4.5 - Organic I Flashcards
pure substances - e.g. element or a compound, melt and boil at
fixed temperature
mixtures melt and boil
over a range of temperatures.
hydrocarbon
a compound of hydrogen and carbon only
A functional group
an atom or a group of atoms that determine the chemical properties of a compound
a homologous series is a group of substances with:
- the same general formula
- similar chemical properties because they have the same functional group
- a trend (graduation) in physical properties
isomers
molecules with the same molecular formula but with a different structure
crude oil
a mixture of hydrocarbons
describe how the industrial process of fractional distillation separates crude oil into fractions
Crude oil is separated by fractional distillation.
Crude oil is heated and the oil evaporates.
The gas goes into the fractional distillation tower.
- As the gas rises the temperature falls.
Fractions with higher boiling points condense –> collected nearer the bottom of the tower
1 carbon
meth-
2 carbons
eth-
3 carbons
prop-
4 carbons
but-
5 carbons
pent-
6 carbons
hex-
prefix for compounds
MEPB
monkeys eat peanut butter
alkanes - ane
C-C
C-H
alkenes - ene
C=C
alcohols - ol
OH
if given molecular formula is C2H6 what is the structural formula
C2 = two Cs
H6 - six Hs
CH3 CH3
addition reactions involve
one product
substitution reactions involve
two products
combustion involves reaction of a
fuel with oxygen
if products are water and carbon dioxide its a hydrocarbon
how does fractional distillation separate crude oil into fractions
- oil heated in fractionating column
- oil evaporates and condenses at diff temps
- hydrocarbons in crude oil are separated into fractions
- fractions contain molecules with similar number of carbon atoms
- vaporised oil rises up column and fractions are tapped off at different levels where they condense
refinery gases used for
domestic heating and cooking
gasoline used for
fuel for cars
kerosene
fuel for aircraft
diesel
fuel for trains and some cars
fuel oil
fuel for large ships and in some power stations
bitumen
surface roads and roofs
order of main fractions
refinery gases, gasoline, kerosene, diesel, fuel oil and bitumen
short molecules /BP/viscosity of main fractions
short molecule - lower temp which it condenses - lower BP - less viscous
colours darker at the bottom fractions
longer molecules
fuel
substance that releases heat energy when burned
products of complete combustion
CO2 and H2O produced
products of incomplete combustion
carbon monoxide released
- solid particles of soot(carbons) and unburnt fuel released
incomplete combustion
not enough oxygen -> some fuel doesn’t burn
why is carbon monoxide poisonous
- prevents RBC carrying oxygen around body
- lead to difficulty breathing and death
in car engines how is oxides of nitrogen produced
temperature in high enough to allow nitrogen and oxygen from air to react
- forms nitrogen monoxide or nitrogen dioxide
how does combustion of impurities in hydrocarbon fuels results in sulphur dioxide
most fuels contain carbon and/or hydrogen and may contain sulphur
- when fuels are burnt sulphur is oxidised to product sulphur dioxide
how does sulphur dioxide and oxides of nitrogen contribute to acid rain
- when emitted they react with rain water to create H+ ions
- acid corrodes rocks/buildings
- alters soil pH in soil/rivers, affects ecosystem
- corrodes limestones in statues
how are long-chain alkanes converted to alkenes and shorter chain alkenes
hydrocarbons cracked to produce smaller and more useful molecules
- heat hydrocarbons to vaporise them
- passed over hot catalyst (silica)
- mixed with steam and heated to high temp (600-700) so the thermal decomposition reactions occur
alkenes general formula
CnH2n
products of cracking
alkanes
unsaturated hydrocarbons - alkenes
alkanes general formula
CnH2n+2
why are alkanes saturated hydrocarbons
contains no C=C bonds
saturated - all carbons has max 4 bonds
describe reaction of alkanes with halogens in pre scene of UV radiation
halogen + alkane –(UV)–> halogenoalkane + hydrogen halide
functional group of alkenes
C=C
why are alkenes classified as unsaturated hydrocarbons
contains one or more C=C double bonds
describe reactions to produce dibromoalkanes
alkene + bromine –> dibromoalkanes
- removal of C=C
how can bromine water distinguish alkane and alkene
alkene - reacts with bromine water, orange –> colourless
alkanes - doesn’t reacts with bromine water, remains orange
addition polymer is formed by
joining up many small molecules called monomers
addition polymer drawing
- line through two brackets
- removal of C=C
- brackets with n
- poly(__)
problems in disposal of addition polymers
- unbiodegradable , microorganisms are unable to break them down since they are inert
- produces toxic gases when burnt
- CO2 releases when burnt, global warming
Alkanes reaction with bromine
Substitution
C3H7Br HBr
Alkenes reaction with bromine
Addition
C3H6Br2