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Chemistry- Chapter 14- Haloalkanes
Haloalkanes are the basis of many synthetic compounds such as PVC, teflon and a number
of solvents.
Haloalkanes have a hydrocarbon chain with one or more halogens in place of a hydrogen
atom, (i.e. F, Cl, Br, I)
General formula- CnH2n+1X (where X is the halogen).
Naming haloalkanes
Find the root name as you normally would (i.e. meth, eth, prop, but, pent, hex).
Then find the number of each halogen present and use di-, tri-, tetra- etc as a prefix.
Then, after the "di-/ tri-/ tetra-", use fluoro-, chloro-, bromo-, iodo- in ALPHABETICAL
ORDER!
E.g. 2,3, di-chloro- 3- iodo-hexane
H Cl I H H H
H C C C C C C H
H H Cl H H H
Bond Polarity
The C-X bond in a haloalkane is POLAR because the halogen (X) is more electronegative (ability to
pull bonded pair of electrons closer to itself) than the C is.
This difference in electronegativity results in the C having a slight positive charge and the X having
a slight negative charge.
The polarity (i.e. difference in electronegativity) of the haloalkane INCREASES AS THE "X" IS
FURTHER UP GROUP 7 because the halogens at the top of G7 are more electronegative.
C-F is therefore the MOST POLAR!- Biggest difference in electronegativity between C and F than C
and any other halogen.

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Solubility
The polar C-X bonds are NOT POLAR ENOUGH TO MAKE THE HALOALKANE SOLUBLE IN
WATER.
Main intermolecular forces are van der Waals and dipole-dipole (no hydrogen bonds).
Haloalkanes can remove oily stains (oily stains are mixtures of hydrocarbons).
Boiling point
The boiling point of haloalkanes depends on the number of carbon and halogen atoms.
BOILING POINT INCREASES with INCREASED CHAIN LENGTH as the greater the molecular
weight, the larger the surface area of the molecule meaning more van der Waals forces.…read more

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Nucleophilic Substitution
NUCLEOPHILE- Electron pair donor that attacks and forms covalent bonds with positively charged C
atoms. It is either a negative ion or has a slight negative charge.
E.g. -:OH (hydroxide ion), :NH3 (ammonia), -:CN (cyanide ion)
1. Nucleophilic substitution with aqueous NaOH (sodium hydroxide) or aqueous KOH (potassium
hydroxide): (HYDROLYSIS)
Conditions:
Ethanol is the solvent in which the haloalkane and aqueous NaOH/ KOH mix because
haloalkanes do not mix with water.
Takes place at room temperature.…read more

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Nucleophilic substitution with cyanide ions (-:CN):
The product is called a "nitrile".
Note: When naming, include the new extra "C" in the root name followed by "nitrile.
3. Nucleophilic substitution with ammonia (NH3)
Conditions:
Reaction of haloalkanes with an excess of concentrated solution of ammonia (NH3) in ethanol
is carried out under pressure.…read more

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The product is a primary amine.
*NH3 must be added twice during this reaction.…read more

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Elimination reactions in haloalkanes:
In theses haloalkane reactions, a hydrogen halide (H-X) is removed and a double (C=C) bond is left in
it's place, leaving an alkene.
1. The :OH- ion acting as a base
Although OH:- can act as a nucleophile, under different conditions it can act as a base, removing a H+
ion from a haloalkane.
Conditions:
NaOH/ KOH is dissolved in ethanol and mixed with the haloalkane. There is NO WATER present.
The mixture is heated.…read more

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The lone pair on the OH:- ion bonds with a H atom attached to one of the C atoms next to the C-X
bond. (H2O formed).
2. The electron pair from the C-H bond now becomes a C=C bond.
3. The X now takes the pair of electrons in the C-X bond and leaves.
Substitution or elimination (OH:-) ?
In general we produce a mixture of alcohols (substitution) and alkenes (elimination), but there
are conditions substitution and elimination prefer.…read more

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Haloalkanes and the environment:
Chlorofluorocarbons (CFC's) are haloalkanes containing only chlorine, fluorine and carbon (no
hydrogen).
CFC's are very unreactive under normal conditions.
Short chain CFC's are gases and used in aerosols, propellants, refrigerators etc.
Long chain CFC's are used as dry-cleaning and de-greasing solvents.
CFC's eventually end up in the atmosphere and decompose to give Cl atoms which decompose
ozone, O3, which has caused a hole in the ozone layer.…read more

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This takes place in two stages:
Stage 1: The Cl* free radical takes a hydroen atom from CH4 (methane) to form hydrogen chloride, a
stable compound. This leaves a methyl free radical- CH3*
Cl* + CH4 --> HCl +CH3*
Stage 2- The methyl free radical reacts with a chlorine molecule, producing another chlorine free
radical and a molecule of chloromethane, a stable compound.
CH3* + Cl2 --> CH3Cl + Cl*
3. Termination
Removal of free radicals and can happen in 3 ways:
1.…read more

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