MAKING CIS AND TRANS-POTASSIUM DIOXOCATODIACUCHROMAT (III)

A. BACKGROUND
1. GENERAL REVIEW
Complex compounds according to Ramlawati (2015: 1) are compounds that are composed
of one central atom where these central atoms are in the form of metals or groups of atoms such
as VO, VO2, and TiO which are surrounded by a number of anions or neutral molecules. Where
anion or neutral molecule that surrounds the central atom or group of atoms is called a ligand.
When viewed from the Lewis acid-base system, the central atom or group of atoms in the
complex compound acts as a Lewis acid, while the ligand acts as a Lewis base. Whereas
according to Saito (1996: 122) said that complex compounds are metal ion compounds that
coordinate with ligands. Where most ligands are neutral or anionic substances but cations, such
as tropylium cations are also known. So it can be concluded that complex compounds are
compounds composed of central atoms in the form of metal ions which bind to ligands.
Ramlawati (2005: 1) in his book says that complex compounds can also be called
coordination compounds. Due to the mention of complex compounds, it can directly refer to
coordination compounds, and vice versa. This can happen because at the ligand and the central
atom a bond is known as a coordination covalent bond in which all electrons are used to form
bonds coming from ligands. Where also explained by Saito (1996: 122) that neutral ligands such
as ammonia (NH3) or carbon monoxide (CO) in a free state are also stable molecules, while
anionic ligands, such as Cl- or C5H5-, are stabilized only if coordinated to atoms metal center.
The bond that occurs in complex compounds according to Ramlawati (2015: 1) is a bond
between a ligand and a central atom where this bond is a covalent coordination bond, so complex
compounds are also called coordination compounds. The number of ligands surrounding the
central atom is called a coordination number. The amount of complex charge is determined by
the sum of the central ion charges and the number of ligand loads that make up the complex.
Where also explained by Saito (1996: 122) that ligands with one binding atom are called
monodentate ligands, and which have more than one binding atom called polydentate ligands,
which are also called chelate ligands. The number of atoms tied to the central atom is called the
coordination number. Determination of coordination numbers is influenced by the size of the
atomcentral metal, number of electrons d, ligand steric effect. More explanation about ligand
classification is explained by Ramlawati (2005: 8), ligands that join metal ions can be grouped as
follows:
a. Monodentate ligand
Ligands that are only able to give one electron pair to one central metal ion in a coordinating
compound are called monodentate ligands. For example all halide, ammonia, water and PR3
ions.
b. Bidentate Ligand
Ligands that have two donor atoms so that they can provide two pairs of electrons are called
bidentate ligands. The result of forming the coordination number of the bidentate ligand
produces a ring structure with metal ions.
c. Polydentate ligand
Polydentate ligands include ligands that have more than two donor atoms. These ligands can
be called tri, tetra, penta or hexate depending on the number of donor atoms.
Geometric isomers that have two groups located on one side of the phi bond are called
cis (latin, "on the same side"). Clusters located on opposite sides are called trans (latin,
"opposite"). The physical properties of compounds belonging to the cis isomer and compounds
belonging to the trans isomer are certainly different, even though the sequence of bonds of
atoms and the location of their double bonds is the same. This pair of isomers belongs to the
category of geometric isomers, better known as cis-trans isomers. Cis-trans isomers are
different stereo-isomers because groups are on one side or on opposite sides of the molecular
description (Fessenden & Fessenden: 1986: 113).
Complex compounds experience stereoisomer or space atomism which is the occurrence
of compounds that have the same molecular formula, but have different configurations.
Homogenization is distinguished by geometric atomization and optical atomization. Geometric
isomers are owned by organic compounds that have a double bond between the carbon chains.
The difference in one isomer with another isomer is in the location or substituent of double
bonds. The more double bonds in a compound, the more complex the geometric isomers are.
While the optical isomer is owned by compounds that have asymmetrical carbon atoms. So, this
is owned by compounds that have carbon atoms whose four hands bind atoms or groups that are
different or not the same (Sumardjo, 2009: 48 and 50).
 The cis-trans isomer of cycloalkanes is a type of stereoisomer, also called a geometric
isomer, whose substituents are on the same side called cis or the opposite position is called a
trans on the ring. Example on 1,2-dimethylcyclopentane. Both methyl groups can be on the same
side of the ring plane or on the opposite side.
H H

H tidak
H H H
H H
CH3 CH3 CH3 H
H H H H
berinterkonversi
H H H CH3
cis-1,2-dimetilsiklopentana trans-1,2-dimetilsiklopentana
o
td 99 C td 92oC

The two methyl groups are said to be cis if they are in the same position and trans when they are
in a different position from one another. Cis-trans isomers differ from each other only from the
position of atoms or clusters in the room. These differences provide differences in physical
properties and chemical properties, for example at the boiling point (Hart et al. 2003: 62).
Stereoisomeric stereomomers have the same carbonyl framework and the subtituents have
identical reochochemistry, but they are different in terms of the arrangement of atoms in three-
dimensional space. Each isomer has a relative configuration which can only be configured to
other isomers by breaking and forming bonds. Stereoisomers containing two or more stereogenic
centers are called diastereomers (diastereoisomers). Diastereomers are stereoisomers that are not
enantiomers, in other words one is not another mirror image (Willis and Willis 2004: 68).
2. REVIEW OF RESULT
A complex mixture of cis and trans forms can be made by mixing non-complex
components (complex constituents) based on differences in solubility between the cis and trans
forms so that the two types of isomers can be separated. For example trans-dioxalatodiakuochrom
(II) chloride can be made by slowly crystallizing by evaporating the solution containing a mixture
of cis and trans forms. With evaporation, the equilibrium of the cis ↔ trans form can be shifted to
the right because the isomeric trans isomers are lower than the cis isomers. This separation can
also be done by regulating the conditions of the solution in such a way that the cis and trans
solubility are different (Inorganic Chemistry Lecturer Team, 2019: 30).
The synthesis of pure bis (glycineato) copper (II) isomers was not available through the
main supplier, the cis isomer was synthesized according to preparations reported by O'Brien. The
crude product, after being filtered from the icecooled residual liquid, is recrystallized once from
water/ ethanol 50:50 v/ v, producing bright blue acis-cis-(Glycinato) copper (II). The appropriate
trans isomer is synthesized twice using two procedures reported by O'Brien, producing sparkling
platy products. Saturated isomeric solutions in water are prepared before measurement. After
thorough mixing, the solution is centrifuged for 2 minutes at 13,000 rpm (eppendorf centrifuge
5415 R) to ensure that there is no solid product in the liquid phase. Due to the fact that the mid-
infrared spectrum of solid copper and trans-bis (glycine) copper (II) differs significantly in the
area of low wave numbers, the spectrum is recorded between 1800 and 800 cm - 1 at a resolution
of 4 cm - 1. Pure water used for measurement background correction during IR spectroscopy
which allows detection of dissolved sensivitve. Oxalate ligand is coordinated ochahedrally in
both metal ion nuclei (Lutz et al. 2013: 1505).
Complex compounds that have been successfully synthesized have the chemical formula
K[Cr(C2O4)2(H2O)2].2H2O and [N(n-C4H9)4][CrFe(C2O4)3].H2O. Complex compounds
K[Cr(C2O4)2(H2O)2].2H2O has two isomers, namely cis-K[Cr(C2O4)2(H2O)2]. Purple 2H2O and
trans-K[Cr(C2O4)2(H2O)2].2H2O which is red-purple. Solid trans-K isomer [Cr(C2O4)2(H2O)2].
2H2O can change to cis-K[Cr(C2O4)2(H2O)2].2H2O within five months. This is indicated by
changes in the color of solids of complex compounds. Both K[Cr(C2O4)2(H2O)2 isomers]. 2H2O
dissolves in water and the solution is relatively unstable to produce complex compounds K3[Cr
(C2O4)3]. Similarly, the instability of complex compounds [N(n-C4H9)4][CrFe(C2O4)3].H2O
which changes color from golden yellow to dark brown (Kurnia, 2016: 11).
One of the ingredients used is oxalic acid where oxalic acid has an anhydrous structure,
rhombic pyramid, odorless, hygroscopic and white. Commercially, as a product more commonly
found in its derivative form consisting of monoclinic p-isma, odorless and containing 71.42%
oxalic acid dihydrate and 28.58% oxalic acid dehydrate and 28.58% oxalic acid dehydrate.
Oxalic acid can be smooth to coarse grains. Oxalic acid as well as other organic acids also
experience salting with alkaline and esterification with alcohol (Dewati, 2015: 31).
Cis-siklooktena was accompanied by heat evolution after addition of TBHP, suggesting
that oxidative decarbonation was exothermic. This, at least in part, is responsible for the rapid
conversion to cycloocene oxide together with a smaller dilution factor and thus increases the tofs
(210 - 500 h - 1) at a reaction temperature higher than 55 ° C, conversion of cycloocene to cis
epoxide is very fast and quantitative results are obtained within 10 minutes after addition of
oxidants (Grover, 2014).
B. OBJECTIVE OF EXPERIMENT
Study the making and properties of cis and trans isomers from potassium complex salts
dioxalatodiakuokromat (III)
C. TOOLS AND MATERIALS
1. Tools
a. 100 mL chemical glass
b. 200 mL chemical glass
c. Watch glass
d. Spirits burners
e. Three legs and gauze
f. Vacuum pump
g. Ordinary mouthpiece
h. Stirring rod
i. Evaporation cup
j. Drop pipette
k. 50 mL measuring cup
l. Erlenmeyer flask 250 mL
m. Spray bottle
n. Analytical balance
o. Spatula
2. Material
a. Potassium dichromate (K2Cr2O7)
b. Oxalic Acid (H2C2O4.2H2O)
c. Ethanol (C2H5OH)
d. Dilute Ammonium (NH4OH)
e. Aquades (H2O)
f. Wathman filter paper
g. Regular filter paper
h. Matches
i. Tissue
D. WORK PROCEDURE
a. Preparation of the trans-potassium dioxahalodiacochromatous isomer (III)

Weigh 12 grams of oxalic Put in a 200 mL Dissolve with

acid dihydrate beaker distilled water

II

Weigh 4 grams of Put in a 200 mL Dissolve with hot Cover with a watch
potassium dichromate beaker distilled water glass

II

Strain the crystals Steam at room temperature Steam until the volume is
obtained for the remaining one third half left

Cuci kristal dengan Dinginkan dengan Keringkan

Dry kristal lalu catat hasilnya
the crystals and
Wash the crystals
aquades dingin Cool alkohol
with alcohol dan nyatakan dalam persen
with cold distilled record the results and
water state in percent
b. Preparation of cis-potassium dioxalatodiacochromat isomer (III)

Weigh 4 grams of Weigh 12 grams of Put it into the vaporizer Drop aquades
potassium anhydrous oxalic acid cup
dichromate

Tutup
Coverdengan
withgelas
a
Aduk until
Stir sampai it Tambahkan
Add 20 20mL
mL watch arloji
glass
Lakukan dekantir mengendap etanol
Do decantation settles ethanol

Add more ethanol until the Saring dengan

Strain with pompa pump
a vacuum vakum Weigh the crystals
crystal is fully obtained obtained

Isomer purity test

observed!
cis forms a dark green solution
and quickly spreads

Complex crystals on A small amount of trance forms a light brown solid

filter paper ammonium solution that remains insoluble
is added
E. OBSERVATION RESULT
1. Preparation Of Trans Isomer Potassium Dioxalatodiaquo Chromate (III)
No Activity Result

1 Weight ± 12 g of oxalic acid + aquadest White solution

2 Weight ± 4 g of potassium dichromate + hot aquadest Orange solution

3 Mix oxalic acid solution nd potassium dichromate Dark green solution

solution
4 Evaporate mixture until half volume with heated Dark green solution

5 Evaporate mixture in room temperature until 1/3 Dark green solution

volume
6 Filter mixture and wash with cold water Crystal wasn’t formed

2. Preparation Of Cis Isomer Potassium Dioxalatodiaquochromate (III)

No Activity Result

1 Weight ± 12 g of oxalic acid and ± 4 g of potassium

dichromate

2 Added with 1 drop of aquadest Mixture become black

and there is bubble

3 Added 10 mL of alcohol 95% while stirred There is form dark

green precipitation

4 Mixture was decanted and wash with alcohol 96% until There is form dark
3 times green solution and
crystal

5 Crystal was filtered and weighted Black crystal, 14.911 g

3. Purity Of Isomers Test

No Activity Result

1 Crystal of cis and trans was added with some drops of Crystal was dark green
 dilute ammonia become dark purple

F. DATA ANALYSIS
Knowed : Mass H2C2O4 = 12 gram
Mr H2C2O4 = 126 g/mol
Mass K2Cr2O7 = 4 gram
Mr K2Cr2O7 = 294 g/mol
Mr K[Cr(C2O4) 2(H2O) 2] = 303 g/mol

Trans crystal experiment mass = 0 gr

Cis crystal experiment mas = 14.911 gram
Asked : Crystal Rendement = …?
Solution :
a. Trans
n H2C2O4. 2 H2O = m H2C2O4. 2 H2O
Mr H2C2O4. 2 H2O
= 12 gram
126 gram/mol
= 0,095 mol

n K2Cr2O7 = m K2Cr2O7
Mr K2Cr2O7
= 4 gram
294 gram/mol
= 0,014 mol

Reaction :

7 H2C2O4.2H2O + K2Cr2O7 2 K[Cr(C2O4) 2(H2O) 2] + 6CO2 + 2H2

Initial : 0,095 mol 0,014 mol - - -
Reaction : 0,095 mol 0,014 mol 0,027mol 0,081 mol 0.027 mol
Meaning : - - 0,027 mol 0,081 mol 0.027 mol
mass of K[Cr(C2O4)2(H2O)2] = n x Mr
= 0,027 mol x 303 gram/mol
= 8,181 gram
% Crystal trans Rendement = m experiment x 100%
m theory
= 0 gr x 100%
8,181 gr
= 0%
b. Cis
n H2C2O4. 2 H2O = m H2C2O4. 2 H2O
Mr H2C2O4. 2 H2O
= 12 gram
126 gram/mol
= 0,095 mol

n K2Cr2O7 = m K2Cr2O7
Mr K2Cr2O7
= 4 gram
294 gram/mol
= 0,014 mol

Reaction :
7 H2C2O4.2H2O + K2Cr2O7 2 K[Cr(C2O4) 2(H2O) 2] + 6CO2 + 2H2
Initial : 0,095 mol 0,014 mol - - -
Reaction : 0,095 mol 0,014 mol 0,027mol 0,081 mol 0.027 mol
Meaning : - - 0,027 mol 0,081 mol 0.027 mol
mass of K[Cr(C2O4)2(H2O)2] = mol x Mr
= 0,027 mol x 303 g/mol
= 8,181 gram
% Crystal cis rendement = m experiment x 100%
m theory
 = 14,911 gr x 100%
8.181 gr
= 182.3 %
G. DISCUSSION
This experiment was entitled the making of cis and trans-potassium dioxalodiacochromat
(III). Potassium dioxalatoacochrome (III) complex salts have several isomers. Isomers are
chemical compounds that have the same molecular formula which means that they consist of the
same number of the same type of atom but have different structures or settings in space. The aim
of this experiment was to study the manufacture and properties of cis and trans isomers from
potassium dioxalatoacochromatous (III) salt. Cis-trans isomerism is a form of stereoisomerism
that explains the orientation of functional groups in a molecule. Cis stereoisomers, when
substituent groups are oriented in the same direction, while stereoisomers are trans when
substituents are oriented in the opposite direction.
1. Preparation of the trans-potassium dioxalatodiacochromatous isomer (III)
Trans isomers are geometric isomers when substituent groups are oriented in the opposite
direction. Making trans-potassium isomer dioxalatodiakuochromat (III)
is done by dissolving potassium dichromate (K2Cr2O7) using hot
distilled water and reacting it with oxalic acid dihydrate
(H2C2O4.2H2O) which has been dissolved with a small amount of
distilled water. low so it requires energy (heat) to dissolve it. Potassium
dichromate functions as a provider of central Cr atoms in the salt
compound of the trans-potassium dioxalodiacochromatous (III)
complex. While oxalic acid dihydrate functions as a provider of C2O42-
oxalate ligand and H2O ligand.
Both solutions are mixed and closed using a watch glass, and a black solution is formed.
The closure function uses a watch glass so that there is no equilibrium between cis and trans
crystals and to avoid the occurrence of explosions. During the reaction solution the system
undergoes an exothermic reaction accompanied by the release of CO2 and water vapor. The
reaction produces a black and bubbly solution which indicates that the complex compound
potassium dioxalodiacochromat (III). The reactions that occur are:
 K2Cr2O7(aq) + 7H2C2O4.2H2O(aq) 2 K[Cr(C2O4)2(H2O)2](s) + 6CO2(g) + 17H2O(g)
Orange Colorless Black

The solution obtained is then evaporated until the volume

becomes half of the initial volume then the solution is left to evaporate
itself at room temperature until the volume becomes 1/3 of the initial
volume. This evaporation aims to evaporate unwanted H2O residues so
as not to affect the formation of complex potassium
dioxalodiacochromate (III) compounds. Then filtering the solution aims
to separate the crystals from the solvent. But this treatment is not
obtained by crystals caused by a less than optimal evaporation process
so that there is still a lot of H2O in the solution. The geometric structure
of the trans-potassium dioxalatodiacochromate (III) crystal is octahedral.
O
C OH
O O
C

O OH2
HO
K Cr OH
H2O O

C
O
O
C
HO
O

Trans-potassium dioxalodiacochromate (III)

2. Preparation of cis-potassium dioxalatodiacochromate isomer (III)

Cis isomers are geometric isomers, when substituent groups are oriented in the same
direction. Preparationof cis-potassium dioxalatodiakuochromat (III) isomer was carried out by
mixing H2C2O7.2H2O crystals with K2Cr2O7 crystals in a vaporizer dish. H2C2O4.2H2O functions
as a provider of C2O42- ligand and H2O ligand while potassium dichromate (K2Cr2O7) functions
as a provider of central Cr atoms in the trans-potassium dioxalatodiacochromatous (III) salt
compound. The mixture is stirred so that it mixes, evenly then dripped with distilled water and
covered with a watch glass. The addition of a drop of distilled water serves to shift the cis-trans
equilibrium towards the cis, because cis-potassium dioxalatodiacochromat (III) has a low
solubility. Closing using a watch glass serves to prevent crystals from participating in
evaporating with CO2 and H2O due to the occurrence of exothermic reactions in the solution,
followed by the release of CO2 and water vapor so that the watch glass.
 Then a black solid is obtained and then washed with ethanol to
destroy black solids into crystalline powder and bind unwanted H2O
residues. Washing is done 3 times so that the crystal obtained is clearer.
this solution is added with the function to precipitate/solidify all
deposits formed to form a denser black precipitate. The reactions that
occur are as follows:

7H2C2O4.2H2O(s) + K2Cr2O7(s) + H2O → 2K[Cr(C2O4)2(H2O)2](aq) + 6CO2(g) + 18H2O(l)

Colorless Orange Black

The decantant solution is then used to separate the crystals from

the filtrate and the impurities. Furthermore added with ethanol to
improve the formation of black deposits. The black precipitate is then
filtered using a Buchner funnel. Filtering is done by using a Buchner
funnel to speed up the filtering and to obtain maximum results, until the
results are 14.911 grams. Based on the results of data analysis, the
percent yield was 182.3%. The geometry of the trans-potassium crystal
diocalatodiakuochromat (III) is:
O
HO C
O O
C

H2O O
K Cr
OH

H2O O OH
C O
O
HO C
O

Cis-kalium dioksalatodiakuokromat (III)

3. Isomer Purity Test

The test aims to differentiate between cis and trans isomers from potassium
dioxalodiacakuchromat (III) salts using a dilute ammonia solution as the test material. Ammonia
is used as a test material because ammonia is a strong ligand that can force ligands found in
complex salts. The resulting complex salt will give a different color. The purity testing of trans
potassium dioxalodiacochromate (III) crystals was not carried out because Crystal was not
obtained. While in the cis-potassium dioxalodiacochromat (III) crystals it was also not carried out
according to the theory that the precipitate of the cis-potassium dioxalatodiacochromat (III)
isomer if reacted with ammonium hydroxide produced a green solution and spread on filter paper.
H. CONCLUSSION
The properties that distinguish cis and trans isomers include the nature of their solubility
where cis is of high solubility while trans is low. In addition, the trans isomer has a form that
does not spread while the crystal cis spreads. The crystal mass obtained in the trans is 0 grams
with a yield of 0%. Then the yield obtained for cis is 182,3% with a mass of 14,911 grams
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