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