T7: organic chemistry Flashcards
What is a hydrocarbon?
any compound that is formed from carbon and hydrogen atoms only.
What is the simplest type of hydrocarbon you can get?
Alkane
What is the formula for alkanes?
C(n)H(2n+2)
What is a homologous series?
a group of organic compounds that all react in a similar way and have similar/shared properties as they have the same functional group.
Are alkanes saturated or unsaturated compounds?
Alkanes are saturated compounds- each carbon atom forms four single covalent bonds: C-C single bonds.
What are the first 4 alkanes and what are their formulas
1) Methane (CH(4))
2) Ethane (C(2)H(6))
3) Propane (C(3)H(8))
4) Butane (C(4)H(10))
(Monkeys Eat Peanut Butter)
What happens to a hydrocarbon when the length of the carbon chain changes?
As the length of the carbon chain changes, the properties of the hydrocarbon change.
What are the properties that change in hydrocarbons and what are they like in shorter length carbon chains?
1) The shorter the carbon chain, the more runny a hydrocarbon is; LESS VISCOUS.
2) The shorter the carbon chain, the more volatile the hydrocarbon; LOWER BOILING POINTS.
3) The shorter the carbon chain, the more FLAMMABLE the hydrocarbon is.
What does the properties of hydrocarbons affect?
- affects how they are used for fuels.
e.g. short chain hydrocarbon with lower boiling points are used as “bottled gases”- stored under pressure as liquids in bottles.
When does complete combustion occur?
when there is plenty of oxygen present.
What happens in the complete combustion of hydrocarbons (give the equation)?
The complete combustion of any hydrocarbon in oxygen releases lots of energy.
hydrocarbon + oxygen → carbon dioxide + water
In complete combustion what is oxidised?
the carbon and hydrogen from the hydrocarbon.
Why are hydrocarbons used as fuels?
due to the amount of energy released when they combust completely.
What is crude oil?
crude oil is a fossil fuel.
How is crude oil formed?
- It’s formed from the remains of plants and animals (ancient biomass), mainly plankton, that died millions of years ago and were buried in mud.
- Over millions of years, with high temperature and pressure, the remains turn into crude oil, which can be drilled up from the rocks where it’s found.
What are 3 fossil fuels?
natural gas, oil and coal.
What are fossil fuels called non renewable fuels?
as they take so long to make that they are being used up much faster than they’re being formed. They are finite resources- one day they’ll run out.
What is crude oil? (in terms of hydrocarbons)
Crude oil is a mixture of hydrocarbons, most of which are alkanes.
How are the different compounds in crude oil separated?
fractional distillation.
What are the steps for fractional distillation of hydrocarbons?
1) The oil is heated until most of it has turned into a gas. The gases enter a fractionating column and the liquid bit is drained off.
2) In the column there is a temperature gradient; at the bottom it is hot and it gets cooler as you go up.
3) The longer hydrocarbons have high boiling points so they condense back into liquids and drain out of the column early on, when they’re near the bottom. The shorter hydrocarbons have lower boiling points so they condense and drain out much later on, near to the top of the column where it is cooler.
4) You end up with the crude oil mixture separated out into different fractions. Each fraction contains a mixture of hydrocarbons that all contain a similar number of carbon atoms, so have similar boiling points.
What are the different fractions and what is the approximate number of carbons in the hydrocarbons in that fraction?
- Liquefied petroleum gas (3)
- Petrol (8)
- Kerosene (15)
- Diesel (20)
- Heavy fuel oil (40)
- Bitumen
What is liquefied petroleum gases mostly consisting of?
propane and butane.
What are the uses for each fraction of crude oil?
- LPG (fuel for domestic cooking and heating and in vehicles)
- Petrol (fuel for cars)
- Kerosene (fuel for aircrafts)
- Diesel (fuel for cars and trains)
- Heavy fuel oil ( fuel for ships and power stations and can this can be heating oil, fuel oil or lubricating oil).
- Bitumen (for roads and roofs)
Why is crude oil important in the petrochemical industry?
The petrochemical industry uses some of the hydrocarbons from crude oil as feedstock to make new compounds for use in things like solvents, detergents, lubricants and polymers.
What are the products of crude oil all an example of?
organic compounds (compounds containing carbon atoms).
What is the reason why there is such a The vast array of natural and synthetic carbon compounds?
There is such a large variety of products because carbon atoms can bond together to form different groups called homologous series.
What is cracking?
Where hydrocarbons are broken down into smaller, more useful products.
Why is cracking used?
- Short chain hydrocarbons are flammable so make good fuels and are in high demand. However, long chain hydrocarbons form thick gloopy liquids like tar which are not useful…
- so a lot of the longer alkane molecules produced by fractional distillation are turned into smaller, more useful ones by cracking.
What does cracking produce?
As well as alkanes, alkenes (another type of hydrocarbon) is produced. Alkenes can be used as a starting material when making lots of other compounds and can be used to make polymers.
What is the equation for cracking?
long chain hydrocarbon molecule → shorter alkane molecule + alkene
What type of reaction is cracking?
a thermal decomposition cracking; breaking down molecules by heating them.
What are the 2 types of cracking?
- catalytic cracking
- steam cracking
What are the steps in catalytic cracking?
1) Heat the long chain hydrocarbons to vaporise them into a gas.
2) The vapour is then passed over a hot powdered aluminium oxide catalyst.
3) The long chain molecules split apart on the surface of the specks of the catalyst.
What are the steps in steam cracking?
Vaporise them , mix with steam and then heat them to a very high temperature.
What are alkenes?
Alkenes are hydrocarbons which have. double bond between two of the carbon atoms in their chain. This double bond ( C=C) makes them unsaturated.
How are alkenes different to alkanes?
The C=C double bond in alkenes means that alkenes have 2 fewer hydrogen atoms than alkanes containing the same number of carbon atoms.
What is more reactive and why: alkanes or alkenes?
Alkenes
The C=C double bond can open up to make a single bond, allowing the 2 carbon atoms to bond with other atoms.
What are the first 4 alkenes?
Ethene (2 carbons)
Propene (3 carbons)
Butene (4 carbons)
Pentene (5 carbons)
What is the general formula for alkenes?
C(n)H(2n)
What happens when alkenes combust in large amounts of oxygen?
Alkenes combust completely producing only water and carbon dioxide.
How do alkenes tend to combust in the air and why?
- they tend to go under incomplete combustion when burned in air as there isn’t enough oxygen in the air for alkenes to combust completely.
What is produced when alkenes undergo incomplete combustion?
alkenes + oxygen → carbon + carbon monoxide + carbon dioxide + water
What happens when alkenes undergo incomplete combustion?
results in a smoky yellow flame and less energy is being released compared to complete combustion of the same compound.
What is a function group?
a functional group is a group of atoms in a molecule that determine how that molecule typically reacts.
What is the functional group of alkenes and what does this mean?
All alkenes have the functional group “C=C” so they all react in similar ways.
How does alkenes react?
Via addition reactions. The C=C double bond will open up to leave a single bond and a new carbon atom is added to each carbon.
What is the addition of hydrogen known as?
Hydrogenation.
What happens when an alkene reacts with hydrogen?
The hydrogen reacts with the double bonded carbons to open up the double bond to form the equivalent, saturated alkane.
The alkene is reacted with hydrogen in the presence of a catalyst.
What happens when alcohol react with steam?
When alcohol react with steam, water is added across the double bond and an alcohol is formed.
How can ethanol be made?
By mixing ethene with steam and then passing it over a catalyst.
How can ethene be made industrially?
- The conversion from ethene to ethanol is one way of producing ethanol industrially.
- After the reaction has taken place, the reaction mixture is passed from the reactor into a condenser.
- Ethanol and water have a higher boiling point than ethene so both condense whilst any unreacted ethene is recycled back into the reactor.
- The alcohol can then be purified from the mixture by fractional distillation.
What happens when alkenes react with halogens?
Alkenes react in addition reaction with halogens such as bromine, chlorine and iodine.
The molecules formed are saturated, with the C=C carbons each becoming bonded to a halogen atom.
What is the equation for the reaction between an ethene and bromine?
ethene + bromine → dibromoethene
How can an alkene be tested?
using bromine water; the addition of bromine to a double bond tests for an alkene
What is a positive and negative result for an alkene?
Negative: If the bromine water is added to a saturated compound (e.g. an alkane) no reaction will occur and it will stay bright orange.
Positive: If the bromine water is added to an alkene the bromine will add across the double bond making a colourless dibromo-compound; so the bromine water is colourless (has been decolourised).
orange → colourless
What are polymers and how are they formed?
Polymers are long molecules formed when small molecules called monomers join together. This reaction is called polymerisation.
What does polymerisation require?
- high pressure
- catalyst
What is plastic made up of?
Plastic is made up of long chain molecules called polymers. They’re usually carbon based and their monomers are often alkenes.
What are addition polymers made up of?
The monomers that make up addition polymers have a double covalent bond.
What is addition polymerisation?
Lots of unsaturated monomer molecules (like alkenes) can open up their double bond and join together to form polymer chains.
What is the product in addition polymerisation and what does this mean?
When the monomers react in addition polymerisation reactions, the only product is the polymer, so an addition polymer contain the exact same number and type of atoms as the monomers that formed it.
How can different forms of poly(ethene) be produced from ethene?
use different (reaction) conditions e.g temperature or pressure
What is the functional group of alcohols?
All alcohols have an ‘-OH’ functional group and so they all end in “ol”.
What is the general formula for alcohols?
C(n)H(2n+1)OH
What are the 1st four alcohols and what are their formulas?
1) Methanol CH(3)OH
2) Ethanol C(2)H(5)OH
3) Propanol (C(3)H(7)OH
4) Butanol C(4)H(9)OH
Why must it be written as CH(3)OH not CH(4)O?
CH(4)O does not ahoy the -OH functional group.
What are the similar properties of the 1st for alcohols?
1) Alcohols are flammable. They undergo complete combustion in air to produce carbon dioxide and water.
2) Methanol, ethanol, propanol and butanol are all soluble in water. Their solutions have a neutral pH.
3) They also react with sodium and one of the products of this reaction is hydrogen.
4) Alcohols can be oxidised by reacting with oxygen (e.g. from the air) to produce a carboxylic acid.
5) Different alcohols form different carboxylic acids.
What happens to the solubility of alcohols as the length increases?
the solubility decreases as the length of the alcohol molecule gets longer so distinct layers would be left.
Which alcohols are used in solvents and why?
Methanol and ethanol are used as solvents in the industry as they can dissolve most things that water can but they can also dissolve substance that water can’t dissolve e.g. oil, hydrocarbons and fats.
What are the 1st four alcohol used? (give an example)
As fuels; ethanol is used as a fuel in spirit burners, it burns fairly cleanly and is non-smelly.
What is ethanol used in and how is it made?
Ethanol is the alcohol found in alcoholic drinks such as beer or wine. It’s usually made using fermentation.
How is ethanol produced by fermentation and what state is ethanol?
Fermentation uses an enzyme in the yeast to convert sugars into ethanol. Carbon dioxide is also produced. The reaction occurs in a solution so the ethanol produced is aqueous.
What are the optimum conditions for fermentation?
Fermentation happens the faster at a temperature of around 37C, in a slightly acidic solution and under anaerobic conditions (no oxygen).
What would happen if the conditions of the fermentation were different?
Under these conditions the enzyme in the yeast works best to convert the sugar to alcohol. If these conditions were different, such as a lower pH/higher temperature or higher pH/lower temperature, the enzyme would be desaturated or could work at a much slower rate.
What are carboxylic acids?
Carboxylic acids are a homologous series that all have -‘COOH’ as their functional group. Their names all end in ‘-anoic’.
What are the first four carboxylic acids and what are their formulas?
1) Methanoic acid: HCOOH
2) Ethanoic acid: CH(3)COOH
3) Propanoic acid: C(2)H(5)COOH
4) Butanoic acid: C(3)H(7)COOH
How do carboxylic acids react with carbonates?
Carboxylic acids (like any other acid) react with carbonates to form a salt, water and carbon dioxide.
What are the salts produced by a reaction between carboxylic acids and carbonates like?
The salt ends in “anoate”. For example methanoic acid will form a methanoate and ethanoic acid will form a ethanoate.
What is the word equation for the reaction between ethanoic acid and sodium carbonate?
ethanoic acid + sodium carbonate → sodium ethanoate + water + carbon dioxide
What solution do carboxylic acids dissolve in and what does this mean?
- dissolve in water.
- When they dissolve they ionise and release H+ ions resulting in an acidic solution.
- But they don’t ionise completely (not all acid molecules release H+ ions), they just form weak acidic solutions. This means they will have a higher pH (are less acidic) than aqueous solutions of strong acids with the same concentration.
What is the functional group of esters?
‘-COO-‘
How are esters formed?
- Esters are formed from an alcohol and a carboxylic acid.
- An acid catalyst is usually used (e.g. concentrated sulphuric acid.
alcohol + carboxylic acid → ester + water
What are 4 uses of esters?
- flavourings
- perfumes
- solvents
- plasticisers
What two properties of esters make them suitable for use in perfumes?
fruity smell and volatile (evaporates easily / quickly).
What is the word equation for ethanoic acid + ethanol?
ethanoic acid + ethanol → ethyl ethanoate + water.
This requires an acid catalyst.
(MUST learn ethyl ethanoate)
What does condensation polymerisation involve?
condensation polymerisation involves monomers which contain different (2) functional groups.
What is the brief process of condensation polymerisation?
- The monomers react together and bonds form between them, making polymer chains.
- For each new bond that forms, a small molecule like water is lost, hence it is called condensation polymerisation.
What are the simplest types of condensation polymers?
The simplest types of condensation polymers contain two different of monomers, each with 2 of the same functional group.
Give an example of condensation polymerisation
For example:
ethanediol ( a DIOL) and hexanedioic (a DICARBOXYLIC ACID) acid polymerise to produce a polyester(CONDENSATION POLYMER) and water.
In condensation polymerisation formulas, what do the boxes represent?
The boxes within the displayed formulas represent the carbon chain.
What are the 3 factors that are different in addition polymerisation to condensation polymerisation?
- number of types of monomers
- number of products
- function groups involved in polymerisation
What are the of factors of number of types of monomers , number of products, function groups involved in polymerisation for addition polymerisation?
- number of types of monomers: Only one monomer type with a C=C bond.
- number of products: only one product formed.
- function groups involved in polymerisation: carbon-carbon double bond in monomer.
What are the of factors of number of types of monomers , number of products, function groups involved in polymerisation for condensation polymerisation?
- number of types of monomers:
1) Two different monomers each containing 2 of the same function groups. OR
2) One monomer type with 2 different functional groups. - number of products: Two types of products, a polymer and water.
- function groups involved in polymerisation: Two reactive groups on each monomer.
What do amino acids contain?
two different functional groups; a basic amino group (NH2) and an acidic carboxyl group (COOH).
What is the smallest and simplest amino acid possible?
glycine
(check book to learn the structure).
What can amino acids form?
form polymers known as polypeptides via condensation polymerisation.
How are polypeptides formed?
- An amino group from an amino acid can react with the acid group of another and so on to form a polymer chain. For every new bond that is formed, a molecules of water is lost.
What are one or more chain of polypeptides known as?
proteins.
What are the uses of proteins in the body?
- enzymes work as catalysts
- haemoglobin transports oxygen
- antibodies form a part of the immune system
- the majority of body tissues is made from proteins.
What is DNA?
DNA (deoxyribonucleic acid) is found in every living thing and many viruses. It contains genetic instructions that allow the organism to develop and operate.
What is DNA made of?
Two polymer chains of monomers called ‘nucleotides’. The nucleotides each contain a small molecule known as a ‘base’. There are four different bases, A, C, G, T.
What do the bases do?
The bases on different polymers chains pair up with each other to form CROSS LINKS keeping the 2 strands of nucleotides together and giving the double helix structure.
What does the order of the bases do?
the order of the bases acts as a code for an organism’s genes.
What are sugars?
sugars are small molecules that contain carbon, hydrogen and oxygen.
What happens when sugars react?
Sugars can react together through polymerisation reactions to form larger carbohydrate polymers. E.g. starch, which living things use to store energy, and cellulose, which is found in plant cell walls.
