Organic Chemistry II Flashcards
What does organic menan?
‘from living things’
What is organic chemistry?
the study of carbon compounds - living or once living
What is a hydrocarbon?
a molecule made up of hydrogen and carbon atoms only
Where are hydorcarbons found?
in crude oil
What are alkanes?
they are the simplest hydrocarbons
they have a central chain of carbon atoms, joined by carbon-carbon signle bonds, surronded by hydrogen atoms
Different alkanes have chains of … lengths
Different alkanes have chains of different lengths
What are the first five alkanes?
methane: CH4
ethane: C2H6
propane: C3H8
butane: C4H10
How do you remember the names of alkanes and alkenes after butane/ene?
they take on the names of their mathematical shapes
5C = pentene/ane
6C = hexene/ane
7C = heptene/ane
8C = octene/ane
What is the displayed formula for methane?
What is the displayed formula for ethane?
What is the displayed formula for propane?
What is the displayed formula for butane?
What is the displayed formula for pentane?
Are alkanes saturated or unsaturated hydrocarbons?
saturates
they contain the maximum possible number of hydrogen atoms for a given number of carbons
What is methane a major component of?
natural gas
Alkanes are the simplest …
homologous series
What is a homologous series?
a group of compounds with similar properties because they have similar bonding
they can all be represented by the same general formula
they have the same functional group
they have the same number of electrons on the outer shell
they have similar chemical reactivity
they are differentiated by CH2 group
What is the general formula of alkanes?
CnH2n+2
e.g. butane = C4H10 because it has four carbons so it has to have (2 x 4) + 2 hydrogens
What bonds do carbon and hydrogen form? How many can these atoms form?
carbon and hydrogen form covalent bonds
carbon can form four covalent bonds
hydrogen can form one covalent bond
The first four alkanes are … at room temperature. All the other ones you are likely to come across at GCSE are …. Alkanes are … around C17H36
The first four alkanes are gas at room temperature. All the other ones you are likely to come across at GCSE are liquids. Alkanes are solids around C17H36
As alkanes get bigger, what increases between them? What does this mean?
the intermolecular forces
this means that more energy has to be put in to break the attractions between one molecule and its neighbours
Are alkanes reactive?
they are very unreactive because they have strong covalent bonds
Where do you find alkanes?
in crude oil
What is the written equation for the complete combustion of any alkane? When does complete combustion occur?
alkane + oxygen → carbon dioxide + water (+ energy)
this occurs when there is enough oxygen
Complete combustion releases … and only produces two …. When there’s … and combustion is complete, the gas burns with a … flame.
Complete combustion releases lots of energy and only produces two harmless waste products (carbon dioxide and water). When there’s plenty of oxygen and combustion is complete, the gas burns with a clear blue flame.
Explain why the combustion of hydrocarbon fuels is believed to by some scientists to be responsible for global warming
Include one effect of global warming in your answer
carbon dioxide and water vapour are one of the main greenhouse gases
it rises into the atmosphere but traps all the air so it is re-emmited back out again
one effect of global warming is the melting of ice caps which causes flooding
What is the balanced equation for the complete combustion of methane?
methane + oxygen → carbon dioxide + water
CH4 + 2O2 → CO2 + 2H2O
When does incomplete combustion of an alkane occur?
when there isn’ enough oxygen
Is incomplete combustion of an alkane safe? Why?
no
carbon monoxide or carbon (soot) is produced instead of carbon dioxide
State three things that carbon monoxide is
colourless
odourless
very poisonous
Why is carbon monoxode poisonous?
it combines with haemoglobin (the molecule that carries oxygen in the blood stream), preventing it from carrying oxygen
you are made ill, or even die, because not enough oxygen gets to the cells in your body
What colour is the flame in incomplete combustion?
smoky yellow
What is the balanced equation for the incomplete combustion of methane?
methane + oxygen → carbon monoxide + water
2CH4(g) + 3O2(g) → 2CO(g) + 4H2O(l)
What is made when halogens react with alkanes?
haloalkanes
Halogens, such as chlorine and bromine react with alkanes in the presence of … (e.g. …). This is called …
Halogens, such as chlorine and bromine, react with alkanes in the presence of ultra-violet light (e.g.sunlight). This is called photolysis
Halogens have … bonds that are … to break by U.V. light
Halogens have weak bonds that are easy to break by U.V. light
Do alkenes undergo photolysis?
No, only alkanes
What type of reaction is making haloalkanes by reacting chlorine or bromine with alkanes? Expalin this
a substitution reaction
a hydrogen atom from the alkane is substituted (replaced) by chlorine or bromine
A mixture of bromine and methane is the colour … because …. If exposed to U.V. light, such as sunlight, what is formed and what happens to the colour?
A mixture of bromine and methane is the colour brown because of the presence of the bromine. If exposed to U.V. light, such as sunlight, bromomethane and hydrogen bromide gas is formed and the colour is lost
Alkenes are … but are different to alkanes because they have … bonds
Alkanes are hydrocarbons but are different to alkanes because they have C=C carbon double bonds
Are alkenes saturated or unsaturated?
unsaturated
this is because they contian a double carbon bond
How do you obtain alkenes?
from cracking alkanes
What is cracking?
the process where a long chain alkane is broken down from larger molecules into smaller molecules; more useful alkanes and alkenes
What are the first three alkenes?
ethene: C2H4
propene: C3H6
butene: C4H8
What is the displayed formula for ethene?
What is the displayed formula for propene?
What is the displayed formula for butene?
What is the general formula for alkenes?
C2H2n
The first four alkenes are … at room temperature. All the other ones you are likely to come across at GCSE are …. Alkenes are … around C17H34
The first four alkenes are gas at room temperature. All the other ones you are likely to come across at GCSE are liquids. Alkenes are solid around C17H34
In the complete combustion of alkenes, what is formed?
carbon dioxide and water
What is made when halogens react with alkenes?
haloalkenes
Alkenes undergo … reactions. What does this entail?
Alkenes undergo addition reactions
part of the double bond breaks and the electrons are used to join other atoms onto the two carbon atoms
For bromine to add to alkenes, heat or a catalyst is/isn’t needed
For bromine to add to alkenes, heat or a catalyst isn’t needed
What is often used to test for carbon-cabon double bonds? Explain how this test works
the reaction between bromine and alkenes is often used
when you shake an alkene with orange bromine solution (‘bromine water’), the solution becomes colourless
this is because the bromine molecules, which are orange, are reacting with the alkened to make dibromoalkane, which is colourless
What do alcohols belong to?
a homologous series
What group do alcoholes all contain?
an -OH group
e.g. ethanol is C2H5OH
How are alcohols bonded?
they are covalently bonded onto a carbon chain
What is the familiar alcohol in drinks? What is its chemical formula?
ethanol - C2H5OH
What is the general formula for alcohols?
CnH2n+1OH
The best way to make ethanol often depends on …
The best way to make ethanol often depends on what resource is most easily available - oil or sugar
What are the two different methods of producing ethanol?
fermentation
hydration of ethene
Is yeast a chemical?
yeast is not a chemical but a microorganism
N.B. do not write it as a molecule in a formula but instead out it over the arrow
How is ethanol produced by fermentation?
yeast is added to a sugar or starch solution and left for several days in the warm (30-40oC) with the absence of air (anaerobic conditions)
enzymes (biological catalysts) in the yeast convert the sugar into ethanol and carbon dioxide
Explain the biochemistry of how ethanol is made by fermentation
ordinary sugar (sucrose) is split into two smaller sugars: glucose and fructose
glucose and fructose have the same molecular fomulae, but are differet structures (they are isomers)
enzymes in the yeast convert these sugars into ethanol and water
- C12H22O11 (aq) (sucrose) + H2O (l) (water) → C6H12O6 (aq) (glucose) + C6H12O6 (aq) (fructose)
- C6H12O6 (aq) (glucose) → 2C2H5OH (aq) (zymase) + 2CO2 (g) (carbon dioxide)
Is it possible to make pure ethanol by fermentation? Why?
no, it is impossible
yeast is killed by +15% of alcohol in the mixture
instead, the alcohol is purified by fractional distillation - this takes advantage of the difference in boiling point between ethanol (78oC) and water (100oC)
the liquid distilling over 78oC is 96% pure ethanol and the rest is water - it is impossible to remove this last 4& of water by simple distillation
Which resources are used in the production of ethanol by fermentation?
renewable resources
sugar beet or sugar cane, corn and other starchy materials
Which type of process is used in the production of ethanol by fermentation?
a batch process
everything is mixed together in a reaction vessel, then left for a several days
that batch is removed and a new reaction is set up
this is inefficient
What is the rate of reaction of the production of ethanol by fermentation?
very slow, taking several days for each batch
What is the quality of ethanol produced by fermentation?
very impure - needs further processing
not very concentrated - needs to be distilled to increase its strength (as in whiskey distilleries)
What are the reaction conditions used in the production of ethanol by fermentation?
gentle temperatures (about 30oC)
simple, cheap equipment
ordinary pressures
Is sugarand yeast easily grown?
yes
sugar (sugar cane) is grown as a major crops in several parts of the world, including poorer countries
The alcohol in beer and wine etc… is made by …
The alcohol in beer and wine etc… is made by fermentation
How is ethene produced?
by cracking crude oil
What is meant by ‘hydration’ of ethene?
reacting ethene with steam
What is the equation for the hydration of ethene?
What are the starting materials in the production of ethanol by the hydration of ethene?
ethene and steam
What is the temperature in the production of ethanol by the hydration of ethene?
300oC
What is the pressure in the production of ethanol by the hydration of ethene?
60 - 70 atmospheres
What is the catalyst in the production of ethanol by the hydration of ethene?
phsophoric acid - H3PO4
In the production of ethanol by the hydration of ethene, how much ethene reacts? What happens to the unreacted ethene?
only a small proportion of ethene reatcs
the unreacted ethene is recyled through the process
In the production of ethanol by the hydration of ethene, what happens to the ethanol produced?
it is condensced as a liquid
Which resources are used in the In the production of ethanol by the hydration of ethene?
finite resources (ethene from oil)
once all the oil has been used up there won’t be any more
Which type of process is used in the production of ethanol by the hydration of ethene?
a continuous flow process
a stream of reactants is constantly passed over the catalyst
this is more efficient than a batch process
What is the rate of reaction of the production of ethanol by the hydration of ethene?
rapid
What is the quality of ethanol produced in the by the hydration of ethene?
a much purer ethanol
What are the reaction conditions used in the production of ethanol by the hydration of ethene?
high temperatures: 300oc
high pressures: 60 - 70 atmospheres
needs a high input of energy
What is the difference is labour costs between the production of ethanol by fermentation and hydration of ethene?
fermentation: high labour costs
hydration of ethene: low labour costs
What do alcohols produce when they burn?
carbon dioxide and water
What is meant by ‘dehydration’ in the dehydration of alcohol
the removal of water from a compound
What is the equation for the dehydration of ethanol to form ethene?
How is ethanol dehydrated to form ethene?
ethanol vapour is passed ober a hot catalyst of aluminium oxide, Al2O3
the catalyst provides a large surface area for this reaction
Crude oil is burned for … but this can produce …
Crude oil is burned for energy but this can produce pollutants
How was crude oil formed?
crude oil was formed millions of years from remains of dead organisms (dead sea creatures)
huge numbers of microscopic animals and plants died and fell to the bottom of the sea - their remains were covered in mud
layers of sediment formed on top of them and their shells and skeletons formed limestone
the soft tissue was gradually changed by high temperatures and pressures into crude oil
crude oil is less dense than the water in rocks so it will rise as a result of pressure from below and often escape altogether if the rocks are permeable
(if the rocks are impermeable, oil can’t rise through and gets trapped)
What type of resource is curde oil?
a finite, non-renewable resource
What is crude oil?
a mixture of substances, most of which are hydrocarbons
As hydrocarbons increase their molecular size, what happens to their boiling points? Why?
as the molecules get bigger, the boiling point increases
large molecules are attracted to each other more strongly than smaller ones
more heat is needed to break these stronger attractions to produce the widely separated molecules in the gap
As hydrocarbons increase their molecular size, what happens to their volatility? Why?
as the molecules get bigger, the liquids become less volatile (the more slowly it evaporates at room temperature)
this is because bigger molecules are more strongly attracted to their neighbours and so don’t turn turn to a gas so easily
What does volatility mean?
the tendency of a substance to vaporize
As hydrocarbons increase their molecular size, what happens to their viscosity? Why?
as the molecules get bigger, they become more viscous (flow less easily)
liquids containing small hydrocarbon molecules are runny
those containing large molecules are much stickier because of greater attractions between their molecules
Which burn more easily, bigger or smaller hydrocarbons? What does this mean for their use?
bigger hydrocarbons do not burn as easily as their smaller ones
this limits the use of the bigger ones as fuels
How are the different compounds in crude oil separated?
by fractional distillation
What are the steps of fractional distillation?
- The oil is heated until most of it has turned into gas. The gases enter a fractionalating column (and the liquit bit, bitumen, is drained off at the bottom)
- In the column there’s a temperature gradient (it’s hot at the bottom and gets gradually cooler as you as you go up). When the substances that make up crude oil reach the part of the column where the temperature is lower than their boiling point they condense (turn back into a liquid)
- The longer hydrocarbons have high boiling points. They condense and drain out of the column early on, when they’re near the bottom
- The shorter hydrocarbons have lower boiling points. They turn into liquid and darin out much later on, near the top of the column where it’s cooler
- Bubble caps in the fractioning column stop the separated liquids from running back down the column and remixing. You end up with the crude oil separated into different fractions. Each fraction contains a mixture of hydrocarbons with similar boiling points.
What are the fractions in fractional distillation in order of shortest to longest hydrocarbons
Refinary gases
Gasoline (petrol)
Naptha
Kerosene (paraffn)
Diesel
Fuel oil (gas oil)
Bitumen
As fractions increase in density and boiling point in fraction distillation, what becomes of them?
more carbon atoms
less commercially useful
What is the approximate number of carbons in the hydrocarbon chain of refinary gases?
4 carbons
What is the approximate number of carbons in the hydrocarbon chain of gasoline?
8 carbons
What is the approximate number of carbons in the hydrocarbon chain of naptha?
10 carbons
What is the approximate number of carbons in the hydrocarbon chain of kerosene?
15 carbons
What is the approximate number of carbons in the hydrocarbon chain of diesel?
20 carbons
What is the approximate number of carbons in the hydrocarbon chain of fuel oil?
40 carbons
What is the approximate number of carbons in the hydrocarbon chain of bitumen?
70+ carbons
What type of process is fractional distillation?
a physical process - there are no chemical reactions
What are the uses of refinary gases?
commonly used as liquefied petroleum gas (LPG) for domestic heating and cooking
What are the uses of of gasoline?
fuel (petrol) for cars
What are the uses of naptha?
used in the chemical industry as a ‘feedstock’ (starting material) to make: plastics; dyes; drugs; explosives; paints
What are the uses of kerosene?
fuel for jet engines
domestic heating oil
‘paraffin’ for small heaters and lamps
What are the uses of diesel?
fuels for enginesin some cars, buses, lorries, boats and railways engines where the line hasn;t been electrified
some is also cracked to make other organic chemicals and produce more petrol
What are the uses of fuel oil?
domestic central heating
fuel for big ships
boilers for ships
What are the uses of bitumen?
melted and mixed with rock chippings to make surfaced for roads and asphalt for roofs
What are two problems with fractions form crude oil distillation?
- The amounts of each fraction you get will depend on the properties of the various hydrocarbons in the original crude oil, not the amount in which they are needed. Far more petrol is needed, for example, than is found in crude oil
- Apart from burning, the hydrocarbons in crude oil are fairly unreactive. To make other organic chemicals from them, they must first be converted into something more reactive
Why do we crack long hydrocarbons?
they are not very useful
Long hydrocarbons have … boiling points are are (volatile/viscous)
Long hydrocarbons have high boiling points are are viscous
Shorter hydrocarbons have … boiling points and are much (thinner/thicker) and … in colour
Shorter hydrocarbons have low boiling points and are much thinner and paler in colour
What is cracking a form of? Explain this
cracking is a form of thermal decomposition because the larger molecules are broken down into simpler molecules by heating them
How does cracking work?
the gas oil fraction is heated to give a gas
vaporised hydrocarbons are passed over a powdered catalyst of mixed silicon dioxide/silica (SiO2) and aluminum oxide (Al2O3) at about 600oC to 700oC
What does cracking produce?
amixture of alkanes and alkenes
some reactions even produce a small percentage of free hydrogen
Cracking breaks up molecules in a … way
Cracking breaks up molecules in a fairly random way
What are the steps of cracking paraffin?
- Start by heating the paraffin. After a few seconds, move the Bunsen burner to heat the silica or alumina catalyst. Alternate between the two until the paraffin vaporises and the catalyst glows red
- The heated paraffin vapour cracks as it passes over the heated catalyst
- Smaller alkanes collet at the end of the boiling tube, while alkene gases travel down the delivery tube
- The alkenes are then collected through water using a gas jar
What are two things cracking is useful for?
making alkenes for plastics
turning bitumen and candle wax (of limited use) into things like petrol and cooking gas (which are very useful)
What is polymerisation?
the joining up of lots of little molecules (the monomers) to make one big molecule (the polymer)
What two types of polymer are there?
addition
condensation
A polymer is a chemical … made of … (called ...) linked together
A polymer is a chemical compound made of many smaller, identical molecules (called monomers) linked together
What is additional polymerisation?
Under high pressure and with a cataylst to help them along, many small molecules containing a carbon-carbon double bond will open open up (break) the double bonds and join together (polymerise) to form very long, saturated chains - polymers
In addition polymerisation, … add to themselves
As this addition proceeds further a … is formed
The alkene is a … in the chain (the monomer) - the chain itself is the …
In addition polymerisation, alkenes add to themselves
As this addition proceeds further a long, molecular chain is formed
The alkene is a repeating unit in the chain (the monomer) - the chain itself is the polymer
What is the displayed formula or ethene becoming poly(ethene)
How do you find the repeat unit of a polymer?
find the section of the polymer that’s repeated
How do you name a polymer?
the name comes from the monomer it’s made from - you just put brakets around the monomer and stick the word ‘poly’ in front of it
e.g. poly(ethene)
How do you find the monomer used to form an addition polymer?
take the repeat unit and add a double bond
How are plastics formed?
plastics are formed when lots of small molecules (monomers) join together to make a polymer
Are polymers hard or easy to get rid of?
most polymers are hard to get rid of
Why are most polymers hard to get rid of?
most addition polymers are inert (they don’t react easily) - this is because of the carbon-carbon covalent bonds in the polymer chain are very strong and aren’t broken down easily
this means that it takes a really long time for addition polymers to biodegrade (be broken down by bacteria or other living organisims) - if you bury them in a landfill site, they’ll stil be there years later
burning plastics can release toxic gases
What is the best thing to do with polymers in terms of disposal?
it is difficult to dispose of polymers
the best thing is to reuse them as many times as possible and then recycle them
What two types does poly(ethene) come in?
low density poly(ethene) (LDPE)
high density poly(ethene) (HDPE)
What is low-density poly(ethene) mainly used for? Why?
thin film to make polythene bags
it is very flexible and light but not very strong
What is high-denisty poly(ethene) used more? Why?
plastic bottles such as milk bottles
it hs rather greater strengh and rigidity than low-density poly(ethene)
What is poly(ethene) used for? Why?
packaging such as plastic bags, bottles and other containers
it is a light, stretchable polymer
What is the is the product of the polymerisation of propene?
poly(propene)
What is the displayed formula for poly(propene)?
What are the uses of poly(propene)? Why?
ropes
crates
kettles
food containers
carpets
it’s a very tough polymer, but it’s relatively flexible and resistant to heat
What is the prodcut of the polymerisation of chloroethene? What is it commonly known as?
poly(chloroethene)
it is usually known by is old name, polyvinlychloride or PVC
What is the displayed formula for poly(chloroethene)
What are the uses of poly(chloroethene)? Why?
it is quite strong and rigid: drainpipes, replacement windows
it can be made flexible by adding ‘plasticisers’: sheet floor coverings
it doesn’t conduct electricity: insulating electrical cables
What is condensation polymerisation?
it usually involves two differnt types of monomer joining together alternately
the monomers react together and bonds form between them, making polymer chains
for each new bond that forms, a small molecule (for example, water) is lost
What is the functional group for carboxylic acid? What is an example of carboxylic acid?
- COOH group
e. g. ethanoid acid in vinegar = CH3COOH
Ask her about condensation polymersiation and nylon!!! must make notes on pg.172-173 from textbook
What is a structural formula?
it shows how the atoms are joined up
it can be either be drawn as displayed formula or written out as, for example, CH3CH2CH3 (C3H8)
What do each of the lines in displayed formulae represent?
a pair of shared electrons
What is the displayed formula of methane?
What is the displayed formula of ethane?
What is the displayed formula of propane?
What is the displayed formula of butane?
What is the displayed formula of ethene?
What is the displayed formula of propene?
What is the displayed formula of butene?
How do you name organic compounds?
- identify the largest carbon chain
- number from heaviest side first - a double bond is heaviest (so put it on lowest carbon possible), read left to right or right to left to which carbon
- identify groups attached - e.g. 1C = methyl
- identify type of molecule
- prefix (group) - suffix (type)
What is the name of this formula: CH2=CHCH2CH3?
but-1-ene
What is the name of this formula: CH3CH=CHCH3?
but-2-ene
What is the displayed formula of methanol?
What is the displayed formula of ethanol?
What is the displayed formula of propanol?
What is the displayed formula of butanol?
What is the displayed formula of pentanol?
What does ‘2,3-dimethyl’ mean?
there are two methyl groups attached to the second and third carbon atom in the chan
What are sturctural isomers?
molecules with the same molecular formula, but with different structural formulae
Do methane, ethane and propane have any isomers?
no
What are the isomers of butane? Which structural isomer has a higher boiling point and why?
number 1 as it has higher intermolecular force of attraction as the chain is a straight line - it harder to break
What are the isomers of pentane? Name them
Do ethene and propene have isomers?
What are the isomers of butene?
What are the isomers of pentene?
How do you make sure not to draw the same isomer?
draw the longest carbon chain horizontally
