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homologous series and alkanes - Coggle Diagram
homologous series and alkanes
homologous series
it is organic compounds with
same general formula
same functional group
same chemical properties
gradual change in physical properties
each successive member increases by CH2 group
functional group
an atom or group of atoms within the structure of a organic molecule that gives the molecule its characteristic properties
alkanes
uses of alkanes
natural gas (methane)
gas cartridge for stoves (butane)
jet fuel (kerosene)
naming alkanes.
molecular formula
meth (1 carbon)
eth (2 carbon)
prop (3 carbon)
but (4 carbon)
pent (5 carbon)
hex (6 carbon)
the properties of alkanes change going down the series:
increases by CH2
size of molecule increase
densities increases
stronger intermolecular force
boiling point increases
flammability decreases
the more carbon there is in the molecule the smokier the flame
isomers
isomers are compounds with
same molecular formula
different structural formulae
different melting and boiling points
important in petrol fuel for motor cars
branched chain isomers are preferred over straight chain alkane molecules; engine run better
branched chain isomers are more expensive; petrol cost more
they are also formed by other organic compounds such as alkenes and alcohols
chemical properties
combustion
alkanes burn in excess oxygen to produce carbon dioxide and water vapour (highly exothermic)
complete combustion
propane + oxygen = carbon dioxide + water
incomplete combustion
propane + oxygen = carbon monoxide + water
substitution reaction
alkanes react with halogens (CL, Br) in presence of UV light
a Hydrogen atom in the alkane will be replaced by a halogen atom
CH4 + Cl2 = CH3Cl +HCl