lab report 3 ( aldehyde and ketone ).pdf

aldehyde and ketone

1. ORGANIC CHEMISTRY
PCH10201P
LAB REPORT

EXPERIMENT: 3
ALDEHYDE AND KETONE

NAME ID NUMBER PHOTO
BELLY BRYAN
GEFFRIZO
012020090693


THINESKUMAR A/L
M RAVINDRAN
012020091963

JAYASHRI A/P
SURES
012020091355

RISHNAMALA
NAIDU A/P
SUBRAMANIAM
012020091567

LAVNIYAA
SARAWANAN
012020022225

PROGRAM: DPH
LECTURER: MS NIK NUR SHAMIHA NIK DZULKEFLI
DATE OF SUBMISSION: JUNE 23, 2021

2. Experiment 3

Aldehyde & Ketone
OBJECTIVE (S)
• To carry out chemical test to determine aldehyde and ketone
INTRODUCTION
-State test in laboratory to differentiate between aldehyde and ketone

Tollens’ test, also known as silver-mirror test, is a qualitative laboratory test used to
distinguish between an aldehyde and a ketone. It exploits the fact that aldehydes are readily
oxidized, whereas ketones are not. Tollens’ test uses a reagent known as Tollens’ reagent,
which is a colourless, basic, aqueous solution containing silver ions coordinated to ammonia.
It is prepared using a two-step procedure which is aqueous silver nitrate is mixed with
aqueous sodium hydroxide and aqueous ammonia is added drop-wise until the precipitated
silver oxide completely dissolves. Tollens’ reagent oxidizes an aldehyde into the
corresponding carboxylic acid. The reaction is accompanied by the reduction of silver ions in
Tollens’ reagent into metallic silver, which, if the test is carried out in a clean glass test tube,
forms a mirror on the test tube. Ketones are not oxidized by Tollens’ reagent, so the treatment
of a ketone with Tollens’ reagent in a glass test tube does not result in a silver mirror.

3. RESULTS














Sample
(Aldehyde/Ketone)
Observation (color changes)
Tollen’s Test Fehling’s Test Schiff’s Test


Ethanal

silver mirror

positive
( yellowish-red
precipitate )

positive (violet
colour )

Benzaldehyde

Positive ( silver
mirror )

remain blue
colour

no reaction

Acetone

no reaction

negative

yellow precipitate

4. DISCUSSIONS
1. Draw chemical structure for all samples as stated in the above table.

5. 2. Explain your prediction as stated in the above table for all test referring to theory.

We can observe chemical reaction which is silver ions is reduced to metallic silver which
forms a layer called silver mirror on the inside of container. Therefore, it’s considered as a
positive result. For Benzaldehyde, we can see the similar reactions as above which is Ethanol.
It may happen because functional group for Benzaldehyde is Aldehyde. In additional, it’s a
positive result because we see the colour changes inside the container. We can’t see any
reaction for Acetone in Tollen Test inside the container. It is happening because Ketones do
not react with Tollen’s agent. As we know, Acetone categorized as Ketone functional group.
So, it undergoes as a negative result. In Fehling’s test, we will observe blue colour of the
Fehling’s solution disappears and brick-red precipitate is obtained. Once we used Ethanol as
a reagent for this test, we see that colour changes which is blue colour turns to brick-red. The
changes of colour happens because Ethanol is functional group of Aldehyde. The changes of
colour help us to find out it’s a positive result. Second reagent we used is Benzaldehyde.
Although Benzaldehyde is Aldehyde functional group but it does not provide a positive result
it means the changes of colour which is blue to brick-red doe not happen here. We all well
know about Ketones do not react with Fehling’s reagent. As a result, we can’t see any
chemical reactions while using Acetone because the functional group of Acetone is Ketone.
So, the colour of blue remains in container and it listed as negative result. Formation of
magenta-pink colour refer to a positive result in Schiff’s test. While using the reactant of
Ethanol in this test, we definitely see the different inside the container. We observe the colour
magenta-pink produced as a symptom of chemical reaction inside the container. It is a
positive result since the magenta-pink colour remains inside the container after chemical
reactions happened. For Benzaldehyde, we can’t see any changes of colour inside the
container although Benzaldehyde undergoes with Aldehyde functional group. It did not give
positive result like above. Since we know the functional group of Acetone is Ketone, surely,
we can’t expect the positive result form the test. The unchanged colour causes Acetone gives
a negative result in this test. Generally, Ketones do not react with Schiff’s reagent expect
propanone.

6. 3. Write reagent been used in Schiff’s, Tollen’s and Fehling’s Test.

• The Schiff reagent is the reaction product of a dye formulation such as fuchsin and
sodium bisulfite; pararosaniline (which lacks an aromatic methyl group) and new
fuchsin (which is uniformly mono-methylated ortho to the dye's amine
functionalities) are not dye alternatives with comparable detection chemistry.

Schiff reagent is the product formed in some dye formulation reactions such as the
reaction between sodium bisulfite and fuchsine. It is used to check for the presence
of aldehyde in an analyte. It can be used to differentiate between aldehyde and
ketones. Fuchsine or Ros aniline hydrochloride is a magenta-colored dye with a
chemical formula C20H20N3·HCl,

• Tollens' reagent is an alkaline solution of ammoniacal silver nitrate and is
used to test for aldehydes. Silver ions in the presence of hydroxide ions come out of
solution as a brown precipitate of silver(I) oxide, Ag2O(s). This precipitate dissolves in
aqueous ammonia, forming the diamminesilver(I) ion, [Ag(NH3)2]+

• Fehling's reagent, a blue colored basic solution of bistartratocuprate(II)
complex, is added to three different aqueous sugar solutions immersed in beakers of
warm water. A brick-red precipitate forms in the solutions containing glucose and
fructose. There is no reaction in the test tube containing sucrose solution.

7. REFERENCES
=
https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Che
mistry)/Aldehydes_and_Ketones/Reactivity_of_Aldehydes_and_Ketones/Tollens_Test#:~:text=Tolle
ns'%20test%2C%20also%20known%20as,)%2C%20whereas%20ketones%20are%20not.&text=Step%
201%3A%20Aqueous%20silver%20nitrate%20is%20mixed%20with%20aqueous%20sodium%20hydr
oxide
= https://www.chemistrylearner.com/schiff-reagent.html
= https://chem.libretexts.org/
= https://classroom.google.com/w/MTQ5NjEyNDk2Mzgy/t/all