Organic Analysis Laboratory
SY 2016 - 2017
IDENTIFICATION OF UNKNOWN ORGANIC COMPOUNDS
Department of Chemistry, College of Science, Bicol University, Legazpi City
INTRODUCTION After these preliminary tests, the solubility test
was performed. First, 2mL of water was pipetted into
The analysis and identification of unknown a test tube and then a few crystals of the unknown
organic compounds constitutes a very important were added. The solution was shaken. Solubility of
aspect of experimental organic chemistry. One could the unknown was observed. If the unknown dissolved
easily have an idea of what the unknown compound in water, the same procedure will be done but using
is, in cases such as chemical reactions. However, ether as the solvent. If the unknown is insoluble in
when a compound is isolated from a natural source, water, the solubility of the unknown will be tested
one may be left clueless as to what the compound can with 5% NaOH. The next steps will be done
be. Discovering the identity of an unknown organic according to the solubility flowchart (Figure 1) until it
compound requires figuring out which functional lands into a solubility class. The solubility of the
groups it contains and determining its molecular unknown in the following reagents indicates the class
structure. of compound where it belongs and will be the basis of
the classification tests to be conducted later on.
The purpose of this laboratory activity was to
identify the functional groups present in the given
unknown, and eventually identify what organic
compound the unknown is. In order to accomplish
this, a variety of different tests were done. First,
preliminary tests were conducted. Afterwards,
solubility tests were run. Physical properties (density,
melting point) were also determined. The results of
the solubility tests can indicate the size and polarity of
an unknown compound, which can narrow down the
possible functional groups in the unknown. Once the
options were narrowed, further classification tests
were run. These tests were used to identify specific
functional groups in the unknown sample.
METHODOLOGY
Preliminary tests were first conducted. The
physical characteristics (physical state, color, odor) of Figure 1. Classification of organic compounds by
the unknown was noted. An ignition test was also solubility (see Table 1 for compounds comprising each
performed by heating a small amount of the unknown class). sol. = soluble, insol. = insoluble; litmus red is at
(about 0.1 g) on a metal spatula. The flame produced pH below 4.5 and blue above 8.3.
was observed (luminous or sooty).
Page 1 of 5
, Organic Analysis Laboratory
SY 2016 - 2017
the orange-red color of bromine means the compound
is unsaturated while no disappearance means that the
compound is saturated.
Potassium permanganate Solution
A few crystals of unknown were dissolved in
ethanol. Then, 2% of KMNO4 solution was added
dropwise. Observations were recorded. The
disappearance of the KMNO4’s color and the
appearance of a brown suspension of MnO2 is a
positive test (unsaturated hydrocarbons: alkenes,
alkynes, aldehydes, phenols, aromatic sidechains).
Ferric chloride – pyridine Test
A few crystals of the unknown were added to
2mL pure chloroform in a test tube. Next, 2-3 drops
of 1% solution of anhydrous ferric chloride in
Table 1. Organic Compounds Comprising the Solubility chloroform was added followed by 3 drops pyridine.
Classes of Figure 1 The solution was shaken and the observations were
recorded immediately. The production of a blue,
To determine the density, 5mL of the solvent violet, purple, green, or red-brown solution is a
in which the unknown was not soluble in the previous positive test (phenols).
procedure was placed in a 10mL graduated cylinder.
The volume was read to the hundredth decimal place Iodoform Test
value and recorded as the initial volume. Next, the A few crystals of the unknown were placed in
graduated cylinder containing 5mL of solvent was a test tube and 3mL distilled water and 10 drops of
placed in an analytical balance and then the tare KI/I2 solution were added. Afterwards, 10% NaOH
button was pressed. A few crystals of the unknown were added dropwise until the dark purple-brown
were added until the balance reads about 0.1g. The solution fades to yellow. It was then heated at 60oC in
mass of the unknown was recorded. Making sure that water bath. More KI/I2 solution was added when the
the crystals were completely submerged, the final solution became colorless. Observations were
volume of the liquid in the cylinder was read and recorded. The formation of a yellow precipitate or
recorded as the final volume. The volume of the solid suspension of iodoform is a positive test (ketone).
(Vfinal – Vinitial) was then computed, as well as the
density (D = m/v) and were recorded. Fehling’s Test
An equal volume of Fehling’s A and Fehling’s
The classification tests performed were: B were mixed in a test tube (deep blue color). A few
crystals of the unknown were then added, and the
Bromine Solution solution was shaken well. Afterwards, this was placed
A few crystals of the unknown were placed in in a water bath for 3-5 minutes and then observations
a test tube. A 1 mL distilled water was added and was were recorded immediately. Disappearance of blue
shaken. Bromine in water was then added drop by color and formation of a brickred precipitate means
drop. Observations were recorded. Disappearance of
Page 2 of 5
SY 2016 - 2017
IDENTIFICATION OF UNKNOWN ORGANIC COMPOUNDS
Department of Chemistry, College of Science, Bicol University, Legazpi City
INTRODUCTION After these preliminary tests, the solubility test
was performed. First, 2mL of water was pipetted into
The analysis and identification of unknown a test tube and then a few crystals of the unknown
organic compounds constitutes a very important were added. The solution was shaken. Solubility of
aspect of experimental organic chemistry. One could the unknown was observed. If the unknown dissolved
easily have an idea of what the unknown compound in water, the same procedure will be done but using
is, in cases such as chemical reactions. However, ether as the solvent. If the unknown is insoluble in
when a compound is isolated from a natural source, water, the solubility of the unknown will be tested
one may be left clueless as to what the compound can with 5% NaOH. The next steps will be done
be. Discovering the identity of an unknown organic according to the solubility flowchart (Figure 1) until it
compound requires figuring out which functional lands into a solubility class. The solubility of the
groups it contains and determining its molecular unknown in the following reagents indicates the class
structure. of compound where it belongs and will be the basis of
the classification tests to be conducted later on.
The purpose of this laboratory activity was to
identify the functional groups present in the given
unknown, and eventually identify what organic
compound the unknown is. In order to accomplish
this, a variety of different tests were done. First,
preliminary tests were conducted. Afterwards,
solubility tests were run. Physical properties (density,
melting point) were also determined. The results of
the solubility tests can indicate the size and polarity of
an unknown compound, which can narrow down the
possible functional groups in the unknown. Once the
options were narrowed, further classification tests
were run. These tests were used to identify specific
functional groups in the unknown sample.
METHODOLOGY
Preliminary tests were first conducted. The
physical characteristics (physical state, color, odor) of Figure 1. Classification of organic compounds by
the unknown was noted. An ignition test was also solubility (see Table 1 for compounds comprising each
performed by heating a small amount of the unknown class). sol. = soluble, insol. = insoluble; litmus red is at
(about 0.1 g) on a metal spatula. The flame produced pH below 4.5 and blue above 8.3.
was observed (luminous or sooty).
Page 1 of 5
, Organic Analysis Laboratory
SY 2016 - 2017
the orange-red color of bromine means the compound
is unsaturated while no disappearance means that the
compound is saturated.
Potassium permanganate Solution
A few crystals of unknown were dissolved in
ethanol. Then, 2% of KMNO4 solution was added
dropwise. Observations were recorded. The
disappearance of the KMNO4’s color and the
appearance of a brown suspension of MnO2 is a
positive test (unsaturated hydrocarbons: alkenes,
alkynes, aldehydes, phenols, aromatic sidechains).
Ferric chloride – pyridine Test
A few crystals of the unknown were added to
2mL pure chloroform in a test tube. Next, 2-3 drops
of 1% solution of anhydrous ferric chloride in
Table 1. Organic Compounds Comprising the Solubility chloroform was added followed by 3 drops pyridine.
Classes of Figure 1 The solution was shaken and the observations were
recorded immediately. The production of a blue,
To determine the density, 5mL of the solvent violet, purple, green, or red-brown solution is a
in which the unknown was not soluble in the previous positive test (phenols).
procedure was placed in a 10mL graduated cylinder.
The volume was read to the hundredth decimal place Iodoform Test
value and recorded as the initial volume. Next, the A few crystals of the unknown were placed in
graduated cylinder containing 5mL of solvent was a test tube and 3mL distilled water and 10 drops of
placed in an analytical balance and then the tare KI/I2 solution were added. Afterwards, 10% NaOH
button was pressed. A few crystals of the unknown were added dropwise until the dark purple-brown
were added until the balance reads about 0.1g. The solution fades to yellow. It was then heated at 60oC in
mass of the unknown was recorded. Making sure that water bath. More KI/I2 solution was added when the
the crystals were completely submerged, the final solution became colorless. Observations were
volume of the liquid in the cylinder was read and recorded. The formation of a yellow precipitate or
recorded as the final volume. The volume of the solid suspension of iodoform is a positive test (ketone).
(Vfinal – Vinitial) was then computed, as well as the
density (D = m/v) and were recorded. Fehling’s Test
An equal volume of Fehling’s A and Fehling’s
The classification tests performed were: B were mixed in a test tube (deep blue color). A few
crystals of the unknown were then added, and the
Bromine Solution solution was shaken well. Afterwards, this was placed
A few crystals of the unknown were placed in in a water bath for 3-5 minutes and then observations
a test tube. A 1 mL distilled water was added and was were recorded immediately. Disappearance of blue
shaken. Bromine in water was then added drop by color and formation of a brickred precipitate means
drop. Observations were recorded. Disappearance of
Page 2 of 5
