4) Organic Chemistry Flashcards
Hydrocarbon
Compound that contains only hydrogen and carbon atoms
Types of formulae
-empirical
-molecular
-general
-structural
-displayed
Empirical formula
Shows the simplest possible ratio of the atoms in a molecule
Molecular formula
Shows the actual number of atoms in a molecule
General formula
The simplest algebraic formula of a member of a homologous series
Displayed formula
Shows the relative positioning of atoms and the bonds between them
-all bonds form
Structural formula
Minimal detail that shows the arrangement of atoms in a molecule
-e.g. CH3CH2CH2CH2CH3 - pentane
Homologous series
Series of organic compounds that have similar features and chemical properties due to them having the same functional group
-same general formula
-same functional group
-similar chemical properties
-gradation in their physical properties
-difference in the molecular formula between one member and the next is CH2
Functional group
A group of atoms bonded in a specific arrangement that influences the properties of the homologous series
e.g. alkene C=C
Isomerism
Compounds that have the same molecular formula but different displayed formulae
Naming compounds - prefix/ suffix
Prefix: tells you how many carbon atoms are present in the longest continuous chain in the compound
Suffix: tells you what functional group is on the compound
Naming compounds - stem
Stem: number of carbon atoms
-meth - 1
-eth - 2
-prop - 3
-but - 4
-pent - 5
-hex - 6
Naming compounds - prefix
Cl - chloro
Br - bromo
I - iodo
CH3 - methyl
Naming compounds - suffix
-alkane - ane
-alkene - ene
-alcohol - ol
-carboxylic acid - oic acid
Substitution reaction
Takes place when one functional group is replaced by another
e.g. Methane + Bromine → Bromomethane + Hydrogen Bromide
-methane reacts with bromine under UV light
-alkanes react via substitution (UV light needed)
Addition reaction
Takes place when two or more molecules combine to form a larger molecule with no other products
e.g. Ethene + Bromine → Dibromoethane
-alkenes react via addition
Combustion
An organic substance reacts with oxygen to form carbon dioxide and water
-if it is incomplete: produce carbon monoxide and water
Crude oil
-mixture of hydrocarbons
-not very useful but different hydrocarbons in it are valuable
-therefore needs to be separated from each other - fractional distillation
Process of fractional distillation
- Crude oil is vaporized and pumped into the fractionating column which is cooler at the top than the bottom
- The vapours rise up the column until they reach their boiling points
- The hydrocarbons condense at their boiling points and are pumped out the column in fractions
- Smaller molecules have lower boiling points so condense further up the column
Main fractions of crude oil
Shortest chain
-refinery gases
-gasoline
-kerosene
-diesel
-fuel oil
-bitumen
Longest chain
Trend in characteristics - going from shortest to longest chains
-boiling point increases
-viscosity increases
-colour decreases
-volatility decreases
-usefulness decreases
-abundance increases
Use of refinery gases
-fuel for domestic heating
-cooking
-bottled gases
Use of gasoline
-fuel for cars
Use of kerosene
-fuel for aircrafts
Use of diesel
-fuel for lorries, buses, trains, some cars
Use of fuel oil
-fuel for ships
-fuel for power stations
Use of bitumen
-bitumen for roads and roofs
A fuel
Substance that releases heat energy when burned
Burning fossil fuels - products
-carbon dioxide
-carbon monoxide
-oxides of nitrogen
-oxides of sulfur
Dangers of carbon monoxide
-toxic and odourless gas
-the CO binds well to haemoglobin in the blood, therefore cannot bind oxygen and carbon
-can cause dizziness, loss of consciousness, even death
Nitrogen oxides
-formed when nitrogen and oxygen react in the high pressure and temperature
-reacts with rain water to form nitrous/ nitric acids - acid rain, produces photochemical smog and breathing difficulties
Sulfur dioxide
-from combustion of fossil fuels, which are often contaminated with small amounts of sulfur impurities
-when contaminated fossil fuels are combusted, sulfur in the fuels get oxidized to sulphur dioxide
-dissolves in rainwater - acid rain - causes corrosion to metal structures, buildings, statues made of carbonate rocks
-damage to aquatic organisms
-pollutes crops and water supplies, irritates lungs, throats, eyes
Cracking
Used to convert long chain alkane molecules into short chain molecules which are more useful
-two methods: catalytic cracking and steam cracking
Catalytic cracking
- heating the hydrocarbon molecules to around 600 – 700°C to vaporise them
- vapours pass over hot powdered aluminium oxides (silica or alumina)
-process breaks covalent bonds in the molecules as they come into contact with the surface of the catalyst - thermal decomposition
-molecules are broken up in a random way - produces a mixture of smaller alkanes and alkenes
Need for cracking
-fractions with shorter carbon chains are more in demand
-fractions with longer carbon chains are in excess and are in less demand
-these are cracked to produce shorter carbon chains
General formula for alkanes
CnH2n+2
Saturated definition
Only have single carbon-carbon bonds
-alkanes
Alkanes
-group of saturated hydrocarbons
-colourless compounds
Alkanes are generally unreactive compounds but:
-undergo combustion reactions
-can be cracked into smaller molecules
-react with halogens in the presence of light
Alkanes - substitution reaction
Alkanes undergo a substitution reaction with halogens in the presence of ultraviolet radiation
Alkanes - react with bromine
-in the presence of UV light, methane reacts with bromine in a substitution reaction
-CH4 + Br2 → CH3Br + HBr
methane + bromine → bromomethane + hydrogen bromide
Alkanes - react with chlorine
-CH4 + Cl2 → CH3Cl + HCl
-methane + chlorine → chloromethane + hydrogen chloride
Alkenes
-double carbon bond
-C=C functional group
-they can make more bonds with other atoms by opening the C=C bonds and allowing atoms to form another single bond with each carbon atom
-makes them much more reactive than alkanes - bromination of alkenes, polymerisation
Unsaturated definition
Compounds that have a C=C double bond
Alkene general formula
CnH2n
Bromination of ethene
-undergo addition reactions in which atoms of a simple molecule add across the C=C double bond
-works for any halogen and alkene
ethene + bromine –> 1,2-dibromoethane
Test for alkenes
Bromine water test
-Bromine water is an orange coloured solution
Added to an alkane:
-will remain as an orange solution as alkanes do not have double carbon bonds (C=C) so the bromine remains in solution
Added to an alkene:
-the bromine atoms add across the C=C bond, hence the solution no longer contains free bromine
-becomes decolourised
Addition polymers
Formation of long chain molecules from lots of small molecules (alkenes)
Monomers
Small molecule
-each monomer is a repeat unit and is connected to the adjacent unit via covalent bonds
Drawing polymers
-addition polymers are formed by the joining up of many monomers and only occurs in monomers that contain C=C bonds
-one of the bonds in each C=C bond breaks
-forms a bond with the adjacent monomer with the polymer being formed containing single bonds
Naming polymers
-put the name of the monomer in brackets
-add poly as the prefix
e.g. propene - alkene monomer –> polypropene
Polymerization of ethene monomers
Poly(ethene)
-draw it
Polymerization of chloroethene monomers
Poly(chloroethene)
-draw it
Polymerization of propene monomers
Polypropene
-draw it
Polymerization of tetrafluoroethene
Polytetrafluoroethene
-draw it
Problem with disposing addition polymers
-addition polymers are formed by the joining up of many small molecules with strong C-C bonds
-makes addition polymers unreactive and chemically inert so don’t easily biodegrade
-landfills
-incineration
-recycling
Disposal of addition polymers - landfills
-waste polymers are disposed in landfill
-takes up valuable land
-they are non-biodegradable so micro-organisms cannot break them down
-causes site to quickly fill up
Disposal of addition polymers - incineration
-polymers release a lot of heat energy when they burn and produces carbon dioxide which is a greenhouse gas
-polymers contain chlorine such as PVC release toxic hydrogen chloride gas when burned
-if incinerated by incomplete combustion, carbon monoxide will be produced
Disposal of addition polymers - recycling
-can be recycled but different polymers must be separated from each other
-process is difficult and expensive
