Unit 7- Organic Chemistry Flashcards
What is a hydrocarbon
Any compound that is formed from carbon and hydrogen atoms only
What is crude oil
-finite resource found in rocks
-it is the remains of an ancient biomass consisting mainly of plankton that was buried in mud
-it is a mixture of a very large number of compounds
-Most of the compounds in crude oil are hydrocarbons called alkanes
General formula for alkanes are
Cn H2n+2
What is an alkane
-all have C-C single bond and contain H-H single bonds
-they are a homologous series
-saturated compounds (linked by single bonds)
-the first four are methane , ethane, propane and butane
What is a homologous series
A group of organic compounds that react in the same way
How does properties of hydrocarbons vary with size of their carbon chain
-the shorter the carbon chain the less viscous
-the shorter the carbon chain the more volatile (lower boiling point)
-shorter the carbon chain the more flammable
Word equation for complete combustion
Hydrocarbons + oxygen —> carbon dioxide + water + (energy )
What occurs during complete combustion
-releases a lot of energy
-the carbon and hydrogen in the fuels are oxidised (gain of oxygen)
What does crude oil produce
petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases
What is produced by the petrochemical industry
solvents, lubricants, polymers, detergents
What is fractional distillation
-many hydrocarbons in crude oil can be separated into fractions, each of which contains molecules with a similar number of carbon atoms
-The fractions can be processed to produce fuels and feedstock for the petrochemical industry
Process of fractional distillation
-oil is heated until most of it has turned into a gas
- the gas enters a fractionating column
-in the column there is a temperature gradient (hot at the bottom and gets cooler as you go up)
-the longer hydrocarbons have higher boiling points so they condense back into liquids and drain out of the column near the bottom
-the shorter hydrocarbon have lower boiling points they condense and drain out near the top of the column
-you end up with crude oil separated out into different fractions that all contain similar no of carbon atoms so similar boiling points
What is cracking
-Hydrocarbons are broken down (cracked) to produce smaller more useful molecules
-it can be done by various methods including catalytic cracking and steam cracking
Uses for crude oil in modern life
For modern transport =Petrol,diesel oil, kerosene, liquefied petroleum
Petrochemical industry =solvents , lubricants, polymers
Process of cracking (both of them)
It is a Thermal decomposition reaction.
Catalytic cracking :
-heat long chain hydrocarbons to vaporise them
-then the vapour can be passed over a hot powdered aluminium oxide catalyst
-the long chain molecules split apart on the surface of the speak of the catalyst
Or steam cracking :
-if you vaporise them, mix them with steam and then heat them to a very high temperatures
Why are alkanes often used as fuels in
As they release energy when burnt
General formula for alkenes
Cn H2n
What is a alkene
-all have C=C (carbon double bond)
-carbon double bond means that alkenes have two fewer hydrogens this makes them unsaturated
-more reactive than alkanes
What are the first 4 alkanes
-methane (CH4)
-Ethane(C2H6)
-butane (C3H8)
-propane (C4H10)
What are the first four alkenes
-Ethene (C2H4)
-propene (C3H6)
-butene (C4H8)
-pentene (C5H10)
Incomplete combustion of alkenes word equation
-burn with a smoky flame
Alkene + oxygen —> carbon + carbon monoxide + carbon dioxide + water (+energy)
What is the addition of hydrogen known as
Hydrogenation
What happens during addition reactions
The carbon double bond will open up to leave a single bond and a new atom is added to each carbon
What is needed for an alkene to react with hydrogen
A catalyst
How do halogens react with alkenes
-react in addition reactions with halogens such as bromine, chorine and iodine
-the molecules formed are saturated with the C=C bond opening up and becoming bonded to a halogen
Test for alkenes with bromine water
-when an alkene is added to orange bromine water and then shaken the bromine will turn into a colourless compound
-however when an alkane is added bromine water will remain orange
Steam and alkenes reaction
-an alcohol is formed
-for example Ethene + steam (water) —> ethanol
-the double bond will also open up so H20 is bonded to it
What is a polymer
-Long molecules formed when lots of small molecules called monomers join together
-this reaction is called polymerisation
-plastics are made up of polymers they are usually carbon based and their monomers are alkenes
Process of addition polymerisation
- The monomers that make up addition polymers have a double covalent bond
- lots of unsaturated molecules (alkenes) can open up their double bonds and join together to form polymers chains
- High Pressure and catalyst needed for this to happen
- When the monomers react in addition polymerisation the only product is the polymer so an addition polymer contains the exact same type and number of atoms as the monomers
What is the functional group of alcohols
-OH
What is a homologous series
Group of chemicals that react in similar ways because they have the same functional group
Name the 5 homologous series groups
Alcohols, alkenes, alkanes, carboxylic acid, esters
General formula of an alcohol
Cn H2n+1 OH
What are the first 4 alcohols and there symbols
-methanol (CH3 OH)
-ethanol (C2H5 OH)
-propanol (C3H7 OH)
-butanol(C4H9 OH)
Properties of alcohols
-flammable
-undergo complete combustion to produce carbon dioxide and water
-first 4 alcohols are all soluble in water so solutions have neutral pH
-can be oxidised by reacting with oxygen to produce a carboxylic acid
Uses of alcohols
-methanol and ethanol are uses as solvents in industry this is because they can dissolved most things water can and also things water can’t dissolve (oils)
-first 4 alcohols are used as fuels for example in spirit burners
Fermentation word equation
Sugar —yeast—> ethanol + carbon dioxide
-ethanol produced is aqueous
Conditions for fermentation
-uses an enzyme in yeast to convert sugar to ethanol
-happens fast at 37 degrees temperatures in a slightly acidic solution and under anaerobic conditions
-if conditions were different (higher temp or lower pH the enzyme would denature or work at slower rate)
Functional group of carboxylic acids
-COOH
What are the first four carboxylic acids and their formulas
Methanoic acid- H COOH
ethanoic acid- CH3 COOH
propanoic acid- C2H5 COOH
butanoic acid-C3H7 COOH
What happens when alcohols react with sodium
Salt will be formed + hydrogen
-Bubbles of gas will be seen
-not very violent
-sodium + ethanol —> sodium ethoxide
What happens when carboxylic acids react with carbonates (sodium carbonate)
-they produce a salt + water + carbon dioxide
(Ethanoic acid + sodium carbonate —> sodium ethanoate + water + carbon dioxide)
-all salt formed here will end in -anoate
Why are carboxylic acids a weak acid
They partially ionise in a solution
What happens when carboxylic acid react with water
-can dissolve in water
-when they dissolve they ionise and release H+ ions resulting in an acidic solution
-don’t ionise completely so a weak acid
Functional group of esters
-COO
How are esters formed
-formed from an alcohol and a carboxylic acid
-alcohol + carboxylic acid —> ester + water
-an acid catalyst is needed for reaction to take place (sulphuric acid )
-example = ethanol + ethanoic acid —> ethyl ethanoate + water
What is condensation polymerisation
-involves monomers with two different functional groups
-the monomers react together and bonds form making polymer chains
-for each new bond that forms a small molecule (water) is lost
-the simplest type of condensation polymers contain two different types of monomers with two of the same functional group
Similarities and differences between addition and condensation polymerisation
Similarities = both produce polymers
Differences = addition - only one type of monomers, only one product formed, only react with alkene (carbon carbon double bond)
condensation - two monomer types each containing two same functional group or one monomer type with two different functional group, two products formed (polymer and water)
What is a monomer
Small molecules or atoms that bond together to form polymers
What two functional group do amino acid contain
-basic amino group (NH2)
-carboxyl group (COOH)
Example of an amino acid
Glycine
How can amino acids form polymers
-React by condensation polymerisation
-To form polypeptides
-the amino group can react with the acid group of another to form a polymer chain, for every new bond a molecule of water is lost
-one or more long chain polypeptides are known as proteins
Uses for proteins
Enzymes working as catalysts, haemoglobin transports oxygen, antibodies
What is DNA
-deoxyribonucleic acid
-large molecule essential for life
-it encodes instructions for development and functioning of living organisms and viruses
What is the structure of DNA
-two polymers chains made from four different monomers called nucleotides
-form of a double helix
-each nucleotide contains a small molecule called a base
What are some other naturally occurring polymers in life
Proteins starch and cellulose
How do simple sugar form a polymer
Sugars react together through polymerisation reactions to form starch and cellulose
