FAMILIES IN ORGANIC
CHEMISTRY
• Hydrocarbon contains hydrogen and
carbon only
• Alkanes have a C – C single bond
• Alkenes have a C = C double bond
• Alkynes hace a C = C triple bond
Homologous series
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Series of compounds
Uniform chemical type,
Has a general formula
Similar method of preparation,
Differ from each other by CH2
ALKANES
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contain only hydrogen and carbon
carbons all have single bonds
saturated
named using - ane at end
methane, ethane, propane butane ……..
Physical properties – sweet smell,
colourless
• Found naturally occurring
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1st four alkanes are gases.
Next 12 are liquids.
Higher members are waxy solids.
Draw first five alkanes.
Alkyl groups
• Groups are named from the corresponding
alkane,
• Compounds are named so that these
groups are attached to the lowest number
carbon,
• If alkyl groups are attached, they come
alphabetically in the name of the
compound,
Alkenes
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Contain a carbon = carbon double bond,
Named from the corresponding alkane,
Name ends in - ene,
The number of the carbon where the
double bond starts is put into the name.
• unsaturated
Alkynes
• Named from the
corresponding alkane.
• Name ends in - yne.
• Contains a C = C triple bond.
• Unsaturated
Preparation of ethyne
• Chemicals – calcium carbide(CaC2)- (dark
grey solid) and water
• Word eqn: calcium carbide +water →
Calcium hydroxide + ethyne
• Chemical equation:
• Bubbled through acidified copper II sulfate
• To remove hydrogen sulfide, phosphine,
and ammonia.
• Sweet smell, insoluble in water,
• Burns with a smoky luminous flame, in
excess oxygen to produce carbon dioxide
and water(chemical equation)
• Note – tests for unsaturation
• Bromine / water. Reddish brown turns
colourless
• Acidified potassium permanganate, purple
turns colourless