Organic Chemistry Flashcards
Hydrocarbons
Compounds that contain only hydrogen and carbon
Homologous Series
A family of hydrocarbons with similar chemical properties who share the same general formula
Alkane general formula
Cn H2n+2
Saturated Compound
A compound that only has single bonds e.g. a saturated hydrocarbon only has 4 single covalent bonds
Alkane Properties
- Boiling Point increases with chain length
- Methane, Ethane, Propane and Butane are all gases at room temp. (low boiling points)
- Shorter alkanes are volatile, longer ones are viscous
- Shorter alkanes are more flammable
Hydrocarbon Combustion Equation
Hydrocarbon + Oxygen –> CO2 + H2O
Why is fractional distillation used to separate crude oil?
- Different hydrocarbons in crude oil have different boiling points
- Fractional distillation means they will separate at different temperatures
How does fractional distillation separate crude oil?
- Crude oil is vapourised
- Gas is put into fractionating column which is hotter at the bottom and cooler at the top
- Gas rises up the column and condenses into liquid when it reaches a part of the column at a lower temp. than it’s boiling point
- Different hydrocarbons will condense at different temperatures
Where will longer hydrocarbons condense?
- Near the bottom of the column
- The have high boiling points so they won’t stay gas for long and stay low down the column where it’s hotter
- E.g. Bitumen, heavy fuel petrol
Where will shorter hydrocarbons condense?
- Near the top of the column
- They have lower boiling points so they will stay gas for longer and rise higher up the column where it’s cooler
- E.g. Kerosene, petrol, LGP
What are shorter hydrocarbons used for?
- Fuels
- Short hydrocarbons are more flammable so they produce more fuel
What are longer hydrocarbons used for?
- They are broken down into to shorter chains using cracking
Feedstock
A raw material used to provide reactants for an industrial reaction
Petrochemicals
A substance made from crude oil by fractional distillation e.g.bitumen, diesel oil, kerosene
Cracking
Breaking down large hydrocarbons into smaller, more useful ones
What are the 2 types of cracking?
- Catalytic cracking
- Steam cracking
Catalytic cracking
- Crude oil is vapourised by heating it
- Vapour is passed over a hot aluminium oxide catalyst
- Hydrocarbons come into contact with catalyst and split into smaller hydrocarbons
Steam cracking
- Crude oil is vapourised by heating it
- Vapour is mixed with steam
- The vapour steam mixture is heated to very high temperatures
- This causes the hydrocarbons to split
General formula for cracking
Long chain alkane –> Shorter chain alkane + alkene
What are the leftover alkenes used for
- Production of polymers
- Starter materials for other substances
Alkene Properties
- Have a double bond
- Means they are unsaturated
- More reactive than alkanes
(because of double bond) - Can join together to form polymers by breaking their double bonds into 2 or more bonds
Test for Alkenes
- Add bromine water to a liquid substance
- If alkenes are present, the bromine water goes from orange to colourless
What are the different types of addition reactions?
- Addition of hydrogen
- Addition of water
- Addition of halogens
Hydrogen addition Reaction
- Alkene bonds with hydrogen to form an alkane
- Reaction needs a catalyst
- The product is saturated
- CnH2n + H2 –> CnH2n+2
Water Addition Reaction
- Alkene bonds with water to form an alcohol
- Reaction needs a catalyst and high temperatures
- Product is saturated
- CnH2n + H2O –> CnH2n+1OH
Halogen Addition Reaction
- Alkene bond with a halogen to form a halogen ethane (e.g. dibromoethane)
- Product is saturated
How do you name an addition polymer?
- Add ‘poly’ in front of the monomer’s name
- Put the monomer name in brackets
Addition Polymerisation Conditions
- High pressure
- Prescence of a catalyst
Alcohols
- Homologous Series
- Have an OH functional group
- Names are similar to alkanes (except they have an ‘ol’ instead of an ‘e’
- E.g. ethanol, propanol
- General formula: CnH2n+1OH
Properties of Alcohols
- Flammable: Complete combustion (alcohol + water –> CO2 +water
- Soluble: Dissolve in water to form a neutral pH solution
- Oxidise to form carboxylic acids
Uses of Alcohols
- Used as fuel (as they can combust)
- Used as solvents in industry (can dissolve things water can’t; hydrocarbons, lipid compounds)
- Used in alcoholic drinks
Uses of Ethanol
- Chemical feedstock to produce other organic compounds
- Used as biofuel
- Used in alcoholic drinks (wine, beer, spirits)
Ethene + Steam Method
- C2H4 +H2O –> C2H5OH
- This is addition polymerisation of water
Conditions for Ethene + Steam Method
- High temperatures (300 degrees C)
- High pressure (60-70 atms)
- Phosphoric Acid Catalyst
Advantages for Ethene + Steam Method
- Ethene is cheap
- Overall reaction is cheap and efficient
Disadvantages for Ethene + Steam Method
- Ethene is made from crude oil which is non-renewable
- If crude oil starts to run out then it will become expensive
Fermentation Method
- Glucose –> Ethanol + Carbon Dioxide
- Fermentation is anaerobic respiration of sugars by yeast cells
Conditions for Fermentation Method
- Carried out in fermentation tanks
- Yeast cells should have naturally occurring enzymes to catalyse the reaction
- Temperatures of 30-40 degrees C
- Anaerobic conditions (no oxygen) so ethanol doesn’t oxidise
Advantages of Fermentation Method
- Glucose/sugar is a renewable resource
- Yeast is easy to grow
Disadvantages of Fermentation Method
- Process is slow
- Doesn’t produce pure ethanol so it needs to be separated by fractional distillation which is expensive
Carboxylic Acids
- Homologous Series
- Functional group of COOH
- Names all end in ‘anoic acid’
- E.g. Ethanoic Acid, Propanoic Acid
- General Formula CnH2n+1COOH
Properties of Carboxylic Acids
- Weak Acids (partially ionise)
- Ionisation of carboxylic acids is written as a reversible reaction
- E.g Propanoic Acid <–> Propanoate ion + Hydrogen+ ion
- React with metal carbonates to form a salt+water+CO2
How are carboxylic acids made?
By oxidising an alcohol with an oxidising agent
Esters
- Homologous Series
- Functional group of -COO-
- General Formula: R-COO-R
Properties of Esters
- Pleasant smelling
- Smell sweet or fruity so used in food flavouring and perfumes
- Volatile (Evaporate easily)
How are esters made?
- Carboxylic acid + Alcohol
- Presence of sulfuric acid catalyst
- The OH from the carboxylic acid and the H from the alcohol form water
- Products: Ester + Water
Condensation Polymerisation
- Monomers bond to form a polymer + water
- Requires a diol monomer and a dicarboxylic acid
- The diol gives up a hydrogen atom
- The dicarboxylic acid gives up an OH group
Polyester
- Biodegradable
- Bacteria breaks down the ester links
- This is different to addition polymers that aren’t biodegradable
Naturally occurring polymers
- Polypeptides
- DNA
- Carbohydrates
Polypeptides
- Long chains of amino acids
- Chain folds up to form a protein
- Amino acid contain an amine group and a carboxylic acid group (COOH)
- Amino group means an amino acid can join with other amino acids by condensation polymerisation
DNA
- Made from nucleotides
- All nucleotides contain bases
Carbohydrates
- Only made from carbon, hydrogen and oxygen
- Polymers are called polysaccharides
- Monomers are called monosaccharides
