1. No category

Combustion of alcohols
A. Draw out and state what kind of alcohol the
following are:
1. Butan-1-ol
2. Butan-2-ol
3. 2-methylbutan-2-ol
4. 2,4-dimethylpentan-3-ol
5. 4,4-dibromo-3-ethyl-2-5-dimethyl-hexan-1,3-diol
6. 1,1,4-trichloro-2,3-diiodo-5-6-diethyloctan-1,4,6,8tetraol
B. Write out the equation for the complete
combustion of the first four alcohols
Combustion and oxidation of
alcohols
L.O.:
Describe the combustion of alcohols.
 Describe the oxidation of primary and
secondary alcohols.
Outline the resistance to oxidation of tertiary
alcohols
Aldehydes and ketones: Recap
1. What’s the difference between an aldehyde
and a ketone?
2. Draw a 3 carbon and a 5 carbon aldehyde
and name it.
3. Draw a a 3 carbon and a 5 carbon ketone
and name it.
Oxidation recap
Element
Usual oxidation
state
Elements joined to
themselves, e.g. Cl2
ALWAYS 0!!! None
Group 1 metals
always +1
Group 2 metals
always +2
Fluorine
always -1
Oxygen
usually -2
except in peroxides and
F2O
Hydrogen
usually +1
except in metal hydrides
where it is -1
Chlorine
usually -1
except in compounds with
O or F
Exceptions
Oxidation of propan-1-ol to the aldehyde
propanal
Oxidising carbon
• More hydrogen bound to the carbon LOWERS
(makes it more negative, or reduced) its
oxidation number
• More oxygen bound to the carbon RAISES
(makes it more positive, or oxidised) its
oxidation number
Oxidising alcohols
Reaction conditions:
1. The oxidising agent is always acidified
potassium dichromate written above the
arrow like this:
K2Cr2O7/H2SO4
2. The reactants are the alcohol and “[O]”
symbolising the oxidation agent
3. Heat is always needed
Potassium dichromate
In its oxidised state it is a
bright orange liquid
• What kind of bonds hold
this compound together?
Oxidising primary alcohols
• Write out the equation using displayed
formula of the oxidation of ethanol to ethanal
(water is also made)
(The reaction conditions require GENTLE HEAT
with immediate distillation)
Aldehydes vs acid problem
Further oxidation of a primary alcohol
• Using a process known as REFLUX, the
reaction contents are continually heated at
their boiling point temperature, so HOTTER
and LONGER heating then alcohol conversion
to an aldehyde
• Still uses acidified potassium dichromate
Primary + Oxidising  Carboxylic + water
alcohol
agent
acid
Reflux apperatus
Clamp stand
Cooling tube (tap water
goes in at the top and out
at the bottom
continuously)
Reaction container
Heat source
Draw out the conversation of ethanol
to ethanoic acid using the displayed
formula
Oxidation of secondary alcohols
• Like primary alcohols, also require acidified
potassium dichromate and heat (but not
reflux)
• Converts the alcohol into a ketone
Write out, using displayed formula, the
oxidation of hexan-2-ol to hexa-2-one
Oxidation of tertiary alcohols
• The carbon attaching to the OH doesn’t have
any hydrogens attached to it, so these can’t
be oxidised.
Esterefication and dehydration of
alcohols
L.O.:
Describe the esterification of alcohols with
carboxylic acids.
Describe elimination of H2O from alcohols to
form alkenes.
The esterification reaction between propanoic acid
and methanol
Naming esters
The alcohol becomes the alkyl group, the
carboxylic acid becomes the alkanOATE part
e.g. ethanol and methanoic acid form ethyl
methanoate
Diagram to show the bonds broken during
esterification
Simple laboratory preparation of an ester
Sweet-smelling esters
Write out your own esterification reaction
between methanol and methanoic acid
using displayed formula
Now draw out the reaction between:
1.
Ethanol and ethanoic acid
2.
3,3-dichloro-2-methylhexanoic acid and butan1-ol
3.
Propanoic acid and hexan-3-o
Draw these esters and name the alcohols
and the carboxylic acids that made them:
The smell of oranges is from the ester:
1. Octyl ethanoate
Banana is made from:
2. Pentyl ethanoate
Dehydration of ethanol to form ethene
Dehydration of cyclohexanol to form cyclohexene