THE
DETERMINATION OF UNKNOWN SOLID ORGANIC COMPOUND BY QUALITATIVE ANALYSIS
By
Ni
Luh Gede Enik Karnila Yanti
Chemistry
Education Department, Faculty of Mathematics and Natural Sciences, Ganesha
University of Education
email:
enikkarnilayanti@yahoo.co.id
Abstract
The aim of the
experiment was to determine (1) physical
properties of unknown solid organic compound, (2) the elements contained in the
unknown solid organic compound, (3) the
functional groups contained in the unknown solid organic compound, and (4) derivation compound of the unknown
solid organic compound. Laboratory assistant prepared the unknown solid organic
compound as subjects of the experiment. The object was the structure of the
unknown solid organic compound. It was obtained through qualitative analysis
are the physical and chemical properties of the unknown solid organic compound.
The physical properties of the unknown solid organic compound has melting point
of 1200C-120.50C. The element analysis of unknown solid
organic compound results carbon, hydrogen and oxygen. The functional group and
derivative analysis it has unsaturated bond, aromatic structure, positive of
phenol group and phenol derivative. The physical and chemical properties of the
unknown organic compound were similar to the physical and chemical properties
of 2-Naphthol, that means that the unknown sample is definitely 2–naphthol.
Key word: organic
compound, qualitative analysis, 2-Naphthol
INTRODUCTION
Chemical
compounds are abundant compound in nature and it has many types. To facilitate
the studied of its properties required an identification steps. The
identification of organic compound can be done with the chemical test
especially in the functional groups (Muderawan & Suja, 2008). Qualitative analysis is important to be done for knowing
the uknown organic substances, that are physical properties, analysis of element,
identification of functional group and determination of derivative (Nurlita
& Suja, 2004)
The physical properties for solid organic substance is melting point. Melting point is temperature where solid
substances change to liquid substance at one atmosphere. In general melting
point of organic substance easy to observe because the temperature when start
to melt almost the same when all sample melt (the range of the temperature not
more than 0.50C).
To identify the
existence of carbon and hydrogen element in organic compounds, can be done by
adding copper (II) oxide, the test carbon and oxygen can be continued with
testing CO2 and H2O. The presence of H2O can
be observed in the presence of water vapor and the test of CO2 can
be seen the turbid was formed.. The reaction is as follows.
CxHy
+ CuOàCu(s)
+ H2O(g) + CO2(g)
Detection the
existence of oxygen was used ferox reagent. Ferox reagent is prepared by
dissolving separately KSCN and FeCl3, in methanol, and then it were
mixed. Then it solution was dropped into filter paper and cause the red color.
This paper called ferox paper. Then the substance will be tested oxygen content
was dissolved in benzene, hydrocarbons or toluene, after that dropped into
ferox paper. If positive of oxygen, ferox paper will changes to bright red
color.
Identify the
existence of nitrogen, sulfur, and halogen can be done by Lassaigne test. The
principle of this test is transforming the elements that bond in the form of
covalent bond in organic substance into ionic sodium salt (Nurlita & Suja, 2004) . In this
reactions, the nitrogen in hydrocarbon turn into dark purple of sodium cyanide,
halogen turn into sodium halide, and sulfur turn into sodium sulfide (Anwar, Purwono, Pranowo, & Wahyuningsih, 1994)
Functional
groups were very large influence for the properties of organic compounds.
Several functional groups that are often found in organic compounds are
hydroxyl (-OH), carbonyl (-CO), amino (-NH2), carboxyl (-COOH), oxo
group (-O-), nitro (-NO2), double bond and triple bond. To identify
organic compounds, can be done with a series of test with chemical reactions to
determine the functional groups present in organic compounds.
The test can be
done to identified double bond in organic compounds are bromine test in CCl4
and with alkaline KMnO4 test (Baeyer test). Baeyer test will
be positive in the double bond and a triple bond, but it cannot be done on
compounds that have aromatic rings. Reaction with KMnO4 can also
occur in compounds that easy to oxidation such as aldehydes, some alcohol,
phenol and aromatic amine compounds. Baeyer test was done by adding an alkaline
KMnO4 solution into the sample. Ion MnO4- will was
reduced to MnO2 so KMnO4 color fading. The reaction is as
follow :
Ethane (colorless
) + 2 MnO4(violet)
+ 4 H2O
à
HO-CH2-CH2-OH(colorless ) + 2 MnO2(brown)
+ 2 OH-
The second test
for identified double or triple bond is bromine test. Organic compounds
containing unsaturated bonds can cause fading color on bromine solution. This reaction
was called addition reactions. The reaction is as follow:
Ethane
+ Br2àBr-CH2-CH2-Br
Colorless red
colorless
Test of
aliphatic or aromatic properties of organic compounds can be done by testing
the fumes. If organic compounds are positive of benzene ring (aromatic) the
fumes will form when heated. This is because the stability of the benzene rings
which makes it difficult to be oxidized. So that when the combustion process
(warming) the fumes form because incomplete combustion (difficult oxidized).
However, if there is positive of aliphatic organic compound, when heating
(combustion) no fumes were formed, because the combustion process is complete.
Phenol is an
alcohol, in which the-OH functional group bond to the benzene ring. The formula
of phenol is C6H5-OH in form of pure colorless
crystalline, odorless (carbolic acid), antiseptic, little soluble in water and
as a weak acid (weaker than carbonic acid). These compounds can react with
bases to form salts, such as NaOH produces Na-phenolic. Identification of
phenol can be done by phenol color test by using FeCl3. Where the compound
(FeCl3) is reacted with phenol will produce complexes of green
color. The reaction is as follows:
6 C6H5-OH + FeCl3 à (Fe(OC6H5)6)3- + 3 Cl-
+ 6H+
Aldehydes group
(R-CHO) can be identified through Tollens Test. The reactions occur is as follows:
RCHO + 2Ag(NH3)2+
+ 2HO- →2Ag(silver
mirror) + RCOO- + H2O + NH4+
+NH3
.Ketone group
(R-CO-R) can be identified through DNP and Iodoform Test. The reactions occur
in DNP test is as follows:
Carboxyl group (R-COOH) can be identified
through sodium bicarbonate and ester formation test. The reactions occur in
Ester formation test is as follows:
RCOOH + R’OH 
RCOOR’ + H2O
RCOOR’ + H2O
METHOD
Equipments and
Materials
Experiment was done at organic chemistry laboratory Ganesha
University of Education. This experiment need time approximately 24 hours to
finish all steps. To conduct the experiment need some equipments and materials.
The equipment used are a capillary pipette, two spatula, three watch glass, a metal
block, a thermometer, three 100 mL beaker glass, six test tube and a rack, a
non pyrex test tube, a graduated cylinder, a Erlenmeyer, a funnel, three drop
pipettes, a stirrer road, a holder, a spirits burner, heater, a electrical
balance, and a box of matches. While the materials was used are solid of
unknown sample, powder of dry copper oxide, KSCN solid, FeCl3 solid,
20 mL methanol, benzene, toluene, small amount of sodium, hydrocarbon, ethanol,
500 mL of distilled water, 2 mL of CH3COOH solution, two drops of Pb-acetate
solution, 5 mL of sodium nitropusid solution, 10 mL FeSO4 solution, 5 mL NaOH
solution, concentrated H2SO4 solution, 10 mL HNO3
solution, AgNO3 solution, NH4OH solution, limestone, 5 mL
CCl4 solution, 5 mL fiber-ammonium-nitrate solution, Br2
solution 5%, 3 drops acetyl chloride solution, strong ammonia solution, 5 drops
FeCl3 solution, 1 mL Fehling A solution (acetate of CuSO4),
1 mL Fehling B solution (NaOH of Rochelle salt), ammonia solution, diluted HCl
solution, I2 solid, KI solid, 2 mL NaOH, 2 mL 10% NaHCO3 solution,
ethyl alcohol solution, strong H2SO4 solution, saturated
hydroxylamine hydrochloride solution, KOH solution, nitric acid solution, CaCl2
solution, dry acetone, benzyl amine solution, NaHCO3 solution 5%, KBr
solid, phenol solution, perchlorate acid solution 60%, ethanol solution 10-20%,
2,4-DNP solid, sodium acetate solid, pyridine solution, carbonyl compound, strong
ammonium hydroxide solution, triethylamine solid, ethyl or ester ethyl, NH4Cl
solid, bromine solution, NaHSO3 liquid solution, filter paper
Determine
of Physical Properties
Unknown solid
sample was refined by using spatula, then open tip off the capillary pipette
was pressed until the sample was down and condensed with height of 0.5 cm.
after that the capillary pipette and thermometer were added into appropriate
hole in the metal block and heated. The temperature when the sample begins to melt
and the temperature when all sample melt were noted.
Analysis
of Element
Detection
of Carbon and Hydrogen
Unknown solid
sample and dry of CuO were mixed, and then it mixture was poured into test
tube. The mixture was heated until the all of the mixture change to CO2
and H2O. Existence of CO2 gas and water vapor that mean
the sample is contained of C and H.
Detection
of Oxygen
To identify oxygen
was used ferox reagent. Ferox reagent was prepared by KSCN and FeCl3, 1
gram of KSCN in 10 mL of methanol and 1 gram of FeCl3 in 10 mL of
methanol were mixed and the precipitate was filtered (the filtrate consist of
complex compound Fe3+[Fe(SCN6]3- ,
that called ferox reagent). After that unknown solid sample was diluted by
using benzene. Filter paper that was given by ferox reagent was prepared and
dried that called ferox paper. Then sample solution was dropped into ferox
paper, the existence of light red color was indicated positive of oxygen.
Detection
of Nitrogen, Sulfur and Halogen
Detection the
existence of nitrogen, sulfur and halogen was used extract of sodium or Lassage
filtrate. Unknown solid sample was placed into test tube and small amount of
sodium that was dried by filter paper was added, and then the sample was heated
until incandescent to found perfect reaction. After that ethanol was added to
remove excess of sodium, next the mixture was heated until produce red color.
Then the mixture was dissolved in distilled water with breaking the test tube.
The solution was filtrated to get Lassaigne filtrate.
Detection of
sulfur element can be done by some process are, 2 mL of sodium extract were acidified
by acetic acid and it were heated. Filter paper was added into solution of
Pb-acetate 10%, then the filter paper was approximated to the test tube and the
change color of filter paper was observed (black color indicated there is
sulfur). After that sodium nitropuside was dropped into the rest of filtrate in
test tube, (black color indicated there is sulfur).
The process needed to detection the
existence of nitrogen element are, 2 mL of sodium extract were added into FeSO4
solution (Mohr salt), then it ware heated until boiling. If there was no
precipitate, NaOH solution was added and it was heated until form green
precipitate. After that the precipitate was cooled and acidified until the
precipitate soluble, and then the change occur was obsrerved (if contain of N
element will appears blue-green or blue suspension).
To indentify the existence of halogen
there are some steps are, 2 mL of sodium extract were acidified by using
concentrated of HNO3 and it was boiled. After that, the mixture was
cooled and 1 mL of AgNO3 was added. If there is halogen, white
precipitate or yellowish precipitate will form. The last, precipitate was
diluted by NaOH to determine the existence of halogen.
Detection
of Functional Group
Detection
of Unsaturated
To detection the
unsaturated was used two method are Baeyer test and bromine test. In Baeyer
test unknown solid sample was diluted by using water, then Baeyer solution
(KMnO4 solution) was added drop by drop, and it was shake. If the color of KMnO4
was fades that mean sample in positive consist of unsaturated bond. The second
method is bromine test, unknown solid sample was diluted by using CCl4
and 5% Br2 solution in CCl4 was added by drop by drop. If
brown colors change to colorless that mean positive of unsaturated bond.
Detection
of Aliphatic or Aromatic
Unknown solid
sample was taken in the spatula, and then it was heated in flame. If produce
fumes that mean consist of aromatic compound.
Detection
of Hydroxyl Group
Detection of
hydroxyl group can be done by two method are fiber test and acetyl chloride
test. In fiber test, unknown solid sample was added by fiber solution (ammonium
nitrate), if there is red color form that mean positive of hydroxyl group.
While in acetyl chloride test, unknown solid sample was added by two drops of
acetyl chloride, if there is gas produce that mean positive of hydroxyl group.
Detection
of Phenol Group
Unknown solid
sample was diluted by using alcohol then FeCl3 was added drop by
drop. If the colors change to purple, blue and green that means positive consist
of phenol group.
Detection
of Adehyde Group
Detection of
aldehyde group can be done by two method are Fehling test and Tollen test. In
Fehling test, one mL of Fehling A and Fehling B was added into the sample, and it
mixture were heated. If there was the blue color change to red color that mean
the sample consist of aldehyde group. While in Tollen test, mixture of AgNO3,
NaOH, and excess of ammonia (until all of precipitate was dissolved) was added
into the unknown solid sample then it were heated. If there is white
precipitate form that mean the sample consist of aldehyde group.
Detection
of Ketone Group
Detection of
ketone group also use two methods are DNP test and iodoform test. In DNP test,
dilute HCl was added into the unknown solid sample and then 2,4-dinitrophenilhydrazine
was added. After that, the mixture was shaked, if the precipitate was form that
means the sample positive of ketone group. While in iodoform test, 2 mL of
solution of NaOH 10% was added into the sample. After that, iodine solution in
KI were added drop by drop into the mixture, if the brown color change to
colorless color that mean positive of ketone group.
Detection
of Carboxyl Group
Detection of
carboxyl group can be done by two method are Na-bicarbonate test and formation
of ester test. In Na-bicarbonate test, saturated solution of NaHCO3
was added into the sample, if there is bubble that mean positive of carboxyl
group. While in formation of ester test, ethyl alcohol and concentrated
sulfuric acid were added into the sample, and then it was heated. If there is
fragrant smell was form that mean positive of carboxyl group
Making
Derivate of Compound from the Substance that will be Analysis
Derivative
of Phenol
2.5 gram of KBr
and 0.5 mL of bromine were mixed and it was diluted by using 15 mL of water.
After that, phenol solution was prepared and the mixture between KBr and
bromine was added until the color change to yellowish color. Phenol precipitate
was stirred in 25 ml of cold water, and then it was filtered and washed by
NaHSO3. Then it was recrystallization wit ethanol, and the melting point
was noted.
Data that was
obtained was gathered to identify the type of organic compound in unknown solid
sample. The identification was done by comparing the experiment result with
organic chemistry references.
RESULT AND DISCUSSION
The
physical properties especially the melting point of the unknown solid sample is
1200C-120.50C. The result of element analysis was
presented in the table 1 bellow
Detection of C
and H element of unknown solid organic compound water vapor and CO2
gas was produced when the sample heated. The detection of O element bright red
color was produced in the ferox paper. In addition, in detection of sulfur element,
there is no black color was produced, in detection of nitrogen no yellow color
was produced, and in detection of halogen, no precipitate was formed.
While, unsaturated detection of unknown
solid sample was positive because the sample turned from the violet color of
KMnO4 into colorless in Baeyer test and turned the solution into
colorless in bromine test. In aromatic and aliphatic test, it was produced fume
so that indicate the aromatic compound.
The result of
functional group analysis was presented in the table 2 bellow
Table 2. Result of Functional group Detection
Functional
Group
|
Identification
|
Hydroxyl
Group
|
Negative
|
Phenol Group
|
Positive
|
Aldehyde
Group
|
Negative
|
Ketone
Group
|
Negative
|
Carboxyl
Group
|
Negative
|
Functional
group detection of unknown solid sample positive consists of phenol group,
because the sample solution was produced green color when FeCl3 was
dropped. This is possible since the compound is aromatic. The picture of green
color produced as follow
The
physical and chemical properties of this unknown solid compound is identical with
2–naphthol. Tokyo
Chemical Industry Ltd states that the melting point of 2–naphthol
is 1210C while Alfa Aesar states 1200C-1240C.
This compound is brown solid at room temperature and has structure as follow
The melting point of solid unknown sample and 2–naphthol was identical. They have brown colour solid and the elements
are the same. They have unsaturated bond and are aromatic. While, the sample is
also has phenol group. This means that the unknown sample is definitely 2–naphthol.
The
last experiment was identifying the derivatives of unknown solid organic
compound. The derivative as result of this experiment has melting point of 109
– 110oC and is brown solid at room temperature.
CONCLUSION
Based on the
analysis, the unknown solid organic compound is 2–naphthol.
ACKNOWLEDGMENT
Firstly, writer is grateful to the God,
for the unlimited knowledge was created. Then, thanks for lecture Mr. I Nyoman
Tika, M.Si who teach Organic Experiment subject. Thank for the laboratory
assistant, Mr. Lasia who guides the writer in conducting experiment and give
information how to work safely. Also thanks, the lecture assistant, Mrs. Dewi
who guides the writer in conducting experiment. Moreover, the last for all
members of VA class who give great motivation to the writer.
REFERENCES
Anwar,
C., Purwono, B., Pranowo, H. D., & Wahyuningsih, T. D. (1994). Pengantar
Praktikum Organik. Yogyakarta: Departement Pendidikan dan Kebudayaan.
L.G.
Wade, J. (2010). Organic Chemistry. Upper Saddle River: Pearson
Eduation, Inc.
Muderawan, I
Wayan dan I Wayan Suja. 2008. Praktikum
Kimia Organik. Singaraja :Universitas Pendidikan Ganesha
Nurlita,Frieda dan I Wayan Suja.2004.Buku Ajar
Praktikum Kimia Organik.Singaraja : IKIP Negeri Singaraja
Anonymous. Accessed at 16th
September 2013 from http://www.chemspider.com/Chemical-Structure.8341.html
Anonymous.
Accessed at 16th September 2013 from http://www.sigmaaldrich.com/catalog/product/aldrich/185507?lang=en®ion=ID
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