NOMENCLATURE:
Hydrocarbons (HC) contain only hydrogen and carbon
and can be classified as saturated or unsaturated. They
are the main components constituents of natural gas
and crude oil. Saturated (unreactive) HC contain
single bonds whereas unsaturated (reactive) contains
double or triple bonds. A homologous series is a
family of compounds that is represented general
molecular formula. A functional group of atoms
giving a compound some characteristic physical and
chemical property. They can be aromatic (having
benzene rings) or aliphatic (everything else)
Alkanes: Branched Alkanes:
• General formula: 𝐶𝑛 𝐻2𝑛+2
Prefix MP BP
Meth- 1 -182 -164
Eth- 2 -183 -89
Prop- 3 -190 -42
But- 4 -138 0
Pent- 5 -130 36
Hex- 6 -95 69
Hept- 7 -91 98
Oct- 8 -57 126
• Flammable and volatile with low BP and ignition temperature (mainly gases)
lower density than water and insoluble in water.
Alkyl Molecular Formula
Methyl Ethyl Propyl Butyl Pentyl
# of same Prefix # same Prefix
2 di 5 penta
3 tri 6 hexa
4 tetra 7 hepta
• As molecular mass increases, ignition temperature, BP, MP increases
o Gas → Liquid → Solid
• Colourless and Odourless
• Nomenclature: Find the longest chain, look for the branched alkanes and add the prefix alphabetically
and add assign numbers to groups with lowest numbers.
Alkenes:
• General formula 𝐶𝑛 𝐻2𝑛
• Consists of double bonds. The more double bonds, the more reactive it
is.
o Pi bonds make it more reactive and is formed by the overlap of
orbitals in a side to side fashion.
o Sigma bonds formed from overlaps of orbitals in an end to end
fashion. o Sigma (σ) bonds are strong since they involve orbitals that overlap o Pi (π) are weak since orbitals don’t overlap
▪ C=C has 1π bond and 1σ bond ▪ C≡C bond has 2π and 1σ bond
• It can accept more H atoms. It is necessary to assign a number to describe
location of double bond.
• Flammable and volatile, strong odour, BP less than alkanes, insoluble and
less dense than water.
• As molecular mass increases, ignition temperature, BP, MP increases
o Gas → Liquid → Solid
Alkynes:
• General formula 𝐶𝑛 𝐻2𝑛−2
• It can accept more H atoms. It is necessary to assign a number to describe
location of triple bond.
• Consists of triple bonds. The more triple bonds, the more reactive it is.
o Pi bonds make it more reactive and is formed by the overlap of
orbitals in a side to side fashion.
3-methylhexane
o Sigma bonds formed from overlaps of orbitals in an end to end fashion. o Sigma (σ) bonds are strong since they involve orbitals that overlap o Pi (π) are weak since orbitals don’t overlap
▪ C=C has 1π bond and 1σ bond ▪ C≡C bond has 2π and 1σ bond
• Volatile and flammable, no odour, insoluble and less dense in water.
• As molecular mass increases, ignition temperature, BP, MP increases
o Gas → Liquid → Solid
Cyclo HC
• Ring Structure and can be saturated or unsaturated. o C-C →cycloalkanes o C=C →cycloalkenes o C≡C → cycloalkynes
• Aromatic HC → ring of C- atoms linked such that they have delocalised e-. E.G Benzene
• Has greater stability and usually unreactive
Properties of Alkanes/Alkenes/Alkynes
• Alkanes
o Non-polar → The C-H bonds have dipole-dipole as strongest
intermolecular forces but the molecules general shape causes it
to be non-polar. Hence, the strongest intermolecular force is
dispersion forces as it is formed from temporary e- distribution.
Resultingly, it has low MP/BP as little energy is required to
overcome the forces. Being non-polar, it is not soluble in polar
substance like water and is a poor conductor of electricity. It is
relatively stable and unreactive.
• Alkenes/Alkynes
o Non-polar with dispersion forces. They are unsaturated due to
bond type and hence are more reactive as they can form extra
bonds. Similar physical properties to alkanes.
Alcohols
• Contains hydroxyl functional group.
• Naming: Identify longest chain and use corresponding prefix, write
alkane without ‘e’ and put ‘ol’, state the position of alcohol before the
suffix and then name substituents.
• Note: The OH group takes precedence over HC side chains, halogen substituents, double and triple bonds.
o If there is a double bond and hydroxyl group, the location of double bond goes before prefix (4-Penten-2-ol). If something else
takes more precedence than alcohol, it is named using hydroxyl.
• Primary: One carbon attached to OH
• Secondary: Two carbon attached to OH
• Tertiary: Three carbons attached to OH
Aldehydes and Ketones
• Considered as carbonyl compounds (carbon atom double bonded with
oxygen)
• Aldehyde
o Carbonyl located at end of the chain
o Naming: Identify longest chain with -CHO, then for an alkane replace ‘e’ with ‘al’ and then use normal naming convention.
• Ketone
o Located anywhere but on the end chains.
o Naming: Identify longest chain with -CO, then for an alkane replace ‘e’ with ‘one’, identify lowest position number and then use
normal naming convention
Carboxylic acids
• Carboxyl functional group (COOH)
• Found at the ends of chains.
• Naming: Identify longest chain with COOH, delete the ‘e’ of alkane and replace it with ‘oic acid’ and then
use normal naming convention.
Amines and amides
• Amines:
o Amine functional group (NH2)
o Primary: has one alkyl group
o Secondary: has 2 alkyl groups on nitrogen
o Tertiary: has 3 alkyl groups on nitrogen
o Naming: Identify longest chain with N, delete ‘e’ of alkane and replace
with ‘amine’. For primary, make N have lowest position number (propan-
2-amine). Else, name other alkyl groups in alphabetical order, and give them position N (N-methyl, N,N-dimethyl)
• Amides:
o Amide functional group (CO-NH2)
o Just like amines, amides are primary, secondary and
tertiary.
o Naming: Identify longest chain with connected to N,
delete ‘e’ of an alkane and insert ‘amide’ and give it the
lowest position number, then name other alkyl groups
connect to N in alphabetical order and then normal
naming conventions.
Naming priority
ISOMERS: Compounds with same molecular formula but
a different structural arrangement. It affects
chemical and physical properties of
compounds. There are different types of
isomerism: structural, geometric and optical.
Property Butane 2-methylpropane
Density 0.601 0.551
Melting point -138.4 -159.6
Boiling point -0.5 -11.7
Flash point (lowest temperature at which a liquid can gives off vapor to form an ignitable mixture in air near the surface of the liquid)
-60 -83
• Chain isomer
o Isomers with different placement of substituents on main chain
o Rearrangement of chains into different branches.
o Longer the chain = more isomers
o Pentane C5H12 has 3 chain isomers
• Position isomers
o Basic carbon skeleton remains unchanged but important groups are
moved around.
o These are structural isomers with different functional groups.
• Functional group isomer
o Molecules with same molecular formula but different functional group and structural formula.
o The isomer contains different functional group
o Eg: C2H6O can be ethanol or dimethyl ether
Eg: C3H6O can be propanol or propanone
HYDROCARBONS: Models are a simplified version of a part of an organic compound.
Ball and stick models are usually used. Organic compounds can be
described mainly in 5 ways. Benefits of modelling: Beneficial in
illustrating differences between each homologous group by
showing single, double and triple bonds that are present, provide a
better understanding of isomers and visualise the processes which
cannot be seen. Limitations are: There are no sticks in reality so its
an inaccurate representation of the molecules shape and it is
obviously not to scale.
Shapes of HC: Types of organic formulae
Bonds around carbon
Angle Shape
4 Single 109.5 Tetrahedral
2 single, 1 double
120 Trigonal planar
2 double or 1 triple and 1 single
180 Linear
Type of formula Method Of Drawing
Molecular formula: shows number of each type of atoms present
C6H14
Structural formula: not all bonds are shown
Condensed formula: all bonds listed (except benzene)
Investigation
Aim: To investigate the structures of hydrocarbons through modelling.
Method:
1. Construct ethane, ethene and ethyne with black balls representing carbon atoms and smaller white balls representing hydrogen atoms.
2. Construct simple alkanes, alkynes and alkenes.
Homologous Series
• Series of compounds with same functional group
• Many physical properties such as BP gradually increase with increasing molecular mass
• Five main characteristics
o Same series represented by general formula
o Successive members differ by CH2
o Physical properties change regularly with increasing number of carbons which has extra dispersion forces creating stronger
intermolecular forces
o Similar chemical properties
o Prepared using same method
▪ Ethanol, Propanol and Butanol prepared by hydration of alkanes.
Compare and Contrast Properties of Alkane, Alkyne, Alkene
Property Alkane Alkene Alkyne
MP/BP Middle Lowest Highest
Conductivity No No No
Solubility Soluble in non-polar
Soluble in non-polar
Soluble in non-polar
• Explain the properties
o BP/MP
▪ Molecules with a variety of intermolecular forces cannot move easily and require more kinetic energy to break these
bonds to form liquids/gases. So stronger the intermolecular forces, higher the MP/BP
• Alkanes: longer chain → higher Molecular mass → greater number of electrons so higher dispersion forces →
higher MP/BP
Non-branched chains have higher MP/BP than branched as branches reduce contact area resulting in weaker
dispersion forces. As chain increases, surface area increases which increases the intermolecular forces between
each molecule.
straight chain alkanes have greater surface area than branched alkanes
• Alkenes: longer chain/Fewer branches increases MP/BP
However it is lower than alkanes as they will have 2 fewer electrons for each double bond present as it decreases
molar mass.
• Alkynes: have the highest MP/BP due to the triple bond, fewer H atoms allows alkyne molecules to lie closer
together, creating stronger dispersion forces.
o Volatility
▪ Tendency for substance to vaporise at room temperature. It relates to molecular weight. Smaller alkenes have weakest
intermolecular forces allowing them to vaporise more easily. The lower the MP/BP, the higher the volatility.
o Polarity
▪ Since there are no significant differences in electronegativity, they are non-polar and cannot conduct electricity. They can
only dissolve in non-polar substances
Intra/Intermolecular forces
• Polarity
o Non-polar, C-H bond weakly polar due to differences in electronegativity, however due to the symmetry of C-H bonds, any
dipoles are balanced out so alkanes cannot mix with water.
• MP/BP
o Low MP/BP due to weak intermolecular forces. Methane, ethane, propane and butane gas at room temp
o Longer chain = stronger intermolecular force = more energy to break them
• Electrical Conductivity
o Can’t conduct as they are non-polar
o Have no dipole charges or ionic charges that would allow them to conduct electricity
• Viscosity
o Increasing chain = more intermolecular forces holding molecules together. Substance becomes denser. Molecules get larger they
are able to roll or slide past each other making liquid less able to flow freely and become more viscous.
• Saturation
o Maximum number of hydrogen atoms intramolecularly bonded with carbon. They are better fuels as they release more energy in
combustion reaction.
Safety with hydrocarbons
Hazard Safety/Consequences
Flammability Hydrocarbons/organic compounds burn readily if exposed to flame. Keep Ignition sources away from hydrocarbon. Volatile vapours need to be controlled using fume cupboards. Be aware of the production of CO in insufficient oxygen as CO is poisonous
Asphyxiants High levels of volatile vapour in air leads to breathing difficulties. Use in fume cupboards.
Cytotoxicity Ingestion will lead to cell death and necrosis of body tissue. Wash hands prior to eating or drinking,
Carcinogenic Benzene and many aromatic compounds are possible cancer-causing agents. proper safety equipment must be worn and avoid breathing vapours and skin contact with compounds.
• Disposal
o Should not be disposed in sewerage as they are cytotoxic, they can kill organisms that are part of treatment at sewage treatment
plant.
o Should be disposed in suitable container which is collected by a license waste disposal contractor.
How are hydrocarbons found
• Majority comes from mining petroleum
• Petroleum is a fossil fuel
• Millions of years ago algae and plants died and sank to the bottom of the sea floor. High pressure and temperature transformed the
corpses into fossil fuels.
Environmental implications
• Fossil fuels extracted by mining for coal or drilling for natural gas
• Mining causes:
o Erosion, formation of sinkholes, contamination to soil, ground water, surface water and deforestation
• Drilling causes:
o Deforestation, erosion, long term exposure causes cancer, production of methane which is a more effective greenhouse gas than
carbon dioxide and extensive land degradation.
• Impacts of fossil fuels:
o Increasing effect of global warming, air pollution, production of nitrogen oxides which contribute to acid rain, production of
sulphur dioxide creating acid rain, widespread production of polymer plastic pollutes waterways oceans and lands.
Economic implications
• We are dependent on fossil fuel for energy, viral growth to economy, runs agricultural industry and power generation, oil prices are one
of the main causes of inflation as we are dependent on it, natural disasters that damage oil storages causes oil prices to rise and as more
technologies run on renewable energy, tech which is dependent on fossil fuels will become outdated and no longer be produced.
Sociocultural implications
• Health
o Millions of people die each year from exposure to atmospheric pollution. Exposure to toxic waste increases risk of lung/skin
cancer and kidney and heart disease
• Social
o Creates wider division between poor and rich. Oil companies use large amounts of water in production which may impact local
communities who depend on the same water sources.
• Industrial
o Tourism impacted by climate change, great barrier reefs corals are dying and sea levels rising impacts small island states.
o Climate change causes a shift in precipitation, temperature and agricultural zones, making it harder to grow crops
Products of reactions involving
hydrocarbons Unsaturated hydrocarbons are highly reactive due
to the presence of the double/triple bond. The
double and triple bonds are weaker, easier to break
and results in higher reactivity of molecules
containing these bonds.
• Alkanes are fairly unreactive unless exposed to heat/light. They can undergo combustion
reactions.
• In the presence of light or in high temperatures (800 degrees Celsius), alkanes react with
halogens to form alkyl halides.
• General reaction:
CnH2n+2 (g) + X2 → CnH2n+1X+HX
Example: C2H6 (g) + Cl2 (g) → C2H5Cl (g) +HCl (g)
• Alkenes and alkynes undergo reactions that add atoms to compounds by
breaking the bonds. This is addition reaction. No atoms are left over in this
reaction
o Hydrogenation
▪ Adding hydrogen to alkenes/alkynes
▪ Since the bond is weaker than single bond, it can be broken
easily and is reactive
▪ Addition of hydrogen creates single bond with additional
hydrogen added to structure.
▪ Done in the presence of a catalyst.
• This reaction is quite slow
• Hydrogen molecule reacts with the metal catalyst,
breaking one of its bonds between the 2 hydrogen
atoms, forming 2 weak metal hydrogen bonds. The
alkene molecule reacts with catalyst, breaking the
double bond. Metal catalyst causes hydrogen atom to
join with carbon atom.
• Only uses so reaction does not occur in high
temperatures. The reaction is exothermic, and
temperature should not be too high.
▪ Used in manufacture of margarine as raw fats and oils used are
unsaturated. After saturating it, only side affect is that it creates
trans-fats.
▪ Used in petroleum industry, it is used to convert alkenes and
aromatics into saturated alkanes which is less toxic and reactive
o Halogenation
▪ Adding halogen across double/triple bond
▪ Reacts readily with halogens so no catalyst required
▪ Addition of fluorine reacts explosively with alkenes and
produces carbon and hydrogen fluoride gas
▪ Instead of slow should be fast
CnH2n (g) + X2 → CnH2nX2
Example: C2H4 (g) + Cl2 (g) → C2H4Cl2 (g)
o Hydrohalogenation
• Adding H-X
• Forms haloalkane (alkyl halide)
• Hydrohalogenation of asymmetric alkenes and
alkynes form major and minor product. Symmetrical
alkenes and alkynes form only one product.
o Due to Markovnikov rule: the hydrogen from the H-X attaches to the carbon with more hydrogen
attached while the halogen prefers carbon with less hydrogen attached
o Products following this rule will be formed at higher concentrations (major product)
o Products that don’t will be
formed at lower concentrations
(minor product)
o Hydration
▪ Adding water to alkene produces alkanol as we
consider water to have H-OH structure. It
requires a catalyst of dilute sulfuric acid.
▪ When water is added across a double bond, one
of the hydrogens form the water molecule
attaches to one carbon originally bonded in the
double bond
▪ Follow Markovnikov rule
▪ Hydration of alkynes is catalysed by mercury
(II) compounds and sulfuric acid
▪ Addition of water to alkyne produces ketone
• An exception is hydration of ethyne as that
only produces ethanol
Alcohols They have a general formula of CnH2n+1OH and show isomerism in the
same way as alkanes, alkenes and alkynes.
Primary: one carbon atom is bonded to carbon atom attached to OH
Secondary: two carbon atoms bonded to carbon atom attached to OH
Tertiary: three carbon atoms bonded to carbon atom attached to OH
Properties
• Boiling point
o Alkanes/ens/ynes have relatively low MP/BP as they only form dispersion forces.
Compared to alcohols of the same number of carbons, they have a high BP. This is
because of the OH (Hydrogen bonding) to occur between alcohol molecules. This is
much stronger than dispersion forces.
o Longer the chain = higher BP
• Solubility
o Relies on the balance between polar functional group and non-polar hydrocarbon chain.
o Small alcohols completely soluble in water because they easily form hydrogen bonds in water
o When small alcohol molecules placed in water, alcohol-alcohol and water-water H bonds must be broken to be mixed. Energy
released by the formation of new alcohol-water H bonds approximates the energy needed to break the original H bonds, allowing
them to be mixed.
o For C<4, effect of the polar hydroxyl group outweighs effect of non-polar hydrocarbon chain hence becoming soluble. Else, most
of the molecule is a hydrocarbon tail which outweighs the polar hydroxyl forcing the water and alcohol not to mix.
o For big carbons to be soluble in water, you must have multiple hydroxy groups.
• Viscosity
o Property of fluid that resits force tending to cause the fluid to flow
o This increases in size for alcohol as molecule increases due to the increase in strength of the intermolecular forces which hold the
molecules more firmly
• Flammability
o Decreases as the size and mass increases
o Combustion breaks the covalent bonds of the molecules, so as size/mass increases, there are more covalent bonds to break in
order to burn that molecule, so more energy is required to break all of them.
• Polarity
o Amide>acid>acid>alcohol>ketone≈aldehyde<amine<ester<ether<alkane
o Ranked third due to its hydrogen bonding capabilities and presence of 1 oxygen
o Carboxylic acid is more polar as it has 2 oxygen molecules
Bonding in alcohol
• Hydrogen bonding
o Hydrogen atom on one alcohol molecule forms hydrogen bonds with oxygen atom of another molecule. Ince Hydrogen bonds are
extremely strong, more energy is need to break these bonds hence it has a higher BP/MP than equivalent alkane
• Dipole-dipole
o Due to the electronegativity difference between oxygen and hydrogen atoms which results in a dipole. The C-O bond is also a
polar covalent bond because Oxygen is much more electronegative than carbon so it pulls electrons away from the carbon which
results in another dipole forming between carbon and oxygen atoms
• Dispersion forces
o The non-polar hydrogen tail experiences dispersion forces. As the tail gets longer, the affect of the hydrogen bond gets smaller
relative to the size of the molecule so there will no longer be a significant difference between boiling points of alcohols and
alkanes.
• Intramolecular forces
o Alcohols consist of non-polar covalent bonds and polar covalent bonds. Since alcohols contain covalent bonds only, they cannot
conduct electricity. This is because there are no free ions.
Investigation enthalpy
Aim: To determine and compare the heat of combustion per gram and per mole of 3 alkanols using a calorimeter
Safety issues: Conduct in well-ventilated area since incomplete combustion may occur
Methodology:
1. Weigh empty aluminium can with an electronic balance
2. Fill can with 100ml water
3. Re-weigh can to find mass of water
4. Measure the initial temperature with a thermometer
5. Weigh the spirit burner containing the alkanol.
6. Heat the can for 10 minutes for all three alkanols
7. Record waters final temperature
8. Extinguish the burner and reweigh it to calculate moles
Results:
Heat released from combustion calculated by Q=mC∆T
ℎ𝑒𝑎𝑡 𝑜𝑓 𝑐𝑜𝑚𝑏𝑢𝑠𝑡𝑖𝑜𝑛 𝑐𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 𝑏𝑦 ∆HC=-Q/nfuel
Methanol has lowest heat of combustion, then ethanol then propan-1-ol
Justification of method:
• Aluminium can used as it’s a better thermal conductor than glass and allows for a greater transfer of heat
• The 3 alkanols chosen most likely to undergo complete combustion
Limitations and improvements Limitations Improvements
Molar heat of combustion only refers to complete combustion Too much heat lost to environment
Digital thermometer used Using heat lids and shields Considering specific heat of calorimeter
Specific heat of aluminium was not considered
Reactions of alcohols
• Combustion
o All alcohols undergo combustion when ignited in presence of oxygen and burn cleanly to produce carbon dioxide and water
o Complete combustion: Excess oxygen → produces carbon dioxide and water
▪ C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(g)
o Incomplete combustion: Insufficient oxygen → produces CO, C and water
▪ Dangerous because CO prevents oxygen reaching organs and hinders cell respiration and if carbon soot is inhaled, it coats
the lungs decreasing its ability to take in oxygen.
▪ C2H5OH(l) + 3/2O2(g) → C(s) + CO(g) + 3H2O(g)
• Dehydration
o Removal of OH plus hydrogen from adjacent hydrogen. Results in the formation of alkene and water
o Must be in presence of a strong acid (sulfuric/phosphoric acid)
o For more complex alcohols, more than 1 alkene is produced (Butan-2-ol)
▪ If OH is removed, then there are 2 possible hydrogens that can be removed as well.
▪ The products become but-1-ene and but-2-ene. Also, but-2-ene has two geometric
isomers, cis-but-2-ene and trans-but-2-ene.
▪ However, its randomly made.
o Temperature range
▪ Primary alcohols: 170 to 180 degrees
▪ Secondary alcohols: 100 to 140 degrees
▪ Tertiary alcohols: 25 to 80 degrees
o Steps:
▪ Acid donates H to OH, water is released from molecule and
them water takes another H from the molecule and the
remaining charged carbons form a double bond
• Substitution with HX
o Alcohols react with hydrogen halides by substituting the halide for the OH group and creating water.
o Reactivity order: Tertiary>secondary>primary>methyl
o Hydrogen halide reactivity order: HI>HBr>HCl>HF
o Steps:
▪ H-X ionises into H+ and X-, then the H+ attaches to the OH group and the
group is released to form water then the X replaces OH
Butan-2-ol + HBr → 2-bromobutane+water
C4H9OH(aq)+HBr(aq)→C4H9Br(aq)+H2o(l)
• Oxidation
o Can be oxidised into aldehyde, carboxylic acid or ketones
o Primary
▪ Oxidised to form aldehyde and further oxidation creates
carboxylic acid
▪ To produce aldehyde: excess alcohol used compared to
oxidising agent to prevent aldehyde from being oxidised as it is formed. The aldehyde also need to be removed from the
reaction vessel quickly to minimise with the oxidiser
▪ To produce acid: Excess oxidiser used such as alkaline potassium permanganate (KMnO4) or potassium dichromate
(K2Cr2O7)
o Secondary
▪ Oxidised into Ketone
▪ Cannot oxidise into acid as there are no free hydrogens on carbonyl
carbon to create hydroxyl group
▪ Produces water as well
o Tertiary
▪ Cannot be oxidised into anything
▪ Oxidation removes hydrogen from OH and a hydrogen from the carbon it is attached to.
▪ In this case, the carbon has no hydrogens
o When dichromate ions used in oxidation, its orange colour changes to green
o Under acidic conditions, permanganate ions go from purple to colourless
Fermentation
• Process in which glucose is broken down into ethanol and carbon dioxide is because of enzymes in yeast
• Conditions required for fermentation
o Yeast
o Water
o Suitable temperature for fermentation (15-30 degrees)
o Low pH to kill unwanted microbes or unwanted reactions
o Anaerobic conditions (prevents oxidation of alcohol into acid)
• Ethanol concentrations past 15% by volume, yeast cannot survive
• Once fermentation finished, ethanol is separated from mixture by fractional
distillation to convert ethanol into higher concentrations (95-100%)
• In anaerobic conditions, yeast is fermented into ethanol and carbon dioxide
Structures of haloalkanes
• Haloalkanes can be primary, secondary or tertiary
• Primary: one carbon bonded to carbon with halogen attached
• Secondary: 2 carbons bonded to carbon with halogen attached
• Tertiary: 3 carbons bonded to carbon with halogen attached
• Tertiary>secondary>primary
Substitution with haloalkanes
• Addition of water to haloalkane reacts to form a H-X and alcohol
• Nucleophile: electron rich species donates electron pair to electrophile to form a bond. Attracted to regions of positive charge
• Electrophile: positively charged or neutral species which is attracted to regions of negative charge
• Alkyl halides undergo a nucleophilic substitution reaction with water or OH- to form alcohol
• Nucleophilic water/OH- will react with carbon attached to the halogen group, forcing the halogen to leave molecule
o Carbon halogen bond easier to break than carbon hydrogen bond
• Exception: Carbon-fluorine bond is an exception
Organic fuels vs Biofuels
Organic fuels Biofuel's
Examples Coal, natural gas, petroleum Bioethanol
Sources Buried plant exposed to high heat and pressure over millions of years to form fossil fuels
Fermenting sugar canes or corn starch
Time Frame Hundreds of millions of years Hours or days
Advantages Currently abundant and accessible High energy density and efficiency Low cost
Produces fewer greenhouse gasses can be produced quickly using wastes from other materials and can be produced anywhere
Disadvantages Causes environmental degradation and greenhouse gases Non-renewable and uses massive amounts of resources to produce
Heavy machinery to harvest material higher cost due to lower production much more fuel needed to produce same amount of energy
Ethanol
Ethanol has great potential to be used as a renewable
alternative fuel, however, its widespread use is
currently limited due to its cost barriers as the cost of
producing ethanol is higher than petrol.
Organic biomass crushedand grinded into pulp
Hyrdolysed with dilute H2SO4 into
glucose
Mixture filtered and solid residue is
hydrolysed again and reurned to glucose
solution
Yeast added to glucose for fermentation in optimal conditions then ethanol mixture is extracted and
fractionally distilled for high concenrrated ethaonl
Ca(OH)2 to neutralise acid
Organic acids and bases
• Bonding in carbonyl group
o Oxygen is far more electronegative than carbon and so has a strong tendency to pull electrons in a carbon-oxygen bond towards
itself making it highly polar.
o Aldehyde has hydrogen atom attached to this group making it easy to oxidise. Since ketones don’t have this, they are resistant to
oxidation except when exposed to Powerful oxidising agents which break C-O bonds
• BP and MP of carbonyl group
o Has higher MP and BP than hydrocarbons of similar molecular weight
o This is due to the dipole-dipole forces formed between aldehydes and ketones.
o Lower MP and BP than alcohols due to hydrogen bonding
• Solubility of carbonyl group
o Highly polar, forms an attraction to highly polar water making them more soluble than hydrocarbons but less soluble than
alcohols
o Small aldehydes and ketones soluble in water
o Longer the chain, less solubility (C<4 are soluble as they form H-bonds with water)
• BP and MP
o BP and MP of amines
▪ Very polar due to N bond. Primary and secondary amines can form hydrogen bonds however its weaker than alcohols
▪ BP and MP lower than alcohols
o BP and MP of amides
▪ Primary and secondary also polar due to N-H and C=O bonds
▪ Tertiary has no N-H
▪ Primary and secondary can form hydrogen bonds between molecules and form dimers
▪ Very high MP and BP
o SECONDARY>PRIMARY>TERTIARY
• Odour of amines
o As chain increases, odour becomes stronger
• Solubility of amines and amides
o Primary and secondary amines and amides of C<6 are soluble in water because they easily form H-bonds with water molecules.
However, as the hydrocarbon tails get longer, they force themselves between molecules and break H-bonds, making amines and
amides longer lengths insoluble in water
o Tertiary amines and amides are soluble but less soluble than primary and secondary
• Carboxylic acid properties
o Can form a range of intermolecular forces
o Hydrocarbon chain forms dispersion forces, C=O forms dipole-dipole and -OH forms hydrogen bonding
• Acid BP AND MP
o Increases as chain increases.
o Higher than corresponding alkane and alcohol due to larger dipole-dipole forces and formations of dimers (a molecule or
molecular complex consisting of two identical molecules linked together)
• ACID solubility
o Small acids like methanolic acid and ethanoic acid are soluble in water, however for larger acids, the non-polar tail prevents the
acids from being soluble. Rather they line up at the surface and is called surfactants
Intermolecular forces
• Amines: strongest bonds are hydrogen bonding and dipole-dipole making it polar
• Amides: strongest bonds are hydrogen bonding and dipole-dipole giving it high MP and BP
• Carboxylic acids: strongest bonds are hydrogen bonding and dipole-dipole increasing MP and BP. Dispersion forces of an increasing
chain increase MP and BP.
• Amides/Amines: strongest force is dispersion and as chain increases, solubility decreases due to hydrocarbon tail being non-polar
Intramolecular forces
• Carboxylic acid/Amides/Amines: has non-polar covalent bonds (C-H produce this and are not good conductors of electricity as they
can’t ionise in water). Has polar covalent bonds between elements: C=O, O-H, N-H contributing to dipole-dipole and hydrogen bonds
Esters
• Living Things store their energy as esters. Many flavours and odours of fruits are esters.
An alcohol + carboxylic acid forms an equilibrium with ester and water.
Naming esters
• First part is the alkyl group, methanol becomes methyl, propanol becomes propyl etc
• Second part is the carboxylic acid. Replace ‘lic acid’ with oate
• Examples
o CH3OH+HOOCCH3⇄CH3OOCCH3+H2O
o methanol + ethanoic acid ⇄ Methyl ethanoate + water
o CH3CH2OH+HOOCH⇄CH3CH2OOCH+H2O
o Ethanol + methanoic acid ⇄ethyl methoate+water
Properties
• BP/MP
o Polar molecule, liquids at room temperature and BP much lower than carboxylic acids as main intermolecular forces are dipole-
dipole which is weaker than hydrogen bonding
• Solubility
o Most esters are not soluble in water due to lack of hydrogen bonding and presence of hydrophobic alkyl group. Soluble organic
solvents
• Flammability
o Esters are highly flammable and easily evaporated.
How to make ester
• Preparation
o Esterification: Reaction that forms an ester through the
reaction between a carboxylic acid and alcohol molecule
o Formed when carboxylic group and hydroxyl group react
releasing small water molecule and ester and is done using a reflux
• Conditions
o Slow process so concentrated sulfuric acid acts as a catalyst for process to occur in slower amounts of
time
o Mixture heated to increase rate of reaction. However, using a Bunsen burner results in loss of mixture.
The organic chemicals are volatile and will evaporate even when low heat is applied
o Reflux: Process of extended heating of mixture without it evaporating. As mixture is heated, volatile components evaporate and
move to a vertical condenser where the gases are cooled so thy return to the flask.
o Heating mantle: since organic chemicals are highly flammable, naked flame not used. Heating mantle designed to provide heat
without a flame
o To increase yield of ester, one reagent is added in excess as LCP predicts equilibrium will then shift to favour more ester
• Purification
o After refluxing, you get organic components (Ester (not soluble in water), Carboxylic acid, alcohol) and inorganic compounds
(water, sulfuric acid)
o Separating funnel is used.
▪ The entire mixture from the reaction flask is poured into a funnel and water is added.
▪ Organic layer is less dense and goes to the top.
▪ Inorganic layer removed.
o Sodium carbonate is added to remove any carboxylic acid as they will react to form carbon dioxide gas
o Distillation can be used to locate ester.
Prac: Synthesising octyl acetate
Aim: To synthesise the octyl acetate ester from octanol and acetic acid
Equipment:
• Flask
• Boiling chips
• Condenser tube and water hoses
• Bunsen burner and gas hose
• Separating funnel
• Beakers for waste
Method
1. Transfer about 12mL of octanol and about 10mL of acetic acid into a flask
2. Add several boiling chips and about 1Ml of concentrated sulfuric acid to the flask
3. Attach a condenser tube to the flask and run water through the outer case of the tube
4. Heat the flask with a Bunsen Burner such that mixture is evaporating and condensing but not escaping
5. Allow mixture to cool and then transfer it to a separating funnel
6. Add water to the separating funnel, swirl and allow it to stand
7. Open the tap of the separating funnel and allow the aqueous layer to run out, leaving the octyl acetate remaining
8. Open the tap of the separating funnel and allow aqueous layer to run out
Discussion
• Sulfuric acid used as a catalyst by acting as a dehydrating agent, forcing equilibrium to move to move to the right. Mixture is also boiled
to speed reaction
• Reflex should be used as it improves safety.
Organic acids and bases
• Organic acid: most common is carboxylic acid. These are weak acids that do not completely ionise in water.
• Organic acids unusually acidic due to -OH bond. However, they vary in degree of ionisation due to 2 factors.
o Strength of the bond being broken (usually O-H bond)
o Stability of ion formed
• Acid strength: Sulfonic acid>carboxylic acid> phenol
o Sulfuric acid ionises to form a conjugate base containing extremely stable SO3- while carboxylic acids ionise to give carboxylic
ion which is less stable and is a conjugate base
o Phenol least acidic as their conjugate (phenoxide ion) is less stable than carboxylic ion due to high electronegative C-O bond
• Examples: lactic acid, citric acid, acetic (ethanoic acid), formic (methanoic acid)
• Organic base: Usually based around nitrogen compounds. Amines most common type of organic bases. Exist in nature (DNA bases-
Adenine, thymine, cytosine and guanine). Basic due to presence of a proton acceptor, usually nitrogen. E.g ammonia
o Strength depends on how easily lone pair picks up H+
o The stability of the ions formed: More the charge is spread around the molecule, more stable it is, more basic
Acid properties Base properties
weak acids in solution and partially ionise in water react with active metals, bases and carbonates carboxylic acids react with metal to produce salt and hydrogen gas carboxylic acids react with base to produce salt and water carboxylic acids react with carbonates to produce salt, water and carbon dioxide
React with acids to form salt and water in a Bronsted Lowry reaction Reaction with an acid forms a compound called a protonated amine (conjugate acid of the amine). This compound has substantial differences in properties to the original amine, mostly due to the presence of the charge, affecting solubility, BP and chemical reactivity A protonated amine forms when am acid Is added to an amine
Saponification
• Hydrolysis of fatty esters. The saponification reaction typically refers to the reaction that is carried out by a strong base
• It is the reverse of esterification and is used to produce soaps from natural fats and oils.
• Soaps: ionic compounds contains a long hydrocarbon tail and a negatively charged head that will dissociate with water. The tail is non-
polar/organic tail/hydrophobic tail while head is polar head/hydrophilic head/inorganic head.
• Soaps are made through hydrolysis of fats in saponification reaction.
• Fats are triglyceride (molecules of 3 hydrocarbon chians containing 10-20 carbon atoms joined to a propane backbone by 3 ester bonds.
• Soap curdles are formed by heating fats.
• The curdles can be scraped off and dried to form solid soap. The remaining soap ions in solution are precipitated out by adding a solution
of NaCl.
How soap works
• Long hydrophobic tail and hydrophilic head acts as surfactants which decrease surface tension of water. When soap is dissolved in water.
Polar heads are stabilised and disrupt water’s H-bonding network, improving the ability of water to cling to dirt/oil particles.
• The hydrophilic head is attracted to water via H-bonding while hydrophobic tail interacts with the dirt/oil via dispersion forces.
• With agitation, soap molecules lift oil particles creating micelles
• Micelles are stabilised via the repulsion between negative polar heads. This stable mixture is an emulsion
• When a material is rinsed in water, the soapy emulsion of oil and water is washed off.
Emulsion
• Stable dispersion of small droplets of one liquid throughout another liquid (where 2 liquids don’t mix)
• Requires emulsifier to stabilise them
• Soap, water and oil form an emulsion
• Oil in water → small droplets of oil in water
o These dissolves and mix well with polar solvents and can be coloured with water soluble dyes to their high-water content.
• Water in oil → small droplets of water in oil
o Dissolves and mix well with organic solvents and can be coloured with oil soluble dyes die to their high oil content
Detergent
• Man-made surfactant with a long hydrophobic tail and hydrophilic head
• Synthesised to be used instead of sap as soap is ineffective against hard water (contains high levels of calcium/magnesium ions)
• Works like soaps but is synthesised from fossil fuels
• Soap readily precipitates with the ions to form scum
Ca2+/Mg2+(aq)+2CH3(CH2)16COO-
(aq)→Ca(CH3(CH2)16COO)2 (s)
• In highly acidic solutions, soap can also precipitate out to form another type of scum
H+(aq)+CH3(CH2)16COO-
(aq)→CH3(CH2)16COOH(s)
• Most detergents don’t form precipitates. However, anionic detergents may form soluble complexes with these ions which disrupts the
cleaning action, not as bad as soaps though.
Anionic Detergents
• Containing a long hydrocarbon tail and a negatively charged head
• Most common is alkyl benzenesulfonates
• Excellent for cleaning natural fibres and glass
• Not used for personal hygiene as they remove too much oil form skin and hair
Cationic Detergents
• Contain a long hydrocarbon tail and a positively charged head
• Positively charged head is usually and alkylated quaternary ammonium group
• Cationic head binds strongly to negatively charged surfaces, which helps reduce static friction and tangling of fibres. Therefore, they are
used in fabric softeners and hair conditioners
• Can be used in household disinfectants and sanitisers such as antiseptic soaps and mouthwashes
Non-ionic Detergents
• Contain long hydrocarbon tail and a polar segment marked by repeating ethoxy groups (CH3CH2O-) and OH head
• Produces much less foam than ionic detergents so they are used in dishwasher powders to prevent foam clogging up water jets.
• Used in paints, adhesives and cosmetics
Summary
Types of detergent Uses Characteristics
Anionic Laundry detergents, dishwashing, detergents, household cleaners
Creates a good lather, negative charge, harsh action, cheap
Cationic Fabric softeners, hair conditioners, disinfectants, sanitisers
Bond very strongly to negatively charged surfaces, kills bacteria, expensive
Non-Ionic Dishwasher detergents, glass cleaners Expensive
Soaps Detergents
Made from Fatty acids in animal and vegetable oil Hydrocarbon chain from petroleum
Composition Sodium or potassium salts of long chian fatty acids Usually hydrocarbons with a sulphate/sulfonate end
Structure polar head and non-polar tail anionic
Similar to soap head may be anionic, cationic, non-ionic
Manufacture Saponification heating fats or oils with NaOH precipitation with NaCl
Alkanol from petroleum is reacted with H2SO4 TO FORM SULFONINC ACID AND THIS IS REACTED WITH NaOH TO FORM SODIUM SULFONATE
Reaction with hard water
Do not lather well in hard water Soap anions forms precipitates with calcium/magnesium ions
Do not precipitate with mineral salts In hard water
Biodegradability Yes Yes, only if hydrocarbon is straight chained
Phosphates No May be mixed with phosphates that pollute environment
Other Cheaper to make Not soluble Deteriorates with age
More expensive Soluble In water Does no deteriorate Very stable
Reaction pathways
Polymers Ethylene is the same substance as
ethene. Polyethylene is the cheapest
plastic. The weight of polyethylene
produced each year is greater than the
total of all other plastics.
When petroleum undergoes fractional
distillation, some fractions are in
demand and of high economic value.
Other fractions consisting of larger
molecules than in petrol and of low
value can be passed over a heated
catalyst that cracks the larger molecules
into smaller molecules. A major by-
product of this cracking is ethylene.
• This is the chemical reaction in which many small identical repeating unit molecules
combine to form one long chain macromolecule
• The small identical molecules are called monomers and the long chain
macromolecule is called polymers.
• Because of its reactive double bond, ethylene is able to undergo addition
polymerisation → ethylene a monomer forms the polymer poly(ethylene)
• Polymers can be synthetic (plastics) or natural (silk, proteins, DNA)
• All plastics synthetic polymers, not all synthetic polymers are plastics
• Plastics are malleable, pliable and can be moulded into heat and pressure. Those that
can be melted are called thermoplastic while those that can’t are called themoseting.
Thermoplastic can be recyclable whereas thermosetting polymers can’t.
• Naming:
o Place poly Infront of monomer name
o Brackets are used when the monomer name is more than one word, or begins with a number
▪ Poly(monomer name) or poly(1-chloroethene)
Addition polymers
• An unsaturated monomer undergoes chain growth through the opening of its
double bonds to form a saturated polymer molecule
• Forms only one product: The polymer molecule with no extra molecule is
produced. Polyethylene is an addition polymer that forms by opening the double
bond within each ethylene monomer unit to attach and form a polymer
• 3 stages
o Initiation
▪ UV light is used to first break the bonds of weak halogen-
halogen bonds to make radicals.
▪ Can also use any peroxides
o Propagation
▪ Once a radical is made, it can react with stable molecules to form new radicals.
One halogen radical then pulls away the hydrogen from the C-H bond, leaving a
C- on the alkane. The C- pulls a halogen atom away from its molecule and
terminates as a C-X bond but leaves behind another X- to continue process
▪ The free radical uses one of the electrons in the pi bond to help form a new bong
between itself and the left-hand carbon atom. The other electron goes to the right-
hand side. The new bond between the radical and carbon is stronger than the
broken pi bond. You get more energy breaking the new bond. More energy
release= more stability.
o Termination
▪ Stops after another radical is added or 2 growing units add together
• Does not usually require a catalyst
Polymers of Ethene compounds
• Polyethylene
o Structure
▪ Repeating units of ethylene monomers
▪ Formula: n(CH2-CH2)
▪ Also called polyethene and is widely used plastic in the world
o LDPE (low density PE)
▪ High branching and less packed together= less dispersion forces.
Impermeable to eater, thermoplastic, high flexibility, low melting
point, high ductility, and low tensile strength
o HDPE (high density PE)
▪ Low branching and more closely packed, impermeable to water,
thermoplastic, strong and stiff, highly crystalline structure and higher
MP than LDPE. Ideal for rubbish bins, cutting board as its non-
reactive
o LLDPE (linear low-density PE)
▪ Lots of short chain branching, at equal density and thickness, LLDPE
has higher impact strength, tensile strength, puncture resistance and
elongation than LDPE, used in high performance garbage bags, ice
bags.
• Polyvinyl Chloride
o Structure
▪ Repeating units of vinyl chloride monomers
▪ Formula: n(CH2-CHCl)
▪ Also called polychloroethene
o Properties
▪ Impermeable to water, thermoplastic, very hard, rigid and brittle. C-
Cl is vulnerable to UV decomposition
▪ Additives are added to alter pure PVC properties: often softened to increase distance between polymer chain and UV to prevent quick
decomposition. Used in drainage pipes (chemically modified), credit card (pure), garden hoses (softened)
• Copolymers
o To design a polymer with specific properties, more than one monomer can be used.
o Combining a butadiene monomer with a styrene monomer improves the strength of the polymer
• Polystyrene
o Structure
▪ Repeating units of styrene molecule. Its an ethylene molecule with one of its hydrogen atoms replaced by benzene ring.
▪ Formula: n(CH2-CHC6H5)
o Properties
▪ Crystalline Polystyrene
• Impermeable to water, thermoplastic, hard and rigid. Used in screwdriver handles, kitchen door handles.
▪ Expanded Polystyrene
• formed by blowing gas into liquid polystyrene
• Lightweight and excellent thermal conductor, excellent shock absorber.
• Used in Styrofoam cups, surfboards, eskies
• Polytetrafluorethylene
o Structure
▪ Repeating units of terfluorene monomers
▪ Formula: N(C2F4)
o Properties
▪ HYDROPHOBIC, NON-REACTIVE DUE TO STRENGTH OF c-f BONDS, THERMOPLASTIC, HIGH MP, STRONG BUT
FLEXIBLE
▪ Used in cookware, pipelines.
▪ Deteriorates at 260 degrees Celsius
Condensation of polymerisation
• Formed by chemically joining 2 saturated bi-functional monomers, releasing a small molecule (usually water)
• There is no-double bond that opens (like in addition); the functional group of 2 monomers react together forming a new bond and water.
• Natural (DNA, cellulose, starch) synthetic (Nylon, polyester)
Nylon
• Structure
o Formed when monomers with carboxylic acid and amine double functional groups react via condensation polymerisation to release water
o Repeating units are connected via amine links and can be mixed with a variety of additives to achieve different properties
• Properties
o Semi-crystalline due to H-bonding between polymers
o High tensile strength, high melting point, heat resistant, UV resistant, electrically insulating
o Used to make carpets, airbags, parachutes
• Naming
o Name reflects the number of carbons in the monomer
o If 2 monomers, prefix is di
o Nylon-6 is made of 1 monomer containing 6 carbons with an amino group at one end and a carboxyl group at the other.
o Nylon-6,6 is made from 2 monomers, making it a copolymer. It has a diamine monomer with 6 carbons and a dicarboxylic acid containing 6
carbons
Polyesters
• Structure
o Formed when monomers with carboxylic acid and alcohol double functional groups react via condensation polymerisation to release a water
molecule.
o Repeating units are connected to ester link
o Most common is PET n(C10H8O4)
o Made from terephthalic acid and ethylene glycol monomer
• Properties
o Polyester fibres are strong and durable, resistant to most chemicals, shrink and stretch resistant, hydrophobic, retains its shape.
o Depending on shape its either thermoplastic or themosetting
o PET is thermoplastic, colourless, lightweight. Used in plastic bottles, flexible food packaging, blister packs and trays for frozen dinner
o Can be recycled and repeatedly melted and reshaped.
Testing for unsaturation
• Bromine test
o Bromine is added to a sample to test presence of double or triple bond and the sample is shaken
o If its an alkene/alkyne, a positive result is the disappearance of the colour → it decolourises
o If its an alkane nothing happens
• Permanganate test
o Dilute alkaline potassium permanganate (KMnO4) is added to sample
o Positive result when colour goes from purple to green and forms a brown precipitate
Test for Hydroxyl group
• Sodium test
o A small piece is added to sample and a positive test is the effervescence of hydrogen gas
2R-OH+2Na → 2R-O-Na+ + H2
• Oxidation test
o Small volume of acidified dichromate ion (Cr2O72-) is added
o
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