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