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1. Conclusion:
In conclusion, this experiment aimed to investigate a selection of diagnostic tests
used to identify carbonyl compounds and use the product(s) to identify unknown
carbonyls. We utilized DNP to test for the presence of the carbonyl group in five
unknown organic reagents provided by the instructor. The results obtained from the
experiment were recorded, and the theoretical melting points of each of the isolated
DNP derivatives were determined. The experiment provides valuable insight into the
properties of carbonyl compounds and the various methods used to identify them.
INTRODUCTION
The aim of this experiment is to investigate a selection of diagnostic tests used to
identify carbonyl compounds and use the product(s) to identify unknown carbonyls.
Aldehydes and ketones are organic compounds that contain the carbonyl group. The
carbonyl group is composed of oxygen bonded to the carbonyl carbon. Aldehydes
and ketones have various industrial applications, and each of these compounds
shows different chemical properties based on the position of the carbonyl group.
There are standard reactions that can be used to distinguish between aldehydes and
ketones and therefore, these reactions can be used to identify the presence of the
carbonyl group. In this experiment, we will use 2,4-dinitrophenylhydrazine (DNP) to
test for the presence of the carbonyl group in five unknown organic reagents
provided by the instructor.

2. (a) Observations:
 Solution A (benzaldehyde) - orange precipitate formed
 Solution B (propanal) - orange precipitate formed
 Solution C (acetone) - no reaction observed
 Solution D (2-butanone) - no reaction observed
 Solution E (phenol) - no reaction observed
(b) Based on the observations above, complete the sentence:
Since there was a positive test with DNP for unknowns A and B, it can be
deduced that each of these contain a carbonyl group. Since there was a
negative test for unknowns C, D, and E, it can be deduced that these
organic species are not aldehydes nor ketones.
(c) Observations:
 Solutions turned from orange to yellow.
(d) Based on the observation in (c), it can be deduced that the general
identification of the organic species in these tubes is that they are
aldehydes or ketones since they have reacted with DNP.
(e) Observations:
 Solutions fizzed and effervescence was observed.
(f) Based on the observation in (e), the deduced identity of the organic
species that were present in these tubes from the original five organic
reagents used in this experiment are:
Tube A contains benzaldehyde. Tube B contains propanal. Tube C, D, and E
do not contain aldehydes or ketones.
(g) Chemical reactions:
Tube containing benzaldehyde (A):
Chemical reaction: 2,4-dinitrophenylhydrazine + benzaldehyde → orange
precipitate (DNP derivative)

3. Tube containing propanal (B):
Chemical reaction: 2,4-dinitrophenylhydrazine + propanal → orange
precipitate (DNP derivative)
(h) If a sample of 2-methylpropan-2-ol was subjected to part 2 of the
method above, no reaction would be observed since it does not contain a
carbonyl group.
(j) The addition-elimination reaction between DNP and pentanal can be
represented as follows:
(k) Two additional diagnostic tests that could be used to confirm the
presence of the original organic species are:
1. Tollens' test: This test is used to identify the presence of aldehydes but not
ketones. In this test, a small amount of Tollens' reagent (ammoniacal silver
nitrate) is added to the organic species. If an aldehyde is present, a silver
mirror will form on the walls of the test tube. The test is positive because
the aldehyde is oxidized to a carboxylic acid and the silver ions are reduced
to silver metal. The observation of a silver mirror confirms the presence of
an aldehyde.
2. Iodoform test: This test is used to identify the presence of methyl ketones.
In this test, a small amount of iodine and potassium hydroxide are added to
the organic species, and the solution is heated gently. If a methyl ketone is
present, a yellow precipitate of iodoform (CHI3) will form. The observation
of a yellow precipitate confirms the presence of a methyl ketone.