Post on 15-Jul-2015
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CHAPTER 2
Carbon Compounds
2.1 Carbon Compounds
• Carbon compounds:
Compounds that contain carbon as one of their constituent elements
Carbon compounds
Organic compounds Inorganic compounds
• Carbon-containing compounds that can be obtained from living things
• Except oxides of carbon, carbonates, cyanides and metallic carbides
• Examples:
Non-carbon-containing compounds that can be obtained from non-living things
Include oxides of carbon, carbonates, cyanides and metallic carbides
Examples:
Hydrocarbon
• Hydrocarbon: Organic compounds which contains carbon and
hydrogen only • Examples: Petroleum, coal, natural gas, rubber tree • Non-hydrocarbon: Organic compounds containing carbon, hydrogen
together with a few other elements • Examples: Sugar
Organic compounds
Hydrocarbons
C and H
Saturated hydrocarbon
Unsaturated hydrocarbon
Non-hydrocarbons
C, H and O, N, P, S, F, Cl, Br and I
Contain only single bonds
Contain at least one multiple bonds
C C C C C C
Combustion products of organic compounds
• When an organic compound burnt in excess oxygen, the main product are carbon dioxide, CO2 and water, H2O
C6H12O6 + 6O2 → 6CO2 + 6H2O
glucose
Alkanes, alkenes, alcohols, carboxylic acids and esters
1. Molecular formula
• Meaning
The formula that shows the actual numbers and types of atoms present in a molecule.
Molecular formula Explanation
Propane, C3H8 Contains 3 carbon atoms and 8 hydrogen atoms
Pentane, C5H12 Contains 5 carbon atoms and 12 hydrogen atoms
2. Structural formula
• Meaning
The formula that shows how the atoms in a molecule are bonded together and by what types of bonds
Molecular formula Structural formula
Propane, C3H8
C C C
H H H
H
H H H
H
3. Naming of carbon compound (IUPAC)
• Guideline to naming the carbon compound:
Have 2 components
Root Ending
Show the number of carbon atoms in
the molecules
Show the family of the compound
a) stem/root
Number of carbon atom
1 2 3 4 5 6 7 8 9 10
Stem Meth Eth Prop But Pent Hex Hept Oct Non Dec
b) suffix/ending
• Ending; different followed by the homologous series
Homologous series Ending
Alkane ……ane
Alkene ……ene
Alcohol ……ol
Carboxylic acid ……oic acid
Ester ……yl ……..oate
B. ALKANES
Physical properties of alkanes
• Alkanes are covalent compounds which consist of simple molecules
• Molecules are held together by weak intermolecular force
Physical properties of
alkanes
Electrical conductivity
• Cannot conduct electricity
• Because there are no free moving ions
Density
• Less dense than water
Solubility
• Dissolve in organic solvents
• Insoluble in water
Melting and boiling point
• Low melting & boiling point
Physical state at room temperature
• C1 to C4 are gases
• C5 to C17 are liquid
• C18 > are solid
Explain the effect of the increase in number of carbon atoms in alkane molecules
Size of molecule increase
Melting point & boiling point increase
• The higher the number of carbon atoms, the higher the melting & boiling point
• As the number of carbon atoms increases, the molecule become bigger
• The force of attraction between the molecules become stronger
• More heat energy is needed to overcome the strong force of attraction between molecules
Why melting and boiling point propane is higher than ethane? • Propane have more number of carbon atoms per
molecule than ethane • Size of propane is bigger than ethane • The force of attraction between propane
molecule increase • More heat energy is needed to overcome the
force of attraction between propane molecule • So, melting and boiling point of propane is higher
than ethane
Chemical properties of alkanes
Combustion
a) Complete combustion: produce CO2 + H2O
C2H6 + O2 → CO2 + H2O
b) Incomplete combustion: produce CO/C gas + H2O
2CH4 + 3O2 → 2CO + 4H2O
CH4 + O2 → C + 2H2O
Halogenation
• Reactions of alkanes with halogens
• Take place readily in sunlight/ultraviolet
• Example of substitution reaction
Reaction that occurs when one atom or a group of atoms in a
molecule is replaced by another atom or group of atoms
• CH4 + Cl2 → CH3Cl + HCl
• CH3Cl + Cl2 →
• CH2Cl2 + Cl2 →
• CHCl3 + Cl2 →
C. ALKENES
Physical properties of alkenes are similar to alkanes
• Molecules are held together by weak intermolecular force
Physical properties of
alkenes
Electrical conductivity
• Cannot conduct electricity
• Because there are no free moving ions
Density
• Less dense than water
Solubility
• Dissolve in organic solvents
• Insoluble in water
Melting and boiling point
• Low melting & boiling point
Explain the effect of the increase in number of carbon atoms in alkene molecules
Size of molecule increase
Melting point & boiling point increase
• The higher the number of carbon atoms, the higher the melting & boiling point
Why melting and boiling point butene is higher than ethene? • Butene have more number of carbon atoms per
molecule than ethene • Size of butene is bigger than ethene • The force of attraction between butene molecule
increase • More heat energy is needed to overcome the
force of attraction between butene molecule • So, melting and boiling point of butene is higher
than ethene
Chemical properties of alkenes
Combustion
(a) Complete combustion: produce CO2 + H2O
C2H4 + O2 → CO2 + 2H2O
(a) Incomplete combustion:
produce CO/C gas + H2O
C2H4 + 2O2 → 2CO + 2H2O
C2H4 + O2 → 2C + 2H2O
Hydrogenation
• Alkenes react with hydrogen at 180 °C at presence of nickel/platinum (catalyst) to produce alkanes
C2H4 + H2 C2H6
Ni, 180 °C
Halogenation
• No catalyst or ultraviolet is needed
• Alkenes react with halogen at room temperature in the presence of tetrachloromethane, CCl4
C2H4 + Cl2 → C2H4Cl2
C4H8 + Br2 → C4H8Br2
Used to test for the presence of a carbon-carbon double bond
Hydration
• Alkenes reacts with steam, H2O at 300 °C and 60 atm in the presence of concentrated H3PO4 (as catalyst) to produce alcohol
C2H4 + H2O C2H5OH
H3PO4
300 °C, 60 atm
Addition of hydrogen halides – HX
• Hydrogen halides: Hydrogen chloride, HCl or hydrogen bromide, HBr
• Alkenes reacts with hydrogen halide, HX at room temperature to produce haloalkane
C2H4 + HCl → C2H5Cl
Addition of hydroxyl group
• Alkenes react with acidified potassium manganate(VII), KMnO4 to produce diol compound
C2H4 + H2O + [O] → C2H4(OH)2
or
C2H4 C2H4(OH)2
KMnO4
Used to test for the presence of a carbon-carbon double bond
Polymerization reaction
• Small alkene molecules undergo an addition reaction with one another at high pressure of 1000 atm and temperature 200 °C
C C
H H
H H n C C
H H
H H n
Compare & contrast alkanes with alkenes
• What do alkanes and alkenes have in common?
• How do they differ from each other?
Comparing chemical properties
Reactivity
Procedure:
1. Pour 2 cm3 of propane and propene into each crucible.
2. The liquids are lighted.
3. When burning occurs, filter paper is placed on top of the flame.
4. All the observation is recorded.
Observation:
Propane:
Burn in air, producing yellow sooty flame
Propene:
Burn in air, producing yellow and a very sooty flame
Conclusion:
Propene is more reactive than propane
Describe two chemical test to differentiate between hexane and hexene
• Reaction with bromine water Procedure: 1. Pour about [2-5 ] of hexane into a test tube. 2. Add 4-5 drops of bromine water and shake it. 3. Observe any changes and repeat with hexene. Observation: Hexane: Brown colour of bromine remains unchanged Hexene: Brown colour of bromine decolourise/turn
colourless
• Reaction with acidified potassium manganate(VII) solution Procedure: 1. Pour about [2-5 ] of hexane into a test tube. 2. Add 4-5 drops of acidified potassium manganate(VII)
solution and shake it. 3. Observe any changes and repeat with hexene. Observation: Hexane: Purple colour of KMnO4 remains unchanged Hexene: Purple colour of KMnO4 decolourise/turn colourless
Determine which one is more soot between hexane and hexene when burn in oxygen. Give your reason.
Hexane, C6H14
= 6(12) x 100
[6(12)+14(1)]
= 83.72%
Hexene, C6H12
= 6(12) x 100
[6(12)+12(1)]
= 85.71%
Hexene has high percentage of carbon by mass than hexane.
So, hexene burn with more sooty flame
Physical properties of
ester
State
• Simple ester is colourless liquid at room condition
Solubility
• Slightly soluble in water but readily dissolve in organic solvent
Density
• Low density
Boiling point
• Low boiling point
Odour
• Sweet pleasant smell (fruity smell)
E. ALCOHOL
Industrial production of ethanol
• Two main process:
(a)From sugar and starch by fermentation
(b)From petroleum fraction by hydration
1. Fermentation
C6H12O6 → 2C2H5OH + 2CO2
• From sugar & starches
• Yeast added
• Left in warm place (absence of oxygen)- anaerobic
Temperature = 18 – 20 °C
Catalyst = yeast (zymase)
Other condition = absence of oxygen
2. Hydration
C₂H₄ + H2O → C2H5OH
• From petroleum fractions
Temperature = 300 °C
Pressure = 60 atm
Catalyst = phosporic acid, H3PO4
Chemical properties of alcohols
Combustion
(a) Complete combustion: produce CO2 + H2O
C2H5OH + 3O2 → 2CO2 + 3H2O
Oxidation reaction
• React with the oxidation agent:
a) acidified potassium manganate(VII), KMnO4
(purple → colourless)
b) acidified potassium dichromate(VI), K2Cr2O7
(orange → green)
C2H5OH+ 2[O] → CH3COOH + H2O
Ethanol Ethanoic acid
Dehydration • Removal of water molecule from alcohol
molecule C2H5OH → C2H4 + H2O
• Method: (a) Heated under reflux at 180 °C with excess
concentrated H2SO4 or (b) Pass over a heated catalyst (porcelain chips,
porous pot, Al2O3
Ethanol Ethene
Uses of alcohols
As a solvent in
• Perfumes, cosmetics, toiletries
As a thinner in
• Lacquer, varnish, shellac, ink
As a cleaner for
Compact disc, video cassette recorder head
As a fuel
• Clean fuel, biofuel, gasohol
As a raw material in manufacture of
• Vinegar, fibre, explosive, plastic
As a raw material to make pharmaceutical products
• Tincture, antiseptic, cough syrup, rubbing alcohol
F. CARBOXYLIC ACIDS
Functional group
• Carboxyl group ( -COOH )
General formula
• CnH2n+1COOH
Physical properties of
carboxylic acids
State
• Larger molecules (C10 above) are wax-like solids
Solubility
• Simple molecules are very soluble in water
• Due to water molecule being strongly attracted to the –COOH group
• Solubility ↓ when number of carbon per molecule ↑
Colour
• Colourless liquid
Boiling point
• High boiling point
Odour
• Sharp/unpleasant smell
Synthesised/making of ethanoic acids
Oxidation of alcohol
C2H5OH+ 2[O] → CH3COOH + H2O
• Reflux ethanol with acidified potassium dichromate(VI) solution or acidified potassium manganate(VII) solution
Ethanol Ethanoic acid
Chemical properties
Acid properties
• CH3COOH is a weak monoprotic acid
• Only one hydrogen atom can ionize in water to produce H+ ion
CH3COOH ↔ CH3COO- + H+
• Partially dissociate in water
• Turn moist blue litmus → red
• React slowly with metals, bases and carbonates
Ethanoic acid Ethanoate ion
Reaction with metals
Carboxylic acid + metal → salt + H2
2CH3COOH + Zn → Zn(CH3COO)2 + H2
Ethanoic acid Zinc ethanoate
Reaction with bases
Carboxylic acid + bases → salt + H2O
CH3COOH + NaOH → CH3COONa + H2O
2CH3COOH + CuO → Cu(CH3COO) 2 + H2O
Ethanoic acid Sodium ethanoate
Ethanoic acid Copper ethanoate
Reaction with carbonates
Carboxylic acid + carbonates → salt + CO2 + H2O
2CH3COOH + CaCO3 → Ca(CH3COO)2 + CO2 + H2O
Ethanoic acid Calcium ethanoate
Reaction with alcohols
Carboxylic acid + alcohol → ester + H2O
Catalyst: Concentrated H2SO4
CH3COOH + C4H9OH → CH3COOC4H9 + H2O Ethanoic
acid Buthyl ethanoate Butan-1-ol
Uses of carboxylic acids
Ethanoic acid • As a flavouring • As a preservative • Used with other chemicals to make drugs, dyes, paints,
insecticides and plastics Methanoic acid • Used to coagulate latex Fatty acids (long-chain carboxylic acids) • Used in making soaps Benzoic acid • Preservative in food
G. ESTER
Functional group
• Carboxylate group ( -COO- )
General formula
• CnH2n+1COOCmH2m+1
Naming ester
Physical properties of
alcohol
State
• C1 to C11 are liquid at room temperature
Solubility
• Simple alcohols are very soluble in water
• Because has –OH group
Colour
• Colourless liquid at room temperature
Boiling point
• Low boiling point compare to water
Odour
• Very sharp smell
Highly volatile
Formation of ester
Esterification reaction
• Catalyst: Concentrated H2SO4
Natural sources
Fruit
Pineapple – C3H7COOC2H5
Ethyl butanoate
Flower
Jasmine – CH3COOCH2C6H5
Benzyl ethanoate
Use of ester
• Preparation of cosmetics & perfumes
• Used as food additives (enhance the flavour & smell of processed food)
• Production of soap & detergent