c6 organic chemistry Flashcards
what is crude oil?
a finite resource found in rocks. its a mixture of very large compounds. it is also the remains of an ancient biomass consisting mainly of plankton that was buried in mud
what are most of the compounds that are found in crude oil?
hydrocarbons called alkanes
what are the members of alkanes and how many carbons do they have?
methane- 1
ethane- 2
propane- 3
butane- 4
pentane- 5
hexane- 6
what are alkanes?
a homologous series (group of compounds that react in a similar way)
are alkanes saturated or NON saturated hydrocarbons?
saturated hydrocarbons- each carbon atom forms 4 covalent bonds
what can hydrocarbons be separated into?
they can be separated into fractions, which contain molecules with a similar number of carbon atoms
how can hydrocarbons be separated?
through fractional distillation
what can be done to fractioned compounds to make them useful?
they can be processed to produce fuels and livestock for the petrochemical industry
which fuels are made from crude oil?
- petrol
- diesel oil
- kerosene
- heavy fuel oil
- liquefied petroleum gas
what useful materials in our daily lives are produced by the petrochemical industry?
- solvents
- lubricants
- polymers
- detergents
why do the vast array of natural and synthetic carbon compounds occur?
due to the ability of carbon atoms to form families of similar bonds
describe how fractional distillation works
1) the oil is heated until most of it turns into gas
2) in the column, there is a temperature gradient (hot at the bottom, cooler as u go up)
3) the longer chains have high BPs, so they condense and drain out and turn back into liquids very early on, near the bottom. the opposite happens to shorter chains who have lower BPs who condense and drain out later on, near the top.
4) so therefore we end up with crude oil mixtures separated out into different fractions
what do some of the properties of hydrocarbons depends on?
and what do they influence?
- example
- size of their molecules
- boiling point
- viscosity
- flammability
they influence how hydrocarbons are used as fuels
EG: shorter chains with lower BPs are used as ‘bottled gasses’
how does the length of a hydrocarbon chain influence it’s viscosity?
VISCOSITY- how gloopy it is
the shorter the chain, the less viscous it is.
the longer the chain, the more viscous it is.
how does the length of a hydrocarbon chain influence it’s volatility?
VOLATILITY- how easily a substance can evaporate
the shorter the chain, the more volatile it is.
the longer the chain, the less volatile it is.
how does the length of a hydrocarbon chain influence it’s flammability?
FLAMMABILITY- how easily it can ignite
the shorter the chain, the more flammable it is.
the longer the chain, the less flammable it is.
when does complete combustion occur?
when there is plenty of oxygen
what does complete combustion of any hydrocarbon release?
energy
what is the word equation for complete combustion?
hydrocarbon + oxygen= (energy) + carbon dioxide + water
what happens during complete combustion?
both carbon and hydrogen from the hydrocarbon are oxidised. they GAIN oxygen
why can hydrocarbons be used as fuels?
because of the amount of energy released when they combust completely
what can be done to hydrocarbons to produce smaller, more useful molecules?
they can be cracked
what are some different methods of cracking?
catalytic cracking and steam cracking
what is cracking?
cracking is a thermal decomposition reaction
how does catalytic cracking happen?
1) heat long chain hydrocarbons to vaporise them.
2) then the vapour can be passed over a hot powered aluminium oxide catalyst.
3) the long chain molecules split apart on the surface of the specks of calalyst
what are the general conditions for cracking?
steam
high temperatures
high pressure
heated catalyst (for catalytic)
what are the products of cracking?
alkenes
whats the reactive difference between alkanes and alkenes
alkenes are more reactive
what is the test for alkenes and what is the positive result? what is the negative result?
bromine water.
a) POSITIVE result- bromine turns from orange liuid to colourless liquid as it takes the place of the missing hydrogen atoms
b) NEGATIVE result- no colour change. as this means that it is an alkane and they are already saturated
why can some of the products of cracking be useful?
some of the products of cracking can be useful as fuels
because there is a high demand of fuels with smaller molecules
what are alkenes used for?
for the production of polymers as starting materials for the production of many other chemicals
what are alkenes?
unsaturated hydrocarbons because the have a C=C bond
what is the general formula of alkenes?
Cn H2n
explain WHY alkenes are unsaturated?
the C=C bond means that alkenes have two fewer hydrogens compared with the alkanes.