Paper 1- Organic Chemistry Flashcards
What is a general formula?
- algebraic formula that can describe any member of a family of compounds
- e.g. CnH2n
What is an empirical formula?
simplest whole number ratio of atoms in compound
-e.g. CH2
What is a molecular formula?
actual number of atoms of each element
-e.g. C2H4
What is the displayed formula?
shows how atoms are arranged
What is the structural formula?
shows arrangement of atoms carbon by carbon
-e.g. CH2CH2
What is a homologous series?
a group of compounds that can be represented by the same general formula
What is a functional group?
a group of atoms that determine how a compound typically reacts
What are the stem words for number of carbons?
meth eth prop but pent hex
What are isomers?
two or more molecules with the same molecular formulae but different structural formula
What is a hydrocarbon?
a compound of hydrogen and carbon only
Why are isomers hard to spot
- differently shaped carbon chains
- functional groups in different places
- different functional groups
What is crude oil?
a mixture of hydrocarbons
How are compounds in crude oil separated?
fractional distillation
What is crude oil separated in?
fractionating column
Where is the hottest part of a fractionating column?
bottom
What do longer hydrocarbons have?
high boiling points
What do shorter hydrocarbons have?
lower boiling points
What do bubble caps do?
stop separated liquid from running out down the column and remixing
What are the two types of hydrocarbons?
saturated and unsaturated
What are saturated hydrocarbons?
only contain single bonds between carbon atoms
What are unsaturated hydrocarbons?
have double or triple bonds between carbon atoms
Describe the process of how crude oil is sepretaed into different hydrocarbon fractions
- oil is heated until most of it has turned into gas
- gases enter a fractionatin column and the liquid bit, bitumen, is drained off
- in the column there is a temperature gradient
- when the substances that make up crude oil reach a part of the column where the temp is lower than boiling point they condense (turn back into liquid)
- longer hydrocarbons have high boiling points- so drain out of column early on (near bottom)
- short hydrocarbons have lower boiling points so turn to a liquid and drain out later on (near top of column where its cooler)
- bubble caps prevent the separated liquid from running back down the column and remixing
What is the order fractions from top to bottom?
- refinery gases
- gasoline
- kerosene
- diesel
- fuel oil
- bitumen
What is cracking?
splitting up long chain hydrocarbons
Describe long hydrocarbons?
- high boiling points
- viscous (thick and gloopy)
Describe shorter hydrocarbons?
- lower boiling points
- thinner
- paler
Which hydrocarbon (short or long) is higher in demand
Demand for short hydrocarbons, which is used in petrol, is higher than for longer-chain hydrocarbons
What occurs to long-chain hydrocarbons to make them more useful
-they are split into more useful short-chain molecules using cracking
What is diesel cracked into?
- petrol
- paraffin
- ethene for polymers
What is cracking a form of?
thermal decomposition
What does cracking also produce as well as breaking molecules down
alkenes
What are the conditions for cracking?
Describe the process that occurs
- heat, plus a catalyst
- vaporised hydrocarbons are passed over a powdered catalyst at about 600-700 degrees
- Silica (SiO2) or Alumina (al2O3) are used as the catalyst
- alkane is heated until vaporised
- then breaks down when it comes into contact with catalyst producing short- chain alkanes and alkenes
Which catalysts can be used in cracking?
- silica
- alumina
What happens when you burn a fuel?
releases energy in form of heat
What is burning a fuel also known as?
-combustion reaction
Why do hydrocarbons make great fuels?
as the combustion reaction that happens when you burn them in oxygen gives out lots of energy
hydrocarbon + oxygen =
carbon dioxide + water
What is complete combustion
-when you burn hydrocarbons in plenty of oxygen, the only products are CO2 and water
What type of reaction is hydrogen + oxygen?
complete combustion
What does incomplete combustion produce?
carbon monoxide + soot + carbon
When does incomplete combustion occur?
when there is not enough oxygen around
How is carbon monoxide is poisonous?
- It combines to red blood cells and stops blood doing proper job of carrying oxygen round the body
- lack of oxygen in blood supply can result in death
What is acid rain caused by?
- sulfur dioxide
- nitrogen oxides
When may sulfur dioxide and nitrogen oxides be produced?
when fractions from crude oils are burned
Where does sulfur dioxide come from?
comes from sulfur impurities in hydrocarbon fuel
How are nitrogen oxides formed?
- when temp is high enough for nitrogen and oxygen react in the air
- this often happens in car engines
What is made when sulfur dioxide and nitrogen oxides mix with water vapour in the clouds?
- dilute sulfuric acid and nitric acid
- the rain that then falls from these clouds is known as acid rain
Why is acid rain an issue?
- causes lakes to become acidic
- many plants and animals die as a result
What are alkanes?
- saturated hydrocarbons
- they are chains of carbon atoms surrounded by hydrogen atoms
- single bonds between carbon atoms
What is the general formula for alkanes?
CnH2n+2
What are the names of the first five alkanes?
methane ethane propane butane pentane
What do alkanes burn in?
complete combustion reactions
Write the word equation for the burning of propane
propane + oxygen -> carbon dioxide + water
What do alkanes react with and what is this called?
alkanes react with halogens to form haloalkanes
What type of light is needed to make a haloalkane?
ultraviolet light
What type of reaction is a haloalkane made in?
substitution reaction
What is a substitution reaction?
hydrogen atom from alkane is substituted with chlorine or bromine
Write the word equation for the reaction of bromine with an alkane (methane)
methane + bromine -> bromomethane + hydrogen bromide
What are alkenes?
- unsaturated hydrocarbons
- double bond between two carbon atoms
Name the first three alkenes?
ethene
propene
butene
What is alkenes general formula?
CnH2n
What do alkenes react with to form?
alkenes react with halogens to form haloalkenes
Write the word equation for the reaction of bromine with an alkene (ethene)
ethene + bromine -> dibromoethane
What type of reaction is a haloalkene made in?
-why
addition reaction
-as C=C double bond is split and a halogen atom is added to each of the carbons
How do you test for an alkene?
- shake an alkene with orange bromine water
- solution will become colourless
- as bromine molecules which are orange are reacting with alkene to make a dibromoalkane which is colourless
Molecular formula for ethene
Structural formula for ethene
Displayed formula for ethene
Molecular formula for ethene: C2H4
Structural formula for ethene: CH2CH2
Displayed formula for ethene:
H H
\ /
C = C
/ \
H H
What is alkenes functional group?
C=C
what is the prefix for alkanes?
-ane
What is the prefix for alkenes?
-ene
What are addition polymers made from?
-unsaturated monomers
How is an addition polymer formed?
by joining up many small molecules called
monomers
What are polymers?
-A large molecule made when many small molecules (monomers) join together. Consists of many repeat units.
What is addition polymerisation
When lots of unsaturated monomer molecules open up their carbon-carbon double bonds and join together to form polymer chains
What are Monomers?
Molecules which can join up to form a polymer.
What does ethene become in addition polymerisation?
-how does its displayed formula change
poly(ethene)- (c2H4)n
ethene displayed formula:
H H
\ /
C = C
/ \
H H
—> pressure and a catalyst
H H H H H H
-C-C-C-C-C-C-
H H H H H H
poly(ethene)
What does propene become in addition polymerisation?
-how does its displayed formula change
poly(propene)- (C3H6)n
propene displayed formula:
H H
\ /
C = C
/ \
H CH3
—> pressure and a catalyst
H H
(-C-C-) n
H CH3
poly(propene)
Why is it diffiuclt to get rid of addition polymers
- as most addition polymers are inert - they don’t react easily
- as the carbon-carbon bonds in the polymer are very strong and aren’t easily broken
- this means it takes a v long time for addition polymers to biodegrade
- the burning of plastics also release toxic gases, so you can’t get rid of addition polymers that way
Name 2 ways why polymers are hard to get rid of
- it takes a long time for addition polymers to biodegrade
- you can’t burn them either as that releases toxic gases
What is condensation polymerisation
Polymerisation of monomers in which each time two monomers combine, a small molecule such as water or hydrogen chloride is removed (e.g. a dicarboxylic acid and a diol).
When do polyesters form
-when dicarboxylic acid monomers and diol monomers react together
write the displayed formula of a polyester,
look in book
What is a Biopolyester
A polyester which is biodegradable.
-they decompose and don’t stay in the land forever
