ALCOHOLS AND OXIDATION Flashcards
What is the name of this alcohol?
Pentan-2-ol
what is the general formula of alcohols?
CnH2n+1OH
Alcohol can be subdivided into 3 categories
primary / secondary / tertiary
How to recognise a primary alcohol.
The –OH is attached to a C which is attached to only one other carbon atom.
Position: at the end of the carbon chain.
How to recognise a secondary alcohol
The –OH is attached to a C which is attached to 2 other carbon atoms.
Position: join to an intermediate carbon atom.
How to recognise a tertiary alcohol
The –OH is attached to a C which is attached to 3 other carbon atoms.
Position: Joined to an intermediate C which also has a branched attached.
what is the polarity of alcohols?
they are polar because of the OH results in hydrogen bonding high bp and viscosity
What happens to the BP and MP of alcohols as the number of OH increases?
The MP and BP increase as more hydrogen bonds can be formed between molecules.
what do alcohols dissolve in?
polar liquids such as water
but not in non-polar liquids like hydrocarbons.
What happens to the MP and BP of alcohols as the number of carbon atoms increase.
More intermolecular forces = MP and BP increase
What happens to the solubility of alcohols in water as the number of carbon atoms increase
Less soluble as makes hydrogen bonding with the -OH group but the rest of the chain made of carbon and hydrogen is non-polar and therefore won’t dissolve in water.
primary, secondary or tertiary alcohols?
Secondary
primary, secondary or tertiary alcohols?
primary
primary, secondary or tertiary alcohols?
Tertiary
Primary alcohols can be oxidised to
Aldehyles then carboxylic acids
Secondary alcohols can be oxidised to
ketones
Tertiary alcohol get oxidise to
NOTHING, tertiary alcohols don’t get oxidised.
What is the functional group of aldehyde?
C=O
Carbonyl group
What are the oxidising agent used to oxidise primary alcohols to aldehydes then carboxylic acids or secondary alcohols to ketone?
give the result of the reaction
Hot copper oxide (black) become brown solid when it has oxidised an alcohols (itself get reduced, it is an oxidising agent)
Acidified dichromate (orange) become blue when it has oxidised an alcohols (itself get reduced, it is an oxidising agent)
Acidified dicrhomate solution can be used to identify between aldehydes and ketones.
What are the other two oxidising agent that can be use for that purpose?
(give results of the reaction/colour change)
Blue Fehling’s solution forms a brick red precipitate
and
Colourless Tollen’s reagent forms a silver mirror.
What happen to the O:H ratio as an oxidation takes place?
O:H ratio increase
either number of Oxygen increases or number of hydrogen decreases
What happen to the O:H ratio as a reduction takes place?
O:H ratio decreases
Either number of oxygen decreases of number of hydrogen increases
Solution A and B were reacted with Blue Fehlings solution.
Solution A stayed blue
Solution B formed a red brick precipitate
Which solution is an aldehyde and which one is a ketone?
Aldehyde can get oxidised further to carboxylic acid, therefore B is the aldehyde as it has been oxidised by the oxidising agent.
Reaction A, did not get oxidised further, therefore it is a ketone.
