To identify carbonyl compounds as aldehyde and ketone using qualitative analysis.

INTRODUCTION             O

Carbonyl compounds have functional group called carbony         C       and there are two types of carbonyl compound that is aldehydes and ketones. Both aldehydes and ketones have general formula, CnH2nO

                                                            O                                          O

General structure of aldehyde is R-C-H whereas ketone is R-C-R’. Aldehyedes are named by using the suffix-AL while for ketones, it was named by using the suffix-ONE.

Carbonyl compounds can be prepared from the following reactions.

  1. Oxidation of alcohol
  2. Ozonolysis of alkene that involve the breaking of C=C carbon double bond.
  3. Friedle-Craft Acylation ( aromatic ketone ) in the presence of ALCL3 as a catalyst.

In Fehling’s test, only aliphatic aldehydes ( not aromatic aldehyde, ketone) react with Fehling’s reagent. In the reaction, aldehyedes is oxidized to form a carboxylate and copper (11) ion is reduced to copper (1) oxide which appear as brick-red precipitate.

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Both aliphatic and aromatic aldehyde (not ketone) react with Tollen’s reagent. In the reaction, aldehyde is oxidized to form carboxylate and the Ag(NH3)2  positive ion which appear as silver mirror on the wall of the test tube.

An aldehyde will react positively with schiff’s reagent giving pinkish purple colour solution. However it is not a good confirmatory test as benzaldehyde gives negative result and propanone gives positive result.

Similar to alcohol, carbonyl compounds can also react with iodine in warm alkaline solution, NaOH to form yellow precipitate of triiodomethane, CHI3.


Stopper, test tube, water bath, thermometer

Chemical reagents


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Mark: 3/5 This report is lacking in some key components, and the discussion section is confusing. The results section is clear and the introduction outlines some key aspects of carbonyl chemistry. To gain 4/5, a method section would need to be introduced, outlining the quantities of reagents used. For a mark of 5/5, this work would need significant improvement. More in-text referencing from reliable sources, as well as a better formulated discussion, would give rise to a much better mark.