Organic Chemistry Flashcards
What is a hydrocarbon?
Any compound that contains carbon and hydrogen only
What is an alkanes?
Alkanes are the simplest type of hydrocarbon you can get. They are a homologous series - a group of organic compounds that react in the same way. Each carbon atom forms four single covalent bonds.
What is the general formular for alkanes?
CnH2n+2
What are the first four alkanes?
Methane
Ethane
Propane
Butane
What are the properties of alkanes?
The shorter the carbon chain the more runny the hydrocarbon is - less viscous. They are also more volatile i.e lower boiling points. The shorter they are the more flammable.
Give a uses of hydrocarbons with small chains of carbon
Bottled gas - short chains
What is the reaction of complete combustion of a hydrocarbon?
hydrocarbon+oxygen->carbon dioxide+water
The carbon and hydrogen are both oxidised.
What is the balanced equation for complete combustion of a hydrocarbon?
CH4 + 2O2 -> CO2+2H2O
What is crude oil?
Crude oil is a fossil fuel, it is the remains of dead plants and animals mainly plankton - over millions of years high pressure and temperature turned the remains into crude oil. It is a non renewable energy source as it is finite.
What is fractional distillation?
This is how crude oil is separated by fractional distillation.
The oil is heated until most of it has turned into gas. The gases enter the fractionating column.
In the column there’s a temperature gradient
The longer hydrocarbons have high boiling points.
They condense condense back into liquids and drain out of the column early on, when they are near the bottom.
The shorter hydrocarbons have lower boiling points. They condense and drain out much later on much later on, near to the top where it is cooler.
What is crude oils various uses?
Oil provides the fuel for most modern transport
Feed stock to make new compounds for use in things like polymers,solvents,lubricants and detergents
Organic compounds
What is cracking?
It is the process of making alkanes made by fractional distillation smaller and more useful. It is also used to produce alkenes these are used for starting materials when making polymers
Give the process of cracking
Cracking is a thermal decomposition reaction
The first step is to heat long-chain hydrocarbons to vaporise them (turn them into gas)
The vapour is passed over a hot aluminium oxide catalyst
The long chain molecules split apart on the surface of the specks of catalyst - this is catalytic cracking.
You can also crack hydrocarbons by mixing it with steam then heating.
A long-chain hydrocarbon molecule will turn into a shorter alkane and alkene.
What are Alkenes?
Alkenes are hydrocarbons with a double bond between two of the carbons atoms in their chain. Alkenes have two fewer hydrogen’s but the same amount of carbon making them unsaturated. Alkenes are reactive as this double bond can break allowing the two carbons to bond with the other atoms. The first four alkenes are ethene (with two carbon atoms) propene (three C’s), butene (four C’s) and pentene (five C’s).
What is the general formula for alkenes?
CnH2n
What is the formula for an alkene going through incomplete combustion?
alkene+oxygen=>carbon+carbon monoxide+water+energy
How can you tell when there is incomplete combustion with an alkene?
There is a smoky yellow flame, and less energy is being released.
What is the symbol equation for this?
C4H8+5O2=>2CO+2CO2+4H2O
What is a functional group?
Is a group of atoms in a molecule that determine how that molecule typically reacts.
How does hydrogen react with an alkene?
The addition of hydrogen is known as hydrogenation, hydrogen can react with the double bonded carbons to open up and become saturated.
What is crude oil?
It is a finite resource made from plankton remains over millions of years it is found in rocks. Crude oil is a mixture of hydrocarbons.
Give properties of alkanes
They are saturated molecules
The carbon atoms are fully bonded
Give properties of the alkane group
As the size of the hydrocarbon increases the molecules get more viscous
The shorter the chain of hydrocarbon the more flammable.
The longer the hydrocarbon the higher the boiling point
How are hydrocarbons used as fuels?
Hydrocarbon fuels release energy when burned. During the combustion the carbon and hydrogen atoms react with oxygen and oxidise. If the oxygen is unlimited there will be complete combustion and the products will be CO2 and water.
Why do we use fractional distillation for crude oils?
So they are more useful - fuels such as kerosene, heavy fuel oil and liquefied petroleum gas
What are other uses for the fractions of crude oil other than fuel?
Feed stock - solvents, lubricants, detergents and polymers.
What are the results of cracking?
You produce a smaller chain alkane and an alkene
What are the types of cracking?
Catalytic cracking - This is were heat is used as a catalyst
Steam cracking - this is were we use heat and steam
What is the difference between alkenes and alkanes?
Alkenes are more reactive.
How do you test for alkenes?
You use bromine water - the water should turn colourless.
Why are alkene molecules unsaturated?
They have two fewer hydrogen atoms than the equivalent alkane
Describe the combustion of alkenes
Combusting alkenes also produces carbon particles you can view this as it burns in air with a smoky flame
Describe the reaction with alkenes and hydrogen
This reaction requires a temperature of 150 degrees Celsius you will also need a nickel catalyst. The alkene will react to produce a alkane.
What is a homogoulus series?
This is a functional group of a molecule that all react the same way.
Descibe the reaction of alkenes with water
All akenes react in the same way due to their functional group - the product is ethanol when reacting ethene with steam (hydration) this is done under 300 degree conditions and a 70 atmosphere pressure with phosphoric acid as a catalyst. This reaction is reversible. The HO and H atoms add to the carbon double bond.
Descibe the reaction of alkenes with halogens
The reaction is rapid - When ethene and chloride react the product is dichlroethane, the chlorine atoms have added across the double bond of carbon and the double carbon bond has turned into a single carbon bond.
How can you increase the yield of the product when reacting an alkene and water?
Any unreacted alkene and steam are passed back through the catalyst.
Describe the main uses of alcohols
Fuels
Solvents
Drinks
How is ethanol produced?
Hydration - non renewable, alkene mixed with water. Requires a lot of energy.
Fermentation - a sugar solution mixed with yeast this converts the sugar solution to a solution of ethanol. Carbon dioxide is produced. The temperature should be around 30 degrees and the conditions most be anaerobic conditions. It does not take a lot of energy to make the ethanol and it is renewable as the sugar is taken form plant sugars.
What are the first four alchohols
Methanol
Ethanol
Propanol
Butanol
What is the functional group of alcohols?
The OH
What are the disadvantages of fermentation?
The product is an aqueous solution which then needs to be purified through distillation.
Describe the solubility of alcohols in water
Alcohols are soluble in water and form neutral solutions. As the number of carbon atoms increases the solubility decrease.
Describe how alcohols react with sodium
The product are a sodium oxide and hydrogen. When methanol reacts with sodium the products are sodium methoxide and hydrogen.
Describe how alcohols react with an oxidising agent
The products are a carboxylic acid and water. For example propanol + oxidising agent => Methanoic acid +water
Describe the combustion of alcohols.
This produces carbon dioxide and water in air.
Describe the structure of the carboxylic acids
They have the functional group of COOH the carbon and singular oxygen have a double bond. The rest of the atom is made of carbon and hydrogen like an alkane.
Describe what happens when carboxylic acids dissolve in water
In water they are weak acids, they ionise to make the an ion and a H+. For example ethanoic acid=>ethanoate ion+H+
Describe what happens when carboxylic acids dissolve in water
In water they are weak acids, they ionise to make the an ion and a H+. For example ethanoic acid=>ethanoate ion+H+.
This is a reversible reaction as it only partially ionises.
Describe the reaction of carboxylic acids with metal carbonates
Metal carbonate - the products are a salt water and carbon dioxide gas.
Ethanoic acid + sodium carbonate => sodium ethanoate + CO2 +H2O.
Describe the reaction of carboxylic acids and alcohols
We make esters and water. This reaction requires sulphuric acid as a catalyst. It is a reversible reaction.
Ethanoic acid + ethanol => ethyl ethanoate
How are esters named?
The alcohol as the first name and the carboxylic acid as the second
Why do we want to produce esters?
They are really useful molecules and often have a pleasant smell used in a lot of foods.
Describe what is meant by an addition polymer
A polymer is made by joining together thousands of small identical molecules - monomers.
Describe what is meant by an addition monomer
These are the small molecules that form to make a polymer. These are usually alkenes.
Describe what is meant by a repeating unit
This is the pattern that repeats throughout the polymer. To display a repeating unit find where it begins and ends put it in brackets and write a small n on the outside - this tell us there is a large number of repeating units in that polymer.
What are the two different types of polymers?
Addition polymers and condensation polymers
What is the meaning of poly?
Many
What us an addition polymer?
The repeating unit has the same atoms as the monomer this is because no other molecules are formed in the reaction. The repeating unit does not contain a double carbon bond.
Describe what is meant by a condensation polymer
These are mode of monomers however the monomers are not alkenes. When these monomers react we lose small molecules such as water.
How are condensation polymers produced?
We start with two different monomers. Each monomer has two of the same functional group. One monomer has two carboxylic acid functional groups and the other has two alcohol groups. The carboxylic acid reacts with the alcohol this makes an ester and water.
What is the repeating unit for condensation polymer?
Pick any two adjacent monomer units and draw them out. Put them in brackets and write a letter n
How are condensation polymers produced?
We start with two different monomers. Each monomer has two of the same functional group. One monomer has two carboxylic acid functional groups and the other has two alcohol groups. The carboxylic acid reacts with the alcohol this makes an ester and water. This polymer is then called a polyester
What is the structure of amino acids?
They have two different functional groups
