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Hydrocarbons. Organic Chemistry. Chemistry of carbon compounds First carbon compounds studied came from living organisms ∴ Organic Approx 90% of all compounds are organic Other compounds are referred to as inorganic. Properties of Organic Compounds. - PowerPoint PPT Presentation
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Organic Chemistry Chemistry of carbon compounds First carbon compounds studied
came from living organisms ∴Organic Approx 90% of all compounds are
organic Other compounds are referred to as
inorganic
Properties of Organic Compounds All contain carbon. Usually contain hydrogen
and often oxygen and nitrogen. Sometimes sulfur, phosphorus and chlorine
All covalent compounds: Generally insoluble in water Have low melting and boiling points Don’t conduct heat or electricity
Almost all burn and many are used as fuels
Properties of Organic compounds Organic reactions proceed slowly
because they require the breaking and forming of strong covalent bonds. Heat and catalysts are often used to speed up organic reactions
Carbon Atomic number: 6 Electronic configuration 2,4 Tetravalent: Forms four covalent
bonds Bonds can be Single, Double or Triple Can form covalent bonds with other
carbon atoms to form chains of any length
Hydrocarbons
Hydrocarbons often contain long chainsof C-C bonds
Homologous series Conform to a general formula Have the same functional group which
is the reactive part of the molecule Each members formula differs from
the one before it by CH2 Similar chemical properties due to the
functional group
Example
CH4
C2H6 C3H8
Methane Ethane Propane
Homologous series Physical properties gradually
change as chain length changes Melting and boiling points increase
with increasing chain length Solubility in water decreases as the
chain length increases
Naming Organic compounds Referred to as Nomenclature Unsystematic (common) names are
often used for many chemicals Eg Acetic acid for ethanoic acid Often a new substance will be given
a common name because its structure is not completely understood
Naming Organic compounds
No. of carbon atoms
1 2 3 4 5 6 7 8
Prefix Meth Eth Prop But Pent Hex Hept Oct
AlkanesNo. Carbons in
ChainMolecular Formula Name
1 CH4 Methane2345678
No of Carbons Name No of isomers1 Methane 12 Ethane 13 Propane 14 Butane 25 Pentane 36 Hexane 57 Heptane 98 Octane 189 Nonane 35
10 Decane 75
Systematic Nomenclature1) Find the longest continuous chain
of carbon atoms2) Identify side chains (not part of the
main chain)3) Number the main chain so that side
chains are numbered as low as possible
4) If there are two or more identical groups use the following prefixes
Systematic Nomenclature
No. of branches
2 3 4
Prefix Di Tri Tetra
Side groups
Name Methyl Ethyl Propyl Butyl
Alkyl group
CH3- C2H5- C3H7- C4H9-
C
H
H
H C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
C HH
H
C
H
H
H
C
H
H
H C
H
C HH
H
C
H
H
H
Butane2 Methyl Propane
Structural Isomers
Longest C chain = 3 Propane Methyl Side Chain at 2 position
1 2 3
C
H
H
H C
H
H
C
H
CH H
H
C
H
H
C
H
C HH
H
C
H
CH H
CH H
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
H
C
H
CH H
H
C
H
H
C
H
C HH
H
C
H
CH H
CH H
H
C
H
H
C
H
H
C
H
H
H
6 Ethyl 3,5 Dimethyl Nonane
C13H28
1 2 3 4 5 6 7 8 9
Longest C Chain = 9 Nonane2 Methyl Side Chains at 3 and 5 positions 3,5 Dimethyl
Ethyl Side Chain at 6 position 6 Ethyl
C
H
H
H C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
C HH
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
C HH
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
H
C
H
C HH
H
C
H
H
C
H
H
H
C
H
H
H C
H
H
C
H
C HH
H
C
H
H
C
H
H
H
C
H
H
H C
CH H
H
C HH
H
C
H
H
C
H
H
H
C
H
H
H C
CH H
H
C HH
H
C
H
H
C
H
H
H
C
H
H
H C
H
C HH
H
C
H
CH H
H
C
H
H
H
C
H
H
H C
H
C HH
H
C
H
CH H
H
C
H
H
H
C
H
H
H C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
C HH
H
C
H
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
C HH
H
C
H
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
H
C
H
C HH
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
H
C
H
C HH
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
CH H
H
C HH
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
CH H
H
C HH
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H C
H
C HH
H
C
H
CH H
H
C
H
H
C
H
H
H
C
H
H
H C
H
C HH
H
C
H
CH H
H
C
H
H
C
H
H
H
C
H
H
H C
H
C HH
H
C
H
H
C
H
CH H
H
C
H
H
H
C
H
H
H C
H
C HH
H
C
H
H
C
H
CH H
H
C
H
H
H
C
H
H
H C
H
H
C
CH H
H
C HH
H
C
H
H
C
H
H
H
C
H
H
H C
H
H
C
CH H
H
C HH
H
C
H
H
C
H
H
H
C
H
H
H C
H
H
C
H
C HH
C HH
H
C
H
H
C
H
H
H
C
H
H
H C
H
H
C
H
C HH
C HH
H
C
H
H
C
H
H
H
C
H
H
H C
CH H
H
C HH
H
C
CH H
H
H
C
H
H
H
C
H
H
H C
CH H
H
C HH
H
C
CH H
H
H
C
H
H
H
Physical Properties of Alkanes Non polar compounds Insoluble in water Less dense than water and so will
float on top of the water Dissolve in organic solvents (eg
dry cleaning fluid) and in each other (eg Petrol is a mixture of alkanes)
Low melting and boiling points
Chemical Properties of Alkanes Very unreactive Don’t react with concentrated
sulfuric acid or concentrated bases Don’t react with strong oxidants
(dichromate or permanganate ions) Will react with bromine but only if
heated or in strong sunlight
Substitution Reactions Where an atom or group of atoms is
displaced by an atom or group of atoms
CH4 + Br2 → CH3Br + HBr Non specific reaction. Can not control
which hydrogen is substituted or how many are substituted
CH3Br + Br2 → CH2Br2 + HBr
Substitution reactions Very slow with heat or sunlight Product is a mixture of
bromoalkanes Products would need to be
separated by fractional distillation giving only a very small yield of each
Combustion of Alkanes Very useful group as fuels Fuels burn completely when there
is sufficient oxygen, forming CO2 and H2O
If oxygen is limited then incomplete combustion occurs and carbon (soot) and carbon monoxide (CO) are formed as well as CO2 & H2O
Combustion of Alkanes Incomplete combustion is less
efficient and so produces less energy per mole that complete combustion
Balancing Combustion Equations Write correct formula
Alkane + O2 → CO2 + H2O Balance carbon Balance hydrogen Balance oxygen (Fractional
coefficients are acceptable in combustion equations)
