Oxidation Reactions of Alcohols Flashcards
what does oxidation mean in terms of these reactions
the loss of hydrogen from an alcohol molecule
what does oxidation affect in these reaction
one carbon atom
when an alcohol is oxidised, what atoms are removed from it
- the hydrogen atom from the OH group
- and the hydrogen atom bonded to the carbon atom with the OH group
if a hydrogen from the OH group and a hydrogen from the carbon atom with the OH group are removed, what new bond is formed
a double bond between the carbon atom and the oxygen atom
what is an organic product that contains a C=O group
carbonyl group
what kind of alcohols can be oxidised in this way in order to become a carbonyl group containing molecule and why
- primary and secondary alcohols can be oxidised this way
- this is because primary and secondary ones are only bonded to 1 and 2 other carbon atoms, meaning both of them are bonded to a hydrogen and OH group
- this means that the oxidation can take place
what kind of alcohols cant be oxidised in this way in order to have a carbonyl group and why
- tertiary alcohols
- because the carbon atom with the OH group would be bonded to three other carbon atoms
- meaning it isnt bonded with a singular hydrogen in order for the oxidation to take place
what is produced when a secondary alcohol is oxidised
a homologous series called ketones
what is the simplified formula for a ketone and what does this refer to
- RCOR
- the carbon atoms the main carbon tom is bonded to on the left and right is R
- while it has a double bond with an oxygen atom in the middle
what is the first organic product that is produced when a primary alcohol is oxidised
a homologous series called aldehydes
what is the simplified formula for an aldehyde
RCHO
what is the product for the oxidation of aldehydes
a homologous series called carboxylic acids
why does this reaction even occur
- because although aldehydes are the product of the oxidation of primary alcohols
- they are more easily oxidised
- so they can simply oxidise further
what happens during the oxidation of aldehydes
- they gain an oxygen atom but dont lose a hydrogen atom
- the gained oxygen atom goes between the C and H of the CHO group (from RCHO)
if the O goes in between the CHO group, what is the simplified formula of carboxylic acids
RCOOH
what therefore are the products of the oxidation of primary and secondary alcohols
- primary alcohol = aldehyde = carboxylic acid
- secondary alcohol = ketone
what is the usual reagent for these oxidation reactions
- a mixture of potassium dichromate (V)
- and sulfuric acid
how would you write the mixture of potassium dichromate and sulfuric acid when writing out equations and why
- you would just write [O]
- which represents an oxygen atom supplied by the oxidising agent
- and you write this because writing the equations with the reagents in would be too complicated
what colour change should be seen when the oxidising agent is used
orange to green
what would be the name and structural equation for the reaction between propan-1-ol and the oxidising agent
- CH3CH2CH2OH + [O] = CH3CH2CHO + H2O
- called propanal
what would be the name and structural equation for the oxidation of propanal
- propanoic acid
- CH3CH2CHO + [O] = CH3CH2COOH
what would be the name and structural equation for the reaction between propan-2-ol and the oxidising agent
- propanone
- CH3CH(OH)CH3 + [O] = CH3COCH3 + H2O
what two techniques are used when trying to collect ketones, aldehydes or carboxylic acids
- heating under reflux
- distillation with addition
when is heating under a reflux used
- when the oxidation is intended to be complete
- in order to obtain a ketone or carboxylic acid
how does heating under a reflux work
- the reaction mixture is heated until everything reacts
- the products of the oxidation stay in the mixture because if they boil off they condense in the vertical condenser
- then return back down to the heating flask
when is distillation with addition used
- when the oxidation is intended to be incomplete
- in order to obtain an aldehyde, not a carboxylic acid
how is distillation with addition done
- only the oxidising agent is heated
- while the alcohol is slowly added to the oxidising agent
- when the aldehyde is formed it immediately distills off and is collected in the receiver
- as it has a much lower boiling point than the alcohol used to make it
what do the methods of heating under a reflex and distillation with addition involve
- the heating of a reaction mixture with a condenser fitted vertically
- the heating of a reaction mixture, but adding another liquid and distilling off the products as it forms
