a functional group?
a group of atoms in a molecule that determine how a molecule typically reacts
What is the functional group of Alkenes?
C=C
How do alkenes usually react?
- react via addition reactions
- double bond opens up to leave a single bond + new atom is added to each carbon
What is Hydrogenation?
Addition of hydrogen
- opens up double bond, forms saturated alkane
- reacted with a catalyst
How is an Alcohol formed?
Alkenes react with steam, water is added across double bond-> alcohol is formed
ethene + steam ->(catalyst) Ethanol
What happens when Halogens react with Alkenes?
- Form saturated molecules
- C=C bond becomes C-halogen
-Bromine + Ethene-> Dibromoethane
How do you make ethanol industrially?
- react ethene + steam over a catalyst-> ethanol
- mixture passed from reactor to condenser (ethanol + water condense, unreacted ethene = recycled back to reactor)
- Alcohol purified from mixture through fractional distillation
How do you test for alkenes?
Addition of bromine to a double bond
-Orange bromine water added to a saturated compound (alkane), Alkane-> no reaction, stays bright orange
-Alkene-> bromine added to double bond, colourless compound
Bromine water + alkene -> (shake) colourless solution
OR
burn it, and it should have a smokier, yellower (luminous) flame
What are polymers?
long molecules
What are monomers?
small molecules
What is polymerisation?
When long molecules are formed by monomers joining together
What are addition polymers made from?
Unsaturated monomers (alkenes), double covalent bonds
What are plastics made of?
Polymers
- carbon based
- monomers: often alkenes
What is additional polymerisation?
- alkenes open up their double bonds
- join together to form polymer chains
ethene molecules-> polyethene/ polythene
What is the functional group of alcohol?
-OH
What is the general formula of an alcohol?
CnH2n+1OH
What are the properties of alcohols?
- flammable
- complete combustion in air-> carbon dioxide + water
- first 4 alcohols are soluble in water
- neutral pH
- react with sodium, produce hydrogen
- oxidised with oxygen, produce carboxylic acids
Methanol + oxygen-> methanoic acid
What are uses of alcohols?
- solvents in industry (methanol, ethanol) (dissolve most things water can and can’t dissolve ie hydrocarbons, oils, fats)
- fuels (ethanol-> spirit burners, non-smelly, burns fairly clearly)
What is fermentation?
The process of using an enzyme in yeast to convert sugars into ethanol + carbon dioxide
- 37 degrees
- slightly acidic solution
- anerobic conditions
What is the fermentation reaction?
Sugar-> ethanol + carbondioxide
(yeast)
What is the functional group of Carboxylic acid
-COOH
- end in -Anoic acid
What are the 4 carboxylic acids?
Methanoic acid, Propanoic acid, Butanoic acid, Pentanoic acid
How do Carboxylic acids react?
Like other acids.
- with carbonate-> salt + water + carbon dioxide
-anoate (methanoate, ethanoate)
- dissolve it water, partially dissociate, weak acidic solutions formed (higher pH)
What is the functional group of Esters?
- COO
How are esters formed?
with an alcohol and carboxylic acid
- use an acid catalyst
What is the process of condensation polymerisation?
- monomers that have different functional groups
- monomers reacts, bonds form, creating polymer chain
- for each bond that is formed, a small molecule is lost (ie water)
Diol + Dicarboxylic acid -> condensation polymer + small molecule (water)
What is a diol?
a compound containing two hydroxyl (OH) bonds.
- 2 alcohol functional group
What is a dicarboxylic acid?
a compound containing 2 carboxyl groups (COOH)
What are the 3 differences between addition polymerisation and condensation polymerisation?
Number of monomers
- AP: 1 monomer type, C=C
- CP: 2 monomer types, each have 2 of same functional group OR 1 monomer type with 2 different functional groups
Number of products
- AP: 1 product
- CP: 2 types of product, polymer + small molecule
Functional groups involved
- AP: C=C
- CP:: 2 reactive groups on each monomer
What are the functional groups of an amino acid?
- NH2 (amino group)
- COOH (acidic carboxyl group)
What polymers do Amino acids form?
polypeptides -> condensation polymerisation
How do amino acids form polymers?
amino group from each amino acid reacts with acid group of another, forming a polymer chain. For every bond a molecule of water is lost
What are proteins?
Long chain of polypeptides
- enzymes as catalysts (in body)
- haemoglobin transports oxygen
- antibodies form part of immune system
- body tissue
What gives proteins their different properties and shapes?
the order of amino acids
What is DNA?
Deoxyribonucleic acid
- contains genetic instructions develop, operate organisms
- large molecule, double helix structure
What are nucleotides?
2 polymer chains of monomers that DNA is made up of
- contain bases (1 each)
- A, T, C, G
How is DNA structured?
- Bases on different polymer chains pair up with each other, form cross links, keeps 2 sides of nucleotides together (double helix structure)
- order of bases acts as code for organisms genes
What are sugars?
small molecules that contains carbon, oxygen and hydrogen
How do sugars form larger carbohydrate polymers?
By reacting through polymerisation reactions
- starch- stores energy in living things
- cellulose-> plant cell walls
