Organic chemistry (up to esters) Flashcards
What is a hydrocarbon?
any compound formed from only hydrogen and carbon atoms
What is a homologous series?
a group of organic compounds that react in a similar way
What are saturated compounds?
compounds where each carbon atom forms four single covalent bonds
What are alkanes?
the smallest type of hydrocarbon with single carbon bonds (C-C)
a homologous series (all react in a similar way)
saturated compounds
What is the general formula for an alkane?
CnH2n+2
What are the first four alkanes?
methane
ethane
propane
butane
How do the properties of hydrocarbons change as the chain gets shorter?
the shorter the chain…
- the more runny and less viscous (gloopy) it is
- the more volatile it is (turns into a gas at a lower temp so has a lower boiling point)
- the more flammable the hydrocarbon is
When does complete combustion occur?
when there is a plentiful supply of oxygen
What are the waste product of the complete combustion of any hydrocarbon?
carbon dioxide and water vapour
(complete combustion of a hydrocarbon)
hydrocarbon + oxygen ->
carbon dioxide + water (+ energy)
What is crude oil?
a fossil fuel formed from remains of organisms buried in mud over millions of years, which can be drilled up to be used
it is also a mixture of lots of different hydrocarbons
What is fractional distillation used for?
used to separate hydrocarbon fractions in crude oil
Explain the process of fractional distillation.
- the oil is heated and the gas enters a fractioning column
- there’s a temperature gradient (hotter at the bottom and cooler towards the top)
- longer hydrocarbons have higher boiling points so condense into liquids lower down the column so drain off lower down the column
- shorter hydrocarbons have lower boiling points so condense towards the top of the column
What is cracking?
splitting long chain hydrocarbons into smaller hydrocarbons
because shorter chain hydrocarbons are more useful
What are the two types of cracking?
catalytic cracking (using a catalyst) steam cracking (using steam)
What happens in catalytic cracking?
- long chain hydrocarbons are heated to vaporise them
- the vapour is passed over a hot powdered aluminium oxide catalyst
- the long chain hydrocarbons split apart on the surface of the catalyst
What happens in steam cracking?
- long chain hydrocarbons are heated to vaporise them
- the long chain hydrocarbons are mixed with steam
- then they are heated to a very high temperature
What are alkenes?
unsaturated hydrocarbons with a double carbon bond (C=C)
they are much more reactive than alkenes
What is the general formula for alkenes?
CnH2n
What are the first four alkenes?
ethene
propene
butene
pentene
(incomplete combustion of alkenes in air)
alkene + oxygen ->
carbon +carbon monoxide + carbon dioxide + water (+ energy)
What is a functional group?
a group of atoms in a molecule that determine how the molecule typically reacts
eg. all alkenes have a C=C bond so all act in a similar way
What is hydrogenation?
the addition of hydrogen
hydrogen can react with the double bonds of carbon (in an alkene) to open up the double bond and form the equivalent alkane
Alkenes react via addition reactions, what does this mean?
the carbon-carbon double bond will open up to leave a single bond and a new atom is added to each carbon
How do alkenes react with halogens?
in addition reactions
the molecules formed are saturated, with the C=C carbons each becoming bonded to a halogen atom
How can you test for alkenes?
alkenes turn bromine water colourless (whereas if it is added to a saturated compound it would remain bright orange)
What happens when steam reacts with alkenes?
water is added across the double bond and an alcohol is formed
eg. ethene and water in the presence of a catalyst produce ethanol, which can be used to make alcohol in industry
What are polymers?
long molecules formed when lots of small molecules (monomers) join together
What is polymerisation?
the reaction where monomers join together to form polymers
What is addition polymerisation?
when lots of unsaturated monomer molecules (alkenes) open up their double bonds and join together to form polymer chains
(the only product is the polymer)
What is the general formula of an alcohol?
CnH2n+1OH
What are alcohols?
a homologous series formed from steam and alkenes which have an -OH functional group
(they all end in -ol)
What are the first four alcohols?
methanol
ethanol
propanol
butanol
What properties do the first four alcohols have?
- are flammable
- undergo complete combustion in air (to produce carbon dioxide and water)
- are all soluble in water (their solutions have a neutral pH)
- react with sodium
- can be oxidised by reacting with oxygen to form carboxylic acids
What can alcohols be used for? (And why?)
used as/in…
- solvents in industry (because they can dissolve things water can and can’t dissolve)
- fuels (because they are not smelly)
- alcoholic drinks (ethanol can be made for this by fermentation)
What is fermentation?
The reaction where (an enzyme in) yeast converts sugars into ethanol and carbon dioxide.
What conditions are required for fermentation?
around 37°C
in a slightly acidic solution
under anaerobic conditions
What are carboxylic acids?
a homologous series of compounds made when alcohols react with oxygen which have the functional group -COOH
(they all end in -anoic acid)
What are the first four carboxylic acids?
methanoic acid
ethanoic acid
propanoic acid
butanoic acid
How do carboxylic acids react?
- they react with carbonates to produce a salt, water and carbon dioxide (these salts start with the first part of the carboxylic acid’s name and end in -anoate)
- they dissolve in water and ionise to release H+ ions but they don’t ionise completely so form weak acidic solutions
What are esters?
a group formed from an alcohol and a carboxylic acid (in the presence of an acid catalyst) with the functional group -COO
alcohol + carboxylic acid ->
ester + water
What is condensation polymerisation?
where monomers which contain different functional groups react together so that bonds form between them to make a polymer chain
for each bond formed, a small molecule (eg. water) is produced
What are the differences between addition polymerisation and condensation polymerisation?
- addition uses only one monomer type (with the functional group C=C) but condensation uses two monomer types (each with two of a different functional group to eachother) or one monomer type (which has two different functional groups)
- addition only forms a polymer but condensation forms a polymer and a small molecule
Name some examples of naturally occurring polymers
- proteins
- DNA
- carbohydrates
What is formed from the monomers amino acids?
proteins via condensation polymerisation
What is formed from the monomers nucleotides?
DNA
What is formed from the monomers simple sugars?
larger polymers like starch and cellulose
