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Structure of Aliphatic Hydrocarbons

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Structure of Aliphatic Hydrocarbons Powered By Docstoc
					 Structure of
  aliphatic
hydrocarbons
Aliphatic hydrocarbons

   Aliphatic hydrocarbons are hydrocarbons
    that consist of straight or branched chains of
    carbon atoms, or rings of carbon atoms other
    than those containing a special ring called a
    benzene ring
Pentane – a straight chain
aliphatic hydrocarbon
A branched chain hydrocarbon
Cyclohexane – a cyclic aliphatic
hydrocarbon
Homologous series

   A homologous series is a family of organic
    compounds with the same general formula,
    similar chemical properties, and successive
    members differing by CH2
   Alkanes, alkenes and alkynes are three
    different homologous series of aliphatic
    hydrocarbons
Alkanes

   Alkanes are a homologous series of
    hydrocarbons with the general formula
    CnH2n+2

   They are named systematically, with a prefix
    indicating the number of carbon atoms per
    molecule, and the ending “ane”
Alkanes

   Methane CH4       Pentane C5H12

   Ethane C2H6       Hexane C6H14

   Propane C3H8      Heptane C7H16

   Butane C4H10      Octane C8H18
Alkanes

   Alkane molecules
    are tetrahedral, e.g.
    propane
Structural formulas

   The structural formula of an alkane indicates
    the way atoms in a molecule of the alkane
    are bonded together
   The following slides show the structural
    formulas of some of the alkanes
Methane
Ethane
Propane
Butane
Pentane
Structural isomers

   Structural isomers are compounds that have the
    same molecular formula but different structural
    formulas
   Butane (C4H10)is the simplest alkane which has
    structural isomers, called butane and 2-
    methylpropane respectively
   The name 2-methylpropane indicates that there is a
    methyl (CH3) group attached instead of one of the
    hydrogen atoms to the second carbon in propane
Isomers of butane
An isomer of octane (C8H18)

                    2,2,4-trimethylpentane
                     is so called because
                     there are two methyl
                     groups attached (in
                     place of hydrogen
                     atoms) to the second
                     carbon atom and one
                     (in place of another
                     hydrogen atom) to the
                     fourth carbon atom in a
                     pentane molecule
Physical properties of alkanes

   Physical state: The first four alkanes are
    gases, while pentane and higher alkanes are
    liquids
   Insoluble in water
   Soluble in non-polar solvents such as
    cyclohexane
Alkenes

   Alkenes are a homologous series of
    hydrocarbons with the general formula CnH2n

   They are named systematically, with a prefix
    indicating the number of carbon atoms per
    molecule, and the ending “ene”
Alkenes

   Ethene C2H4

   Propene C3H6

   But-1-ene C4H8

   But-2-ene C4H8
Ethene
Propene
But-1-ene
But-2-ene
Physical properties of alkenes

   Physical state: Gases

   Insoluble in water

   Soluble in non-polar solvents such as
    cyclohexane
Alkynes

   Alkynes are a
    homologous series
    of hydrocarbons
    with the general
    formula CnH2n-2
   Ethyne (C2H2) is the
    first member of the
    series
Physical properties of ethyne

   Physical state: Gas
   Insoluble in water
   Soluble in non-polar solvents such as
    cyclohexane

				
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