what are the tests to distinguish between an aldehyde and a ketone?

Answer 1

Tollens' Test - Silver mirror.
Using the appropriate chemicals formation of a silver mirror will indicate that your unknown is an aldehyde. If not, it is a ketone. This test is only useful if you have done tests to rule out other chemical possibilities.

Answer 2

Ketone is non-reactant to the Benedicts test and turns Brick Red. Tollens test for aldehyde creates a shiny silver mirror as it does react with the Tollens reagent.

Answer 3

1.) add tollens reagent to both aldehyde and ketone, the aldehyde is oxidized to a carboxilic acid showing a silver mirror . the ketone yields no reation with tollens reagent. 2.) again, oxidize bothe the aldehyde and the ketone using potassium permanganet as catalyst, the aldehyde will be oxidized to a caboxilic acid where as the shall be no reaction with the ketone

Answer 4

tollens mirror test only works half the time and is sketchy at best. whenever doing functional tests be sure to run a control POSITIVE and control NEGATIVE to ward off false positives and negatives. DNP test normally works well though.

DNP test
2-3 drops unknown (50mg) in a few drops of methanol. 1mL 2,4 dintropheylhydrazine reagent and shake. if no ppt. boil for 1 min and cool on ice.

yellow ppt - saturated carbonyl
orange ppt - alpha, beta, unsaturated carbonyl
red ppt - aromatic carbonyl



Iodoform test
2-3 drops unknown (50mg) unknown in 1:1 THF:H2O. 2-3 drops 3M NaOH, 3mL iodine soln. Disappearance of brown coloration and formation of pale yellow ppt indicates presence of methyl ketone. acetaldehyde, ethanol and some secondary alcohols give false positive.

Answer 5

I'd just stick it through MS, and look at the peaks, if the molecule is small enough, then NMR it to check.

Answer 6

what is dat