Organic Chemistry Flashcards
What are hydrocarbons?
Molecules made up of hydrogen and carbon atoms ONLY.
What is the general formula for the homologous series of alkanes?
Cn H2n+2
Meth
One carbon
Eth
Two carbons
Prop
Three carbons
But
Four carbons
Pent
Five carbons
What ending signifies an alkane molecule?
ane
What are the first four members of the alkanes?
-methane
-ethane
-propane
-butane
How can alkanes be represented?
Using formulae e.g. C₂H₆
or using a displayed formula.
What do some properties of hydrocarbons depend on?
The size of their molecules.
What does the properties of different hydrocarbons influence?
How the hydrocarbons are used as fuels.
How does boiling point change with increasing molecular size and why?
The larger the molecules the higher the boiling point because the intermolecular forces between molecules are stronger and so require more energy to overcome.
How does viscosity change with increasing molecular size?
The larger the molecules the more viscous the hydrocarbon (i.e. the more gloopy/less runny).
How does flammability change with decreasing molecular size?
The smaller the molecules, the more flammable the hydrocarbon is (i.e. its easier to ignite).
Hydrocarbons with large molecules are often referred to as what?
Long-chain hydrocarbons
Hydrocarbons with small molecules are often referred to as what?
Short-chain hydrocarbons
What type of fuels are short-chain hydrocarbons often used as?
‘Bottled gases’.
Because they have lower boiling points they can be stored under pressure as gases in bottles.
What is a homologous series?
A group of organic compounds that have similar chemical properties, due to them having the same general formula/functional group.
Isomers
Molecules made of the same atoms but are arranged in different ways.
What are alkanes?
The simplest type of hydrocarbon where each carbon atom forms FOUR SINGLE covalent bonds.
Saturated compound (for understanding)
One which contains the maximum possible number of hydrogen atoms bonded to its carbon atoms, with no carbon-carbon double or triple bonds present.
basically only single bonds present!
What is crude oil?
Crude oil is a finite resource found in rocks.
It is a mixture of a very large number of compounds.
Most of the compounds in crude oil are hydrocarbons, most of which are alkanes.
How is crude oil formed?
Crude oil is formed from the remains of an ancient biomass consisting mainly of plankton that was buried in mud.
Over millions of years - with high temperature and pressure - the remains turn to crude oil (which can be drilled up from the rocks where it’s found).
How is crude oil separated into fractions?
Fractional Distillation
Describe and explain how crude oil is separated into fractions by fractional distillation.
Crude oil is heated to vaporise the hydrocarbons and they are fed into the bottom of a fractionating column.
The temperature of the column decreases from bottom to top so the fractions condense at different heights.
This is because they have different boiling points.
What are fractions? (chemistry)
Groups of hydrocarbons with a similar number of carbon atoms and therefore similar melting and boiling points.
What can fractions be processed to produce?
Fuels (e.g. for transport) and feedstock for the petrochemical industry.
Give examples of fuels we depend on for our modern lifestyle (highest to lowest boiling point = bottom to top of fractionating column).
heavy fuel oil, diesel oil, kerosene, petrol/gasoline, liquefied petroleum gases (LPG)
What is gasoline/petrol used for?
Fuel in car engines
What is kerosene used for?
Aircraft fuel
Feedstock
A raw material used to provide reactants for an industrial reaction.
(these reactions make new compounds for use in things such as polymers, solvents, lubricants, and detergents.)
Why is there such a vast array of natural and synthetic carbon compounds?
Due to the ability of carbon atoms to form families of similar compounds. (homologous series)
Petrochemical
A substance made from crude oil, via chemical reactions.
Feedstocks vs petrochemicals
The different hydrocarbons in crude oil are feedstocks and the things we make from them (polymers, lubricants, etc.) are petrochemicals.
What does the combustion of hydrocarbon fuels release?
Energy
What happens to carbon and hydrogen in the (hydrocarbon) fuels during combustion?
They are oxidised because they gain oxygen.
What are the products of the complete combustion of a hydrocarbon?
Carbon Dioxide + Water
(Water is in the gaseous form, aka water vapour).
Students should be able to write balanced equations for the complete combustion of hydrocarbons…
…with a given formula.
Complete combustion
Oxygen burns fully (as there’s an unlimited supply).
How do we test for carbon dioxide (product of complete combustion)?
Bubble the CO₂ gas through limewater.
For a positive result, the limewater turns cloudy.
How do we test for water (product of complete combustion)?
Add anhydrous copper sulfate powder.
For a positive result, the crystals will go from white to blue as the anhydrous copper sulfate goes to hydrated copper sulfate. (CuSO₄·5H₂O)
Alternatively use anhydrous cobalt chloride (blue to pink when hydrated).
When does incomplete combustion occur?
When there’s a limited supply of oxygen.
What are the products of incomplete combustion?
Carbon monoxide + Carbon + H₂O
Why is incomplete combustion bad?
-Not much energy is given out
-Carbon monoxide is a toxic gas: it binds to haemoglobin instead of oxygen leading to unconsciousness and death
Are longer or shorter hydrocarbons more useful? Why?
Short- chain hydrocarbons have lower boiling points so are more flammable and therefore make better fuels. They are in high demand.
Long-chain hydrocarbons are more viscous, forming thick gloopy liquids like tar which aren’t as useful.
Why are hydrocarbons used as fuels?
A large amount of energy is released when they combust completely.
Which reactants are oxidised (gain oxygen) during complete combustion?
Both hydrogen and carbon from the hydrocarbon.
What is cracking?
The breaking down of long-chain hydrocarbons into smaller ones.
What are the products of cracking?
A smaller alkane and an alkene.
What are some of the products of cracking useful as?
Fuels e.g. petrol for cars and kerosene for planes.
What type of reaction is cracking?
It is a type of thermal decomposition because molecules are broken down by heating them.
Hydrocarbons can be broken down (________) to produce _______, more _______ molecules
cracked
smaller
useful
Explain why compounds with the highest boiling points are found at the bottom of the fractionating column.
They have the longest molecules and therefore the strongest intermolecular forces.
Why is cracking needed?
To meet the high demand for more short-chain hydrocarbons such as petrol, which are useful as fuels.
Describe the conditions used for catalytic cracking.
-High temperatures
-A catalyst
Describe the conditions used for steam cracking.
-High temperatures
-Steam.
How can cracking be done?
By various methods including catalytic cracking and steam cracking.
Are alkanes or alkenes more reactive?
Alkenes, hence they react with bromine water.
What is the test for an alkene?
Bromine water is used to test for an alkene product.
For a positive result, the solution will go from orange to colourless.
What is the colour change when bromine water reacts with an alkene?
Orange to Colourless (if the hydrocarbon is indeed unsaturated).
Saturated
Contains only single bonds.
Unsaturated
Can contain (Carbon-Carbon) double bonds.
Practice some…
cracking equations!!!
Explain how modern life depends on the uses of hydrocarbons.
Petrol is an example of an alkane in high demand in modern life for its use as a fuel in car engines.
Liquefied petroleum gas (LPG) is another example of a hydrocarbon and can be used as fuel for commercial vehicles like forklifts or cooking and heating in homes off-grid.
What are alkenes used to produce?
Alkenes are used to produce polymers and act as starting materials for the production of many other chemicals.
What are alkenes?
Hydrocarbons with a double carbon-carbon bond.
(the functional group C=C)
What is the general formula for (the homologous series of) alkenes?
Cn H2n
Explain why alkene molecules are unsaturated.
Alkene molecules are unsaturated because they contain two fewer hydrogen atoms than the alkane with the same number of carbon atoms.
Name the first four members of the homologous series of alkenes.
-ethene
-propene
-butene
-pentene
How many bonds does a carbon atom make?
4
Why are alkenes more reactive than alkanes?
The C=C double bond can open up to make a single bond, allowing two carbon atoms to bond with other atoms.
When drawing alkenes using displayed formula, what MUST we do?
Make sure the 2nd carbon only has four bonds, not a sneaky extra C-H bond!
What determines the reactions of organic compounds?
The generality of reactions of functional groups.
How do alkenes react with oxygen?
In combustion reactions, the same way as other hydrocarbons.
They combust completely in large amounts of oxygen to form carbon dioxide and water.
Without enough oxygen, they undergo incomplete combustion to form carbon monoxide, carbon, water, and sometimes carbon dioxide.
Do alkenes tend to combust completely or incompetely when burned?
Alkenes tend to undergo incomplete combustion when burned because there isn’t enough oxygen in the air for complete combustion.
Why do alkanes tend to burn in the air with smoky flames?
Alkanes tend to burn in the air with smoky yellow flames because of incomplete combustion.
-Why is it yellow?
Does complete combustion or incomplete combustion release more energy?
Complete combustion
What is meant by ‘functional group’?
A group of atoms in a molecule that determines how that molecule typically reacts.
e.g. the functional group of alkenes is C=C so they all react in similar ways.
(this allows us to predict the products of a reactions).
How are alkenes able to react with hydrogen, water and the halogens?
The C=C double bond can open up to make a single C-C bond, allowing for the addition of other atoms on the 2 carbons.
These are examples of addition reactions.
What is an addition reaction?
A chemical reaction where two or more reactants combine to form a single product.
Alkene + Hydrogen → ?
Alkane
Hydrogenation
The addition of hydrogen (H₂)
Describe the conditions necessary for the addition of hydrogen to alkenes.
-A temperature of 60°C
-A nickel catalyst
Hept
7
Alkene + Water → ?
Alcohol
Describe the conditions necessary for the addition of water to alkenes.
-Steam
-A catalyst
-As water must be in the gaseous form, temperatures must be high
Describe the conditions necessary for the addition of halogens to alkenes.
-Room temperature
-Shake to mix
Describe one way of making ethanol industrially.
React ethene with steam in an addition reaction to form ethanol.
Pass the reaction mixture into a condenser.
Ethanol and water have a higher boiling point than ethene, so will condense.
Any unreacted ethene gas is recycled back into the reactor.
The alcohol can then be purified from the mixture by fractional distillation.
What is an alcohol?
A homologous series of organic compounds containing the functional group -OH.
What is the suffix for an alcohol?
anol
What is the general formula for an alcohol?
Cn H2n +1 OH
(using subscripts!!)
Alkene + Halogen → ?
Halogenoalkane.
e.g. Ethene + Bromine → Dibromoethane
Ethene + Iodine → ?
Diiodoethane
List the possible products of: ethane + halogen → ?
(the ones you need to know)
Difluoroethane
Dichloroethane
Dibromoethane
Diiodoethane
Name the first four alcohols
Methanol
Ethanol
Propanol
Butanol
What are the ways we can show ethanol? (formulaically)
C₂H₅OH
CH₃CH₂OH (this shows the structure of the alcohol better)
What are the main uses of alcohols?
-They are burned as fuels, used in antibacterial gels, and used as solvents.
Describe what happens when any of the first four alcohols react with sodium.
Fizzing.
Hydrogen gas would be produced.
Describe what happens when any of the first four alcohols burn in air.
They undergo complete combustion to produce carbon dioxide and water.
What are the products of complete combustion of an alcohol?
Carbon dioxide + Water
You need to be able to balance equations for the combustion of alcohols.
How should you go about doing this?
-The number of carbons is the same as the number of carbon dioxides
-Then check the number of hydrogens are the same
-Re-balance the oxygens using a 1/2
-Double to get whole numbers
Describe what happens when any of the first four alcohols react with an oxidising agent/ oxygen from the air.
Alcohols are oxidised (gain oxygen) to form a carboxylic acid.
Are alcohols flammable?
Yes! Therefore, they make very good fuels.
What is the pH of alcohols?
7 (neutral=green)
Why are alcohols such as methanol and ethanol used as solvents in industry?
They can dissolve things that water can’t dissolve like hydrocarbons, oils, and fats.
Does ethanol smell?
No
What is ethanol?
The alcohol found in alcoholic drinks such as wine or beer.
How is ethanol usually made?
Using fermentation
How is ethanol made less often?
Cracking crude oil (to form a shorter alkane and ethene)
Then reacting ethene produced with steam in the presence of a catalyst (hydration)
Producing aqueous solutions of ethanol by fermentation.
-Sugar solutions are fermented using yeast
-An enzyme in yeast converts the sugars into ethanol (aqueous state as in a solution)
-Carbon dioxide is also produced
What is the word equation for producing ethanol using sugar cane?
(in yeast)
glucose → ethanol + carbon dioxide
What are the conditions for the fermentation of sugar using yeast?
-A temperature of around 37°C (optimum)
-A slightly acidic solution
-Under anaerobic conditions
What would happen if sugar was fermented in the wrong conditions? (using yeast)
Different pH’s or temperatures would cause the enzyme to denature or work at a slower rate.
Describe how carboxylic acids can be produced from alcohols.
Alcohols can be oxidised to produce carboxylic acids either by leaving them exposed to oxygen in the air or by using an oxidising agent.
What are carboxylic acids?
A homologous series of compounds with the functional group -COOH.
What is the suffix for carboxylic acids?
-anoic acid.
What are the first four carboxylic acids?
methanoic acid
ethanoic acid
propanoic acid
butanoic acid
Draw the first four carboxylic acids.
Get out of bed and do it
don’t be confused. y the reactions- water is produced too x
How can the structures of carboxylic acids be represented?
CH₃ COOH
or using the structural formula (double bonded O and single bonded O-H)
What is the general formula for carboxylic acids?
CnH2n+1COOH
Carboxylic acid + Metal Carbonate → ?
Salt + Water + Carbon dioxide
How do we work out the name of the salt produced from a carboxylic acid + a metal carbonate?
1st name = name of metal
2nd name = eth/prop/but…ANOATE
Ethanoic acid + Sodium carbonate → ?
Sodium ethanoate + carbon dioxide + water
What happens when carboxylic acids dissolve in water?
They partially ionise/dissociate into H⁺ ions, forming weak acidic solutions.
Explain why carboxylic acids are weak acids.
They are only partially ionised in an aqueous solution.
The reaction is reversible (⇄).
pH is 4 to 5
Ethanoic acid in water equation?
CH₃COOH ⇄ CH₃COO⁻ + H⁺
Carboxylic acid + alcohol → ?
ester + water
What do carboxylic acids need to react with an alcohol?
An acid catalyst (e.g. concentrated sulfuric acid).
What is the only ester you could be asked about/to name?
Ethyl ethanoate.
CH₃COOC₂H₅
What are the reactants that produce ethyl ethanoate (and water)?
Ethanoic acid + Ethanol
CH₃COOH + C₂H₅OH
Draw ethyl ethanoate.
DO IT (It’s an ester x)
What type of reaction produces ethanoic acid from ethanol?
Oxidation.
What does volatile mean?
Evaporates easily.
Explain why the solution of ethanoic acid has a higher pH than the solution of hydrochloric acid.
Ethanoic acid is a weaker acid because it only partially dissociates into hydrogen (H⁺) ions in water.
How do we test for an alcohol vs a carboxylic acid?
Add a a named carbonate e.g. sodium carbonate
The carboxylic acid will effervesce
The alcohol won’t.
Uses of esters?
-flavourings
-perfumes
What is addition polymerisation?
The reaction by which many small molecules (monomers) join together to form very large molecules (polymers).
Name some polymers that can be made from alkenes, by addition polymerisation.
poly (ethene)
poly (propene)
In addition polymers, the repeating unit (bit inside the bracket) has the same atoms as what?
The monomer, because no other molecule is formed in the reaction.
BUT the C=C bond becomes a C-C bond!
Which functional group exists in alkene monomers?
C=C
In terms of addition polymerisation, you should be able to…
-recognise addition polymers and monomers from diagrams and the functional group C=C in the monomers
-draw diagrams to represent the formation of a polymer from a given alkene monomer
-relate the repeating unit to the monomer.
Practice…
Drawing diagrams to represent the formation of a polymer from a given alkene monomer. xx
What are plastics made of?
Polymers, which are usually carbon based (with alkene monomers.)
What are the conditions necessary for addition polymerisation?
-Pressure
-A catalyst
Does it matter what’s attached to the repeating unit in polymers?
No - the only thing reacting is the carbons in the middle! You could get a funny lil’ shape or something but ignore and do the normal process!
What polymer would tetrafluoroethene form?
poly (tetrafluoroethene)
its as easy as putting poly (name of o.g. compound)
What must we remember when drawing addition polymerisation reactions?
The little n both in front of the alkene, and outside the bracket of the polymer.
Which alcohol is found in wine and beer?
Ethanol.
In catalytic cracking, what is the catalyst used?
Powdered aluminium oxide, which the vaporised long- chain hydrocarbons are passed over to be broken down.
Is an alkene a saturated or unsaturated hydrocarbon?
Unsaturated
Alkenes join together by __________ polymerisation.
addition
Why can’t butane be used as a monomer in addition polymerisation?
Butane is an alkane so doesn’t have any double bonds, which are required for addition polymerisation.
What does condensation polymerisation involve?
Monomers with two functional groups.
Where do condensation polymers get their name?
When monomers with two functional groups react they join together by losing small molecules such as WATER.
What are the simplest (condensation) polymers produced from?
Two different monomers with two of the same functional groups on each monomer.
e.g. a diol and a dicarboxylic acid.
How are polyesters made?
By the condensation of a diol and a dicarboxylic acid.
Diol monomer
Contains two -OH (alcohol) functional groups.
HO-▭-OH
Dicarboxylic acid monomer
Contains two -COOH functional groups.
HOOC-▭-COOH
How do we recognise a poly(ester)?
It will contain the functional group -COO (in an ESTER LINK).
How can condensation polymers be made?
specifically poly (ester)
By joining dicarboxylic acid monomers and diol monomers together by ester links.
In condensation polymerisation reactions, what does a square box represent?
The rest of the molecule in its simplified form.
How do we draw the repeating unit produced by condensation polymerisation?
- Eliminate the waters from the inside and outside
- Join molecules in the middle together using the left over bonds
- Place square brackets over the left over bonds either side
- Put an n on the outside
- Include 2n H₂O if required
Can condensation polymerisation happen between two of the same type of monomer?
Yes! The monomer units can be identical if each has 2 different functional groups.
e.g. amine on one side and carboxyl on the other.
Amine functional group?
NH₂
What is a dimer?
Two monomers combined.
Compare the functional groups involved in addition vs condensation polymerisation.
Addition - Carbon-carbon double bond in monomer
Condensation - Two functional groups on each monomer
Compare the number of products from addition vs condensation polymerisation.
Addition - Only one product made
Condensation - Two products are made (a polymer and a small molecule like water
Compare the monomers involved in addition vs condensation polymerisation.
Addition - Only one monomer type is involved, containing a C=C bond.
Condensation - Can involve 2 monomer types, each containing two of the same functional group
OR
One monomer type with two different functional groups e.g. amino acids.
When doing a polymerisation comparison…
…don’t overcomplicate it!
e.g. you can mention whether a substance is a hydrocarbon or not.
How many functional groups are in an amino acid molecule?
2
How do amino acids react?
By condensation polymerisation to produce polypeptides.
What are polypeptides?
The chains of amino acids that fold into unique proteins.
In an amino acid, what does ‘R’ represent?
The side group.
Different amino acids have different R groups.
Name the two functional groups found in amino acids.
-Amine group
-Carboxyl group (carboxylic acid group)
Draw the general displayed formula for…
…an amino acid!!! x
Write out the polypeptide that glycine polymerises to form.
Hints:
-The functional groups COOH and NH₂ react
-Water is lost.
What is the R group of alanine?
CH₃
Different amino acids can be combined in the same chain to produce what?
Proteins.
What are the monomers called that make up cellulose?
Glucose monomers
What are the monomers called that make up starch?
Glucose monomers
Name the two polymers that can be formed from glucose monomers.
-Cellulose polymers (+H₂O)
-Starch polymers (+H₂O)
Name the monomers from which proteins are made.
Amino acids.
What is the use of cellulose?
-It’s found in plant cell walls, with the function of providing the cell with structural support and protection.
What is the use of starch?
-Living things use starch to store energy (as a complex carbohydrate)
What is a poly saccharide?
A large(complex) carbohydrate molecule, composed of long chains of smaller sugar units (monosaccharides) bonded together.
e.g. starch
What is a mono saccharide?
A simple sugar unit. e.g. glucose
What are sugars?
Small molecules that contain the elements carbon, oxygen, and hydrogen.
How can sugar molecules react together?
Through polymerisation reactions , to form larger carbohydrate polymers (poly saccharides)
What does DNA stand for?
Deoxyribonucleic acid.
Why is the large molecule DNA essential for life?
It encodes genetic instructions for the development and functioning of living organisms and viruses.
Describe the structure of DNA.
-Two polymer chains
-Made from four different monomers called nucleotides
-In the form of a double helix
What gives DNA its double helix structure?
The bases on different polymer chains pair up to form cross-links (hydrogen bonds).
These bonds keep the 2 polymer chains together to give the double helix structure.
The amine group of one amino acid can react with the ________ group of another, and so on, to form _ _______ ____.
carboxylic acid/carboxyl
a polymer chain
In condensation polymerisation reactions, for every bond that is formed…
…a new molecule of water is lost.
What are the three main uses of ethanol?
-It is used as a chemical feedstock to produce other organic compounds
-It can be burned to be used as biofuel
-It can be used to make alcoholic drinks
Evaluate steam cracking to form ethanol.
Advantages: Ethene is cheap and the reaction itself is cheap & efficient.
Disadvantages: Ethene is made from crude oil which is a non-renewable resource, so if it starts to run out it will become expensive.
What is fermentation?
The anaerobic respiration of sugars by yeast cells to produce ethanol and carbon dioxide.
Where does the fermentation of sugar to form ethanol occur?
Fermentation tanks, requiring yeast cells which have naturally occurring enzymes to catalyse the reaction.
Evaluate fermentation to form ethanol.
Advantages: The sugar/glucose used is a renewable resource so can’t run out. Yeast are easy to grow.
Disadvantages: The process can be relatively slow. The ethanol produced isn’t pure so must be distilled by fractional distillation.
Carboxylic acids partially dissociate in water to form a _______ and a _______.
The negative ion has a name ending with ‘______ ion’.
negative ion
hydrogen ion
anoate
What does each functional group lose when carboxylic acid reacts with an alcohol to form an ester?
The carboxylic acid loses its OH group, and the alcohol loses the H from its OH group.
Which names can be used for the ester functional group?
Ester link
Ester bond
(ester group- but not in polymerisation reactions)
Which functional groups does an amino acid have?
An ‘R’ group
An amine group
A carboxylic acid group
What are the three elements that make up carbohydrates?
Hydrogen
Oxygen
Nitrogen
How are poly(esters) made?
The condensation of a diol and a dicarboxylic acid.
NH₂
amine group
