MM2002
Badges: 9
Rep:
?
#1
Report Thread starter 6 months ago
#1
When you oxidise ethanol with potassium dichromate as the oxidising agent does the mixture go from orange to green in both the formation of aldehyde and ketone. Is that why we use mirror test and fehlings test to differentiate?

Thanks
0
reply
wannabeDr2020
Badges: 11
Rep:
?
#2
Report 6 months ago
#2
yeah cos the colour change just shows that oxidation has taken place I think because the K2Cr2O7 has been reduced? Correct me if I’m wrong
0
reply
Apad121
Badges: 12
Rep:
?
#3
Report 6 months ago
#3
(Original post by MM2002)
When you oxidise ethanol with potassium dichromate as the oxidising agent does the mixture go from orange to green in both the formation of aldehyde and ketone. Is that why we use mirror test and fehlings test to differentiate?

Thanks
Hi there

To put it simply, yes that is correct.

Best of luck!
0
reply
Pigster
Badges: 19
Rep:
?
#4
Report 6 months ago
#4
(Original post by MM2002)
When you oxidise ethanol with potassium dichromate as the oxidising agent does the mixture go from orange to green in both the formation of aldehyde and ketone. Is that why we use mirror test and fehlings test to differentiate?

Thanks
When dichromate does its thing, it becomes Cr3+, which is green*.

Dichromate doesn't care whether an aldehyde, ketone or carboxylic acid forms, if it oxidises something, the green* colour will appear.

To be pedantic, ethanol cannot form a ketone on oxidation. To be further pedantic, your threat title mentions primary alcohols, which also don't form ketones.

Either Tollens' or Fehlings can be used to tell the difference between an aldehyde and a ketone (both give positive results for aldehydes).

*Cr3+ isn't really green, but hey.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Has your university communicated any last minute changes?

Yes, and they were what I was expecting (6)
16.22%
Yes, and they were not what I was hoping for (10)
27.03%
Yes, and they don't change my view on attending uni (3)
8.11%
No, I haven't received any communication (18)
48.65%

Watched Threads

View All