Section 6 - Organic Chemistry P1 Flashcards
What are the different ways you can represent organic compounds?
- general formula
- empirical formula
- molecular formula
- displayed formula
- structural formula
What does a general formula show you?
an algebraic formula that can describe any member of a family of compounds
What does an empirical formula show you?
the simplest whole number ratio of atoms of each element in a compound (numbers cancelled down if possible)
What does a molecular formula show you?
The actual number of atoms of each element in a molecule
What does a displayed formula show you?
Shows how all the atoms are arranged and all the bonds between them
What does a structural formula show you?
Shows the arrangement of atoms carbon by carbon, with the attached hydrogens and functional groups
(ethene - CH₂CH₂)
What is a homologous series?
A homologous series is a group of compounds that can be represented by the same general formula
-molecules in the same homologous series contain the same functional group
What is the general formula for alkanes?
CₙH₂ₙ₊₂
What is a functional group?
A functional group is a group of atoms that determine how a compound typically reacts
-means compounds in a homologous series often react in similar ways
What is the functional group for alkenes?
a carbon carbon double bond
What is organic chemistry?
Chemistry involving molecules that contain carbon
What is nomenclature?
Naming organic compounds
What is the IUPAC system?
It is the system fornaming organic compounds, it was invented as an international language for chemistry
What determines the stem of the name of a carbon compound?
The number of carbons in a chain
What stem do you get for 1 carbon?
meth-
What stem do you get for 2 carbon?
eth-
What stem do you get for 3 carbon?
prop-
What stem do you get for 4 carbon?
but-
What stem do you get for 5 carbon?
pent-
What stem do you get for 6 carbon?
hex-
What tells you the prefix or suffix of the name of a carbon compound?
The main functional group of the molecule usually tells you what homologous series the molecule is in
What is the prefix/suffix of alkanes?
-ane
What is the prefix/suffix of alkenes?
-ene
How do you name compounds when there are more than one identical functional group?
1- (1) di- (2) tri- (3) tetra- (4) BEFORE THE SUFFIX
What are isomers?
Two molecules are isomers of each other if they have the same molecular formula but the atoms are arranged differently
-have different structural formula
What can make compounds isomers of each other?
- the carbons could be arranged differently
- the functional group could be attached to a different carbon atom
What comparisons are there of the properties of isomers?
Isomers have similar chemical properties
Isomers have different physical properties (because of the change in shape of the molecule)
What is crude oil?
Crude oil is a mixture of substances, most of which are hydrocarbons
What are hydrocarbons?
Hydrocarbons are molecules only made up of carbon and hydrogen
How are the different compounds in crude oil separated?
They are separated by fractional distillation
Describe the process of fractional distillation to separate out compounds in crude oil:
- the oil is heated (until most is turned into gas), and enters a fractionating column
- in the column there’s a temperature gradient (causing substances to be removed at different layers)
- end up with the crude oil mixture separated into different fractions
What is the first thing to be extracted from a fractionating column?
Bitumen (it is drained off as a liquid at the bottom)
What is the temperature gradient in a fractionating column?
-it is hottest at the bottom and gradually gets colder as you go up
How does the temperature gradient of the fractionating column separate different substances in crude oil?
When the substances that make up the crude oil reach a part of the column where the temperature is lower than their boiling point they condense and are drained out at the layer which they are liquid
Which hydrocarbons are drained out of a fractionating column first?
Longer hydrocarbons have high boiling points
-they condense and drain out early (near the bottom)
Shorter hydrocarbons have lower boiling points
-they condense later and drain out near the top (where the column is cooler)
What do bubble caps do in the fractionating column?
They stop the separated liquids from running back down the column and remixing
What does each fraction separated out in a fractionating column share?
Each fraction contains a mixture of hydrocarbons with similar boiling points
-containing saturated or unsaturated hydrocarbons
What are saturated hydrocarbons?
Saturated hydrocarbons only contain single bonds between carbon atoms
What are unsaturated hydrocarbons?
Unsaturated hydrocarbons have double or triple bonds between carbon atoms
What are the different fractions that come out of the fractionating column (from the top down)? And what are the approximate number of carbons in the fraction?
Refinery Gases (3 carbons) Gasoline(petrol) (8 carbons) Kerosene (15 carbons) Diesel (20 carbons) Fuel oil (40 carbons) Bitumen (70+ carbons)
What are the uses of refinery gases?
Refinery gases are used in domestic heating and cooking
What are the uses of gasoline?
Gasoline is used as fuel in cars
What are the uses of kerosene?
Kerosene is used as a fuel in aircrafts
What are the uses of diesel?
Diesel is used as fuel in some cars and larger vehicles (e.g. trains)
what are the uses of fuel oil?
Fuel oil is used as a fuel for larger ships and also in some power stations
What are the uses of bitumen?
Bitumen is used to surface roads and roofs
What is cracking?
Cracking is splitting up long-chains of hydrocarbons
- a form of thermal decomposition
- produces alkenes which are also used to make polymers
What are the features of long hydrocarbons?
- high boiling points
- viscous
- lower demand
What are the features of shorter hydrocarbons?
- lower boiling points
- thinner and paler in colour
- higher demand
How is the demand for shorter chain hydrocarbons met?
By cracking to split up longer chain hydrocarbons into more useful shorter chain hydrocarbons
What is thermal decomposition?
Breaking down molecules into simpler molecules by heating them
What are the conditions required for cracking?
- vaporised hydrocarbons are passed over a powdered catalyst (Silica - SiO₂, Alumina AlO₃) - the alkane breaks down when it comes into contact with the catalyst, producing short-chain alkanes and alkenes
- 600°C - 700°C
What happens when you burn a fuel?
It releases energy in the form of heat
What is a combustion reaction?
Burning
When the substance being burned reacts with oxygen
What molecules make great fuels?
Hydrocarbons make great fuels
-their combustion reactions gives out lots of energy (very exothermic reaction)
What is complete combustion?
When you burn hydrocarbons in plenty of oxygen, the only products are carbon dioxide and water
What are the products of complete combustion?
carbon dioxide
water
What is incomplete combustion?
When you burn hydrocarbons in restricted oxygen, the products are carbon dioxide, water, carbon monoxide (a toxic gas) and carbon (in the form of soot)
What are the products of incomplete combustion?
carbon dioxide
water
carbon monoxide (a toxic gas)
carbon (in the form of soot)
What are the dangers of carbon monoxide?
- CO can combine with haemoglobin in red blood cells and stop oxygen from binding to it so oxygen can’t be carried round your body
- a lack of oxygen supply to the brain can lead to fainting, coma or death
What greenhouse gases can be produced from burning crude oils?
- carbon dioxide
- sulphur dioxide and nitrogen oxides (can be produced)
Where does sulphur dioxide come from when burning crude oils?
Sulphur impurities in the hydrocarbon fuels
Where do nitrogen oxides come from when burning crude oils?
- when the temperature is high enough nitrogen and oxygen in the air react (often happens in car engines)
- nitrogen oxides include: nitrogen monoxide and nitrogen dioxide
What are the environmental dangers of nitrogen oxides and sulphur dioxides?
- they mix with water vapour in the clouds and form dilute sulphuric acid and nitric acid (acid rain)
- acid rain causes lakes to become acidic and many plants and animals die as a result
What are alkanes?
- saturated hydrocarbons
- chains of carbon atoms surrounded by hydrogen atoms
- different alkanes have different chain lengths
What is molecular formula and structural formula of butane?
molecular formula: C₄H₁₀
Structural formula: CH₃CH₂CH₂CH₃
What reactions do alkanes take part in?
- combustion reactions(tend to combust completely with a good supply of oxygen)
- halogens react with alkanes to make haloalkanes
Describe the reactions of halogens react with alkanes to make haloalkanes:
- chlorine and bromine react with alkanes in the presence of UV light
- in these reactions a hydrogen atom from the alkane is substituted with chlorine or bromine (substitution reaction)
What are the features of alkenes?
- Hydrocarbons which have a double bond between two of the carbons in their chain
- unsaturated molecules (can make more bonds, the double bond can open up)
What are the first three alkenes?
ethene (2 carbons)
propene (3 carbons)
butene (4 carbons)
What is the general formula of alkenes?
CₙH₂ₙ (have twice the number of hydrogens as carbons)
What do halogens react with alkenes to form?
haloalkenes
What is an example of a haloalkenes?
bromine and ethene reacting together to form dibromoethane [two bromines hence di-] (the carbon-carbon double bond open up and the diatomic halogen attaches to a carbon each)
What are addition reactions?
When two reactants form one product (they combine together)
Describe a test for carbon-carbon double bonds:
- reaction between bromine and alkenes
- when you shake an alkene with orange bromine water the solution becomes colourless (dibromoalkane is colourless)
- alkanes don’t react with bromine water as they don’t have a double bond (so if you add an alkane to bromine water it will remain orange)
What are polymers?
They are substances of high average relative atomic mass made by joining up lots of small repeating units called monomers
What do monomers which make up addition polymers have?
monomers that make up addition polymers have a double covalent bond
What is addition polymerisation?
When lots of unsaturated monomer molecules (alkenes) can open up their carbon-carbon doubles bonds and join together to form polymer chains
How do you determine the name of a polymer?
- It comes from the type of monomer it is made from
- you put brackets round the name of the monomer and then put the word ‘poly’ in front of it
- e.g. propene becomes poly(propene)
How do you determine the formula of a polymer?
-You put the formula of the monomer in brackets and put a subscript n after it
How do you draw the repeating unit of a polymer when given the displayed formula of its monomer?
- join the carbons together in a row with no double bond between them, stick a pair of brackets around the repeating bit and put a subscript n after (to show there are lots of monomers)
- you should also draw bonds that pass through the brackets, to show the chain continues
How do you draw the displayed formula of a monomer from the displayed formula of the polymer?
- draw the repeating bit of the polymer
- get rid of the two bonds going out through the brackets and put a double bond between the carbons
Why are polymers often hard to get rid of?
- most addition polymers are inert (because their carbon-carbon bonds in the polymer chain are very strong and aren’t easily broken)
- they take a really long time to biodegrade (still be there years later)
What does biodegrade mean?
Be broken down by bacteria and other organisms
What is the issue with burning plastics?
-can release toxic gases
What is the best way to deal with disposing of polymers?
- best thing is to reuse them as many times as possible
- and recycle them is you can
