International Chemistry Olympiad 2021 Japan
53rd IChO2021 Japan
25th July – 2nd August, 2021
https://www.icho2021.org

Practical Tasks
Final version

Since 53rd IChO Japan was held in remote form, practical tasks were not included in thecompetition. Therefore, the practical tasks were not discussed by the International Jury.
This booklet is the final version of Practical Tasks prepared for 53rd IChO by the Science
Committee. Since these tasks were not discussed in the International Jury, these tasks are
not official. However, in order to reinforce the importance of the laboratory work inchemistry, we decided to open the unofficial practical tasks prepared for 53rd IChO, despite
they were not approved by the International Jury.
We also prepared videos where all tasks were demonstrated with explanation, andpublished them as one of the activities during 53rd IChO. You can see these videos from the
Web site of 53rd IChO:
https://www.icho2021.org/problems/practical/
We are delighted if those who are inspired by the demonstration will prepare and submit
their original videos in which they will attempt the practical tasks and discussions. Any
reports on the tasks are also highly welcome.
Vice-chair of Science Committee
Nobuhiro Kihara, Kanagawa University

Contents:
Practical Task 1.
Partition coefficient of 2,5-furandicarboxylic acid in a 1-octanol/water system.

P.10

Practical Task 2.
Separation and determination of metal ions using anion-exchange resins.

P.16

Practical Task 3.
Brevity is the soul of wit in organic synthesis.

P.23

2

Physical Constants and Equations
Constants
Speed of light in vacuum, c = 2.99792458 × 108 m s–1
Planck constant, h = 6.62607015 × 10–34 J s
Elementary charge, e = 1.602176634 × 10–19 C
Electron mass, me = 9.10938370 × 10–31 kg
Electric constant (permittivity of vacuum), ε0 = 8.85418781 × 10–12 F m–1
Avogadro constant, NA = 6.02214076 × 1023 mol–1
Boltzmann constant, kB = 1.380649 × 10–23 J K–1
Faraday constant, F = NA × e = 9.64853321233100184 × 104 C mol–1
Gas constant, R = NA × kB = 8.31446261815324 J K–1 mol–1= 8.2057366081 × 10–2 L atm K–1 mol–1
Unified atomic mass unit, u = 1 Da = 1.66053907 × 10–27 kg
Standard pressure, p = 1 bar = 105 Pa
Atmospheric pressure, patm = 1.01325 × 105 Pa
Zero degree Celsius, 0 °C = 273.15 KÅngström, 1 Å = 10–10 m
Picometer, 1 pm = 10–12 m
Electronvolt, 1 eV = 1.602176634 × 10–19 J
Part-per-million, 1 ppm = 10–6
Part-per-billion, 1 ppb = 10–9
Part-per-trillion, 1 ppt = 10–12pi, π = 3.141592653589793
The base of the natural logarithm (Euler's number), e = 2.718281828459045

3

Equations

PV = nRTThe ideal gas law:

, where P is the pressure, V is the volume, n is
the amount of substance, T is the absolutetemperature of ideal gas.
ΔU = q + w

The first law of thermodynamics:, where ΔU is the change in the internal energy, q
is the heat supplied, w is the work done.
Enthalpy H:

H = U + PV

Entropy based on Boltzmann's principle S:

S = kB lnW, where W is the number of microstates.

The change of entropy ΔS:

∆𝑆 =

𝑞!"#
𝑇

, where qrev is the heat for the reversible process.
Gibbs free energy G:

G = H – TS
ΔrG 0 = –RT lnK = –zFE 0, where K is the equilibrium constant, z is thenumber of electrons, E 0 is the standard electrodepotential.

Reaction quotient Q:

ΔrG = ΔrG 0 + RT lnQ
For a reaction

aA+bB⇌cC+dD
𝑄=[𝐶]$ [𝐷]%[𝐴]& [𝐵]', where [A] is the concentration of A.
Heat change Δq:Δq = ncmΔT, where cm is the temperature-independent molar
heat capacity.

Nernst equation for redox reaction:

𝐸 = 𝐸( +

𝑅𝑇
𝐶)*
ln Q
R
𝑧𝐹
𝐶+,-

, where Cox is the concentration of oxidized
substance, Cred is the concentration of reduced
substance.

4

Arrhenius equation:

𝑘 = 𝐴 exp Q−

𝐸&
R
𝑅𝑇

, where k is the rate constant, A is the preexponential factor, Ea is the activation energy.
exp (x) = e x

A = εlc

Lambert–Beer equation:, where A is the absorbance, ε is the molar
absorption coefficient, l is the optical path length,c is the concentration of the solution.
Henderson−Hasselbalch equation:

For an equilibrium
HA ⇌ H+ + A–
, where equilibrium constant is Ka,[A. ]pH = p𝐾& + log ^_[HA]

Energy of a photon:

𝐸 = ℎ𝜈 = ℎ𝑐
𝜆, where ν is the frequency, λ is the wavelength ofthe light.
When x ≠ 1,

The sum of a geometric series:

0/0

1 + 𝑥 + 𝑥 +. . . +𝑥 = j 𝑥 1 =12(Approximation equation that can be used to solve

When 𝑥 ≪ 1,

problems:

1
~1+𝑥
1−𝑥

5

1 − 𝑥 0341−𝑥Periodic Table

6

13

O

H

O

12

-COOH
-SO3H

11

Δδ for one alkyl group-substitution: ca. +0.4 ppm

7
10

-CHO

9
8

Ar H

-CONH2

7

6

H

Ar OH

5

4

RO CH3

Ar NH23

R2N CH3

2

Ar CH3CH3

RCO CH3

R OH

R NH2

1

R CH3

0
b (ppm)

R3Si CH3

1

H NMR Chemical Shifts

Safety
Participants in the Olympiad must be prepared to work in a chemical laboratory and beaware of all relevant rules and safety procedures. The organizers will strictly enforce thesafety rules given in Appendix A of the IChO Regulations during the Olympiad.
The Preparatory Problems are designed to be carried out in properly equipped chemicallaboratories under competent supervision only. We did not include specific and detailed
safety and disposal instructions as regulations are different in each country. Mentors must
carefully adapt the problems accordingly.
The GHS hazard statements (H-phrases) associated with the materials used are indicatedin the problems. Their meanings are as follows:
Physical Hazards
H225

Highly flammable liquid and vapor.

H226

Flammable liquid and vapor.

H227

Flammable liquid.

H228

Flammable solid.

H271

May cause fire or explosion; strong oxidizer.

H272

May intensify fire; oxidizer.

H290

May be corrosive to metals.

Health Hazards
H301

Toxic if swallowed.

H302

Harmful if swallowed.

H303

Maybe harmful if swallowed.

H304

May be fatal if swallowed and enters airways.

H305

May be harmful if swallowed and enters airways.

H311

Toxic in contact with skin.

H312

Harmful in contact with skin.

H313

May be harmful in contact with skin.

H314

Causes severe skin burns and eye damage.

H315

Causes skin irritation.

H316

Causes mild skin irritation.

H317

May cause an allergic skin reaction.

H318

Causes serious eye damage.

H319

Causes serious eye irritation.
8

H320

Causes eye irritation.

H331

Toxic if inhaled.

H332

Harmful if inhaled.

H333

May be harmful if inhaled.

H334

May cause allergy or asthma symptoms or breathing difficulties if inhaled.

H335

May cause respiratory irritation.

H336

May cause drowsiness or dizziness.

H351

Suspected of causing cancer.

H361

Suspected of damaging fertility or the unborn child.

H361d

Suspected of damaging the unborn child.

H361f

Suspected of damaging fertility.

H362

May cause harm to breast-fed children.

H370

Causes damage to organs.

H371

May cause damage to organs.

H372

Causes damage to organs through prolonged or repeated exposure.

H373

May cause damage to organs through prolonged or repeated exposure.

Environmental Hazards
H400

Very toxic to aquatic life.

H401

Toxic to aquatic life.

H402

Harmful to aquatic life.

H410

Very toxic to aquatic life with long lasting effects.

H411

Toxic to aquatic life with long lasting effects.

H412

Harmful to aquatic life with long lasting effects.

H413

May cause long-lasting harmful effects to aquatic life.

Chemicals or substrates with GHS hazard statement H300, H310, H330, H340, H350, andH360 are not allowed to be used in IChO and according activities.

9

Practical Task 1. Partition coefficient of 2,5-furandicarboxylic acid in a 1-octanol/water
system.
‘Biomass chemistry’ is attracting attention as a strategy to break away from the oildependence of human society. Furan derivatives are plant-derived chemicals that can beused as building blocks for new materials. They are made from furfural, which can be easily
synthesized from agricultural waste containing sugars. One furan derivative, 2,5furandicarboxylic acid, has been extensively studied as a raw material for bioplastics.
When using a new material, it is essential to elucidate the effects of the chemical on thehuman body, animals, and plants. It is known that the accumulation of a chemical in livingorganisms is related to its hydrophobicity. The 1-octanol/water partition coefficient is one of
the best indicators of hydrophobicity/hydrophilicity.
The purpose of this experiment is to calculate the partition coefficient of 2,5-furandicarboxylic
acid in a 1-octanol/water system by examining the 2,5-furandicarboxylic acid concentrationsin the 1-octanol phase and the aqueous phase and analyzing its aggregation state in 1octanol.

Chemicals
Substance

Name

State

GHS Hazard
Statement

C6H4O52,5-Furandicarboxylic acid

1-Octanol solution

H319(0.020 mol L-1 )C8H17OH

1-Octanol

LiquidH319, H412

NaCl

Sodium chloride

Aqueous solution

NA

(10%)
NaOH

Sodium hydroxide

Aqueous solution (ca.

H290, H314

0.01 mol L-1)*
C20H14O4

Phenolphthalein

Ethanol solution*Exact concentration will be shown at the examination.

10

H226, H320

Glassware and Equipment- 2 Volumetric flasks, 100 mL- 2 Pipettes- 1 Silicone dropper- 3 Erlenmeyer flasks with stopper, 100 mL- 4 Volumetric pipettes, 20 mL- 3 Volumetric pipettes, 10 mL- 1 Pipettor- 1 Laboratory stand with burette clamp- 1 Burette, 25 mL- 1 Funnel- 3 Conical beakers, 50 mL- 1 Magnetic stirrer- 1 Stirrer bar
For the procedure “Taking an Aliquot of Aqueous Phase B”- 3 Pipettes- 3 Beakers, 50 mL
Procedure
1.

Transfer two 20 mL portions of 0.020 mol L-1 2,5-furandicarboxylic acid solution(Solution A) to a 100 mL volumetric flask (total volume: 40 mL). Fill the flask with 1octanol using a pipette. Homogenize the solution, which is henceforth called Solution
B.

2. Transfer 20 mL of Solution A to another 100 mL volumetric flask (total volume: 20 mL).
Fill the flask and homogenize the solution as above. This solution is called Solution C.
3. Transfer two 20 mL portions of Solutions A, B, and C to 100 mL Erlenmeyer flasks withstoppers (total volume: 40 mL each).
4. Add two 20 mL portions of 10% aqueous NaCl solution to each Erlenmeyer flask (total
volume of the aqueous solution: 40 mL). Seal the Erlenmeyer flasks.
5. Hold each Erlenmeyer flask firmly so that the stopper does not come off, shake itvertically 30 times, and let it stand for 5 minutes. Shake the flask and let it stand 5
times in total. (In general, the partition coefficient depends on the temperature. However,the partition coefficient does not change in the range of 20-30°C in this system. Therefore,
this experiment can be conducted at room temperature without temperature control.)11

6. Transfer 10 mL of the aqueous phase of Solution C to a conical beaker with a 10 mL
volumetric pipette (*Refer to “Taking an Aliquot of Aqueous Phase A or B”). Add a stirrer
bar and 1 drop of phenolphthalein solution. Titrate using 0.01 mol L-1 aqueous sodiumhydroxide solution with stirring. Repeat the titration as needed (the titration can be done
up to 3 times). Similarly, titrate Solution B and A in that order.

* “Taking an Aliquot of Aqueous Phase A”
a. Insert a volumetric pipette into the solution so that the tip is near the center of theaqueous phase.
b. Blow out a small amount of air using a pipettor and push out the solution at the tip.
c. Pull up the aqueous phase so that the none of the oil phase remaining on the bottom
and sides of the Erlenmeyer flask is drawn in.
d. Pull the volumetric pipette out of the solution and wipe off the solution on the outside of
the pipette.
e. Align the meniscus of the solution and the line marked on the pipette.
f.

Transfer the aqueous phase to a conical beaker.

* “Taking an Aliquot of Aqueous Phase B”
a. Insert a pipette into the solution so that the tip is near the center of the aqueous phase.
b. Blow out a small amount of air using a silicone dropper and push out the solution at thetip.
c. Pull up the aqueous phase (more than 10 mL) so that none of the oil phase remaining
on the bottom and sides of the Erlenmeyer flask is drawn in.
d. Pull the pipette out of the solution and wipe off the solution on the outside of the pipette.
e. Transfer the aqueous phase to a beaker.
f.

Transfer the aqueous phase from the beaker to a conical beaker using a volumetricpipette.

12

Results
Record the titration volume.
No.

Volume forVolume forVolume for

Solution Ａ [mL]

Solution B [mL]

Solution C [mL]1
2
3
Volume determined[mL]*It is not necessary to fill in all rows.
Questions1.

Calculate the concentration of 2,5-furandicarboxylic acid in the aqueous phase, 𝐶5 ,and log𝐶5 from the determined titration volume.
Solution Ａ

Solution B

Solution C

Ｃw [mol L-1]
logＣw

2.

Calculate the concentration of 2,5-furandicarboxylic acid in 1-octanol, 𝐶6 , and log𝐶6
using the total amount of 2,5-furandicarboxylic acid.
Solution Ａ

Solution B

Ｃo [mol L-1]
logＣo

13

Solution C

3.

If 2,5-furandicarboxylic acid is present in water at a concentration of 𝐶5 as a single
molecule and in 1-octanol at a concentration of 𝐶6 as an n-molecule aggregate, thepartition coefficient K is calculated using the following equation.
𝐶6
=𝐾
𝐶5 0
Taking the logarithm of both sides, the equation can be transformed as follows:
log𝐶6 = 𝑛log𝐶5 + log𝐾
Taking points A, B, and C as (log𝐶5 (A), log𝐶6 (A)), (log𝐶5 (B), log𝐶6 (B)), and (log𝐶5 (C),log𝐶6 (C)), respectively, calculate n and K from the equations of the straight lines AB,
BC, and AC, and average them. If necessary, use the graph paper on the next page.
n

K

AB
BC
AC
Average

4.

Draw the structure of the aggregated 2,5-furandicarboxylic acid that is expected to bepresent in 1-octanol from the calculated value of n.

14

15

Practical Task 2. Separation and determination of metal ions using anion-exchange
resins.
Introduction
The separation and quantitative analysis of metal ions is of pivotal importance in thecompositional analysis of a variety of materials, such as alloys and metal complexes. In
aqueous solution, most metal ions exist as cations (aqua complexes). In hydrochloric acid,on the other hand, some metal ions are in equilibrium with chloride complexes and can bepresent as anions. The ratio of the cationic and anionic forms in solution depends largely on
the chloride concentration, and this mechanism can be used to separate metal ions. In thistask, you will separate Co(II) ion impurities from a sample solution containing Fe(III) ions
(Sample X) using an anion-exchange resin column and determine the Fe(III) content in
Sample X by chelate titration.
Background
The ion-exchange resin is a synthetic polymer with a three-dimensional network structure;
the functional substituents responsible for the ion-exchange reaction are introduced on its
surface. Resins that perform a cation-exchange reaction, i.e., the adsorption of cations andrelease of the initially adsorbed cations, typically protons, are called cation-exchange resins,
while those that exchange anions are referred to as anion-exchange resins. Various types ofion-exchange resins with different characteristics are commercially available, and an
example of the structure of an ion-exchange resin obtained from the copolymerization of
divinylbenzene and a styrene derivative that bears a quaternary ammonium group is shown
below.

This resin can exchange the anions contained in a solution for the chloride ions associatedwith the ammonium groups. The adsorption and dissociation of the anions are reversible
reactions because they are based on the electrostatic interaction between the ammonium
group and the anion. Therefore, specific anions can be retained or eluted by appropriately
adjusting the concentration of chloride ions.
16

In this task, we will use a strongly basic anion-exchange resin manufactured by Dow
Chemical Co., Ltd. (DOWEX™ 1×8 100-200 Mesh Cl− Anion Exchange Resin), which canreplace the anions in solution with chloride ions. In our experiment, we use achromatographic column packed with the resin, and the analyte is passed through the column
using hydrochloric acid as the eluent. Assuming that the generation of chloride complexes
and their reaction with the resin are in equilibrium, it is possible to elute the desired anionsfrom the column by appropriately adjusting the concentration of the hydrochloric acid.
The partition ratio, D, is defined as the ratio of the total concentration of the substance in thesolid phase (mol g−1) to the total concentration of the substance in the liquid phase (mol cm−3).

𝐷=total concentration of the substance in the solid phase (mol g .4 )total concentration of the substance in the liquid phase (mol cm.7 )The relationship between D and the concentration of hydrochloric acid, [HCl], for Fe(III) andCo(II) ions is given below. The figure shows that Fe(III) has a large D and is more easily
adsorbed on the resin at all [HCl] values. For example, when 4 M HCl is used as the eluent,Fe(III) is about 1000 times more likely to be adsorbed on the resin than Co(II). Therefore,
under this condition, Co(II) ions will elute from the column first. By lowering [HCl] after
removing the Co(II) ions, the adsorbed Fe(III) can be eluted.

17

Chemicals
Substance

Name

State

GHS Hazard Statement

HCl

Hydrochloric acid

Aqueous solution

H290, H301, H314, H318,(6, 4, 0.5 M)
NH3 (1 M)

H332, H334, H370, H372, H400
Ammonia

Aqueous solution

H290, H302, H314, H318,
H370, H401

VBB indicator

Variamine Blue B

Diluted with KCl

NA

EDTA (0.01 M)

Disodium dihydrogen

Aqueous solution

NA

Acidic solutionNAethylenediaminetetraacetate
Sample X

Glassware and equipment
1 Column packed with DOWEX™ 1×8 100-200 Mesh Cl− Anion Exchange Resin (i.d. = 10mm)
1 Burette, 25 mL
1 Laboratory stand with burette clamp
7 Conical beakers, 100 mL
1 One-mark pipette, 2 mL
1 One-mark pipette, 20 mL
1 Volumetric flask , 100 mL
3 Pipette s
2 Pasteur pipettes
1 Pipetting bulb
1 Glass vial
1 Glass rod
1 Alcohol thermometer1 Spatula (spoon)
1 Hot plate- Congo Red Paper

18

Procedure
A. Separation of the Co(II) and Fe(III) ions contained in Sample X
1.

The column is packed with anion-exchange resin and pre-conditioned with 6 M HCl.
Lower the liquid level to the cotton on the top of the column, being careful not to let air
bubbles enter.

2.

Transfer 2 mL of Sample X into a sample bottle and then gently load the entire volume
on the top of the column using a Pasteur pipette so that the sample is charged evenly.

3.

Lower the liquid level to the cotton. Rinse the sample bottle and inner wall of the column
with a small amount of 6 M HCl and load the washings onto the column in a similarmanner. Repeat this operation several times to adsorb all the metal ions on the anionexchange resin.

4.

Elute the column with 4 M HCl and collect the first fraction in a 100 mL conical beaker.
You can easily recognize the fraction by color.

5.

Elute the column with 0.5 M HCl once you observe that all the first fraction has beencollected. Collect the second fraction in another 100 mL conical beaker until all thesecond fraction has eluted.

6.

Elute the column with H2O to collect the remaining residue adsorbed on the resin.

Note
To repeat the experiment, wash the column with 20 mL of water followed by 10 mL of 6 M
HCl before repeating the procedure.

B. Determination of Fe(III) ions
In this experiment, the concentration of Fe(III) ions contained in Sample X is determinedusing the fraction containing Fe(III) ions obtained in Experiment A.
1.

Dilute the fraction containing Fe(III) ions separated in Experiment A to 100 mL.

2.

Transfer 20 mL of the diluted solution to a 100 mL conical beaker.

3.

Adjust the pH to 2-3 using 1 M aqueous ammonia. In this pH range, the Congo Red test
paper turns purple. If a precipitate appears, add a small amount of HCl to redissolve all
the precipitate.

4.

Warm the solution to approximately 50 ℃ using a hot plate.

19

5.

Add VBB indicator to the solution until the solution turns dark purple. You do not haveto weigh the VBB, but judge the appropriate amount by the color of the solution.
Approximately 50 mg is required.

6.

Titrate the sample solution with 0.01 M EDTA quickly so that the solution does not cool.

7.

Determine and record the amount of EDTA added to reach the equivalence point where
the sample solution changes from the initial purple color to a pale yellow, and the color
does not change further even if additional EDTA solution is added.

8.

Repeat the titration using the remaining diluted sample solution. Although titration canbe performed up to 4 times, it is sufficient to perform it only as many times as you
need.

Questions
I.

Draw the chemical structure of the chemical species that the Fe(III) ion is expected toform in 6 M HCl.

II.

Report the amount of 0.01 M EDTA solution needed to reach the equivalence point. You
only need to report the number of times you titrated.
#

１

２

Amount of 0.01 M
EDTA solution / mL

20

３

４

III. Report the number of Sample X analyzed and calculate the molar concentration of
Fe(III) ions contained in Sample X.
# of Sample X

Molar concentration of Fe(III) ions in Sample X

mol dm−3

Discussion
What causes the color change of the first fraction before and after elution from the column?

21Instructions for mentors
Preparation of Sample X
Dissolve NH4Fe(SO4)2・12H2O (M = 482.25) and CoCl2・6H2O（M = 237.93）in 6 M HCl.
Concentrations of Fe(III) ions between 0.1–0.2 M are appropriate, while that of Co(II) shouldbe less than 0.1 M.
Note
FeCl3・6H2O can also be used as the source of Fe(III) ions. However, it may be difficult toknow the prepared concentration accurately due to the hygroscopic nature of the salt.

Preparation of VBB indicator diluted with KCl
Mix 1 part VBB with 200 parts KCl in a mortar. Store the mixture in a brown bottle.

Preparation of the anion-exchange resin column
Note
The following procedure can be included in the task if the students have time to spare.
Wash the anion-exchange resin (about 5 g per person) with deionized water (hereafterreferred to as water) and let the resin swell in water overnight. Loosely pack absorbent cotton
at the bottom of the chromatography column and add water to remove air bubbles. Using afunnel, pour the swollen resin into the column (10 cm in length) and open the cock to drain
the excess water. Note that no air bubbles should enter the top of the resin. Place a small
amount of absorbent cotton on top of the resin so that its surface is not disturbed and add asmall amount of water to remove air bubbles. Check that there is no resin outflow from thecolumn and that the flow rate is around 15 drops/min (typically 10–20 drops/min). If thecolumn is not to be used immediately, add an appropriate amount of water so that the upper
part of the column does not dry out. Prior to the experiment, lower the liquid level to the cottonand gently add 10 mL of 6 M HCl to flow through for conditioning.

22

Practical Task 3. Brevity is the soul of wit in organic synthesis.
Introduction
In organic synthesis, C–C-bond-forming reactions to build molecular frameworks are someof the most basic yet also most important reactions. Many C–C-bond-forming reactions
require large amounts of organic solvents and complicated procedures for separation andpurification of the target compounds and are thus associated with a relatively highenvironmental load. In this task, a C–C-bond-forming reaction is carried out between
triphenylmethanol (1) and malonic acid (2) to synthesize 3,3,3-triphenylpropionic acid (3) asshown in equation (1). This is a well-designed synthetic method in which the reaction
proceeds via the simple heating of two solid raw materials, and the target product 3 can beobtained in high purity using only recrystallization without performing complicated separation
procedures. The purpose of this task is to consider the reaction mechanism based on theexperimental results and understand the well-designed reaction system.

(1)

Chemicals
Substance

Name

State

GHS Codes(C6H5)3C–OH

Triphenylmethanol

Solid

H302

CH2(CO2H)2

Malonic acid

Solid

NA

C2H5OH

EthanolLiquidH225- H320

23

Glassware and equipment- 1 Erlenmeyer flask (30 mL)- 1 Hot plate with digital temperature display (or a thermometer for the surface
temperature)- 1 Pipette (5 mL)- 1 Spatula- 1 Screw-top bottle (20 mL)- 1 Apparatus for filtration- 1 Paper for wrapping powdered medicine- 1 Pair of work gloves

Experimental procedure
CautionIn this task, gases with low toxicity but a strong smell are generated. Perform in anenvironment where a fume hood or other air exhauster can be used appropriately.
During heating, the hot plate reaches high temperatures. Be careful to avoid burns.
1.

Set the surface temperature of the hot plate to 170 °C. Control of the surface
temperature is essential. If the hot plate does not have a digital temperature display, its
surface temperature should be measured using a thermometer (such as a radiation
thermometer).

2.

Add triphenylmethanol (Ph3C–OH, 1.041 g) and malonic acid (2.082 g) to an Erlenmeyer
flask (30 mL) and mix the reactants by gently swirling the flask by hand.

3.

Place the Erlenmeyer flask on the hot plate at 170 °C.

4.

Heat the Erlenmeyer flask for 30 min while observing the reaction.

5.

Wearing the work gloves, remove the Erlenmeyer flask from the hot plate and place it
on a stack of Kimwipes on the workbench.

6.

Set the surface temperature of the hot plate to 120 °C.

7.

Allow the flask to cool for 1 min.

8.

Add a solution of EtOH:H2O (5/1, v/v, 1 mL) to the reaction mixture and stir the solution
to initiate crystallization.

9.

If no crystals form, rub the wall with a spatula to induce crystallization.

10. Add additional EtOH:H2O (5/1, v/v, 5 mL).
11. Place the Erlenmeyer flask on the hot plate at 120 °C.

2412. After complete dissolution, move the Erlenmeyer flask onto the Kimwipes on the
workbench.
13. Allow to cool for ca. 2 h. Caution: even after cooling to room temperature, the crystals
continue to grow slowly.
14. Break the crystals gently with a spatula.
15. Collect the crystals by filtration under reduced pressure.
16. Place the crystals into a screw-top bottle (20 mL) and submit the sample.

For the evaluation of the purity
1. Melting point
Pure 3,3,3-triphenylpropionic acid has a melting point of 182 °C.
2.

1

H NMR spectroscopy

The methylene protons and the aromatic protons of pure 3,3,3-triphenylpropionic acidshow an integration ratio of 2:15. Use a deuterated solvent other than CDCl3, C6D6, or
methanol-d4, because the residual protons in CDCl3 and C6D6 overlap with the aromatic
protons, while methanol-d4 causes deuterium exchange of the methylene protons in
3,3,3-triphenylpropionic acid.
3. HPLCThe main contaminant would be triphenylmethanol, which can be quantified by highperformance liquid chromatography using a reversed-phase column such as an
octadecylsilicate column.

25

Questions
1. Calculate the theoretical yield, showing the details of the calculation method. It should
be noted that the crystal water and solvent are not included.

2. Write the chemical formulae of the products X and Y that are generated by the reactionof triphenylmethanol (1) and malonic acid (2) in equation (1).

3. Draw the chemical structure of the ionic intermediate A that is generated from
triphenylmethanol (1).

4. Describe the most important experimental evidence suggesting the formation of the ionicintermediate A.

5. In this task, malonic acid plays multiple roles. Write the role of malonic acid other thanas a stoichiometric reagent and a solvent.

6. This task requires an appropriate air exhauster (such as a fume hood) for removing
compound B generated during the reaction. Write the formula of compound B.

7. The procedure in this task is well designed. If the reaction conditions are changed as
described below, what will occur?
(i) using a 1:1 mole ratio of triphenylmethanol and malonic acid to avoid using a large
amount of malonic acid.
(ii) using a solvent for the enhancement of the reaction selectivity.
(iii) using a Liebig condenser, the generated compound B is refluxed to prevent it fromleaving the system.
(iv) the reaction is carried out at 150 °C to implement milder conditions, or at 200 °C toenhance the reaction rate.

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To further enhance the efficiency of the reaction (e.g., yield, purity, reduced raw material
consumption, reduced energy consumption, reduced waste, simpler procedure), whatkind of method might you propose? Discuss this with your mentor.
“ The best is not, so long as we can say, ‘This is the best.’” – modified from King Lear.

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