1. Chains, Energy and Resources: Module 1
Chemistry AS Revision
Chains, Energy and Resources: Module 1

2. Key Words
Hydrocarbons; organic compounds that contain carbon and hydrogen only
Saturated Hydrocarbon; hydrocarbon with single bonds only
Unsaturated Hydrocarbon; hydrocarbon containing carbon to carbon multiple bonds
Aliphatic Hydrocarbon; hydrocarbon with carbon atoms joined together in straight or branched chains
Alicyclic Hydrocarbon; hydrocarbon with carbon atoms joined together in a ring structure
Functional Group; the part of the organic molecule responsible for its chemical reactions
Homologous Series; series of organic compounds with the same functional group but with each successive member differing by CH2
Alkanes; homologous series with the general formula CnH2n+2
Alkyl Group; an alkane with a hydrogen atom removed.
Stereoisomers; compounds with the same structural formula, but with a different arrangement of the atoms in space

3. Key Words
E/Z Isomerism; stereoisomerism in which different groups attached to each carbon of a C=C double bond may be arranged differently in space because of the restricted rotation of the C=C bond
Radical; species with an unpaired electron.
Nucleophile; an atom (or group of atoms) that is attracted to an electron rich centre or atom, where it donates a pair of electrons to form a new covalent bond.
Electrophile; an atom 9or group of atoms) that is attracted to an electron rich centre or atom, where it accepts a pair of electrons to form a new covalent bond.
Cracking; breaking down of long chained saturated hydrocarbons to form a mixture of shorter chains alkanes and alkenes
Catalyst; substance that increases the rate of a chemical reaction without being used up in the process.
Π Bond; reactive part of a double bond formed above and below the plane of the bonded atoms by a sideways overlap of p-orbitals.
Curly Arrows; symbol used in reaction mechanisms to show the movement of an electron pair in the breaking or formation of a covalent bond
Polymer; long molecular chain built up from monomer units
Monomer; small molecule that Comines with many other monomers to form a polymer
Biodegradable Material; Material that is broken down naturally in the environment by living organisms

4. Types of Organic Reaction
Addition Reaction; reactant is added to an unsaturated molecules to make a saturated molecule
2 reactants  1 product
Substitution Reaction; an atom or group of atoms is replaced with a different atom or group of atoms
2 reactants  2 products
Elimination Reaction; removal of a molecules from a saturated molecules to make an unsaturated molecule
1 reactant  2 products

5. Types of Chemical Formulae
General Formula; simplest algebraic formula for a member of a homologous series.
Displayed Formula; shows the relative positioning of all the atoms in a molecule, and the bonds between them.
Structural Formula; minimal detail for the arrangement of atoms in a molecule.
Skeletal Formula; simplified organic formula, with hydrogen atoms removed from alkyl chains, leaving just a carbon skeleton and associated functional groups.

6. First Ten Members of Alkane Homologous Series
Number of carbon atoms in longest chain
Name 1
Meth ane 2
Eth ane 3
Prop ane 4
But ane 5
Pent ane 6
Hex ane 7
Hept ane 8
Oct ane 9
Non ane 10
Dec ane

7. Types of Isomers
Structural Isomer; same molecular formula but with different structural formulae. (Different order)
Stereoisomer; same structural formula but with a different arrangement in space. (Same order, different places)

8. Tips For Working Out Isomers
Shorten the chain
Move functional groups along chains
If double bond present, move things around it.
Chiral centre; has four different groups attached to one carbon atom, means the mirror images are non super imposable.

9. Types of Covalent Fission
Homolytic Fission; breaking of a covalent bond with one of the bonded electrons going to each atom, forming two radicals
Heterolytic Fission; breaking of a covalent bond with both of the bonded electrons going to one of the atoms forming a cation (+ ion) and an anion (- ion).

10. Percentage Yields and Atom Economy
100( 𝐴𝑐𝑡𝑢𝑎𝑙 𝑚𝑎𝑠𝑠 /𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑏𝑡𝑎𝑖𝑛 𝑀𝑎𝑥 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑚𝑎𝑠𝑠/𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 )
May have high % yield and low atom economy because there may be a lot of waste products.
Atom Economy;
100( 𝑀𝑟 𝑜𝑓 𝑡ℎ𝑒 𝑑𝑒𝑠𝑖𝑟𝑒𝑑 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑆𝑢𝑚 𝑜𝑓𝑀𝑟 𝑜𝑓 𝑎𝑙𝑙 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠/𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠 )
Addition reactions have an atom economy of 100%
Reactions with atom economies nearer 100% are better because there are fewer waste materials

11. Fractional Distillation
Takes place in a fractional column, decreases in temperature from 400°C at the bottom to 20°C at the top.
Crude oil vaporised by heating, passed into column
Gases pass through the different levels of the column until they reach a temperature that is lower than their boiling point
Vapour condenses to liquid, which are tapped off.
Short chain hydrocarbons (lower BPs) condense near the top, longer ones near the bottom.

12. Van der Waals’ Forces and Boiling Points
As chain length increases, the boiling point increases because the Van der Waals’ between molecules become stronger.
More energy required to break the increasing number of Van der Waals’ forces.
A branched isomer has a lower BP than an unbranched one.
Fewer points of contact between molecules, so fewer Van der Waals’.
Cannot get as close together, decreasing the Van der Waals’

13. Combustion and Incomplete Combustion of Alkanes
Occurs in plentiful supply of oxygen.
CH4 (g) + 2O2 (g)  CO2 (g) + 2H2O (l)
Incomplete Combustion;
Occurs in limited supply of oxygen.
C8H18 (l) + 81/2O2 (g)  8CO (g) + 9H2O (l)
CO is colourless and odourless.
CO is poisonous, prevents haemoglobin binding with oxygen

14. Catalytic Cracking
Short chain hydrocarbons used as fuels and for polymer production
Cracking; breaking down long chained saturated hydrocarbons to form a mixture of short chained alkanes and alkenes

15. Isomeration
Unbranched alkanes converted into branched alkanes into branched alkanes.
Promotes more efficient combustion

16. Reforming
Unbranched hydrocarbons converted into cyclic hydrocarbons. H2 (g) is always produced as a result.
Promotes more efficient combustion

17. Rely on it for electrical generation and transport Feedstock
Contrasting The Value of Fuels for Energy with Over Reliance and Plant Based Fuels. Increased CO2, Global Warming, Climate Change
Rely on it for electrical generation and transport
Feedstock
Reducing reserves of oil has pushed the price up, scientists looking for alternatives
Environmental impact, scientists looking for alternatives
Leads to release of atmospheric pollutants: carbon monoxide, carbon dioxide, nitrogen oxides and sulphur dioxide
Green house gases lead to global warming leading to change in climates.
Bio fuels are alternatives.

18. Free Radical Substitution
Halogenation of Alkanes
Initiation
Cl-Cl bond in chlorine molecule is broken by homolytic fission, forming two chlorine radicals. UV provides the energy for this bond fission
Cl-Cl  2Cl•
Propagation
Methane reacts with chlorine radical. Single C-H bond is broken by homolytic fission, forming a methyl radical •CH3. HCL also formed
CH4 + Cl•  •CH3 + HCl
Methyl radical reacts with chlorine molecule, creating chloromethane and a further chlorine radical.
•CH3 + Cl2  CH3Cl + Cl•
Termination
Two radicals combine to form a molecule. Number of possible termination steps, because of the large numbers of radicals.
Cl• + Cl•  Cl2
•CH3 + •CH3  C2H5
•CH3 + •Cl  CH3Cl

19. Addition reactions of Alkenes
Addition of Hydrogen (Hydrogenation)
H (g) and alkene (g) passed over nickel catalyst at 150°C
Alkane is formed, double bond broken
Hydrolysis
Addition of to an alkene to make an alcohol

20. Electrophilic Addition
Formation of dihalogenoalkanes.
Can be tested for using bromine water (Orange to colourless)
Halogenation

21. Addition Polymerisation of Alkenes

22. Processing of Waste Polymers
Separated into types and then recycled
Combustion for energy
Use as a feedstock for cracking in the production of plastics and other chemicals

23. Role of Chemists in Minimising Environmental Damage
Removal of toxic waste products
Removal of HCl formed during the disposal by combustion of halogenated plastics (PVC)
Development of biodegradable and compostable polymers.