Ethylene
Basic Petrochemicals
Prefixes - “ane ” – Alkanes ; “ene” – alkenes ; “anol” - Alkanols
Meth – C ; eth - 𝐶2 ; pro - 𝐶3 ; but - 𝐶4 ; pent - 𝐶5 ; hex - 𝐶6 ; hept - 𝐶7 ; oct - 𝐶8 ; non - 𝐶9 ; dec - 𝐶10
State C - 𝐶4 Gas ; 𝐶5 - 𝐶17 Liquid ; 𝐶18 - Solid
Structural Isomers are different structures of hydrocarbons with the same molecular formula (same number of
different atoms)
Saturated - Alkanes; has maximum no. of hydrogen atoms
Unsaturated - alkenes; has less than maximum no. of hydrogen atoms
Fractional Distillation process
where petroleum crude oil is
separated into its different parts.
Crude oil is heated in a oxygen free
environment until it evaporates .
The vapours are funnelled into a
tower condensed and separated
depending on boiling point with the
gases (lowest boling points at the
top) liquids e.g. octane at the
middle and the solids e.g. bitumen
at the bottom (highest boiling
point)
Cracking
Ratio of hydrocarbons found in
petroleum is different to market
demands.
Some Hydrocarbons of lower
demand (heavy hydrocarbons) are
synthesised into hydrocarbons of
higher demand (lighter
hydrocarbons).
Catalytic Cracking
Modern cracking – Heavy fractions
(feedstock) heated with Zeolite
catalyst. Crystalline comp. Of
aluminium silicon + oxygen in fine
powder. Feedstock absorbed into
pores of catalyst reducing activation
energy.
𝐶18 𝐻38 (𝑔) → (𝑧𝑒𝑜𝑙𝑖𝑡𝑒 𝑐𝑎𝑡𝑙𝑦𝑠𝑒) → 4𝐶𝐻2 = 𝐶𝐻2(𝑔) + 𝐶10 𝐻22(𝑔)
Thermal Cracking
Cracking first achieved using this but inefficient due to high energy needs
Steam cracking
Cracking of ethane and propane from natural gas – major source of ethylene. Mixture of steam and feedstock
heated 750 - 900℃
𝐶2 𝐻6(𝑔) → (𝑠𝑡𝑒𝑎𝑚 𝑐𝑟𝑎𝑐𝑘𝑖𝑛𝑔) → 4𝐶𝐻2 = 𝐶𝐻2(𝑔) + 𝐻2(𝑔)
Ethane
Ethene
Hydrogen
Reactions of Ethylene
Ethylene is reactive due to its double bond – a place of high electron density
Readily undergoes addition reactions where the double bond opens up and atoms add on and discolours brome
water. IN CONTRAST alkanes undergo slow substitution reactions in UV light.
Hydrogenation(adding hydrogen)
𝐶𝐻2 = 𝐶𝐻2(𝑔) + 𝐻2(𝑔) → 𝐶𝐻3 = 𝐶𝐻3(𝑔)
Ethylene
Hydrogen
Ethane
Halogenations (adding halogens)
𝐶𝐻2 = 𝐶𝐻2(𝑔) + 𝐵𝑟2 (𝑙) → 𝐶𝐻2 𝐵𝑟 − 𝐶𝐻2 𝐵𝑟(𝑙)
Ethylene
Bromine
1,2-Dibromoethane
In presence of water
𝐶𝐻2 = 𝐶𝐻2(𝑔) + 𝐵𝑟2 (𝑎𝑞) → 𝐶𝐻2 𝑂𝐻 − 𝐶𝐻2 𝐵𝑟(𝑙) + 𝐻𝐵𝑟(𝑎𝑞)
2 – bromo-1-ethanol
𝐶𝐻2 = 𝐶𝐻2(𝑔) + 𝐻𝐶𝑙 (𝑔) → 𝐶𝐻3 − 𝐶𝐻2 𝐶𝑙(𝑙)
Chloroethane
𝐶𝐻2 = 𝐶𝐻2(𝑔) + 𝐻2 𝑂(l) → (𝐻2 𝑆𝑂4 𝑐𝑎𝑡𝑎𝑙𝑦𝑠𝑡) → 𝐶𝐻3 − 𝐶𝐻2 𝑂𝐻 (𝑙)
Ethanol
Hydrohalogenation (adding hydrogen halides)
Hydration (adding water)
Polymers
Synthetic polymers – Man made e.g. PVC, HDPE, PET, Teflon, polyester, nylon
Natural Polymers – Naturally made by organisms e.g. cellulose, rubber, silk, wool, starch
Polymerisation Reactions
Addition Polymerisation
Monomers add to growing polymer chain, involved unsaturated monomers (double bonded), all atoms in monomer
is in polymer.
Process – Catalyst (free radical free unpaired electron compound) starts reaction by breaking open double bond
allowing more monomers to link and bond , is spontaneous chain reaction until two sections of polymer chain bond.
𝑛𝐶𝐻2 = 𝐶𝐻2 → 𝑛(… 𝐶𝐻2 − 𝐶𝐻2 … ) → 𝑛(−𝐶𝐻2 − 𝐶𝐻2 − 𝐶𝐻2 − 𝐶𝐻2 −)
Ethene
double bond breaks
Polyethylene
Condensation Polymerisation
Reaction between molecules containing 2 different functional groups and between 2 func groups; usually between 2
diff. Monomers; a small molecule is eliminated and 2 functional groups link; Occurs in many natural polymers.
Production of Polyethylene
Monomers >>> free radical R-O• initiator attacks double bond forming >>> ethene + free radical 𝑅 − 𝑂 − 𝐶𝐻2 𝐶𝐻2 •
which is a radical >> attacks another ethylene adding it >>> Propagation; monomers >>> termination 2 end free
radicals forming covalent bond >>> Complete polymer
Cellulose (C6H10O5)
Polymer of Glucose monomers; Straight Chain due to beta bonds and inversion of every 2nd
monomer; OH groups form hydrogen bonds with neighbouring chains ; polysaccharide;
made by dehydration synthesis of glucose
Common polymers
Poly Vinyl Chloride 𝑛(−𝐶𝐻2 − 𝐶𝐻𝐶𝑙 − 𝐶𝐻2 − 𝐶𝐻𝐶𝑙 −)
Monomer: Chloroethene (Vinyl chloride) 𝐶𝐻2 = 𝐶𝐻𝐶𝑙 ; Properties: Garden hoses, water
pipes, guttering – depending of additives; Pure PVC too hard brittle and decomposes in
heat; thermoplastic
Polystyrene
Polyphenylethylene; Uses: Styrofoam by blowing hydrocarbon gas thrown liquid polystyrene >> insulating,
lightweight , can be made into hard clear brittle plastic for CDs Cassettes
𝑛 𝐶𝐻2 = 𝐶𝐻𝐶6 𝐻6 → 𝑛(− 𝐶𝐻2 − 𝐶𝐻𝐶6 𝐻6 −)
𝐶6 𝐻6 = 𝑏𝑒𝑛𝑧𝑒𝑛𝑒 𝑟𝑖𝑛𝑔
HDPE
HDPE: uses ionic Ziegler-Natta Catalyst, 𝑇𝑖𝐶𝑙4 𝐴𝑙(𝐶2 𝐻5 )3 mixture, ethylene monomers added on surface of catalyst
reducing branching; Uses: natural gas pipes, petrol, oil, acid containers buckets etc. Properties: hard thermoplastic
LDPE
When chain grows during polymerization radical curls back removing a hydrogen from middle of chain>>> branching
resulting in low density
Uses: tough, flexible transparent film packaging (GLAD wrap), moulded for plastic bags, squeezable bottles, wire
insulation
Factors affecting Polymer properties
The length of polymer Chain
Plastics with longer chains are stronger – due to more dispersion forces between them
Arrangement of polymer chains
Crystalline areas > Lined up and compact molecules > ∴ stronger less flexible polymer
Amorphous regions > molecule chains in random arrangement > ∴ weaker polymer
Drawing polymer fibres through small hole (spinneret) > aligns molecule > ∴ stronger polymer
Degree of branching from polymer chain
Greater branching > restricts orderly arrangement > ∴ reduces density, hardness but increases flexibility (diff.
between HDPE , LDPE)
Functional groups in monomers
Polar functional groups > increases intermolecular forces between polymer chains (hydroxyl –OH and amine -N𝐻2
result in hydrogen bonding) > increased intermolecular forces results stronger polymer
Cross linking between polymer chains
Thermosetting poly > bonds linking polymer chains > making polymer hard to melt without decomposing.
Thermoplastic s >no cross linking > longer chains with weaker intermolecular forces > heating allows rearrangement.
Elastomers > overlapping polymer chains + less cross linking > elastic plastic
Inclusion of additives
Few polymers used in pure form ; additives to improve or extend properties of polymer
Additives include : Pigments , plasticisers (to soften polymer), stabilisers (increase resistance to decomp. By heat,
UV) and flame retardants (reduce flammability)
Biopolymers
Biopolymers are made from biomass e.g. cellulose
Advantages > Biodegradable, renewable, useful properties, natural abundant sources
Disadvantages > expensive + difficult to produce
Ethanol 𝑪𝑯𝟑 − 𝑪𝑯𝟐 𝑶𝑯
Alkanols
Carbon compounds with hydroxyl (-OH) functional group(s) > alkane with 1 or more H atom replace with –OH;
General formula for alcohols ROH
Naming Conventions
Alkanol = Alkane with “-e” replaced with “-ol”
Number used to show position of carbon atom –OH is on e.g. 2-propanol
When more than –OH group suffixes used “-diol” (2 ), “-triol” (3)
Sometimes “-ol” not dropped
Primary alcohol = 1 Carbon, 2 H joined to carbon bonded to –OH group
Secondary alcohol = carbon atom bonded to –OH group has 2 C bonded to it
Tertiary alcohol = carbon atom bonded to –OH group has 3 C bonded to it
Ethanol Reactions
Combustion
Ethanol burns cleanly and easily as the small molecule is easily attacked by oxygen
CH3 − CH2 OH + 3O2 → 3H2 𝑂 + 2𝐶𝑂2 + 1267𝑘𝐽
Hydration of ethylene
𝐶𝐻2 = 𝐶𝐻2 (𝑔) + 𝐻2 𝑂(𝑔) → (𝑑𝑖𝑙𝑢𝑡𝑒 𝐻2 𝑆𝑂4 𝑐𝑎𝑡𝑎𝑙𝑦𝑠𝑡 ) → 𝐶𝐻3 − 𝐶𝐻2 𝑂𝐻(𝑔)
Ethylene reacted with water to make ethanol
Dehydration of ethanol
The production of ethylene via dehydration of ethanol ; industrially > heating ethanol vapour with catalyst 350℃
𝐶𝐻3 − 𝐶𝐻2 𝑂𝐻(𝑔) → (𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑒𝑑 𝐻2 𝑆𝑂4 ) → 𝐶𝐻2 = 𝐶𝐻2 (𝑔) + 𝐻2 𝑂(𝑔)
In laboratory heating ethanol with excess conc. Sulphuric acid catalyst
Only concentrations of 15% as at this conc. yeast is killed and fermentation stops
Fermentation
Main method of producing ethanol
Yeast metabolises in anaerobic environment releasing enzymes which react glucose into ethanol and carbon dioxide
𝐶6 𝐻12 𝑂6 (𝑎𝑞) → (𝑦𝑒𝑎𝑠𝑡 𝑒𝑧𝑦𝑚𝑒𝑠) → 2𝐶𝐻3 − 𝐶𝐻2 𝑂𝐻(𝑎𝑞) + 2𝐶𝑂2 (𝑔) + ℎ𝑒𝑎𝑡
Molar heat of combustion
Experimentally calculated heat of combustion inaccurate due to heat loss + incomplete combustion
Calculated using ∆𝐻 = −𝑀𝐶∆𝑇
m = mass of heated substance
c = heat capacity of heated substance
∆𝑇 = Temperature change of substance
When more than 1 medium is heated and the temperature measured the heat gain by the 1st substance is added to
heat gained by second e.g. using ∆𝐻 = −(𝑀𝑐𝑜𝑝𝑝𝑒𝑟 𝐶𝑐𝑜𝑝𝑝𝑒𝑟 ∆𝑇2 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒𝑠 ) + (𝑀𝑤𝑎𝑡𝑒𝑟 𝐶𝑤𝑎𝑡𝑒𝑟 ∆𝑇2 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒𝑠 )
Advantages and Disadvantages of ethanol as fuel
Advantages = renewable as fermented from biomass, cleaner burning, carbon neutral, reduced green house gas in
cars, reduces oil dependency
Disadvantages = requires adequate biomass i.e. clearing land for farming, energy needed to refine, transport etc.
Car engines need mods when running conc. over 15%
Ethanol properties
Polar due to hydroxyl (-OH)
Solvent for polar substances due to polar nature of –OH hydroxyl func. group .
Polar for non-polar substances due to non-polar akyl 𝐶𝐻3 𝐶𝐻2− end forming dispersion forces with non polar solutes
Electrochemistry
Metal Displacement Reactions
Redox reactions with Oxidation and Reduction occurring simultaneously
Transfer of electrons in Redox reactions utilized to make electricity
Oxidation = loss electrons Reduction = Receiving electrons
All electro chemical process involve redox
Displacement reactions = more reactive element displaces a less reactive element from solution as a solid or a gas caused by the transfer of electrons
Electron transfer occurs at surface of metal placed in the solution
Oxidation states – system used to identity oxidation reduction of elements when cannot be easily identified + keep
track of electrons transferred or shared in redox reac.
Utilizes the assigning of oxidation state i.e. arbitrary numbers to atoms according to set rules
Increased oxidation state = oxidation
Decreased oxidation state = reduction
Assigning oxidation state rules
1. Elemental state substances ; Oxidation state = 0
2. Monatomic Ions; Oxidation state = charge on ion
3. Neutral molecule or ionic compound; sum of oxidation states of all atoms = 0
4. Polyatomic Ion; Sum of oxidation states of all atoms = charge on ion
5. Fixed states; Group 1 metals Ox. Stat. = (+1) ;
Group 2 metals Ox. Stat = (+2);
Combined oxygen Ox. Stat = (-2), except in peroxides Ox. Stat = (-2) and 𝐹2 𝑂 Ox. Stat = (+2);
Combined Hydrogen Ox. Stat = (+1) except in metal hydrides Ox. Stat = (-1)
Galvanic (Voltaic) Cells
When 2 metals are placed in electrolyte (ionic solution in water)a potential diff. exists between them. Can be
measure if metals joined by wire current flows.
Consists 2 half-cells; each with a metal or other non metal and a aqueous solution of a compound which contains
that element(electrolyte), the cells are linked by a salt bridge to allow the movement of ions to maintain the neutral
charge of the cells.
Operation
More reactive anode oxidises leaving electrons and ions which become dissolved in solution >>> electrons flow
through wire into the cathode, ions in the electrolyte reduce and displace from the solution as gas or as metal
plating on the cathode >>> nitrate ions travel down into solution to balance charge in anode half cell and potassium
ions balance cathode solution
ANode OXidation, REDuction CAThode
Naming Metal|metal ion||metal ion|metal or reductant|reductant ion||oxidant ion|oxidant
e.g. 𝑍𝑛|𝑍𝑛2+ ||𝐴𝑔+ |𝐴𝑔
Oxidising/Reducing agents
Oxidant/Oxidising Agents cause oxidation + reduces ; Found near bottom of reduction potentials list i.e. less reactive
Reductant/Reducing Agent cause reduction + oxidises; found near top of list i.e. more reactive
Calculating cell potential (e.m.f)+ predicting reaction tendency
E.M.F = electromotive force, maximum voltage a cell can deliver
Steps:
1. ID half-cell equations + standard reduction potentials from chart
2. ID oxidation reaction (lowest EMF / most reactive) + reverse direction/change sign of this reduction potential
(𝐸°)
3. Calculate the cell voltage - Add the Ox. + Red. Potentials
4. If the calculated voltage is > 0 the reaction is spontaneous
If reaction is not spontaneous voltage must be applied to make it occur
Commercial Galvanic cells
Leclanche Cell
Anode: 𝑍𝑛(𝑠) → 𝑍𝑛2+ (𝑎𝑞) + 2𝑒 −
Cathode 2𝑀𝑛𝑂2 (𝑠) + 2𝐻 + (𝑎𝑞) + 2𝑒 − → 𝑀𝑛2 𝑂3 (𝑠) + 𝐻2 𝑂(𝑙)
Electrolyte 𝑁𝐻4+ (𝑎𝑞) ↔ 𝑁𝐻3 (𝑎𝑞) + 𝐻 + (𝑎𝑞)
Overall 𝑍𝑛(𝑠) + 2𝑀𝑛𝑂2 (𝑠) + 2𝐻 + (𝑎𝑞) → 𝑍𝑛2+ (𝑎𝑞) +
𝑀𝑛2 𝑂3 (𝑠) + 𝐻2 𝑂(𝑙) or
𝑍𝑛(𝑠) + 2𝑀𝑛𝑂2 (𝑠) + 2𝑁𝐻4+ (𝑎𝑞) → 𝑍𝑛2+ (𝑎𝑞) + 𝑀𝑛2 𝑂3 (𝑠) +
𝐻2 𝑂(𝑙) +2 𝑁𝐻3 (𝑎𝑞)
e.m.f. = 1.48V
Electrolyte = Manganese dioxide paste + ammonium chloride + zinc
chloride
Lead Acid Batteries
Anode: 𝑃𝑏(𝑠) + 𝑆𝑂42− (𝑎𝑞) → 𝑃𝑏𝑆𝑂4 (𝑠) + 2𝑒 −
Cathode: 𝑃𝑏𝑂2 (𝑠) + 4 𝐻 + (𝑎𝑞) + 𝑆𝑂42− (𝑎𝑞) + 2𝑒 − → 𝑃𝑏𝑆𝑂4 (𝑠) +
2𝐻2 𝑂(𝑙)
Overall: 𝑃𝑏(𝑠) + 𝑃𝑏𝑂2 (𝑠) + 4𝐻 + (𝑎𝑞) + 2 𝑆𝑂42− (𝑎𝑞) →
2𝑃𝑏𝑆𝑂4 (𝑠) + 2𝐻2 𝑂(𝑙)
Electrolyte = 𝐻2 𝑆𝑂4 (𝑎𝑞) 1𝑚𝑜𝑙/𝐿
Reaction can be reversed (battery recharged)
Used in cars, trucks to power lights start engine etc.
Supply High surge currents need for high current demands of start
motors.
Each cell produces 2V cells 6 series linked to make 12V
Fuel Cells
Anode: 𝐻2 (𝑔) → 2𝐻 + (𝑎𝑞) + 2𝑒 −
Cathode: 𝑂2 (𝑔) + 4𝐻 + (𝑎𝑞) + 4𝑒 − → 2𝐻2 𝑂(𝑙)
Overall: 2𝐻2 (𝑔) + 𝑂2 (𝑔) → 2𝐻2 𝑂(𝑙)
Unique – cell does not store reactants or products
Max e.m.f. = 1.23 Volts
Nuclear Chemistry
Types of Radioactive decay
Beta
Occurs when a neutron converts into a proton
1
1
−1
0𝑛 → 1𝐻 + 0𝑒
Mass number stays same, atomic number + 1
Gamma
Energy emission usually accompanying an alpha or Beta decay, allows nucleus to lose energy
Positron
0
1𝑒 - positively charged electron (antimatter electron)
Emitted when protons convert to neutrons
1
1𝐻
→ 10𝑛 + 01𝑒
Mass number of decayed atom is same but atomic number decreases by 1
Electron Capture
Occurs when inner shell/orbital electrons captured by nucleus
1
0
1
1𝐻 + 1𝑒 → 0𝑛
Abbreviation Conventions
𝐴
𝑧𝑀
Isotopes are atoms of the same element but with different mass number, mass number determines
nuclear stability. Isotopes have same chemical properties
Reactions – In contrast to chemical reactions -Nuclear reactions are not affected by temp. pressure,
concentration, catalysts + the atoms are not preserved
A = mass number (protons + neutrons)
Z = atomic number or charge where appropriate
M = particle abbreviation
Nuclear Stability
Radioactivity is used to describe the spontaneous change of unstable nuclei via the emission of radiation
(particles + energy).
Determined by number of diff. particles in nucleus.
Rules of Stability
1. All nuclei atomic no. > 83 unstable – undergo alpha decay
2. Elements with atom number <20 are stable when neutron: proton ≈ 1:1
3. For higher atomic no. Neutron: proton is higher for stable nucleus
4. All Nuclei in zone of stability are stable
5. Neutron: proton > stable zone (region B) – Beta decay to lower ration
6. Neutron: proton < stable zone(region A) – Positron emission and/or electron capture to increase ratio
Detecting Radiation
Half life = the time taken for ½ of initial number radioactive nuclei to decay, considered when determining the use of
isotopes.
Photographic film - radiation cause the darkening of film, increased darkening ∝ intensity and duration of exposure
Ionisation counter: Geiger counter –Ionising radiation causes Argon gas in a metal tube to ionise forming positive
ions and free electrons which are attracted to electrodes which conduct electricity to recording device. The current
is measured and converted to audible clicks
Scintillation Counter - some substance (e.g. zinc sulfide) when struck by radiation emit light. The electrons become
excited and release photons which are electronically counted to measure radiation.
Producing Radioisotopes
Produced for medical + industrial purposes. Involves Nuclear transformation/ Transmutation. Creates unstable new
atoms
Transuranic element =Element with atomic no. > 83 and is synthetic
Bombardment with charged particles
Target nucleus is bombarded with nuclei of other elements. They are accelerated in a particle accelerator to
overcome the electrostatic repulsion of the charged particles.
Particles accelerators include: Linear accelerators, cyclotrons and synchrotrons.
Technetium-99m
for produced by bombarding molybdenum-98 with hydrogen-2 nuclei
98
2
99𝑚
1
42𝑀𝑜 + 1𝐻 → 43𝑇 𝑒 + 0n
Properties: 6 Hour Half-life, can bond with other elements to target organs, release weak gamma rays
Bombardment with neutrons
Most artificial radioisotopes made by neutron bombardment due to uncharged, not repelled ∴ easily absorbed by
nucleus. Source of electrons is nuclear reactor
59
Example: 27
𝐶 𝑜 + 10𝑛 → 60
27𝐶 𝑜
Uses of Radioisotopes
Medical
Diagnostic – Radiography to image inside of body (radiation emitted by ingested radioisotopes are detected and
measure to create image) the radioisotopes are combined with compounds to targeted organs to reduce radiation
widespread exposure. Technicium-99 primarily used for this.
Industrial
Detecting: Leaks in underground gas, water pipes, hand held detectors used to locate areas of high radioactivity i.e.
leaks.
Thickness of paper – radiation loses energy as it passes through matter , decrease in energy proportional to
thickness, density
Metal flaws
Irradiation of food
Food is exposed to Gamma radiation to kill pathogens, improve shelf life, sterilize
Radioactive Dating
The level of diff. radioisotopes is related to age due to half life of isotopes, by knowing the amount of radioisotope in
artefact and the half life the age can be determined.