
So far in this unit we have discussed
hydrocarbons and their isomers

We have also learned about organic
compounds with different functional
groups

Throughout this we have learned naming
rules for each

Now we are going to focus on several
types of organic reactions

There are many types of organic
reactions

We are only going to focus on a few.
› Substitution
› Elimination
› Addition
› Esterification

Any reaction in which one atom is
replaced by another

Used to place a halogen onto an alkane

The products are always a halocarbon
and the acid of the halogen

Reaction requires ultraviolet light to
initiate the reaction
› This provides the energy needed to form the
excited state
ethane + chlorine  chloroethane + hydrochloric acid
The Cl atom will replace a H atom resulting in an
alkyl halide and the acid of the halogen
(hydrochloric acid)

You can also have an alcohol react with
a halogen resulting in an alkyl halide and
water
Ethanol + hydrochloric acid  chloroethane + water

Any reaction in which atoms are
eliminated from another molecule

Done in three ways:
› Elimination of H2
› Elimination of HX
› Elimination of H2O

Called dehydrogenation

Occurs in the presence of a base (eg.
NaOH) and heat
ethane

ethene + hydrogen

Alkyl halides undergo elimination reaction

This is known as dehydrohalogenation

Occurs in the presence of a base
Base extracts H+ and X- will leave; resulting in double
bond formation
Alcohol can undergo elimination via the
loss of water
 Known as dehydration

Acid protonates the OH group, water leaves and C+
remains behind
b) An adjacent H+ leaves next leaving electron pair to
form double bond
a)

Takes place with unsaturated compounds
which are usually more reactive than
saturated compounds

Takes place with double and triple bonds

Two atoms are added across the electron
rich bond

Four types of addition:
›
›
›
›
Addition of X2 (halogen)
Addition of H2
Addition of H2O
Addition of HX (hydrogen halide)

Normally occurs in dissolved solvents such
as CCl4

Alkenes form dihaloalkanes

Alkynes produce dihaloalkenes or
tetrahaloalkanes
ethene +
chlorine 
1,2-dichloroethane
Catalysts used such as Pt, Pd or Ni
 Known as hydrogenation
 Alkene becomes alkane
 Alkyne becomes alkene or alkane

ethene
+ hydrogen 
ethane
ethyne
+ hydrogen 
ethyne + (2 mol) hydrogen
ethene
 ethane
Occurs in the presence of an acid
 Know as hydration
 Alkene becomes alcohol
 Alkyne produces ketone or aldehyde

ethene
+ water

ethanol

HX = HCl or HBr or HI (NOT HF)

Alkene becomes alkyl halide

Alkynes form monohalo alkenes or dihalo
alkanes (with halogen on the same C)

Rule for adding H and X
› The halogen (X) will always add to the more
substituted carbon atom – the carbon that is
bonded to the most carbon atoms
1-propene + hydrobromic acid  2-bromopropane
Step1:
1-propyne + hydrobromic acid  2-bromo-1-propene
Step 2:
2-bromo-1-propene+ hydrobromic acid  2,2-dibromopropane

Alcohol + organic acid  water + ester

Used to make perfumes, scents and
flavours

Combination reaction which involves
dehydration

Alcohol becomes the alkyl group and
the acid becomes -oate
propanol
+
ethanoic acid 
propyl ethanoate
+ water