carbon compound [part 4]
SPM Form 5 – Terminology and Concepts: Carbon Compounds
1. Comparing (Similarities and Differences) Properties of Alkanes and Alkenes
Physical Properties | Alkanes | Alkenes |
Physical state | Physical state changes from gas to liquid when going down the series. | Same with alkanes. |
Electrical conductivity. | Do not conduct electricity at any state. | Same with alkanes. |
Boiling points and melting points | Low boiling points and melting points (number of carbon atoms per molecule increases). | Same with alkanes. |
Density | Low densities (number of carbon atom per molecule increases). | Same with alkanes. |
Solubility in water | Insoluble in water (soluble in organic solvent) | Same with alkanes. |
Chemical Properties | Alkanes (Substitution reaction) | Alkenes (Addition reaction) |
Reactivity | Unreactive | Reactive |
Combustion | Burn in air and produce yellow sooty flame. | Burn in air and produce yellow and sootier flame compare to alkanes. |
Reaction with bromine solution | No reaction. | Decolourise brown bromine solution. |
Reaction with acidified potassium manganate(VII) solution | No reaction. | Decolourise purple acidified potassium manganate(VII) solution. |
2. Isomerism
Isomerism – phenomenon that two or more molecules are found to have the same molecular formula but different structural formulae.
Isomerism in alkanes
Molecular formula | Number of isomers | Structure name |
CH4 | - (no isomer) | Methane |
C2H6 | - (no isomer) | Ethane |
C3H8 | - (no isomer) | Propane |
C4H10 | 2 | Butane2-methylpropane |
C5H12 | 3 | Pentane2-methylbutane2,2-dimethylpropane |
Isomerism in alkenes
Molecular formula | Number of isomers | Structure name |
C2H4 | - (no isomer) | Ethene |
C3H6 | - (no isomer) | Propene |
C4H8 | 3 | But-1-eneBut-2-ene2-methylpropene |
C5H10 | 5 | Pent-1-enePent-2-ene2-methylbut-1-ene 3-methylbut-1-ene 2-methylbut-2-ene |
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