AMBIENT AMMONIA ANALYSIS VIA THE MODIFIED BERTHELOT’S REACTION

A Thesis

Presented to the

Faculty of

California State Polytechnic University, Pomona

In partial fulfillment

Of the requirement for the Degree

Master of Science

In

Chemistry

By

Zaw T. Naing

2021

SIGNATURE PAGE

THESIS: AMBIENT AMMONIA ANALYSIS VIA THE MODIFIED BERTHELOT’S REACTION

AUTHOR: ZAW T. NAING DATE SUBMITTED: Spring 2021

Department of Chemistry and Biochemistry

Dr. Yan Liu Thesis Committee Chair Chemistry and Biochemistry Dr. Alex John Chemistry and Biochemistry Dr. Gregory A. Barding, Jr. Chemistry and Biochemistry

ii

ACKNOWLEDGEMENTS

Throughout my graduated studies here at California State Polytechnic University,

Pomona I have received a wonderful deal of support and assistance. First and foremost, I

am extremely grateful to my academic advisor, Dr. Yan Liu for mentoring me, always

supporting me, encouraging me to explore new things and having lot of patience with me

throughout my entire college career. Without him, I would not be the same person as I am

now. My gratitude extends to the faculty members of Chemistry and Biochemistry

Department for their wonderful support through funding my studies and made my

graduated studies more memorable. I would also like to thank my colleagues, lab mates,

Kevin J. Liang, Jacob Brannon, Haocheng Liang, Andrew Thai, Tierra J. Webb, Desiree

Joyce Sarmiento, Hayley Blockinger, and Thanuja Samaranyaka for the wonderful time

we spent together in a classroom setting and in social setting. Finally, I would like to thank

my family and friends for their loving support through my studies.

iii

ABSTRACT

Ammonia is the most abundant basic gas in the atmosphere, and plays a vital role

in numerous environmental, biological, natural, and industrial processes. Traditionally,

ambient ammonia was analyzed by spectrophotometric, electrochemical, and separation

methods. The latter two require more delicate instrument operation and training than

spectrophotometric methods. The spectrophotometric method mainly relies on the

measurement of indophenol produced in the Berthelot’s reaction. Although the Berthelot’s

reaction itself is simple and easy to perform, the overall reaction kinetic process is slow

and takes about an hour to complete. In addition, the toxic phenol used in the Berthelot’s

reaction raises a great safety concern. A novel method to analyze ambient ammonia is still

desired in the field. This project investigated the kinetic process of the Berthelot’s reaction

first, and modified the amount of nitroprusside used to fasten the reaction process.

Additionally, it was determined kinetically that the reaction order for each reactant in the

Berthelot’s reaction is one. More importantly, less toxic o-, m-, and p-phenylphenols were

used to replace phenol in the reaction, and the results obtained in the analysis of ambient

ammonia collected by an ammonia diffusion sampler were comparable with the classic

Berthelot’s method.

iv

TABLE OF CONTENTS

SIGNATURE PAGE ......................................................................................................... ii

ACKNOWLEDGEMENTS ............................................................................................. iii

ABSTRACT ...................................................................................................................... iv

LIST OF TABLES .......................................................................................................... vii

LIST OF FIGURES ........................................................................................................ viii

CHAPTER 1 Introduction ................................................................................................ 1

CHAPTER 2 Experimental Design .................................................................................. 9

2.1 Berthelot’s reaction solution preparation ...................................................................... 9

2.2 Spectrophotometric monitoring of the Berthelot’s reaction ........................................ 10

2.3 Kinetic analysis of the Berthelot’s reaction ................................................................. 10

2.4 Phenylphenol study ..................................................................................................... 11

2.5 Diffusive collection of ambient ammonia ................................................................... 11

CHAPTER 3 Quantitation of Active Chlorine ............................................................. 13

3.1 Preparation of potassium iodate solution .................................................................... 13

3.2 Standardization of sodium thiosulfate solution ........................................................... 13

3.3 Quantifying active chlorine ......................................................................................... 17

CHAPTER 4 Spectrophotometric Characterization of the Berthelot’s Reaction ..... 19

4.1 Reaction with phenol ................................................................................................... 19

4.2 Reactions with phenylphenol ...................................................................................... 22

4.3 Experimental Condition ............................................................................................... 27

CHAPTER 5 Reaction Kinetics ..................................................................................... 28

5.1 Reaction rates .............................................................................................................. 28

5.2 Reaction order of phenol ............................................................................................. 32

5.3 Reaction order of hypochlorite .................................................................................... 34

5.4 Reaction order of ammonia ......................................................................................... 35

5.5 Overall reaction order of Berthelot’s reaction ............................................................. 36

5.6 Kinetics under more basic conditions .......................................................................... 36

CHAPTER 6 Reaction mechanisms ............................................................................... 38

6.1 Reaction mechanism I ................................................................................................. 38

6.2 Reaction mechanism II ................................................................................................ 39

v

CHAPTER 7 Quantitation of Ambient Ammonia ....................................................... 41

7.1 Calibration curves ........................................................................................................ 41

7.2 Analysis of ammonia in extracts ................................................................................. 43

CONCLUSION ................................................................................................................ 46

REFERENCES ................................................................................................................ 47

vi

LIST OF TABLES

Table 1. Standardization of Na2S2O3 ............................................................................... 16

Table 2. Values of Student’s t obtained from Harris Quantitative Chemical Analysis 8th

edition ................................................................................................................ 18

Table 3. The maximum absorbance wavelength for phenylphenol reaction mixture ...... 26

Table 4. Determination of ambient ammonia .................................................................. 44

Table 5. Determination of same ambient ammonia concentrations by using Phenol and

Phenylphenols.....................................................................................................45

vii

LIST OF FIGURES Figure 1. Nitrogen Cycle .................................................................................................... 2

Figure 2. AMoN 2012 annual ambient ammonia report .................................................... 4

Figure 3: ALPHA, Radiello, Ogawa Passive samplers design ........................................... 5

Figure 4. Overall Reaction of Berthelot’s reaction ............................................................ 6

Figure 5. A general chromatogram of an experimental sample.......................................... 7

Figure 6. An example of using calibration curve using Ion Selective Electrode ............... 8

Figure 7. Diffusive ambient ammonia collection ............................................................. 12

Figure 8. Titration process: a. before the equivalent point; b. close to the equivalence

point; c. addition of starch indicator; d. end of titration ................................... 15

Figure 9. Image of the Berthelot’s reaction vessel ........................................................... 20

Figure 10. UV/vis spectrum of the Berthelot’s reaction ................................................... 20

Figure 11. UV/vis spectrum of indophenol ...................................................................... 21

Figure 12. Reaction vessel with NaOH dilution ............................................................... 22

Figure 13. Phenylphenol reaction, from left to the right: o-, m-, and p-phenylphenol ........................................................................................................................... 23

Figure 14. o-phenylphenol reaction vial (left) concentrated and (right) dilu ted .............. 23

Figure 15. Phenylphenol reaction under more basic conditions: from left to right, o-, m-,

and p-phenylphenol ........................................................................................... 24

Figure 16. o-phenylphenol reaction spectrum .................................................................. 25

Figure 17. m-phenylphenol reaction spectrum ................................................................. 25

Figure 18. p-phenylphenol reaction spectrum .................................................................. 26

Figure 19. Representative spectra through continuous absorbance measurement ........... 28

Figure 20. Kinetic curve of the Berthelot’s reaction . ....................................................... 29

Figure 21. First derivative of the Berthelot’s reaction kinetic curve . ............................... 31

Figure 22. Kinetic curve of the Berthelot reaction with concentrated phenol .................. 33

Figure 23. First derivative of the concentrated phenol Berthelot’s reaction .................... 33

Figure 24. Kinetic curve of concentrated hypochlorite in the Berthelot reaction ............ 34

Figure 25. First derivative of kinetic curve of double amount of hypochlorite ................ 35

Figure 26. Kinetic Curve of the half the amount of Ammonia in Berthelot’s reaction .... 36

Figure 27. Kinetic curve of m-phenylphenol reaction with NaOH dilution ..................... 37

Figure 28. Berthelot’s reaction path ................................................................................. 38

viii

Figure 29. Proposed the reaction product for phenylphenols ........................................... 40

Figure 30. Ammonium calibration curve based on phenol reaction ................................. 41

Figure 31. Ammonium calibration curve based on o-phenylphenol reaction .................. 42

Figure 32. Ammonium calibration curve based on m-phenylphenol reaction .................. 42

Figure 33. Ammonium calibration curve based on p-phenylphenol reaction .................. 43

ix

CHAPTER 1

Introduction

Gaseous ammonia (NH3) is the most prominent basic gas in the atmosphere coming

from many sources1,2. Agriculture, more specifically the feces of livestock and the

ammonium-based fertilizers, is the primary source of ambient ammonia1,3. Industry is

another major source for ambient ammonia1,3, and gaseous ammonia may be released or

formed in the industrial process of any nitrogen-containing compounds such as nitric acid,

amines, amides, cyanides, and so on4–6. Additional sources of ammonia come from the

burning of biomass, including wild fires1,7.

Being the most abundant basic gases in the atmosphere, ammonia plays an

important role in many environmental/biological cycles, due to the presence of nitrogen8,9.

Nitrogen is one of the essential components in nature which can be found in numerous

organic and inorganic forms. For example, nitrogen is the key element in many biological

molecules, including amino acids, nucleotides, nucleic acids, protein, and so on, and

nitrogen can transfer from one compound to another via biological processes10,11, which is

illustrated in Figure 1 below. Nitrogen-fixing bacteria in the soil absorb atmospheric

nitrogen, producing ammonium. Sequentially, the ammonium in the soil goes through

nitrification process, becoming nitrite. The nitrite can be further oxidized to nitrate with

the assistance of nitrifying bacteria. The fate of nitrate goes in two different directions: one

becomes denitrified and is released back to the atmosphere in the form of nitrogen; and the

other becomes absorbed by plants through assimilation. The atmospheric nitrogen can also

1

ffJ Nitrogen-fixing bacteria in root

nodules of legumes

~

Decomposers (aerobic and anaerobic

bacteria and fungi)

Assimilation

~ Denitrifying

~--~ bacteria

~ Nitrifying

Ammonification Nitrification ~ bacteria

@ Nitrogen-fixing soil bacteria

Ammonium (NH;) I ~ Nitrifying bacteria

be directly absorbed by the nitrogen-fixing bacteria in root nodule of legumes.

Figure 1. Nitrogen cycle, diagram was from https://microbiologynotes.org/nitrogen-cycle/

Additionally, nitrogen-containing inorganic species, including ammonia and

nitrate, are often produced as the byproducts in industry, agriculture, and aquatic

environment12,13. The presence of ammonia in the atmosphere neutralize inorganic and

organic acids emitted from industry, by forming ionic salts14–16. These ionic products, often

in the forms of ammonium nitrate, ammonium sulfate, and/or ammonium bisulfate, may

float as a small particle in the air, deposit in a large particle or with water onto the ground

and/or enter the soil17. These ionic nitrogen-containing compounds in the atmosphere are

the significant precursors to the formation of particulate matter/aerosol that affects the

2

human and animal respiratory systems and impact the quality of the air17,18. An excess

amount of ammonia, when combining with acids in the atmosphere, produces excessive

minerals into the soil. The extra amount of minerals entering the soil may promote/hinder

the growth of many species, resulting in the changes of biodiversity in the environment19,20.

As reported, inhaling an excess amount of ammonia may cause lung inflammation and

pulmonary edema. Additionally, ambient ammonia reacts with other molecules in the

automobile exhaust to produce secondary organic aerosols, harming the environment and

human health21,22.

To date, the Ammonia Monitoring Network (AMoN) is the only network which

provides the spatial and temporal concentration of ambient ammonia across the United

States23. As an example, Figure 2 illustrates the quarterly concentration of ambient

ammonia observed across the U.S. back in the year of 2012. Different regions of the United

States had different amount of ammonia in the area; and the concentration of ambient

ammonia varied through the seasons.

It was not surprising to observe higher concentration of ammonia in the central

plain of California is present from March to September whose economy heavily relies on

agriculture24. As society advances, human populations have increased dramatically and

more positions are needed and provided in industry/agriculture, which requires the

government to closely monitor the impact that the growth might bring to the environment.

Monitoring the long-term trend in ambient ammonia concentrations helps scientists better

assess the impact and facilitate the new policy making, so that the ecosystems we all live

in will be sustainable.

3

Figure 2. AMoN 2012 annual ambient ammonia report23

Ambient ammonia is often collected via the utilization of an adsorbent25,26 for

analysis. When collecting the ambient ammonia, there are two types of collector: active

collector and passive collector. For active collector, ambient air is pumped, with a flow

regulator, through an air-collection tube over a time period; inside of the tube is packed

with adsorbing beads/fibers/glass bubblers. In the earlier research, the

beads/fibers/bubblers were coated with sulfuric acid, but the use of sulfuric acid gradually

phased out due to the safety concern to lab technicians and acid corrosion to the sampler.

Nowadays, less corrosive and toxic phosphoric acid is commonly used as the adsorbing

chemical27. Either acid used was to capture the basic ammonia in the air and convert it into

soluble ammonium salt.

For passive collector, such as ALPHA sampler, Radiello sampler, Ogawa sampler,

a diffusive collector, uses the same principle to capture ambient ammonia without the use

4

J A

___ _Jf

of pump, which increases the simplicity of sample collection and lowers the overall cost of

the sample collection28,38,39 as shown in Figure 3. As a result, the diffusive collector was

used in this project.

Figure 3. ALPHA, Radiello, Ogawa Passive samplers design26

The adsorbed ammonia is then extracted with DI water and converted into the form

of ionic ammonium which makes it suitable for volumetric analysis. Analysis of

ammonium can be carried out by colorimetry29,30, ion chromatography28,31, ion selective

electrode32,33, and other methods34. Colorimetry or spectrophotometry relies on the blue-

colored products from the reaction between ammonium and phenol with the presence of

hypochlorite under basic conditions29. The overall reaction is called the Berthelot’s

reaction as can be seen in Figure 4, and it is very easy and straightforward to perform.

5

-0 0- -~► =O= -0--NaClO O-+ NH3 +HO OH O NC5FeN6Na2O

Figure 4. Overall Reaction of Berthelot’s reaction

Even with the use the catalyst, the reaction, however, takes about an hour to complete. In

addition to using Berthelot’s reaction method, microfluid paper-based device (µPAD)

which is a portable analytical device can be utilized on site testing37. This paper-based

device is an inexpensive device and does not require any expensive instrument beside a

cell phone that measure the RBG using a free app. There are increasing interests in the

application of µPAD, but it is not as popular as the classic method. This type of application

is foreseen to be widely utilized in future research.

Ion chromatography is based on the equilibrium of ammonium between the mobile

phase and charged sites on the ion-exchange column. Coupling with conductivity detector,

ion chromatography is able to separate and detect all ions in the solution35. An illustration

of how ion chromatography is able to separate ions in a solution through size and charge

can be seen in Figure 540. In this scenario, small size was eluted first followed by large

size.

6

80

NH:

70

60

. "'l L CH3NH2

30

Na'

(CH3)2NH

20

10

0 0 2 4 6 8 10 12 14 16 18 20

Mim••es

Figure 5. A general chromatogram of an experimental sample40

The ion chromatograph, however, is more expensive than the spectrophotometer and

requires special training on instrument operation. Ion selective electrode is considered to

be a very selective method for ammonium analysis, since it measures the potential

difference involving ammonium between the solution inside and outside the ion selective

electrode. Demonstration of quantitative ISE analysis can be seen in Figure 6, whereas the

open circuit potential is linearly proportional to the concentration of NH3. However, special

care of the ion selective electrode is indeed needed to obtain reliable and reproducible data.

7

20

> 0

-S ~

-20

c -40 $

0 0..

-60 ."!::: ::::l (.) ..... -80 ·13 C: ~ -100 0

-120

-140 0.1

156.4 mV/pNH 4 1

E = 56.4 lg CNH,-N - 32.4

1

Concentration of NH3-N (ppm)

10

Figure 6. An example of using calibration curve using Ion Selective Electrode41

This project was aimed to modify the Berthelot’s reaction and overcome the

reaction kinetic drawbacks to make it more suitable for ambient ammonia analysis,

particularly for in field study. Therefore, the reaction kinetics of the Berthelot’s reaction

was investigated, and the reaction conditions, such as phenol substitutes, catalyst

concentration and so on, were optimized, so that the modified Berthelot’s reaction could

be used for the rapid quantitative analysis of ambient ammonia collected by diffusion.

8

CHAPTER 2

Experimental Design

The atmospheric ammonia, collected by diffusion, is processed through the

Berthelot’s reaction and detected spectrophotometrically.

2.1 Berthelot’s reaction solution preparation

The following reagents/solvents were involved in the Berthelot’s reaction: sodium

bicarbonate/carbonate buffer, phenol, nitroprusside, active chlorine (hypochlorite), and

ammonia.

For the buffer solution, 3.04 g of NaHCO3 alongside with 1.10 g NaOH and

distilled water were dissolved in a 1000mL volumetric flask, which gave the 0.036 M

bicarbonate/carbonate buffer with a pH of 10.60.

The phenol solution was made by dissolving ~10.0 g of phenol in a 100 mL

volumetric flask and diluted to the mark by adding ethanol which gave a concentration

of 1.06 M phenol.

The nitroprusside solution was made by dissolving ~0.50 g of nitroprusside with

distilled water in 100 mL volumetric flask along with a few drops of 10% NaOH, which

gave a concentration of 0.0168 M sodium nitroprusside. The nitroprusside solution was

then shielded with an aluminum foil for storage.

The active chlorine solution was made by diluting Sigma Aldrich’s sodium

hypochlorite solution that contain active chlorine 10 -15% to 1% of active chlorine in 0.2

M NaOH.

9

Furthermore, the standard ammonia was made by dissolving 0.0017 g of

ammonium chloride with distilled water in 25.00 mL volumetric flask which gave a

concentration of 0.00127 M ammonium chloride. This was further diluted by taking out 4

mL of 0.00127 M ammonium chloride and diluted with distilled water in 10.00

mL volumetric flask which gave the concentration 0.5 mM ammonium chloride.

2.2 Spectrophotometric monitoring of the Berthelot’s reaction

A 1.000 mL of 0.5-mM ammonia standard was transferred into a 10-mL glass vial

first; then 500.0-uL of 1.06 M phenol, 500.0-uL of 0.0168M sodium nitroprusside were

added one by one. 5.00 mL of 0.0362 M bicarbonate/carbonate buffer solution and

1.00 mL of sodium hypochlorite with 1% of active chlorine were added at last. The reaction

vessel (vial) was then inverted a few times to thoroughly mix all reactants, and the solution

was left untouched till the color of the solution no longer changed.

Following the completion of the reaction, the final product mixture was then

transferred to a quartz cuvette and placed in a Cary 60 UV-vis spectrophotometer (Agilent

Technologies, Santa Clara, California), and a spectrophotometric scan (from 300 nm to

800 nm) was performed to determine the maximum absorbance wavelength of the product.

2.3 Kinetic Analysis of Berthelot’s Reaction

Once the maximum absorbance wavelength was determined, the reaction was

then monitored temporally in 30-second intervals to determine the rate of the Berthelot’s

reaction.

The concentration of each reactant was then changed to investigate the reaction

order for each reactant. The procedures included doubling the amount of phenol, halving

10

the amount of ammonia, and doubling the amount of active chlorine, respectively. For each

study, a total of six trials were completed.

2.4 Phenylphenol study

Due to the toxicity of phenol, less toxic substituted phenols were used to replace

phenol in the Berthelot’s reaction. These substituted phenols include o-phenylphenol, m-

phenylphenol, and p-phenylphenol.

The experimental conditions for all phenylphenol concentrations were initially set

as the same as phenol. Later, the phenylphenol experimental conditions were modified,

mainly lowering the concentration of phenylphenol and active chlorine, to avoid

precipitate formation. More detailed discussion is given in Chapter 4.

2.5 Diffusive collection of ambient ammonia

In order to capture ammonium from air, a Radiello diffusive air collector was used,

as suggested by the literature26. As illustrated in Figure 7, the outside of the collector was

a porous inert support through which ambient gases can diffuse. Inside the collector, there

was a matrix microporous polyethylene cartridge soaked with phosphoric acid. When

ambient ammonia diffused into the porous structure, it became retained by the phosphoric

acid.

The collector was then placed in the fields across adjacent cities of Los Angeles.

After one week, the cartridge inside the collector was taken out and placed in an enclosed

tube filled with ultrapure water. The tube was then placed into an ultrasonic bath to extract

all ammonia from the cartridge. Following the filtration of the extract, the analysis of

ammonia extract was performed using Berthelot’s method.

11

Diffusion Diffusion

Phosphoric acid coating

Figure 7. Diffusive ambient ammonia collection

12

CHAPTER 3

Quantitation of Active Chlorine

Due to the unstable nature of hypochlorite, the active chlorine concentration was

determined experimentally, following the classic iodometric titration method36.

3.1 Preparation of potassium iodate solution

A small amount (practically 2.1337 g) of potassium iodate, KIO3, was weighed out

of the reagent bottle and microwave-dried for 4 min at the 30% power level to remove any

moisture from the solid; and the dried salt is then cooled down to the room temperature in

a dessicator. An exact amount of 1.754 g dried KIO3 was then dissolved in 250.0 mL of

ultrapure water in a volumetric flask, which gave a concentration of 0.03278 M for the

standard KIO3.

3.2 Standardization of sodium thiosulfate solution

About 12.5 g of reagent-grade sodium thiosulfate (Na2S2O3) were weighed and

dissolved in about 250.0 mL ultrapure water. This Na2S2O3 solution was then loaded into

an analytical buret. In the meantime, 25.00 mL 0.03278 M standard KIO3 solution prepared

was pipetted into a 250.0 mL beaker, along with 10 mL of 10% sulfuric acid and ~2 g of

potassium iodide. Under acidic condition, iodate reacts with iodide to form triiodide:

��!" + 8�" + 6�# ⟶ 3�!" + 3�$�

13

Due to the presence of triiodide, the solution has a red-orangish color (see figure 3a). The

triiodide is then subsequently titrated with Na2S2O3, which converts the colored triiodide

into colorless iodide:

"2�$�!$" + �! ⟶ �%�&$" + 3�"

With the continuous addition of sodium thiosulfate which consumed the colored

triiodide, the color of the solution became lighter and lighter (demonstrated as Figure 8a

and 8b). When the solution became straw-colored (as demonstrated in Figure 8b), a few

drops of 1% starch solution was added, which immediately turned the solution blue, due to

the presence of triiodide (as shown as Figure 8c). The end point of the titration was

achieved when the solution became colorless with the addition of sodium thiosulfate

(Figure 8d), which happened just a few more drops of sodium thiosulfate were added after

the introduction of starch indicator. The volumes of sodium thiosulfate inside the buret

were recorded at the beginning of the titration and the end of titration, respectively. The

difference between the two sodium thiosulfate volumes was considered to be the volume

needed for the stoichiometric completion of the reaction.

The titration was then repeated for three more times, and all numerical data were

recorded in Table 1. In addition, the average concentration of sodium thiosulfate was

determined to be 0.1691 M. The standard deviation of the measurement was determined to

0.0052, and corresponded to 3.0% relative standard deviation, which is acceptable for

quantitative chemical analysis.

14

Figure 8. Titration process: a. before the equivalent point; b. close to the equivalence point; c. addition of starch indicator; d. end of titration

15

Table 1. Standardization of Na2S2O3 Data Utilizing Iodometric Titration

Trial 1 2 3 4 Concentration of KIO3

(M) 0.03278

Mass of KI (g)

2.0016 2.0068 2.0030 2.0024

Initial Buret Volume (mL)

0.26 0.20 0.20 0.19

Straw color volume (mL)

29.88 29.21 28.14 28.48

Final Buret Volume (mL)

30.34 29.76 28.30 28.81

Sodium thiosulfate Volume Used (mL)

30.08 29.56 28.10 28.62

Concentration of Sodium Thiosulfate (M)

0.1635 0.1664 0.1750 0.1718

Avg. Conc. of Sodium Thiosulfate

(M)

0.1691

Standard Deviation of Conc. Sodium Thiosulfate (1)

0.0052

% Standard Deviation 3.0

16

3.3 Quantifying Active Chlorine

The active chlorine solution (commercial bleach purchased from Sigma Aldrich)

was first diluted for 10 times because iodine is not very soluble and wants iodine to stay in

an aqueous phase. Following that, 25.00 mL of diluted bleach was pipetted into a beaker,

along with 10 mL 10% sulfuric acid and ~2 g of KI. The following reaction occurred in the

beaker, turning the solution brown.

���" + 3�" + 2�# ⟶ �!" + ��" + �$�

Following the same procedure of sodium thiosulfate standardization, standardized Na2S2O3

was added to the beaker from the buret till the solution changed to straw-yellow. Addition

of a couple of drops of 1% starch solution turned the solution blue, and the solution turned

colorless at the titration end point.

The titration was repeated for three more times; however, the first trial data were

statistically discarded due to the gross error. The data collected from other three trials were

used to determine the moles of sodium thiosulfate used, the moles of hypochlorite, and the

concentration of hypochlorite. It was determined that the hypochlorite concentration in the

bleach was 0.658±0.037 mol/L.

When the student’s t-test was applied, the calculate t was given by

|�̅ − �| |0.658 − 0.700|�'()'*)(+,- = = = 1.135� 0.037

17

The calculated t value is less than the critical t value (=2.353) at 90% confidence level,

therefore, the obtained result is statistically in agreement with the given value (0.700

mol/L) on the household commercial bleach label.

Table 2. Values of Student’s t obtained from Harris Quantitative Chemical Analysis 8th

edition.

Degrees of

freedom

Confidence Level (%)

50 90 95 98 99 99.5

1 1.000 6.314 12.706 31.821 63.656 127.321

2 0.816 2.920 4.303 6.965 9.925 14.089

3 0.765 2.353 3.182 4.541 5.841 7.453

4 0.741 2.132 2.776 3.747 4.604 5.598

5 0.727 2.015 2.571 3.365 4.032 4.773

6 0.718 1.943 2.447 3.143 3.707 4.317

7 0.711 1.895 2.365 2.998 3.500 4.029

18

CHAPTER 4

Spectrophotometric Characterizing of Berthelot’s Reaction

Once all the chemicals used for the Berthelot’s reaction were introduced into the

reaction vessel (a 20-mL capped glass vial), the reaction started right away with a tint of

color appearing in the solution. The solution color inside the reaction vessel was then

monitored spectrophotometrically.

4.1 Reaction with phenol

The reaction vessel was first loaded with phenol, sodium nitroprusside, pH 10.60

bicarbonate/carbonate buffer solution, sodium hypochlorite with 1% of active chlorine, and

sodium hydroxide. When the ammonia solution was transferred into the reaction vessel,

the overall volume of all reagents was 10.00 mL. In the meantime, a very light color started

to appear in the solution. The reaction vessel was then inverted a few times to thoroughly

mix all components.

The color of the solution became darker with the reaction time increasing, from

light greenish blue to dark navy blue. The color of solution did not turn any darker visually

in about 45-60 minutes, and as shown in Figure 9, the blue color of the solution was very

dense.

19

.

Abso

rban

ce

Figure 9. Image of the Berthelot’s reaction vessel.

When the solution was scanned spectrophotometrically, two peaks (390 nm and

510 nm) and one broad shoulder from 550-675 nm were observed, respectively.

0.300

0.250

0.200

0.150

0.100

0.050

0.000 350 400 450 500 550 600 650 700 750

wavelength (nm)

Figure 10. UV/vis spectrum of the Berthelot’s reaction

20

r r + +

+ +

Abso

rban

ce

1.2

1

0.8

0.6

0.4

0.2

0 350 400 450 500 550 600 650 700 750 800

Wavelength (nm)

When a higher concentration of ammonia was used, and the following spectrum

was obtained, the peak at 635 nm was very distinguishable. This peak corresponds to the

indophenol produced in the reaction30.

Figure 11. UV/vis spectrum of indophenol

The same reaction was repeated, with only change being in solvent. Instead of using

0.2 M NaOH to dilute the solution mixture, ultrapure water was used to provide a more

acidic condition for the reactions.

21

Figure 12. Reaction vessel with ultrapure water dilution

Compared to the NaOH-dilution vessel, water-diluted mixture has a bit tint of green

on its color. A faint yet transparent green color solution was caused by an extra proton that

came from water was protonated the indophenol structure that can be seen in Chapter 6. In

term, some of the products were in reduction phase instead of oxidation phase. That meant

in the mixture solution, the reaction is being reversible. This caused the less basic condition

to have transparent green color solution. To be accurately ensure of this theory, H-NMR

should be able to confirm this theory in the future study. In addition, when the solution was

scanned photometrically, the maximum absorbance wavelength was determined to be

about the same as the original condition.

4.2 Reactions with Phenylphenol

Less toxic phenylphenol was also investigated to substitute phenol in the

Berthelot’s reaction under both conditions. When sodium hydroxide was used to dilute the

22

solution, visually, o-phenylphenol and m-phenylphenol had similar color and intensity,

whereas p-phenylphenol appeared to be more in orange color, as indicated by Figure 13.

Figure 13. Phenylphenol reaction: from left to the right, o-, m-, and p-phenylphenol

When ultrapure water was used, the very first thing noticed was that a cloudy

solution obtained for o-phenylphenol reaction vessel which was shown in Figure 14. When

the less concentrated o-phenylphenol was used, the solution became clear.

Figure 14. o-phenylphenol reaction vial (left) concentrated and (right) diluted.

23

In order to perform the comparison among all substituted phenols, the concentration

of all phenylphenol solutions was lowered to such an amount that no precipitate was

formed for o-phenylphenol. It was observed that all three solutions have their own colors:

darker green o-phenylphenol, light green m-phenylphenol, and light orange

p-phenylphenol, illustrated as Figure 15, which may indicate the difference in the kinetic

process. It was noticed that p-phenylphenol solution did not change its color much over the

time, indicating that the p-phenylphenol reaction under the strongly basic condition is not

favored or is a slow process, whereas other two phenylphenol vessels became darker. In

the future, the product of p-phenylphenol should be analyzed using NMR or UV-Vis to see

if there is a new product being form because the products of this reaction may also have

different colors which cannot differentiate with a naked eye.

Figure 15. Phenylphenol reaction under less basic conditions: from left to right, o-, m-, and p-phenylphenol

All three solutions that were in basic conditions were then scanned

spectrophotometrically, and the spectra are shown as below: Figure 16, o-phenylphenol;

Figure 17, m-phenylphenol, and Figure 18, p-phenylphenol.

24

~

• t-

t-t-

t-+

+

•

+

. t

+

+

+

. t

+

+

Abso

rban

ce

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0 300 350 400 450 500 550 600 650 700 750 800

Wavenumber (nm)

+

~

+

t-t-

t-+

t-

+

+

t +

+

t +

+

Abso

rban

ce

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0 300 350 400 450 500 550 600 650 700 750 800

Wavenumber (nm)

Figure 16. o-phenylphenol reaction overall spectrum

Figure 17. m-phenylphenol reaction overall spectrum

25

/ r\.

\/ \ \ \ '\.

.......... ---

1

0.9

0.8

0.7 nc

e 0.6

orba 0.5

Abs

0.4

0.3

0.2

0.1

0 300 400 500 600 700 800

Wavenumber (nm)

Chemical Name Maximum absorbance wavelength Absorbance

o-phenylphenol 690 nm 0.095

m-phenylphenol 690 nm 0.155

p-phenylphenol 685 nm 0.038

Figure 18. p-phenylphenol reaction of overall spectrum

Although visual difference was observed for three phenylphenols, the maximum

absorbance wavelengths are very similar to each other, demonstrated as Table 3. The color

difference lies in the intensity of the color, meaning the product of m-phenylphenol has the

highest concentration than others. In other words, the reaction with m-phenylphenol is

more favorable than other two phenylphenols.

Table 3: The maximum absorbance wavelength for phenylphenol reaction mixture

26

4.3 Experimental Condition

The condition of this experiment was the same condition as from Radiello diffusion

air sampling application of ammonia except of utilizing 0.4 mL of phenol and 0.4 mL of

nitroprusside; this study used 0.5 mL of phenol and 0.5 mL of nitroprusside. Once all of

the reagents were mixed, the solution turned to indophenol blue within an hour. Sodium

hypochlorite that was purchased fresh claimed 10% of active chlorine in it, the sodium

hypochlorite was therefore diluted down to 1% of active chlorine nominally. The formation

of indophenol blue was complete within 10 – 15 minutes which is much shorter than the

traditional condition. Further investigation of this part was discussed in Chapter 6.1

27

Tim

e in

crea

ses

Abos

rban

ce

525 575 625 675 725 775

Wavelength (nm)

CHAPTER 5 Reaction Kinetics

It was noticed that the reaction vessel became much darker with the reaction time

increasing, which prompted the investigation of the reaction kinetics.

5.1 Reaction rates

Once all chemical reagents were introduced in the reaction vessel and thoroughly

mixed, a small portion of the solution, ~1.5 mL, was transferred into a cuvette; and the

cuvette was then placed in the UV-vis spectrophotometer. The full scan of absorbance of

the solution was recorded with an interval of 30 second until the 10 minutes mark. Fig 19.

shows example spectra of such a process.

Figure 19. Representative spectra through continuous absorbance measurement of Berthelot’s reaction, where absorbance was taken every 30 seconds for ten minutes.

28

0.7

0.6

0.5

0.4

0.3

0.2

0.1

Abso

rban

ce

0 0 100 200 300 400 500 600

Time (sec)

Measurements of this solution were repeated five more times, and the average

absorbance value with standard deviation at each measurement time was plotted against

the duration of the reaction. As indicated by Figure 20, the absorbance (measured at 635

nm) of the solution increases with the time, but with different paces in different regions.

At the beginning, it slowly increases, which is the result of reaction initiation. Once in the

middle region on the graph, the absorbance rapidly increased, which indicates a faster

reaction rate. A slightly greater standard deviation is also observed in the middle region,

which shows the rapid changes involved in the reaction. The reaction then slows down

toward the end of the reaction, meaning it is reaching the chemical equilibrium.

Figure 20. Kinetic curve of the Berthelot’s reaction where scans were taken every 30 secs at a room temperature.

When the first derivative function was applied to the above averaged data, which

plots the dABS/dTime versus time, a better understanding of the reaction process can be

29

achieved (Figure 20). The Lambert-Beer’s law correlates the absorbance with the amount

of analyte in the solution. Therefore, dABS/dTime can be rewritten as:

���� �(���) �����

= ��

In this equation, e is the molar absorptivity of the analyte, b is the light path length, and c

is the concentration of the product. Both of e and b are constant for the measurement.

Therefore,

�(���) �� �� = �� ��

As known, the reaction rate is defined as d[product]/dt. The dABS/dTime is,

therefore, linearly proportional to the d[product]/dTime. The value of dABS/dTime can be

considered to be linearly proportional to the reaction rates.

���� �� �� = �� (�������� ����)�����

= ��

As reflected by Figure 21, even though the time interval was the same, the changes

in concentration increased with more products formed and the reaction rate has reached its

maximum at 345 s. When the reaction reaches its equilibrium, the concentration of both

reactants and products stayed unchanged. This result in the dABS/dTime value to be zero.

Figure 21 illustrates that, at the beginning the reaction was moving toward the equilibrium;

30

►

.I ►

I t

► I ►

►

► I

►

►

►

~

►

►

►

►

►

►

+

+ ►

+ ~

► ►

►

+

+

+

~

0.0016

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0.0014

dABS

/dTi

me

0 0 100 200 300 400 500 600 700

Time (sec)

but overall it has not reached the equilibrium yet, due to the downward trend and none-

zero value in dABS/dTime.

Figure 21. First derivative of the Berthelot’s reaction kinetic curve by taking a difference of ABS and time.

Reaction rate can be also written as:

���� = �[�]([�].[�]/,

where [A], [B], and [M] are the reactant concentrations, and a, b, m are the reaction orders

for each corresponding reactant. When determining the reaction order for each reactant, all

experimental conditions except one reactant concentration are kept the same. Using the

variation in A as an example,

����0 = �[�](0[�].[�]/,

and ����$ = �[�]($[�].[�]/.

31

The ratio of the two reaction rates can be used to determine the reaction order.

(����0 �[�](0[�].[�]/

= P[�]0= Q����$ �[�]($[�].[�]/ [�]$

The reaction order of a is given by:

log (����0����$� = ��� P[�]0Q

)

[�]$

5.2 Reaction order of phenol

Initially, 125 mM phenol was used in the Berthelot reaction, as reflected by Figure

20. Once the phenol concentration was doubled to 250 mM, as seen in Figure 22, the

kinetic curve of doubling the volume of phenol was similar to one in Figure 20. However,

the doubling of the phenol amount has made the product generated more quickly than the

previous Berthelot reaction. For example, the absorbance of 0.400 was reached at 420 s for

125 mM phenol, and the absorbance of 0.400 was reached at 330 s with 250 mM phenol

presence. Also reflected by the Figure 22, the lower the standard deviation was obtained

for the higher concentration of phenol, implying that all six trials went through similar

reaction paths and reproducible results were obtained.

Similarly, the first derivative curve was also plotted (Figure 23). Compared to

Figure 10, Figure 23 indicates a drastic inclination at the beginning of values of the

dABS/dTime. The maximum value of dABS/dTime was found to be at 225 secs. After the

225 secs mark, the rate gradually declined over time.

Upon comparison between the reaction rates for two different concentration of

phenol, the reaction order for phenol was determined to be around 1.

32

0.5

0.7

0.6

0.4

0.3

0.2

0.1

0 0 100 200 300 400 500

Time(sec)

Abso

rban

ce

600

+

+

+ +

+

... _,_

+- -,.

+

0.0016

0.0014

0.0012

0.0004

0.0006

0.0008

0.001

dABS

/dTi

me

0.0002

0 0 100 200 300 400

Time (sec) 500 600 700

Figure 22. Kinetic curve of the Berthelot reaction with double the concentrated phenol.

Figure 23. First derivative curve of the Berthelot’s reaction with of the double the concentrated phenol.

33

+ t

( f I

f f

. I I f

f I I [ • f f f

! I t

'

t

t

'

I

I

► 0.6

0

0.1

0.2

0.3

0.4

0.5

Abso

rban

ce

0 100 200 300 400 500 600

Time (sec)

5.3 Reaction order of hypochlorite

The reaction order of hypochlorite was investigated in a similar way, and the

volume of hypochlorite added was doubled while other reagents stayed unchanged. Figure

24 indicates smaller the standard deviations were observed in the measurement of reaction

with a higher concentration, compared to the lower concentration ones.

Figure 24. Kinetic curve of double the concentrated hypochlorite in the Berthelot reaction.

The first derivative plot of hypochlorite was also explored. As seen in Figure 25,

from 15 secs to 225 secs, there is semi-perfect linear trend. However, the reaction did not

hit the plateau until 285 secs. After 285 secs, reaction rate gradually declines.

Upon comparison between the reaction rates for two different concentration of

hypochlorite, the reaction order for hypochlorite was determined to be around 1.

34

► &+ & & &

~ + & ~ &

► + ► & &

~ + &

&

-,.

0.00020

0.00040

0.00060

0.00080

0.00100

0.00120

0.00140

0.00160

dABS

/dTi

me

0.00180

0.00000 0 100 200 300 400 500 600

Time (sec)

Figure 25. First derivative of kinetic curve of double the amount of hypochlorite in the Berthelot’s reaction.

5.4 Reaction order of ammonia

The final step to construct an overall rate of the reaction for Berthelot’s reaction

was to investigate the reaction order for ammonia. For this part, half the amount of original

volume of ammonia was added to Berthelot’s solution to obtain the kinetic curve, as can

be seen in Figure 26. This curve shows that ammonia’s kinetic curve has the maximum

absorbance about half of the original one, due to the half the amount of original ammonia

was added to Berthelot’s reaction.

Upon comparison between the reaction rates for two different concentration of

ammonia, the reaction order for ammonia was determined to be around 1.

35

+ +

: I I I I I I I I t t t I I ·

a a a a i I ! ,

+

+

Abso

rban

ce

0.400

0.350

0.300

0.250

0.200

0.150

0.100

0.050

0.000 0 100 200 300 400 500

Time (sec) 600

Figure 26. Kinetic Curve of the half the amount of Ammonia in Berthelot’s reaction.

5.5 Overall reaction order of Berthelot’s reaction

After calculating each of the reactant order, the overall reaction order of

Berthelot’s reaction can be determined. This is done by adding all of the reactant order

which came out to be third order. The third order meant that the rate of reaction is

proportional to the concentration of each of the three reactants or that all three reactants

have uneven concentrations.

5.6 Kinetics under more basic conditions

The kinetics for all reactions under more basic conditions was also investigated.

Represented in Figure 27 is the continuous monitoring of m-phenylphenol reaction with

NaOH dilution. At the beginning of the measurement, a relatively high absorbance of

~0.400 was observed already; the absorbance was then gradually increasing. A turning

36

T

49 ~

1 ! ! ! ! ! 48 ~

I I I I I ~

I u 47 I C:

I .. I .D :, ! ~ -0,& ! .D

< ! -OS ! I -OA f f

-100 0 100 200 300 400 500 600

Time (sec)

point was observed at 180 s into the reaction. All six trials showed the similar trend, as

revealed in Figure 22. In addition, other phenols had a similar trend. More experiments

should be carried out in the future to investigate all factors involved.

Figure 27. Kinetic curve of m-phenylphenol reaction with NaOH dilution in Berthlot’s reaction.

37

� � � �

p A

Q

y t

t t

0 0

Q

CHAPTER 6

Reaction Mechanism

Reaction mechanism6.1 I

Although different reaction mechanisms have been brought up by many scientists,

the following reaction path has been more commonly accepted than others. During the

Berthelot’s reaction, ammonia will combine with hypochlorite first to produce a

monochloramine. The monochloramine will then combine with one phenol molecule,

forming benzoquinone monochloramine intermediate. This reaction intermediate will then

react with the second phenol molecule, forming blue-colored indophenol, and this reaction

is typically catalyzed by nitroprusside. The reaction process can be written as:

NH3 + NH2ClOCl -

NH2 Cl

NH2 Cl + OH

O NCl

O NCl + OH

O -

O

N

Figure 28. Mechanism of Berthelot’s reaction utilizing phenol

As noticed in the experiments, nitroprusside played a very important role in

indophenol production. It is said that the purpose of nitroprusside is to form aqua

pentacyanoferrate first, which serves as the coupling reagent to accelerate the reaction.

ª º ª º Na Fe CN NO R N a Fe CN H O 2 3 2 ¬ 5 ¼ ¬ 5 ¼

38

Instead of identifying it as a catalyst, it is more appropriate to consider nitroprusside as a

reaction reagent. The peak at 399 nm grew with the time increasing, which was reported to

be due to the presence of sodium aquopentacyanoferrate. An increase in the concentration

of nitroprusside greatly fastened the overall reaction rate, shortening the reaction time.

Compared to literature values, the concentration of nitroprusside that was chosen in this

project shortened the reaction time from over 45 minutes down to 10-15 minutes.

Maintaining a constant pH is also important for this reaction. The significance of

the reaction pH might be due to the pH-independent equilibria involved in this reaction.

For instance, pH will affect the hydrolysis of NH3, the hydrolysis of ClO-, and acid

dissociation of C6H5OH. Therefore, an optimal pH condition must be used for the reaction.

In this experiment, two different pHs, weakly basic and strongly basic, were tested. A

higher concentration of indophenol was obtained for the lower pH condition, while strongly

basic condition precipitated some reagents and does not favor the product formation. pH

could be a sensitive tool to be investigated for the future for reaction optimization.

6.2 Reaction mechanism II

Literature suggested that substituted phenols produced essentially the same end-

product as phenol, but with very variable rates of formation of indophenol blue. 2-

methylphenol and 2-chlorophenol have been proved to be satisfactory reagents with less

toxicity than phenol. For phenylphenols, only o-phenylphenol has been used as the

substitute of phenol in the Berthelot’s reaction. No reaction mechanism has been provided

in the literature, although a few groups have been using o-phenylphenol in aqueous

ammonia analysis.

39

-0 0- ► =0=-0-

0--0 0-0 ► ~0--0

b-o 0--0-

b-o-~► 0--0

o-q--0--0 -0--0 ►

1.

NaClO O-+ NH3 +HO OH O NC5FeN6Na2O

2.

O

O-OHOH

NaClO C5FeN6Na2O+ NH3 +

N

O-3.

OH OH N

NaClO+ NH3 + C5FeN6Na2O

O

O-4.

NNaClO C5FeN6Na2O

HO + NH3 + HO

O

Base on the reaction mechanism reported so far for substituted phenols, the

following product was proposed, as shown in Figure 29. Indeed, the different reaction

rates were observed for different phenylphenols. However, the similarity in the maximum

absorbance wavelength indicates the similarity in the final product. More investigations,

such as NMR testing, are needed to elucidate the reaction mechanism.

Figure 29. Proposed reaction products of o-,m-,p- phenylphenols.

40

•...

+

+

+

+

+

··•·· ..... •··

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

Concentration (ppm)

Abso

rban

ce

y = 0.0818x + 0.0246 R² = 1

0 2 4 6 8 10 12

CHAPTER 7

Quantitation of Ambient Ammonia

7.1 Calibration curves

As known for UV-vis spectrophotometry, the absorbance of a solution is directly

proportional to the analyte concentration. The linear relationship is expressed as the

Lambert-Beer’s Law,

A = ebc,

where e is the molar absorptivity of the analyte, b is the light path length, and c is the

concentration of the absorbing species.

In the Berthelot’s reaction investigated, ammonia was the limiting reagent.

Therefore, a standard calibration curve was constructed by plotting the measured

absorbance versus the concentration of ammonium (Figure 30-33). The R2 values of ~0.99

indicates an almost perfect linearity between the measured absorbance and the ammonium

concentration.

Figure 30. Ammonia calibration curve based on phenol reaction

41

0.9

0 2 4 6 8 10 12

Concentration (ppm)

y = 0.0836x - 0.0275 R² = 0.9977

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Abso

rban

ce

.... •·· r +

+

+

+-

... ··· ..... •••••• +-

_,_

_,_

0.7

0 0 2 4 6 8 10 12

Concentration (ppm)

y = 0.0575x + 0.0753 R² = 0.9867

0.1

0.2

0.3

0.4

0.5

0.6

Abso

rban

ce

Figure 31. Ammonia calibration curve based on o-phenylphenol reaction

Figure 32. Ammonia calibration curve based on m-phenylphenol reaction

42

•... •

+ + + +

+ + + ••• •••

: .... •·········: ................... ~················ : ••• •· +- +­

... •···· +- +- +-

•• .... .. ... •····

+

+-

+-

+-

y = 0.01x + 0.0161 R² = 0.9971

0.02

0.04

0.06

0.08

0.1

0.12

Abso

rban

ce

0.14

0 0 2 4 6 8 10 12

Concentration (ppm)

Figure 33. Ammonia calibration curve based on p-phenylphenol reaction

Among the substituted phenols, p-phenylphenol has the lowest sensitivity, while

m- and o-phenylphenol has the relatively high sensitivity. In the meantime, the relatively

high background value was observed for o-phenylphenol. Taking all factors into

consideration, m-phenylphenol is more suitable for the ammonia analysis with relatively

low concentrations.

7.2 Analysis of ammonia in extracts

All samples collected at different sites were extracted with DI water first according

to the method mentioned in Chapter 2, and then processed with the Berthelot’s reaction.

The absorbance of the solution was measured next, and the concentration of ammonium in

the extract was calculated by applying the best linear fit equation obtained in Figures 30-

33. The results were within the range of the values reported by another student, indicating

43

the different ammonia concentrations were observed at different locations, which is the

result of different primary sources of ambient ammonia.

Table 4. Determination of ambient ammonia to compare with another student value

Sample Number Concentration of Ammonium in Extract (ppm)

1 0.386

2 0.752

3 2.621

4 1.026

5 0.771

6 0.923

7 4.462

8 1.708

9 1.854

10 1.237

11 4.115

Afterward, quantification of ambient ammonia samples was compared using different

types of phenylphenols. As can be seen in Table 5, all of the results were within the range

of phenol except for o-phenylphenol. This might be because of not waiting enough time

for reaction to be completed or o-phenylphenol are more sensitive than other

phenylphenols. This can be further investigated in the future.

44

Table 5. Comparison of ambient ammonia quantification by using Phenol and Phenylphenols.

Regents Concentration of Ammonium (ppm)

Phenol 0.57

o-phenylphenol Undetermined

m-phenylphenol 0.72

p-phenylphenol 1.11

45

CONCLUSION

Ammonia is the most abundant basic gas that can be found in anywhere around the

world, by utilizing Berthelot’s reaction, and scientists rely on the ammonia data and address

ammonia problems within certain regions. This in terms can result in less pollution around

the world and cleaner environment. However, using Berthelot’s reaction have some major

setbacks, such as having phenol as a toxic reagent and the reaction takes long to complete.

Nevertheless, recent studies have shown that o-phenylphenol was able to replace the phenol

as a less toxic reagent. For this project, the Berthelot’s reaction was modified and studied

in the areas of the reaction rates and substitution of phenol with o-, m-, and p-

phenylphenols. During the studies, the Berthelot’s reaction time was able to reduce to 10

minutes by using a higher active chlorine concentration. With the shortened Berthelot’s

reaction time, this can be potentially used in on site studies in the future by utilizing

microfluid paper-based device along with colorimetry.

46

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