Flashcards in Organic chemistry Deck (44):
What is a hydrocarbon?
Any compound that is formed from hydrogen and carbon atoms only
What are alkanes?
The simplest type of hydrocarbon you can get. They are a homologous series (react in a similar way) and are saturated compounds (each carbon atom forms four single covalent bonds)
What are the first four alkanes?
Methane, ethane, propane and butane
What is the general formula for alkanes?
C n H 2 n+2
How do hydrocarbon properties change with the chain length?
Shorter chains are more runny (less viscous), more volatile (have lower boiling points) and are more flammable
Give the word equation of the complete combustion of a hydrocarbon
Hydrocarbon + oxygen --> carbon dioxide + water (+energy)
Why are hydrocarbons used as fuels?
They release a large amount of energy when combusted completely
How can fractional distillation be used to separate hydrocarbon fractions?
Oil heated until turns to gas, gas goes into fractionating column, longer hydrocarbons have high boiling points, condense near bottom (hot at bottom), shorter hydrocarbons have lower boiling points, condense at top (cold at top)
What is crude oil used for in modern life?
Fuel for transport and is used used in petrochemical industry to make new compounds in things like polymers, solvents, lubricants and detergents
What is cracking used for?
As short-chain hydrocarbons are more flammable, they make better fuels, so to achieve this, longer hydrocarbons are split up through cracking
What are alkenes?
A type of hydrocarbon used as a starting material when making lots of other compounds and can be used to make polymers
What type of reaction is cracking?
Thermal decomposition - breaking down molecules by heating them
How do you perform catalytic cracking?
Long-chain hydrocarbons are vaporised, vapour is passed over a hot powdered aluminium oxide catalyst, long-chain molecules split apart on the surface of the specks of catalyst
How do you perform steam cracking?
Long-chain hydrocarbons are vaporised, mixed with steam and then heated to a high temperature
What is the structure of an alkene?
They have a double bond between two of the carbon atoms in their chain, meaning that they have two fewer hydrogens compared to the alkane with the same number of carbons. The C=C bond can open up to make a single bond, allowing them to bond with other atoms
What are the first four alkenes?
Ethene, propene, butene and pentene
Give the general formula for alkenes
Why do alkenes burn with a smoky flame?
Alkenes only combust completely with large amounts of oxygen, which isn't available, so they tend to undergo incomplete combustion, producing carbon and carbon monoxide
Give the word equation for the incomplete combustion of alkenes
Alkene + oxygen --> carbon + carbon monoxide + carbon dioxide + water (+energy)
What is a functional group?
A group of atoms in a molecule that determine how that molecule typically reacts
What is hydrogenation?
The addition of hydrogen; it can react with the double-bonded carbons to open up the double bond and form the equivalent, saturated, alkane
What happens when steam reacts with alkenes?
Water is added across the double bond and an alcohol is formed
How can ethanol be made industrially from ethene?
Steam is mixed with ethene, passed over a catalyst, reaction mixture is passed from reactor to condensor, ethanol and water have a higher bp than ethene so both condense whilst any unreacted ethene is recycled back. Ethanol can then be purified with fractional distillation
What happens when halogens react with alkenes?
The molecules formed are saturated, with the C=C carbons each becoming bonded to a halogen atom
How can the addition of bromine to a double bond be used to test for alkenes?
When orange bromine water is added to a saturated compound, no reaction will happen, but if it is added to an alkene, the bromine will add across the double bond, making a colourless dibromo-compound
How are polymers formed?
Through polymerisation: where lots of small molecules called monomers join together. This usually needs high pressure and a catalyst
What happens when addition polymers are made?
The monomers that make up addition polymers have a double covalent bond. This means that lots of unsaturated monomer molecules (alkenes) can open up their double bonds and join together to form polymer chains. This is called addition polymerisation.
How do you draw the displayed formula of an addition formula from the displayed formula from it's monomer?
Draw the two alkene compounds, replace the double bond with a single bond, add an extra single bond to each of the carbons, fill in the rest of the groups the same way that they surrounded the double bond in the monomer, put a pair of brackets around the repeating bit and put an 'n' after it
What is the general formula of an alcohol?
What are the first four alcohols in the homologous series?
Methanol, ethanol, propanol and butanol
What do all alcohols contain?
An -OH functional group
What are the properties of the first four alcohols?
Soluble in water, solutions have neutral pH, react with sodium to make hydrogen and can be oxidised to make a carboxylic acid
Why are alcohols used as solvents and fuels?
They can dissolve substances that water can't and they burn fairly clearly without releasing odours
Give the word equation of fermentation
Sugar --> ethanol + carbon dioxide
What conditions does fermentation work best at and why?
37°C in a slightly acidic solution with anaerobic conditions because the enzyme in the yeast works best to convert the sugar to alcohol
What are carboxylic acids?
A homologous series of compounds that all have -COOH as a functional group. Their names end in 'anoic acid'
Give the word equation of the reaction between a carboxylic acid and a carbonate
Carboxylic acid + carbonate -> salt (ending in 'anoate') + water + carbon dioxide
e.g. ethanoic acid + sodium carbonate --> sodium ethanoate + water + carbon dioxide
What happens when carboxylic acids dissolve in water?
They ionise and release H+ ions, resulting in an acidic solution. However, they do not ionise completely so form weak acidic solutions
What are esters?
They are formed from an alcohol and a carboxylic acid using an acid catalyst and have the functional group -COO
Give the word equation for the reaction that produces an ester
Alcohol + carboxylic acid --> ester + water
What is condensation polymerisation?
When monomers react together, bonds form between them, making polymer chains. For each new bond that forms, a small molecule (e.g. water) is lost
What makes up an amino acid?
It contains two different functional groups: a base amino group (NH2) and an acidic carboxyl group (COOH)
What are the polymers that amino acids form called?
Polypeptides (made via condensation polymerisation)