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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: appamo on November 22, 2011, 07:18:10 AM

Title: qualitative test for aldehyde and ketone
Post by: appamo on November 22, 2011, 07:18:10 AM
unknown sample was given, the test and the result is as below

1. tollens reagent- no silver mirror
2. 2,4 Dinitrophenylhydrazine - yellow orange precipitate
3. iodoform test - no yellow precipitate

is that indicate that i got a ketone?
Title: Re: qualitative test for aldehyde and ketone
Post by: Dan on November 22, 2011, 08:02:54 AM
Well, if you look up what your tests are for it should be clear. Did you try googling Tollen's reagent, for example?
Title: Re: qualitative test for aldehyde and ketone
Post by: appamo on November 24, 2011, 05:15:26 AM
Quote from: Dan on November 22, 2011, 08:02:54 AM
Well, if you look up what your tests are for it should be clear. Did you try googling Tollen's reagent, for example?

i did..positive test will show silver mirror which means aldehyde present right? but i didnt get silver mirror..so is that mean my sample is ketone...i want to confirm whether im wrong or not?
Title: Re: qualitative test for aldehyde and ketone
Post by: Arkcon on November 24, 2011, 08:13:48 AM
Good work so far.  Now, what do the other tests tell you?
Title: Re: qualitative test for aldehyde and ketone
Post by: appamo on November 25, 2011, 05:22:32 AM
Quote from: Arkcon on November 24, 2011, 08:13:48 AM
Good work so far.  Now, what do the other tests tell you?

first, ignition test- i get non sooty flame which indicates its aliphatic
then, test on litmus paper, i get neutral because no change on the litmus paper
then, solubility test, it soluble in water, acid(dil HCL) and alkali(dil NaOH)
then, testing for the present of nitrogen, which i get no N present
then, 2,4-dinitrophenylhydroxine test, there is precipitate yellow orange
then, tollens test, which i get negative because no silver mirror
then iodoform test, negative also.
 so in conclusion, my sample contain aldehyde or ketone?? based on all test, aldehyde is impossible right?
so its ketone? or something else? IM VERY CONFUSE