14. Alcohols Flashcards
What is the functional group of alcohol?
CnH2n+1OH
Is alcohol saturated or unsaturated?
Saturated
Is alcohol polar or non-polar? Why?
Non-polar, because:
1. the difference in electronegativity of hydrogen and oxygen is big
2. there are weak London forces but there are stronger hydrogen bonds between the polar O—H groups
Is alcohol water soluble? Why?
Soluble, because:
1. hydrogen bonds form between the polar —OH group of alcohol and water
2. as the hydrocarbon chain increases, the influence of —OH group becomes smaller
How is alcohol’s volatility compared to the corresponding alkane?
Alcohols are less volatile, because:
1. hydrogen bonds hold the alcohol molecule together
2. in order to turn liquid alcohol into gas, hydrogen bonds must be broken
3. it requires more energy to break hydrogen bonds than London forces
How is alcohol’s boiling point compared to the corresponding alkane?
Alcohol has a higher boiling point, because:
1. hydrogen bonds hold the alcohol molecule together
2. in order to turn liquid alcohol into gas, hydrogen bonds must be broken
3. it requires more energy to break hydrogen bonds than London forces
How do primary alcohols look like?
The —OH group is attached to a carbon atom that is attached to two hydrogen atoms and one alkyl group.
How do secondary alcohols look like?
The —OH group is attached to a carbon atom that is attached to one hydrogen atom and two alkyl groups.
How do tertiary alcohols look like?
The —OH group is attached to a carbon atom that is attached to no hydrogen atom and three alkyl groups.
Which types of alcohol can be oxidised?
Primary and secondary alcohol
What are the main types of oxidising agents?
- potassium/sodium dichromate (VI)
↳ K2Cr2O7
↳ Na2Cr2O7 - potassium manganate (VII)
↳ KMnO4
WITH dilute sulphuric acid
↳ H2SO4
What is used to represent oxidising agents?
[O]
What happens to the oxidising agent when it reacts with an organic molecule?
It is reduced, often resulting in a colour change.
What is the colour change of dichromate (VI) ions when reacting with alcohol?
Orange > green
What will the number of dichromate (VI) ions change?
Cr2O7 2- > Cr 3+
What is the colour change of potassium manganate (VII) when reacting with alcohol?
Purple > colourless
What is the colour change of dilute sulphuric acid when reacting with alcohol?
No change in colour
What is the product of incomplete oxidation of primary alcohol?
Aldehyde + water
What is the functional group of aldehyde? How to name aldehyde?
C=O. Remove the -e and add -al, eg. propanal.
What condition is required to produce aldehyde when oxidising primary alcohol?
- when distillation is used
- when the alcohol is in excess
What is the product of complete oxidation of primary alcohol?
Carboxylic acid + water
What is the functional group of carboxylic acid? How to name carboxylic acid?
COOH. Remove the -e and add -oic acid, eg. propanoic acid.
What condition is required to produce carboxylic acid when oxidising primary alcohol?
- when reflux is used
- when the oxidising agent is in excess
Can aldehyde be further oxidised? How?
Yes. Aldehyde can be further oxidised to form carboxylic acid when reflux and oxidising agent are used.
What is the product of oxidation of secondary alcohol?
Ketone + water
What is the functional group of ketone? How to name ketone?
C=O. Remove the -e and add -one, eg. propanone.
What condition is required to produce ketone when oxidising secondary alcohol?
When reflux is used
Can ketone be further oxidised?
No
What is the difference between aldehyde and ketone?
Aldehyde: C is bonded with O, H, R
Ketone: C is bonded with O, R, R
Can tertiary alcohol be oxidised? Why?
No, because the central carbon atom is already bonded to three other carbon atoms.
What is an example of elimination of alcohol?
Dehydration
What happens during dehydration?
A water molecule is removed
What is the product of dehydration?
Alkene + water
What condition is required to start dehydration?
- heat under reflux
- acid catalyst, eg. H2SO4
What is the product when alcohol reacts with hydrogen halides?
Haloalkanes + water
What condition is required to start substitution?
Acids, eg. H2SO4
How is aqueous hydrogen halide produced?
Refluxing alcohol with sodium halide (eg. NaBr) and sulfuric acid.
Why do we reflux the alcohol with sodium halide and sulfuric acid?
Because hydrogen halides are gases at room temperature, which are unsafe to use.
