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Topic 7 ­ Basic Concepts
Revision Notes

1) Formulae

Be able to recognise and use the different ways of showing organic compounds.

Molecular formula is the actual number of atoms of each element in a molecule
e.g. C2H6O for ethanol

Empirical formula is the simplest whole number ratio of the…

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5) With more than 1 side chain or halogen, use alphabetical order e.g.

3) Structural isomers

Structural isomers have the same molecular formula but different structural formulae
e.g. the molecular formula C4H19Br can produce four different structures
Differences between structural isomers arise from the position of the functional

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In the following reaction, 2.18g of bromoethane produce 0.75g of ethanol. Calculate the
percentage yield.

Moles of reactant (bromoethane) = mass/molar mass
= 2.18/109
= 0.020 mol
Possible moles of ethanol = 0.020 mol (from equation)
Actual moles of ethanol = 0.75/46.0

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6) More on naming organic compounds

This section covers naming compounds with more than one alkene or alcohol
functional group

a) Dienes

Compounds containing two alkene groups are called dienes e.g.

The name of this compound is buta1,3diene

b) Diols and triols

Compounds containing two alcohol groups are called diols…

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Appendix 1 Skeletal Formulae

Skeletal formulae show carboncarbon bonds and functional groups

Alkane e.g. hexane

Alkene e.g. hex3ene

Alcohol e.g. ethanol

Halogenoalkane e.g. 2chloro2fluoropentane

Aldehyde e.g. butanal

Ketone e.g. propanone

Carboxylic acid e.g. 3methylbutanoic acid

Ester e.g. methyl propanoate

Amine e.g. ethylamine



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Topic 8a ­ Alkanes
Revision Notes

1) General

Alkanes are saturated hydrocarbons with general formula CnH2n+2
Saturated = only single CC bonds
Hydrocarbon = contains C and H only

CH bonds are nonpolar (C and H have similar electronegativities) so:
o The only intermolecular forces in alkanes are Van der…

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The mechanism here is called radical substitution

Initiation step e.g. Br2 2Br
Propagation e.g. CH4 + Br CH3 + HBr } as a
CH3 + Br2 CH3Br + Br } pair
Termination step e.g. 2 CH3 CH3CH3

Further substitution can occur with more H's being replaced by Br's

CH3Br +…

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Topic 8b ­ Fuels
Revision Notes

1) Fractional Distillation

Crude oil is a mixture of many compounds, most of which are alkanes.
Crude oil is separated into fractions, many of which can be used directly as fuels.
The separation process is called fractional distillation. This involves:
o Vaporising the crude…

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Isomerisation increases the octane number of the hydrocarbon
It needs a catalyst and heat

c) Reforming

Reforming turns straight chain alkanes into cyclic alkanes and arenes (and
hydrogen) e.g.
C6H14 C6H12 + H2
Hexane cyclohexane

C6H14 C6H6 + 4H2
Hexane benzene

Arenes contain a benzene ring (see A2 Topic 1).…

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Unsaturated = contain a double C=C bond
Hydrocarbon = contains C and H only

2) Bonding in Alkenes

o The carbons at either end of the double bond and the 4 atoms they are bonded to
are all in a plane (flat). These 6 atoms are joined by single bonds…


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