C14 - Organic Chemistry Flashcards
Organic compound
Organic compounds are those which contain carbon
Hydrocarbons
A hydrocarbon is a compound that contains only hydrogen and carbon atoms
Ways to represent hydrocarbons (3)
- Displayed Formulae
- General Formulae
- Structural Formulae
Structural isomers
Structural isomers are compounds that have the same molecular formula but different structural formulae
Homologous series
This is a series or family of organic compounds that have similar features and chemical properties due to them having the same functional group
Functional group
The functional group is a group of atoms which are bonded in a specific arrangement that is responsible for the characteristic reactions of each member of a homologous series
Saturated compounds
Have molecules in which all carbon-carbon bonds are single bonds (e.g. alkanes)
Unsaturated compounds
Unsaturated compounds consist of molecules in which one or more carbon-carbon bonds are not single bonds (they contain double bonds of carbon)
Fuel
A fuel is a substance which when burned, releases heat energy
* This heat can be transferred into electricity, which we use in our daily lives
Common foosil fuels
Coal, natural gas and hydrocarbons
Main constituent of natural gas
Methane (CH4)
Petroleum
Petroleum is also called crude oil and is a complex mixture of hydrocarbons which also contains natural gas
* It is a thick, sticky, black liquid that is found under porous rock (under the ground and under the sea)
Fraction
A group of molecules with a defined boiling point range which distils off at the same place during fractional distillation
Process of fractional distillation (3 steps)
- Crude oil enters the fractionating column and is heated so vapours rise
- Vapours of hydrocarbons with very high boiling points will immediately turn into liquid and are tapped off at the bottom of the column
- Vapours of hydrocarbons with low boiling points will rise up the column and condense at the top to be tapped off
Fractional distillation
Properties of fractions
- Viscosity: more carbon atoms results in increased attraction between molecules so it is more viscous
- Colour: as carbon chain increases, colour gets darker
- Melting/boiling point: larger molecule results in greater intermolecular force meaning an increased boiling point
- Volatility: (the tendency for a substance to vaporise) the greater molecular size, the less volatile
Uses of fractions
- Refinery gas: heating and cooking
- Gasoline: fuel for cars (petrol)
- Naphtha: raw product for producing chemicals
- Kerosene: for making jet fuel (paraffin)
- Diesel: fuel for diesel engines (gas oil)
- Fuel oil: fuel for ships and for home heating
- Lubricating oil: for lubricants, polishes, waxes
- Bitumen: for surfacing roads
Alkanes
Alkanes are a group of saturated hydrocarbons
* general formula: C(n)H(2n+2)
Properties of alkanes (name 4)
- Colourless compounds
- Generally unreactive compounds
- Can undergo combustion
- Can be cracked into smaller molecules
- Can react with halogens in the presence of light in substitution reactions
Name, molecular formula and display formula of first 4 alkanes
Names of first 10 alkanes
- Ethane
- Methane
- Propane
- Butane
- Pentane
- Hexane
- Heptane
- Octane
- Nonane
- Decane
Substitution reaction
One atom (or group of atoms) is swapped with another atom (or group of atoms)
Complete combustion
When there is enough oxygen to burn the alkane, it is called complete combustion. Carbon dioxide and water are released.
CH4(g)+ 2O2(g)——–> CO2(g)+2H2O(l)
Alkenes
Alkenes are unsaturated hydrocarbons with carbon-carbon double bonds (C=C)
* general formula: C(n)H(2n)
Name the first 10 alkenes
- Ethene
- Propene
- Butene
- Pentene
- Hexene
- Heptene
- Octene
- Nonene
- Decene
- Undecene
Name, molecular formula and display formula of first 4 alkenes
Catalytic cracking (definition and process of 5 steps)
Used to convert longer-chain molecules into short-chain hydrocarbons
1. Heating the hydrocarbon molecules to around 600-700 degrees to vaporise them
2. The vapours pass over a hot powdered catalyst of alumina or silica
3. This breaks the covalent bonds in the molecules as the come in conttact with the surface of the catalyst
4. Causes thermal decomposition reactions
5. Molecules are broken in a random way producing mixture of small alkenes or alkanes
Process of distinguishing between alkenes and alkanes using bromine water
- Bromine water is an orange coloured solution
- When it is shaken with alkane it will remain orange as alkanes do not have a double carbon bond so bromine remains
- When shaken with an alkene bromine turns coloursless
- bromine atoms add across the double bond creating and addition reaction
Alkene and hydrogen addition reaction
- These are hydrogenation reactions and occur at 150ºC using a nickel catalyst
- An alkane is formed as the molecule loses the double bond
Alkene and steam addition reaction
- Alkenes also undergo addition reactions with steam in which an alcohol is formed
- also called a hydration reaction
- Conditions:
- Temperature of around 300ºC
- Pressure of 60 - 70 atm
- Concentrated phosphoric acid catalyst
Alcohols
All alcohols contain the hydroxyl (-OH) functional group which is the part of alcohol molecules that is responsible for their characteristic reactions
* general formula: C(n)H(2n+1)OH
Names of first 5 alcohols
- methanol
- ethanol
- propanol
- butanol
- pentanol
Ethanol
Ethanol (C2H5OH) is one of the most important alcohols
* It is the type of alcohol found in alcoholic drinks such as wine and beer
* It is also used as fuel for cars and as a solvent
Ethanol complete combustion
Alcohols burn in excess oxygen and produce CO2 and H2O
* C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H20 (l)
Two ways of manufacturing ethanol
- Hydration of ethene with steam
- Fermentation of glucose
Process of hydration of ethene to produce ethanol (3 steps)
- A mixture of ethene and steam is passed over a hot catalyst of phosphoric acid at a temperature of approximately 300 °C
- The pressure used is 60 atmospheres (6000kPa)
- The gaseous ethanol is then condensed into a liquid for use
Process of fermentation of glucose to produce ethanol (4 steps)
- Sugar or starch is dissolved in water and yeast is added
- The mixture is then fermented between 25 and 35 °C with the absence of oxygen for a few days
- Yeast contains enzymes that catalyse the break down of starch or sugar to glucose
- If the temperature is too low the reaction rate will be too slow and if it is too high the enzymes will become denatured
- The yeast respire anaerobically using the glucose to form ethanol and carbon dioxide: C(6)H(12)O(6) → 2CO(2) + 2C(2)H(5)OH
- The yeast are killed off once the concentration of alcohol reaches around 15%, hence the reaction vessel is emptied and the process is started again
Polymers
Large molecules built by linking 50 or more smaller molecules called monomers
* connected via covalent bonds
Copolymers
- Some polymers contain just one type of unit (poly-cloroethene)
- Others contain two or more different types of monomer units and are called copolymers (nylon)
Types of linakges of polymers
- Covalent bonds
- Amide links
- Ester links
Addition polymers
Addition polymers are formed by the joining up of many monomers and only occur in monomers that contain C=C bonds
Deducing polymer from monomer (drawing repeat units)
- To draw a repeat unit, change the double bond in the monomer to a single bond in the repeat unit
- Add a bond to each end of the repeat unit
- The bonds on either side of the polymer must extend outside the brackets (these are called extension or continuation bonds)
- A small subscript n is written on the bottom right hand side to indicate a large number of repeat units
- Add on the rest of the groups in the same order that they surrounded the double bond in the monomer
Condensation polymers
When two different monomers are linked together with the removal of a small molecule, usually water
Key difference between condensation polymers and addition polymers
- Addition polymerisation forms the polymer molecule only
- Condensation polymerisation forms the polymer molecule and one water molecule per linkage
Forming Nylon
Nylon is a polyamide made from dicarboxylic acid monomers (a carboxylic with a -COOH group at either end) and diamines (an amine with an -NH2 group at either end)
* Each -COOH group reacts with another -NH2 group on another monomer
* An amide linkage is formed with the subsequent loss of one water molecule per link
Balancing combustion reactions
- carbon
- hydrogen
- oxygen
