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Organic Chemistry

Type of Compound
Aldehyde

Formula

Alcohol
Carboxylic acid

Ketone
Alkane
Alkene




C–C
C=C
Alkanes – CnH2n+2
Alkenes – CnH2n
Alcohol – CnH2n+1OH

Isomerism
Structural isomerism: where molecules have the same molecular formula
however a different structural arrangement
...


For E/Z isomerism a carbon double bond must be present and each carbon
must be attached to two different groups
...

The E/Z system gives priority to groups with a higher atomic number
...


In the CH3 group:
The atoms attached to the carbon are H H H
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In the second list, the C is written first because it has the highest atomic
number
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The first atom in each list is an H in
the CH3 group and a C in the CH3CH2 group
...
So that gives the CH3CH2
group a higher priority than the CH3 group
...
The extra thing that this
illustrates is that if you have a double bond, you count the attached atom
twice
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In the CH2OH group:
The atoms attached directly to the carbon are O H H
...
Remember that the
oxygen is counted twice because of the carbon-oxygen double bond
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How organic reagents react?
Homolytic Fission: Each bonded atom takes an electron from the shared pair
forming a radical
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Heterolytic Fission: One of the bonded atoms takes both of the shared pair of
electrons
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Nucleophile: An atom that is attracted to an atom where it donates a pair
electrons to form a new covalent bond
...
This is
due to the pi electrons in the double bond
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Addition of HBr and ethane
I
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III
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The electron dense area of the pi
bond is then slightly attracted towards the positive hydrogen atom
causing the double bond to break
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The H-Br bond then breaks by heterolytic fission with the electron pair
going to the bromine and forming a Br- ion
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A bromine ion and a carbocation are then formed
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Alkenes
 The C=C double bond of an alkene has two parts to it:
 The sigma bond which is formed between the two carbon atoms due to
the overlap of orbital’s
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This allows the atoms to rotate and and
can happen by the overlap of S and or P orbitals within the same atom
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The electron density is concentrated
within the two regions
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o In a reaction the pi bond breaks however the sigma bond always
stays intact
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o Halogens react well with alkenes this is known as a halogenation
reaction
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Cl2
Cl’ + Cl’
 Propogation – This a chain reaction and stops when all of the chlorine
radicals have been used up
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The methane reacts with a chlorine molecule and a CH bond is
broken by homolytic fission forming a methyl radical and
hydrogen chloride
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The methyl radical then reacts with a chlorine molecule forming
chloromethane and a further chlorine radical for chlorine radical
can be then used again in the first propagation step

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