The Student Room Group

Oxidation of Ethanol

"Describe the complete oxidation of ethanol. Include the conditions, reagents required, and any colour changes."

OK well I know that you add acidified potassium dichromate (prepared from sulphuric acid) and it oxidises first to ethanal and then to ethanoic acid, or vinegar - which is dark brown?

BUT I don't know how to put that in a chemical equation, and I don't know the colour of ethanal or ethanol.

Can anyone help? :smile:
Reply 1
ethanal and ethanol are both transparent
Reply 2
Does acidified potassium dichromate have a colour?
IBeast
Does acidified potassium dichromate have a colour?


If I remember correctly, acidified potassium dichromate (K2Cr2O7) goes from orange to green during oxidation.

Is ethanol produced from sulphiric acid always ethan-1-ol, CH3CH2OH? If not, it could of course mean that you get a ketone when oxidised. Also, don't forget that you have to distil immediately first and then reflux...

So the overall equation for oxidation of ethan-1-ol is:

C2H5OH + [O] ------> CH3COH + H2O (distill upon heating)

or if heated with excess K2Cr2O7

C2H5OH + 2[O] ------> CH3COOH + H2O (heat under reflux)

Hope this helps!
Reply 4
Languages Nutter

Is ethanol produced from sulphiric acid always ethan-1-ol, CH3CH2OH? If not, it could of course mean that you get a ketone when oxidised. Also, don't forget that you have to distil immediately first and then reflux...


Ethanol is always a primary alcohol.........
D'oh! Sorry - my mistake!
Reply 6
Ethanol is always a primary alcohol as it only has 2 carbons. You would heat under reflux with acidified potassium dichromate (vi) (i think its (vi)?). It would go via an aldehyde to ethanoic acid. Yes vinegar is brown but i think you'd write the colour change as being from orange to dark green as thats the colour the oxidisnig agent goes. Ethanol and ethanal are both colourless....

Hope this helps, I expect cos I'm such a slow typer loadsa people will have already said the same thing!! :smile:
Reply 7
Thank you very much :smile: that's all I need to know
Reply 8
For geek points, ask your A level teacher to show you the ammonium dichromate volcano. Get a small heap of said compound, stick an ethanol-soaked splint in it, and light it.

Might want to do it in a fume hood.
IBeast
OK well I know that you add acidified potassium dichromate (prepared from sulphuric acid) and it oxidises first to ethanal and then to ethanoic acid, or vinegar - which is dark brown?


H2SO4 is added to potassium dichromate to form the chromate ion and acetic acid is clear and colourless, whatever you do don't say vinegar :tongue:

Latest