combustion of alcohols a.draw out and state what kind of alcohol the following are: 1.butan-1-ol...
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Combustion of alcoholsA. Draw out and state what kind of alcohol the
following are:1. Butan-1-ol 2. Butan-2-ol3. 2-methylbutan-2-ol4. 2,4-dimethylpentan-3-ol5. 4,4-dibromo-3-ethyl-2-5-dimethyl-hexan-1,3-diol6. 1,1,4-trichloro-2,3-diiodo-5-6-diethyloctan-1,4,6,8-
tetraol
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 recapElement
Usual oxidation state
Exceptions
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 -2except in peroxides and
F2O
Hydrogen usually +1except in metal hydrides
where it is -1
Chlorine usually -1except in compounds with
O or F
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 + wateralcohol agent acid
Reflux apperatus
Clamp standCooling tube (tap water goes in at the top and out at the bottom continuously)Reaction containerHeat 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 butan-1-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 ethanoateBanana is made from: 2. Pentyl ethanoate
Dehydration of ethanol to form ethene
Dehydration of cyclohexanol to form cyclohexene