Extended Essays 2021

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1. Miku ADACHI 2. Leigh AMORES 3. Elsa CHEN 4. Xenia DARIUSH-FAR 5. Jarvis DOVER 6. Helena HAGAN 7. Pippi HARRIS 8. Felix JACKSON-KENNEDY 9. Noah JAY 10. Hannah KENNEDY 11. Chloe MING 12. Brigid MULLINS 13. Lilliana SWAINSON 14. Kushi TUMKAR 15. Andre VASQUEZ 16. Jinjin WANG 17. Maito YAMAGUCHI 18. Tris ZHAO

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International Baccalaureate Diploma Program

THE EXTENDED ESSAY WHAT IS THE

IB DIPLOMA PROGRAM? The International Baccalaureate® (IB) Diploma

Programme (DP) is an assessed programme for students aged 16 to 19. It is respected by leading universities across the globe. Somerset offers the IBDP as an alternative to the Queensland Certificate of Education in Years 11 and 12. Through the DP, we aim to develop students who: - have excellent breadth and depth of knowledge - flourish physically, intellectually, emotionally & ethically - study at least two languages - excel in traditional academic subjects - explore the nature of knowledge through the programme’s unique theory of knowledge course.

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involves community service.

The extended essay is an independent, self- directed piece of research, finishing with a 4,000-word paper.

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One component of the International Baccalaureate® (IB) Diploma Programme (DP) core, the extended essay is mandatory for all students.

Practical preparation for undergraduate research an opportunity for students to investigate a topic of special interest to them, which is also related to one of the student's six DP subjects. Through the research process for the extended essay, students develop skills in: - formulating an appropriate research question - engaging in a personal exploration of the topic - communicating ideas - developing an argument.

Participation in this process develops the capacity to analyse, synthesize and evaluate knowledge.

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EE FINAL GRADEMARK REPORT

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Investigating the Effect of Reflux Time on the Concentration of Synthesized Methyl Salicylate, Determined Using the Ferric Chloride Spectroscopy Calibration Curve

Research Question For the synthesis of methyl salicylate with controlled concentrations of salicylic acid (0.2mol),

methanol (2.1mol) and conc. sulfuric acid (~18mol), how does increasing the duration of reflux

in the procedure from one to five hours in one-hour intervals, affect the yield & percentage

concentration of methyl salicylate in the synthesised solutions, as determined using the ferric

chloride calibration curve from a UV spectrophotometer?

Word Count: 3,991 By: Leigh AMORES

Table of Contents

RESEARCH QUESTION ............................................................................................................................1

INTRODUCTION ........................................................................................................................................3

BACKGROUND RESEARCH ....................................................................................................................3

HYPOTHESIS:............................................................................................................................................6

VARIABLES ...............................................................................................................................................6

METHODOLOGY .......................................................................................................................................7

DATA COLLECTION & ANALYSIS.........................................................................................................10

DISCUSSION: ..........................................................................................................................................12

CONCLUSION:.........................................................................................................................................13

EVALUATION...........................................................................................................................................14

BIBLIOGRAPHY ......................................................................................................................................16

APPENDIX:...............................................................................................................................................17

2

Introduction

Methyl salicylate, or the oil of wintergreen , is an aromatic ester used in pharmaceutical

drugs such as Tiger Balm. It is formed from the esterification of Salicylic acid with the chemical

formula, 8 8 3 . This investigation aims to determine the relationship between reflux duration and the concentration & yield of synthesized methyl salicylate. This was done by initially

preparing a standard ferric chloride calibration curve, in which varying concentrations (10, 20,

30, 40 & 50%) of pure methyl salicylate with a ferric chloride solution ( 3 ) was measured of its absorbance (Au) using the UV Spectrophotometer. This method was based on ferric chloride colorimetry method for methyl salicylate quantification, published by the Journal of Applied Pharmaceutical Science (Vol.4) 1 . Methyl salicylate was then synthesised under varying reflux

durations with modifications to the Vogel’s textbook of Practical Organic Chemistry . The

concentration of the product was finally determined using the ferric chloride method, comparing

absorbance at 515nm to the calibration curve.

In the pharmaceutical industry, understanding the ideal conditions for organic synthesis is

essential to maximise the yield or purity of the products while still considering the limitations of

production cost and other external factors. Hence, identifying the ideal duration of a reaction

which produces the highest concentration of the desired product is necessary to ensure optimum

atom economy and the move towards greener chemistry by reducing organic chemical waste.

Background Research The synthesis of organic compounds is vital in producing various pharmaceutical,

cosmetic, and industrial products, which are all derived from organic molecules. Specifically,

pharmaceutical drugs such the oil of wintergreen is an organic ester formed through the

esterification of salicylic acid. Salicylic acid ( 7 6 3 ) , naturally derived from the bark of willow trees, was used for pain and fever reduction during the nineteenth century. Pure salicylic acid

however, caused issues such as severe stomach irritation, digestive problems, and diarrhea.

Through esterification, the purity of salicylic acid was able to be chemically modified to

formulate milder and safer forms of medicine, such as methyl salicylate.

The oil of wintergreen, or methyl salicylate ( 8 8 3 ), is a mild analgesic used to relieve muscle aches and pain 2 , which is also naturally derived from the fermentation of wintergreen leaves. As

1 (Sajin Kattuvilakam Abbas, 2014) 2 (National Library of Medicine, 2021)

3

an aromatic ester, the oil can also be characterised by its strong ‘peppermint’ scent and is used often for the flavouring/scent of candy and fragrances 3 .

The synthesis of Methyl Salicylate from salicylic acid ( 7 6 3 ) with methanol ( 3 ) and conc. Sulfuric acid ( 2 4 ) , is shown in Figure #1 . This reaction is extremely slow under STP, and like other esterification reactions requires significant energy to facilitate. As a condensation reaction, heat is required to remove the water molecule formed by the acid and alcohol mixture ( + ion from the acid and − ion from the alcohol), to form the ester product. Hence, energy in

the form of high heat/temperature can be used to accelerate the reaction via a reflux system. In

this system, the mixture is heated with a heating mantle, allowing for the reaction to reach its

boiling point. As the mixture is connected to a cooling condenser, the evaporated products or

reactants are condensed back into the mixture preventing any escape of vapour. This allows for

the reaction to proceed at a higher rate. Extending the time under reflux allows the reaction to go

further towards completion, liberating more water molecules and therefore producing a higher concentration/yield of the desired ester 4 . Moreover, rate is also increased using a catalyst (in this case, H 2 4 ) which in addition to high temperatures, is used to speed up the reaction by lowering the activation energy (energy required to initiate a reaction) 5 .

Figure #1: The reaction between salicylic acid and methanol to form methyl salicylate 6

The mechanism for this reaction is outlined in 5 steps as listed and shown below 7 ( Figure #2 ) 1. Cation formation: salicylic acid loses an electron to the catalyst ( + ion), breaking its

oxygen-carbon double bond and forming a carbocation.

2. Delocalized Carbocation: the carboxyl oxygen of the methanol is protonated by the

carbocation - gives the carbocation a delocalized electron, making it a better electrophile.

3. Proton Transfer: A proton from one of the hydroxyl groups is transferred to the oxygen

carboxyl, swapping the hydrogen to the proton donor.

3 (Jill Seladi-Schulman, 2020) 4 (Barnes, 2017) 5 (Oxford University Press, 2014)

6 (Lab Monk, 2020) 7 (BYJUS'S, 2021)

4

4. pi bond formation & water molecule liberation: a pi bond (from the carbon-oxygen double

bond) is formed as the hydroxy group’s alcohol oxygen atom donates a pair of electrons to

the carbon atom, removing the water molecule from the alcohol-acid mixture.

5. Esther Formation: Methyl salicylate is formed as the hydrogen attached to the oxygen in the

pi bond is swapped with a pair of electrons from the anion catalyst.

Figure #2: The Mechanism of the esterification of salicylic acid to form methyl salicylate 8

Credited reports thus far have shown that the concentration of methyl salicylate can be

determined through a multitude of methods, including Nuclear Magnetic Resonance Spectroscopy, TLC 9 , Ultraviolet Spectrophotometry 10 and HPLC methods 11 . The most recent

method was published by the Journal of Applied Pharmaceutical Science (Vol.4), where the

concentration of methyl salicylate in bulk or semi-solid formulations was tested through

colorimetric quantification. Prior to this report, there has not been an established method of

colorimetry, as varying concentrations of methyl salicylate (being colourless) , don’t produce

different absorbance values in the visible spectrum.

To solve this, the report used a ferric chloride solution ( 3 ) , that when reacted with phenols (organic compounds with a hydroxyl attached to the carbon atom of an aromatic ring), produce

a purple-coloured solution. Hence by application of Beers law, it was found that the concentration

of methyl salicylate is directly proportional to the intensity of the purple colour in the final solution and therefore the recorded absorbance at 515nm 12 . Once graphed, the calibration curve can determine the concentration of the unknown product and therefore the absorbance (Au) measured by the UV spectrophotometer 13 .

8 (Lab Monk, 2020) 9 (Springs, n.d.) 10 (Dorwal, 2012) 11 (Technologies, 2018)

12 (Sajin Kattuvilakam Abbas, 2014) 13 (Sajin Kattuvilakam Abbas, 2014)

5

Hypothesis: If the duration of the synthesis of methyl salicylate ( 8 8 3 ) in the reflux system is increased, then the yield and percentage concentration of the synthesized methyl salicylate, determined

through the ferric chloride calibration curve and the UV spectrophotometer, would also increase

in the presence of sufficient reactants. This is because, as an esterification reaction undergoes

reflux for a longer duration, as outlined by the mechanism of the reaction, more water molecules

are be liberated from the alcohol-acid mixture due to the sufficient energy provided by the reflux

system. This therefore produces a higher concentration and yield of the desired ester, methyl salicylate, which is formed from the condensation reaction 14 .

Variables Independent Variable:

 Duration of reflux (1, 2, 3, 4 & 5 hours)

Increased by 1 hour for 5 variations

o

o Time controlled using the iPhone stopwatch/alarm

Dependent Variable:

 The light absorbance (Au) of synthesized methyl salicylate (in ferric chloride solution)

o Measured using the UV spectrophotometer (515nm) ( Appendix #1 )

o Measured 3 trials each for each of the reflux durations

 Mass (g) of synthesised Methyl salicylate solution

Measured using electronic balance

o

Controlled variables:

 Use of UV spectrophotometer to measure the absorbance value & electronic balance to

measure mass of synthesised methyl salicylate: controlled to ensure systematic limitations

associated with these equipment ( ±0.0001 for UV spec & ±0.0001 for electronic

balance) were equal throughout. The variation of equipment would result in varying

uncertainties and errors, directly affecting the accuracy of the data.

 Wavelength for the calibration of the UV spectrophotometer (515nm): Wavelength was

determined through scanning a ‘standard solution’ of methyl salicylate and ferric chloride to

find the peak wavelength, at which absorbs visible light ( Appendix #1 ).

 Concentration & volume of the reactants- Salicylic acid (28g/0.2 ), methanol (80 , 2.1mol) and conc. Sulfuric acid (8 , ~18mol): Concentrations were controlled

14 (Barnes, 2017)

6

by only using the solutions prepared by the lab technicians and by ensuring that the mass of

salicylic acid used was 28g (0.2mol, Appendix #2 ) when measured on the electronic balance.

Any changes would directly affect the data. This is as sulfuric acid is the limiting regent

( Appendix #3 ), as methanol needs to be in excess, and as varying the concentration/volume

of the sulfuric acid catalyst would directly affect the rate of the reaction and hence final

concentration/yield.

 Heating mantle voltage was set to 100Volts: Ensured that the reacting mixture wouldn’t

‘spit’ due to overheat ed liquid. If the voltage were to be changed throughout the experiment,

the variation of heat energy would directly the reaction rate and hence the concentration/yield

of the product.

 Concentration of the ferric chloride solution (0.01%): Kept the same by controlling the

dilution of ferric chloride to ethanol ( Appendix #4 ) to ensure that the absorbance values of

the synthesised solutions could be comparable to the calibration curve, accurately

determining the percentage concentration of the methyl salicylate.

Methodology Development of the method:

Through initial research, it was found that there were numerous reported methods for the

synthesis and refinement of methyl salicylate which all varied significantly. The greatest

difference was the time required for the reaction mixture to undergo reflux (salicylic acid,

methanol & con. Sulfuric acid). Through careful evaluation of the numerous methods, the

procedure which required the greatest duration of reflux and included both the synthesis and

refinement of the methyl salicylate was chosen for this investigation. Published in the Vogel’s textbook of Practical Organic Chemistry, 15 the procedure was amended considering the

limitations of the school laboratory to allow adequate independent variables as outlined in Table

#1 . The considerable safety considerations were also assessed, and appropriate modifications

made as appropriate to the school laboratory setting (Appendix #5).

15 (Vogel's Textbook of Practical Organic Chemistry, 1989)

7

Table #1: Modifications to the Methyl Synthesis & Refinement

Vogel’s methodology

Modifications in my methodology (Appendix #6)

Duration of reflux - kept constant at 5 hours Use of carbon tetrachloride to aid in separation of aqueous layer and methyl salicylate after the reflux Use of Bunsen burner to evaporate excess methanol after the reflux Power of the heating mantle not specified;

For an independent variable, duration of reflux was varied for one, two, three and four hours, as well as the original five. As carbon tetrachloride was inaccessible to a school laboratory, this step was ignored. Consequently, the use of sodium hydrogen carbonate (which would have ended the production of carbon dioxide from the carbon tetrachloride) and the distillation step to remove any excess the carbon tetrachloride after filtration was also removed. Ensuring the methanol would not be burnt during evaporation, the hot plate was used instead of the Bunsen burner. To reduce loss of methanol vapor or the breaking of the condenser f rom the ‘spitting’ of overheated liquid, porcelain chips were placed at the opening of the condenser and the power (voltage) of the heating mantle was kept low at 100V.

porcelain chips not placed in condenser

The method for determination of the ferric chloride calibration curve, published by the Journal

of Applied Pharmaceutical Science (Vol.4), was amended to suit the parameters of the experiment.

Table #2: Modifications to the Ferric Chloride & Methyl Salicylate Calibration Curve

Journal of Applied Pharmaceutical Science method

Modifications to the methodology (Appendix #4 & #7)

Concentration of methyl salicylate were 12, 24, 36, 48 60 & 72 / 3 from Volitra gel (10% of the compound) Preparation and use of 1% ferric chloride solution

As pure methyl salicylate was used in this experiment to produce the calibration curve, 10, 20, 30, 40 & 50% dilutions were created instead.

concentrations of methyl salicylate used in this experiment were higher than in the original method. Hence the concentration of the ferric chloride solution was reduced to 0.01% in aim to dilute the final purple color of the solution for clearer variation. Through trial and error, it was found that the polystyrene cuvettes would weaken and crack due to its high solubility in esters (methyl salicylate) and alcohols (ethanol) 16 . Hence, glass cuvettes were used.

Material of cuvette for absorbance measurement not specified

16 (Bangs Laboratories, Inc., 2015)

8

Procedure:

Appendix #4-7 for risk assessment & extended methodology

Calibration Curve:

1. All chemicals and equipment were organised ( Appendix #8 ).

2. The Ferric chloride calibration curve was graphed by preparing the 0.01% Ferric chloride

solution and five dilutions of pure methyl salicylate (10, 20, 30, 40, 50%) with pure

ethanol as the solvent ( Appendix #9 ).

3. Once volumes of the ferric chloride solution, diluted methyl salicylate and additional

ethanol were combined, the solution was transferred into the glass cuvette and measured

of the light absorbance in the UV spectrophotometer at 515nm

4. The absorbance values of the diluted methyl salicylate with ferric chloride were recorded

for three trials and averaged to graph the calibration curve seen in Figure #4 .

Methyl salicylate synthesis 5. The reaction mixture - Salicylic acid (28g), methanol (80 3 ), and conc. Sulfuric acid (8 3 ) were placed into the 250 3 round-bottom flask and set under reflux for 1 hour

at 100V.

6. After reflux, the solution was refined through the evaporation of methanol on the hot plate

for 30 minutes. 7. Once formed the aqueous layer was separated from the oil by adding 250 3 of deionized water into the separatory funnel with the solution. 8. The oil was transferred into the 50 3 volumetric flask and was ‘dried’ of the excess

water with 5g magnesium sulphate. The flask was then shaken and left to stand for at least

half an hour.

9. The solution was then filtered through the funnel and filter paper.

10. Once filtered, the mass of the solution was weighed on the electronic balance 11. 2 3 of the synthesized solution was then combined with 1 3 of the ferric chloride solution and 7 3 of ethanol. This solution was transferred into another glass cuvette and

measured of its light absorbance value in the UV spectrophotometer.

12. Steps 5-11 were completed for the rest of the reflux durations (2, 3, 4 & 5 hours), three

trials each. The average absorbance for each of the solutions were then used with the

equation of the standard calibration curve to determine the percentage concentration of

synthesized methyl salicylate.

9

Data Collection & Analysis Calibration Curve:

The raw data shown in Appendix #10

Table #3: Average Absorbance for the percentage concentrations (10-50%):

Average absorbance ( ± . )

Concentration of methyl salicylate (%)

10

1.2103

20 30

1.3625 1.6256

40

2.0822

50

2.4376

Figure #4:

Methyl Salicylate & Ferric Chloride Calibration Curve

2.8

2.6

2.4

2.2

y = 0.0317x + 0.7914 R² = 0.969

1 Absorbance (±0.0001Au ) 1.2 1.4 1.6 1.8 2

0.8

0.6

0

10

20

30

40

50

60

Concentration of Methyl Salicylate (%)

Example Calculation #1: the concentration of synthesised methyl salicylate (%)

: ℎ − (1.4704) : ℎ : = 0.0317 + 0.7914 1.4704 = 0.0317 + 0.7914

= 1.4704 − 0.7914 0.0317 = 21.4196 ≈ 21%

Methyl Salicylate Quantification:

The raw data shown in Appendix #11 & 12

Table #4: Percentage concentration of synthesised methyl salicylate from calibration

curve:

Duration of reflux ( ℎ ) Percentage concentration of synthesized methyl salicylate (%) 1.00 21 2.00 23 3.00 27 4.00 30 5.00 33

Table #5: yield of synthesised methyl salicylate: Duration of reflux ( ℎ )

Average mass of the methyl Salicylate solutions ( ±0.0001 g)

Yield of the synthesized methyl salicylate (% mass)

11.2115 11.6969 11.6681 12.5660 12.4630

37 38 38 41 41

1.00 2.00 3.00 4.00 5.00

*Theoretical yield calculated in Appendix #13 = 30.4299g

Example Calculation #2: Percentage yield of synthesised methyl salicylate (%)

11.2115 30.4299

=

× 100 = 36.8437 ≈ 37%

Figure #5:

Percentage Concentration of Synthesised Methyl Salicylate as the Duration of Reflux is Increased

36

34

y = 3.1x + 17.5 R² = 0.9928

22 Concentration of Methyl Salicylate ( %) 24 26 28 30 32

20

18

0

1

2

3

4

5

6

7

Duration of Reflux (hours )

11

Discussion: At the absorbance of 515nm, as expected, and hypothesised by application of Beers law, the

calibration curve in Figure #4 , showed a linear trend between light absorbance value (Au) and

the concentration of methyl salicylate (%) in the ferric chloride solutions. In reference to the

background research, due to ferric chloride’s characteristic reaction to phenols, the concentration

of methyl salicylate in a ferric chloride solution is directly proportional to the intensity of the

purple colour of the solution. Quantitatively, the absorbance value measured by the UV spectrophotometer also increases 17 . As the trend in Figure #4 produced data which supports this

theory, the ferric chloride calibration curve was then validified and able to be used to determine

the percentage concentration of methyl salicylate in the synthesized solutions.

Using the equation calculated from the standard calibration curve [ = 0.0317 + 0.7914] the

percent concentration of methyl salicylate in the synthesised solutions from varying reflux

duration were calculated ( example calculation #1 ) and recorded into table #4 . The data was then

graphed in Figure #5, which produced a linear relationship between the duration of reflux and

the percentage concentration of synthesised methyl salicylate. This trend is supported by the 2

value of the best fit line. As generated by graphical software, the data produces the near perfect

2 of 0.99 (out of 1), showing that the variance of the data points range extremely close to the

trendline and show high chance of the relationship continuing as the duration of reflux and

percentage concentration increase. The range of the percentage concentration increased from

21% for one hour, to 33% for five hours . This indicates that the esterification requires a much

greater duration of reflux to synthesize higher concentrations of methyl salicylate. Using the

trendline equation of Figure #5 [ = 4.040 + 14.838] , it can be theoretically determined that

for a synthesized solution of methyl salicylate to be 100% (under the same conditions as this

experiment), the duration of reflux must be 21 hours. This, however, would be unrealistic to

expect as it would be expected that approaching much higher concentrations would result in a

slowing of the rate due to reduced molecular collisions and at some point, an equilibrium would

be reached with the reverse reaction. However, we can still make the general assumption that

greater hours of reflux would be required to increase the yield of the product. Hence, in terms of

industrial processes, the results from this experiment can be used to understand that to better

balance cost and efficiency, a higher-powered reflux system (higher voltage) would be more

effective in producing methyl salicylate in a shorter time.

17 (Sajin Kattuvilakam Abbas, 2014)

12

In addition, the percentage yield in table #5 , shows that the range of the yield increased from 37-

41%, showing that the significant increase didn’t occur in the first 3 hours. This also shows that

the 4& 5-hour reflux time, did not make any different in terms of percentage yield. This result

does not fully support my hypothesis, however, can be justified by random and systematic errors

associated in the methodology (see evaluation).

The trends found are supported by the background research. When an esterification reaction is in

a reflux system for a longer duration, as outlined by the mechanism of the reaction, more water

molecules are liberated from the alcohol-acid mixture due to the high energy provided by the reflux system. This produces a higher concentration and yield of the desired methyl salicylate 18 .

Conclusion: The purpose of this experiment was to explore the relationship between the increasing duration

of the reflux and the concentration of the synthesized methyl salicylate, using the controlled

concentrations of salicylic acid (0.2mol), methanol (2.1mol) and conc. sulfuric acid (~18mol).

The synthesis was performed by increasing the duration of reflux using the 100V heating mantle

by 1 hour for 5 variations (1, 2, 3, 4 & 5 hours). Prior to the methyl salicylate synthesis, the ferric

chloride colorimetric method was used to determine the relationship between the concentration

of methyl salicylate and the 0.01% ferric chloride solution. Through the investigation, it was

found that the relationship between reflux time and concentration was directly proportional,

forming a linear relationship which validates the hypothesis. The yield with a range of 37-41%,

showed an increasing pattern, however not in a linear trend. This indicates that increasing reflux

time may not be the most economical method for producing greater quantities. Instead, shorter

reflux durations for a quicker turnover for overall yield is more effective. Therefore, this

experiment provided data that is strongly supported by the background research presenting

relevant information regarding the industrial processes of methyl salicylate synthesis, thus

proving the investigation reliable and valid.

18 (Barnes, 2017)

13

Evaluation

Random Errors

Limitation: During the refinement process the synthesised solution was ‘dried’ of water

molecules by adding 5g of anhydrous magnesium sulphate ( 4 ) . In the original method, the solution was to be shaken for 5 minutes then left to stand for at least half an hour. However, in

some instances a trial was not able to be completed within one continuous session. Consequently,

the solution with the drying agent would be left to stand for much longer than the half an hour or

even overnight. This random error could have directly affected the concentration of the final

product, due unequal for the agent to react with the water in the solution to form the hydrated

4 precipitate. Improvement: The duration of the reaction between the solution and drying agent could have

been controlled to 12 hours for instance, to allow for more flexibility while still controlling the

duration for more accurate data.

Limitation: A fter the separation of the aqueous layer and the ‘drying’ of the so lution, there is a

random uncertainty associated with any left-over residue of the synthesised solution being stuck

to the walls of the various glassware at these points in the refinement stage.

Improvement: After the separation of the aqueous layer, a small amount of water could have

been used to ‘wash’ the used separating funnel, as the water added would have been ‘dried’ in

the next step when the solution was exposed to the magnesium sulphate. After transferring to the

funnel after drying, the volumetric flask used could have then been washed with a controlled volume of ethanol (7 3 ) . This is because as a solvent ethanol does not affect the measurement

of absorbance value of the solution. Using ethanol at this point, would also remove the need to

use ethanol at the final steps of the procedure.

Limitation: The reflux time was controlled using the stopwatch. This accounted for an

approximate uncertainty approximately of ±2 minutes (0.03 hours) (reaction time of stopping &

reacting the stopwatch/alarm and turning on/off the reflux system). The uncertainty in reflux time

directly affects the concentration of the product, the error ranging from 1%-3% (Appendix #14) .

Improvement: Another alarm could have been set prior to the desired duration, ensuring that at

the exact time, I was prepared to turn off the reflux system.

14

Limitation: The oil from the aqueous layer relies heavily on the technique when using the

separatory funnel. Throughout the experiment, traces of oil could be visually observed within the

aqueous layer, affecting the yield. Improvement: A centrifuge could have been used to separate

the oil from the aqueous layer, increasing the accuracy of the mass of oil produced by the

synthesis.

Systematic Errors Limitation: For the creation of the calibration curve, the 10 3 measuring cylinders were used to measure the required volumes of methyl salicylate (pure) and ethanol to make up the 10-50% concentrations. However, as the measuring cylinders have the uncertainty of ±0.2 3 , this

directly affects the concentration of methyl salicylate and hence the calibration curve used

throughout the investigation. Through combining the uncertainty for the volume of ethanol and

methyl salicylate for each percentage concentration, it was found that this uncertainty accounted

for 1-2% of error ( Appendix #15 ) Improvement: Larger volumes of the methyl salicylate and

ethanol (keeping the ratios) could have been used to reduce the effect of error on the overall

volume and hence concentration.

Extensions

For further exploration, I could determine the concentration of methyl salicylate in ointments

such as tiger balm though the same ferric chloride calibration curve method and then compare

the value to the concentrations of the synthesised methyl salicylate. This will allow for a more

accurate comparison of this investigation to the real industrial process.

Reliability of Sources

The sources used in this investigation originate from scientific journals, published textbooks and

the internet. A clear limitation in reliability of online sources is that independently published

online references can contain information which is not academically proven. However, as all my

online sources, such as PubChem & Lab Monk, have been either written or verified by qualified

experts, accredited (Ph.D.) authors or credited tutoring platforms, it can be said that the references

are valuable.

15

Bibliography Bangs Laboratories, Inc., 2015. COMMON SOLVENTS AND NON-SOLVENTS OF POLYSTYRENE. [Online] Available at: https://www.bangslabs.com/common-solvents-and-non-solvents-polystyrene [Accessed 5 May 2020]. Barnes, K., 2017. Esterification & Reflux: Purpose & Procedure. [Online] Available at: https://study.com/academy/lesson/esterification-reflux-purpose-procedure.html [Accessed 13 April 2021]. BYJUS'S, 2021. Esterfication. [Online] Available at: https://byjus.com/chemistry/esterification/#:~:text=Esterification%20Mechanism&text=A%20p roton%20is%20transferred%20to,form%20a%20good%20leaving%20group.&text=The%20hy droxy%20group's%20alcohol%20oxygen,%CF%80%20bond%20by%20eliminating%20water. [Accessed 24 April 2021]. Dorwal, D., 2012. Semantic Scholar. [Online] Available at: https://www.semanticscholar.org/paper/Development-of-UV-Spectrophotometric- Method-For-of-Dorwal/01173d48f16ab040e6475508dd236abe9581b15c [Accessed 2021]. Jill Seladi-Schulman, P., 2020. Healthline. [Online] Available at: https://www.healthline.com/health/wintergreen-oil#uses [Accessed 12 January 2021]. Lab Monk, 2020. Synthesis of methyl salicylate. [Online] Available at: https://labmonk.com/synthesis-of-methyl-salicylate National Library of Medicine, 2021. Compound Summary: Methanol. [Online] Available at: https://pubchem.ncbi.nlm.nih.gov/compound/methanol [Accessed 13 January 2021]. Oxford University Press, 2014. Chemistry Course Companion. Oxford: Oxford University Press. Sajin Kattuvilakam Abbas, S. S. R., 2014. Development of colorimetric method for the quantification of methyl salicylate in bulk and formulations, s.l.: Journal of Applied Pharmaceutical Science Vol. 4. Springs, U. o. C. C., n.d. Oil of Wintergreen: Synthesis and NMR Analysis, Colorado: Oil of Wintergreen: Synthesis and NMR Analysis. Technologies, S., 2018. Methyl salicylate. [Online] Available at: https://www.sielc.com/methyl-salicylate.html Vogel's Textbook of Practical Organic Chemistry, 1989. Esters. In: fifth, ed. Vogel's Textbook of Practical Organic Chemistry. London: John Wiley & Sons, p. 1078.

16

Appendix: Word Count: 1,477 Appendix #1: Standard methyl salicylate and ferric chloride wavelength scan

Appendix #2: Mol of Salicylic acid =

28 152 /

=

= 0.2

Appendix #3: Calculating limiting and excess reactant for the synthesis of methyl salicylate Mole values

= 0.2 100% ℎ = 2.1

32 /

Atomic Mass of Methanol Mass of Methanol used

Mass of Methanol used = × = 0.7914 −3 × 80 3 = 63.3

+ → 8 8 3 + 2

Mass of Methanol reacted

7 6 3 + 3

* 1:1 mole ratio 0.2 × 32 / = 6.4 ℎ

63.3 − 6.4 = 56.88 ∴ ℎ 1.35

Appendix #4: Safety & Risk Assessment

17

 Methanol & Ethanol Risk Assess - Highly flammable liquid & vapour, irritant vapours: To reduce the risks associated with these alcohols, the hot plate was used inside the fume hood to evaporate the excess methanol in the procedure instead of a Bunsen burner (to avoid the possible exposure to an open flame). In addition, it was ensured that there were no open flames when handing the ethanol or methanol during the experiment.  Conc. Sulfuric Acid risk assess - causes severe skin burns and eye damaged: To reduce the risks associated, only the teacher/supervisor could handle the chemical  Methyl Salicylate  Risk of skin/eye exposure to chemicals: Safety equipment such as safety glasses, gloves lab coats were always worn, and extra care was taken to reduce this risk  Risk of injury from breaking glass (condenser, measuring cylinders, glass beakers, volumetric flasks): To reduce this risk, extra care was taken when handling glass equipment. For the condenser specifically, the reflux was set-up inside the fume hood,  Disposal of organic waste: To ensure that all chemical produces were properly dispose, all chemical waste was poured into an organic waste beaker and disposed of properly by the lab technicians Appendix #5: Preparation of the Ferric Chloride Solution (Sajin Kattuvilakam Abbas, 2014) 1. The ferric chloride solution was first prepared by adding 1g of Ferric chloride, weighed by the electronic balance, to the 100 3 volumetric flask. 2. 100 3 of ethanol was then measured with the 100 3 graduated measuring cylinder and added to the volumetric flask . 3. The solution was shaken well to ensure that the regent had completely dissolved 4. The ferric chloride solution was then finalised by transferring 1 3 of the previous solution to the 50 3 volumetric flask and adding 9 3 of ethanol, shaken thoroughly (hence the 0.001% solution of ferric chloride was made). Appendix #6: Methyl Salicylate & Ferric chloride calibration curve (Sajin Kattuvilakam Abbas, 2014) 1. Using the 100 3 graduated measuring cylinders, 100 3 labelled beakers and labelled pipettes, five dilutions of pure methyl salicylate (10, 20, 30, 40, 50%) with the ethanol solvent were made in accordance with table appendix #6 2. Once the 10% concentration of methyl salicylate was made, 2 3 of the solution was added to another measuring cylinder, followed by 1 3 of the ferric chloride solution and 7 3 of ethanol. 3. The solution was then transferred to the labelled beaker [‘10%’] and stirred with the glass rod. 4. On e glass cuvette was filled 3⁄4 with the ethanol solvent and calibrated inside the UV Spectrophotometer 5. The cuvette was removed from the Spectrophotometer 6. A new glass cuvette was filled 3⁄4 with the 10% methyl salicylate solution 7. The absorbance value was measured 8. Steps 2-3 & 6-7 were repeated for the rest of the percentage concentrations (20, 30, 40 & 50%) 1. The reflux system, additional set-ups and materials were organized. The pipettes, beakers, measuring cylinders and volumetric flasks were also all labelled to hold their respective solutions or chemicals. 2. Using the electronic balance and weighing boat, 28 g of salicylic acid (0.2mol) was weighed and transferred into the 250 3 round bottom flask. 3. Using the 10 3 and 100 3 measuring cylinders, 80 3 of dry methanol and 8 3 of concentrated H 2 4 and were then measured and transferred into the round bottom flask. 4. Porcelain chips were then added to the round bottom flask and once the flask was connected to the condenser with the safety clip, the mixture underwent reflux for one hour at the set voltage of 100V 5. After the reflux, the reflux apparatus was dismantled. 6. Once cooled the solution was poured into the 250 3 beaker. Appendix #7: Methyl Salicylate Synthesis & Refinement (Vogel's Textbook of Practical Organic Chemistry, 1989)

18

7. The beaker was then placed on top of the hotplate set at ‘high’ heat, and with the retort stand and clamp it was ensured that the glass thermometer was submerged into the liquid. 8. The solution was then heated to evaporate the excess methanol for at least half an hour (Making sure that the temperature was past the boiling point of methanol is 64.7 ℃ (National Library of Medicine, 2021)) until two district layers were present in the mixture 9. The solution was then transferred into a separatory funnel and was allowed to cool 10. 250 3 of cold deionized water was used to rinse the round bottom flask, transferring any of the remaining solution into separatory funnel 11. After about 5 minutes when two layers were able to be distinctly seen, the lower layer was separated carefully into another 100 3 beaker, while the upper aqueous layer was discarded into a 250 3 waste beaker 12. 5g of magnesium salicylate was then measured with the weighing boat on the electronic balance 13. The synthesized solution was then dried by transferring it into the 50 3 volumetric flask with 5g of magnesium sulphate 14. Once the flask was capped, the solution was shaken k for about 5 minutes, and then left to stand for at an hour with occasional shaking 15. Another 100 3 beaker was then weighed and tared on the electronic balance 16. The methyl salicylate solution was then filtered using the retort stand, glass funnel and filter paper into the tared 100 3 beaker 17. The synthesised methyl salicylate was then collected into the tared beaker and weighed on the electronic balance 18. The UV Spectrophotometer was calibrated with a solution of ethanol 19. 2 3 of the synthesised methyl salicylate, 1 3 of the ferric chloride solution and 7 3 of ethanol were measured with separate 1 0 3 measuring cylinders and then added to the 100 3

beaker where the solution was stirred with the glass rod 20. A glass cuvette was then filled ¾ with the solution

21. The cuvette was placed inside the spectrophotometer as the absorbance value was recorded 22. Steps 2-19 were repeated for a total of 3 trials for the rest of the reflux solutions (2, 3, 4 & 5-hours)

Appendix #8: List of all chemicals & apparatus  50g salicylic acid, solid (0.2mol)  1,200 3 Methanol, pure liquid (2.1mol)  120 3 Conc. sulphuric acid (~18M)  75g magnesium sulphate (anhydrous), solid (0.04mol)  300 3 Ethanol, pure liquid (100%)  3,750 3 deionized water  1 x Condenser  1 x Heating mantle  1 x 250 3 round-bottom flask  1 x separatory funnel  7 x 10 3 graduated measuring cylinder  2 x 100 3 graduated measuring cylinder  Safety clip  1 x 250 3 graduated measuring cylinder



2 x water hose



1 x retort stand



2 x clamp



15 x filter paper sheets (No. 103) 2 x 100 3 volumetric flask



3 x 100 3 beaker 2 x 250 3 beaker







2 x weighing boat



1 x glass funnel



Electronic balance



4 x glass cuvette



UV spectrophotometer



5 x pipettes



Porcelain chips



Glass rod



Glass thermometer



Tape & pen (for labelling)

15 3 Methyl Salicylate, pure liquid (100%)



19



1g Ferric chloride, solid (0.0062mol)

Appendix #9: dilutions of pure methyl salicylate with ethanol to make up the varying percentage concentrations of methyl salicylate Percentage Concentration of methyl salicylate (%) Volume of Methyl Salicylate ( ± . ) Volume of Ethanol ( ± . ) 10 1 9 20 2 8 30 3 7 40 4 6 50 5 5 Appendix #10: Raw data – Absorbance for the concentrations of methyl salicylate (10-50%): Percentage concentration of methyl salicylate Absorbance ( ± . ) Trial 1 Trial 2 Trial 3 10 1.2081 1.2052 1.2176 20 1.3495 1.3726 1.3685 30 1.5962 1.6441 1.6366 40 2.1192 2.0107 2.1168 50 2.4335 2.4451 2.4341 Appendix #11: Absorbance (An) of each solution of increasing reflux duration (1-5 hours) Duration of reflux ( ) Absorbance ( ± . ) Trial 1 Trial 2 Trial 3 1 1.4660 1.4697 1.4756 2 1.5340 1.5303 1.5320 3 1.6644 1.6582 1.6563 4 1.7519 1.7478 1.7493 5 1.8316 1.8269 1.8295 Appendix #12: Raw data – mass of the methyl salicylate solutions of increasing reflux duration Duration of reflux ( ) Mass ( ± . g) Trial 1 Trial 2 Trial 3 1 11.7475 11.0429 10.8445 2 11.8275 12.2295 11.0336 3 12.0175 11.9395 11.0475 4 12.0031 12.4975 13.1975 5 12.2375 12.0004 12.1475

Appendix #13: Theoretical mass of methyl salicylate Assuming 1:1 ratio and that the liming reactant is salicylic acid (0.2mol)

=

0.2 152.1494 /

= 30.4299

Appendix #14: The percentage error associated with the average absorbance measured for the synthesise solutions

1: % =

× 100

20

Reflux time (hours)

Percentage Error (%)

±3 ±2 ±2 ±1 ±1

1 2 3 4 5

Appendix #15: Associated percentage error from the percentage concentration of the methyl salicylate Percentage concentration of methyl salicylate (%) Percentage error (%) 10 ±2 20 ±1 30 ±1 40 ±1 50 ±1

21

Extended Essay

Research question: To what extent has the monetary policy been overused in the USA during the Covid-19 pandemic?

Subject: Economics Examination Session: November 2021

Word count: 3992 Supervisor: DOM By: Elsa CHEN

Table of Contents

1.0 INTRODUCTION...........................................................................................................................2

2.0 METHODOLOGY .........................................................................................................................5

3.0 DISCUSSION ..................................................................................................................................6

3.1 T HEORETICAL OF THE IMPACT OF MONETARY POLICY ................................................................6

3.2 I NFLATION RATE ..............................................................................................................................7

3.3 R ECOVERY OF THE REAL GDP .....................................................................................................11

3.4 U NEMPLOYMENT RATE .................................................................................................................13

4.0 EVALUATION .............................................................................................................................15

5.0 CONCLUSION .............................................................................................................................17

6.0 BIBLIOGRAPHY .........................................................................................................................19

APPENDIX..........................................................................................................................................23

1