Kinetics of the Depolymerization of Diacetone Alcohol via Basic Catalysis 2019 (report)

CHM2330 Kinetics of the Depolymerization of Diacetone Alcohol via Basic Catalysis - Amini & Audet.pdf

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Running Head: DEPOLYMERIZATION OF DIACETONE ALCOHOL i

Experiment N:

Kinetics of the Depolymerization of Diacetone Alcohol via Basic Catalysis

Farhang Frank Amini IIIIIIIIIIIIII Bradley Audet IIIIIIIIIIIIII

CHM 2330 - A02

Physical Chemistry, An Introduction to Molecular Properties of Matter

Laboratory

Dr. Wendy Pell

Dr. Tom Woo

Mr. Daniel Luis Do Nascimento

Due Date: February 26, 2019

Submission Date: February 26, 2019

Department of Chemistry and Biomolecular Sciences

University of Ottawa

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Table of Contents

Objectives 1

Introduction 1

Experimental Procedure 2

Description of Chemicals 2

Reaction Procedure 2

Titration Procedure 3

0.2 M NaOH Preparation Procedure 4

Safety 4

Acids 4

Bases 4

DAA 4

Phenolphthalein 4

Setup 5

Uncertainty 5

Results and Discussions 5

Results 6

Data tables 6

Trial 0 6

Trial 1 6

Trial 2 6

Trial 3 6

Titrations 6

Trial 1 (~0.2M) 7

Trial 2 (~0.3M) 7

Trial 3 (~0.4M) 7

Errors 8

Titration 8

Graphs 9

Determining the Order of DAA 9

0th Order 9

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

iii

1st Order 9

2nd Order 9

First order fits 10

Trial 1 10

Trial 2 10

Trial 3 10

Discussion 10

General 10

Calculations 11

Preparation of a 0.2 M NaOH solution 12

Titration 12

Volume to Density correlation 12

Change in height 13

Reaction rate constant 13

Assume [OH-] order is zero 13

Assume [OH-] order is one 13

Assume [OH-] order is two 14

Conclusion 14

Questions 14

Conclusion 17

Bibliography 18

Schedule I 18

Schedule II 19

Schedule III 19

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

List of Figures

Figure 1. Experimental setup of dilatometer................................................................................... 5

Figure 2. A linear fit on the scatter plot of Trial 2 plotting the change in height in the capillary vs time in minutes. ...................................................................................... 9

Figure 3. A linear fit on the scatter plot of Trial 2 plotting ln(change in height in capillary) vs time in minutes. .................................................................................... 9

Figure 4. A linear fit on the scatter plot of Trial 2 plotting 1/(change in height) vs time in minutes. ......................................................................................................... 9

Figure 5. A linear fit on the scatter plot of Trial 1 plotting ln(change in height in capillary) vs time in minutes. .................................................................................. 10

Figure 6. A linear fit on the scatter plot of Trial 2 plotting ln(change in height in capillary) vs time in minutes. .................................................................................. 10

Figure 7. A linear fit on the scatter plot of Trial 3 plotting ln(change in height in capillary) vs time in minutes. .................................................................................. 10

Figure 8. Mechanism for DAA depolymerization (p. 119) 11. ...................................................... 11

Figure 9. Slide 33 of Experimental Kinetics by Keillor for CHM 8304 2 .................................... 19

List of Equations

Equation 1. General rate law equation ............................................................................................ 1

Equation 2. General rate law equation for basic depolymerization of DAA .................................. 1

Equation 3. Rate law with k-observed ............................................................................................ 2

Equation 4. k-observed definition ................................................................................................... 2

Equation 5. Plot to find k graphically ............................................................................................. 2

Equation 6. General DAA and OH- rate law ................................................................................ 11

Equation 7. Rate law with observed k .......................................................................................... 11

Equation 8. Concentration by volume is constant for any solute. ................................................ 12

Equation 9. Equation used to find ln(k). ....................................................................................... 13

Equation 10. General rate equation for reaction of DAA and OH-. ............................................. 14

Equation 11. Solution to general rate equation for reaction of DAA and OH-. ........................... 14

Equation 12. Solution to question seven (7). ................................................................................ 15

Equation 13. Solution to question ten (10). .................................................................................. 16

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

List of Tables

Table 1. The linear relation for reaction order (See Schedule II) 2 ................................................. 1

Table 2. Description of chemicals used in lab N. ........................................................................... 2

Table 3. Instruments used and their uncertainties. .......................................................................... 5

Table 4. Test trial with leak in the seal of the washer present. ....................................................... 6

Table 5. Capillary readings of trial 1 (0.2 M NaOH)...................................................................... 6

Table 6. Capillary readings of trial 2 (0.3 M NaOH)...................................................................... 6

Table 7. Capillary readings of trial 3 (0.4 M NaOH)...................................................................... 6

Table 8. Titration for Trial 1, first run using ~0.2 M NaOH with 0.1000 M HCl. ......................... 7

Table 9. Titration for Trial 1, second run using ~0.2 M NaOH with 0.1000 M HCl. .................... 7

Table 10. Titration for Trial 2, first run using ~0.3 M NaOH with 0.1000 M HCl. ....................... 7

Table 11. Titration for Trial 2, second run using ~0.3 M NaOH with 0.1000 M HCl. .................. 7

Table 12. Titration for Trial 3, first run using ~0.4 M NaOH with 0.1000 M HCl. ....................... 8

Table 13. Titration for Trial 3, second run using ~0.4 M NaOH with 0.1000 M HCl. .................. 8

Table 14. Calculated sodium hydroxide solution concentrations and their averages. .................... 9

Table 15. Values used in sample calculation of base molarity from titration. .............................. 12

Table 16. Rate constant calculation if order of hydroxide is zero. ............................................... 13

Table 17. Rate constant calculation if order of hydroxide is one. ................................................ 14

Table 18. Rate constant calculation if order of hydroxide is two. ................................................ 14

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Objectives

Determining the rate law equation for the depolymerization of diacetone alcohol to acetone using sodium hydroxide solution as a catalyst at 25 °C. This includes the order of the concentration of the hydroxide ions and the concentration of diacetone alcohol as well as the reaction constant.

Introduction

A rate law mathematically represents the relationship between the rate of reaction and the concentration of the reactants in a reaction. For a reaction such as 𝐴+𝐵−>𝐶 , the rate law would take the following form:

𝑟𝑎𝑡𝑒=𝑘[𝐴]𝑎[𝐵]𝑏

Equation 1. General rate law equation

The “rate” is the change in concentration over time. The constant ‘k’ is the rate constant and is unique to each reaction. The exponents ‘a’ and ‘b’ represent the orders of species A and B respectively and the sum of ‘a’ and ‘b’ represents the overall order of the reaction 1. The order of a reaction refers to the extent to which changes in a reactant’s concentration cause a change in the rate of reaction. This concept is best understood by doing the calculations. Using reactant X, compare a zero-order reaction, 𝑟𝑎𝑡𝑒=𝑘[𝑋]0,to a second-order reaction,𝑟𝑎𝑡𝑒=𝑘[𝑋]2. During the zero-order reaction, changes in concentration are raised to the zeroth power, and thus have no effect on the rate. For the second-order reaction, changes in concentration are raised to the second power, meaning that a doubling of the concentration would cause a quadrupling of the rate of reaction.

The order of a reaction can be determined by measuring changes in concentration of the reactive species over time and plotting them graphically. Table 1 states which linear relations correspond to which order of reaction.

Order

Linear Relation

Zero

[A] = kt

First

𝑙𝑛[𝐴]=−𝑘𝑡

Second

1/[𝐴]=𝑘𝑡

Table 1. The linear relation for reaction order (See Schedule II) 2

This experiment studies the reaction 𝐶6𝐻12𝑂2−>(𝐶𝐻3)2𝐶𝑂. The rate equation takes the following form: 𝑟𝑎𝑡𝑒=𝑘[𝐶6𝐻12𝑂2]𝑎[𝑂𝐻−]𝑏

Equation 2. General rate law equation for basic depolymerization of DAA

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

This experiment uses a technique called flooding. Flooding involves using a large quantity of one reactant “[which] allows us to isolate the effect of the other reactant on the rate of change or reaction rate” 1. Specifically, the quantity of OH- is substantially larger than that of 𝐶6𝐻12𝑂2(hereafter “DAA”), its change in concentration is negligible. Therefore, the rate equation is simplified to the following, in which 𝑘𝑜𝑏𝑠=𝑘[𝑂𝐻−]𝑏: 𝑟𝑎𝑡𝑒=𝑘𝑜𝑏𝑠[𝐶6𝐻12𝑂2]𝑎

Equation 3. Rate law with k-observed

Once the order, a, has been determined (based on the relations in Table 1), the observed rate constant, kobs, can be calculated: kobs is the slope of the linear relation, and therefore can be found by performing a linear regression on the data. Once kobs is known, the real rate constant, k, can be derived in the following manner: 𝑘𝑜𝑏𝑠=𝑘[𝑂𝐻−]𝑏

Equation 4. k-observed definition 𝑙𝑜𝑔(𝑘𝑜𝑏𝑠)=𝑙𝑜𝑔(𝑘[𝑂𝐻−]𝑏) 𝑙𝑜𝑔(𝑘𝑜𝑏𝑠)=𝑏∗𝑙𝑜𝑔([𝑂𝐻−])+𝑙𝑜𝑔(𝑘)

Equation 5. Plot to find k graphically

When 𝑙𝑜𝑔(𝑘𝑜𝑏𝑠)=𝑏∗𝑙𝑜𝑔([𝑂𝐻−])+𝑙𝑜𝑔(𝑘)is plotted graphically, the slope is b, the order of DAA, and the y-intercept is log(k), which can be used to find k, the real rate constant of the reaction.

Experimental Procedure

Description of Chemicals

Chemicals

Common Name

Sodium Hydroxide

Hydrochloric Acid

Diacetone alcohol

Phenolphthalein

IUPAC name

Sodium oxidanide 3

Hydrogen chloride 4

4-Hydroxy-4-methyl-2-pentanone 5

3,3-Bis(4-hydroxyphenyl)-2-benzofuran-1-one 6

Molecular formula

NaOH

HCl

C6H12O2 C20H14O4

Structural formula

NaOH

HCl (CH3)2C(OH)CH2COCH3

Not applicable

Concentration

Different concentrations used

0.1000

>95%

0.1 %

Appearance

Clear colourless liquid

Table 2. Description of chemicals used in lab N.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Reaction Procedure

Initially, 100 mL of 0.2 M NaOH was poured into a 100 mL volumetric flask. It was determined that 100 mL was an appropriate quantity by measuring the total capacity of the vessel and choosing a reactant volume that minimizes the amount of air at the top of the vessel but does not overflow out of the bulb vessel. Because of air’s compressible nature, increases in liquid volume due to the reaction would slightly compress the air, thus reducing the amount of fluid forced up the capillary and hindering the accuracy of the results. The volumetric flask containing the sodium hydroxide solution was then clamped and partially submerged in a 25°C water bath where it stayed for 4 minutes to ensure that the reactants inside the flask reached thermal equilibrium.

Approximately 5 mL of DAA was poured into a 50 mL beaker and brought close to the bath. The reaction vessel and capillary tube were rinsed with distilled water to prevent contamination; the capillary tube was blown into to remove any bubbles that would affect the readings. After 4 minutes of submersion, the volumetric flask was removed from the bath and the glass reaction vessel was clamped and partially submerged in the 25°C bath. This was done so that the glass of the bulb would reach the same temperature as the water bath. The NaOH solution was then poured into the reaction vessel via a glass funnel. 1 mL of DAA was measured using a graduated pipette and rubber pipette bulb and poured directly into the reaction vessel. The lid of the vessel with the attached capillary tube was screwed on to the top of the reaction vessel. Care was taken to ensure that the top was proficiently sealed and that the bottom of the capillary tube and that the capillary tube protruded to about half the height of the vessel. The timer was started, a burette was placed over the capillary tube, and readings started to be taken every 2 minutes to record the liquid`s expansion up the capillary tube. Measurements continued until 2 identical readings were recorded, indicating that the reaction had reached equilibrium and that the volumetric expansion was over.

Titration Procedure

During the time that one lab partner recorded the volumetric expansion, the other lab partner performed 2 titrations on the NaOH solution to find an exact measurement of its molarity. Two burettes were rinsed and fixed upright using a double burette clamp. One burette was filled with HCl, and the other with NaOH. 100 mL beakers were placed under each burette to prevent spills. The burettes received a rinse with their respective solutions before being filled so that the drops of water in them left from washing would not the solutions contained in them. Using the burette, 20 mL of 0.1000 M HCl was poured into an Erlenmeyer flask and 3 drops of 0.1% phenolphthalein solution were added to the solution. The initial amount of NaOH in the burette was recorded. A white piece of paper was placed under the Erlenmeyer flask to ease the detection of a colour change. NaOH was gradually added to the HCl and phenolphthalein solution until the mixture turned a light shade of pink, indicating that the solution was neutralized. Upon neutralization, the amount of NaOH that was left in the burette was recorded, the neutral solution was disposed of into the inorganic waste container, and the titration was repeated for accuracy.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

This entire procedure was repeated 2 more times: once with a 0.3 M NaOH, and once with a 0.4 M NaOH.

0.2 M NaOH Preparation Procedure

Only 0.3 and 0.4 M NaOH were readily available, so a 0.2 M NaOH solution was prepared. To make this solution it was assumed that the concentration of provided stock solution was 0.3000 M and was diluted with water. 300 mL of 0.2 solution was made in preparation to be used for running the experiment and performing two titrations. Excess was solution was made in case the experiment needed to be run a second time.

Safety

For all chemicals used in the lab, the respective Material Safety Data Sheet (MSDS) was consulted to ensure safe handling. Additionally, the individuals performing this lab were well-educated on the whereabouts of eyewash stations, fire extinguishers, and emergency exits.

Acids

Protective eyewear was worn constantly during the handling of any acids in the lab, and care was taken to ensure they were handled in well ventilated areas. Furthermore, hands were washed upon any contact with the acid used in this experiment.

Bases

Protective eyewear was worn constantly during the handling of any bases in the lab, and care was taken to ensure they were handled in well ventilated areas.

DAA

DAA causes eye irritation upon contact, so protective glasses were constantly worn; DAA causes respiratory irritation, so care was taken to ensure it was used only in well ventilated areas; and DAA is combustible, so care was taken to ensure it did not become too hot or come into contact with sparks or open flame 7.

Phenolphthalein

Phenolphthalein causes eye irritation upon contact, so protective glasses were constantly worn; Phenolphthalein causes respiratory irritation, so care was taken to ensure it was used only in well ventilated areas; Phenolphthalein is combustible, so care was taken to ensure it did not become too hot or come into contact with sparks or open flame; and Phenolphthalein is a carcinogen, so care was taken to avoid long-term exposure 8.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Setup

Figure 1. Experimental setup of dilatometer.

The capillary is at least half-way down into the bulb.

Uncertainty

Instrument

Uncertainty

50 mL burette

0.050 mL 9

100 mL graduated cylinder

0.5 mL

250 mL volumetric flask

0.05 % 9

10 mL graduated pipette

0.020 mL 9

Water bath thermometer

0.05 °C

Table 3. Instruments used and their uncertainties.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Results and Discussions

Results

Data tables

Trial 0

Time (min)

Capillary reading (mm)

48.5

50.5

>60

Table 4. Test trial with leak in the seal of the washer present.

The reading dropped below the capillary.

Trial 1

Time (min)

Capillary reading (mm)

~too low

~50

48.5

47.5

46.9

46.2

45.8

45.6

45.4

45.2

45.1

45.0

44.9

44.8

44.7

Table 5. Capillary readings of trial 1 (0.2 M NaOH).

Trial 2

Time (min)

Capillary reading (mm)

47.5

47.0

45.4

43.6

42.6

41.8

41.1

40.5

40.1

39.8

39.5

39.3

39.1

39.0

38.9

38.8

38.7

38.6

Table 6. Capillary readings of trial 2 (0.3 M NaOH).

Trial 3

Time (min)

Capillary reading (mm)

~too low

~50

48.5

47.5

46.9

46.2

45.8

45.6

45.4

45.2

45.1

45.0

44.9

44.8

44.7

Table 7. Capillary readings of trial 3 (0.4 M NaOH).

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Titrations

Trial 1 (~0.2M)

Run 1

Acid

Volume of 0.1000 M HCL (mL)

20.0

Base

Initial reading (mL)

31.0

Final reading (mL)

41.5

Amount added (mL)

10.5

Indicator

Drops of phenolphthalein

Table 8. Titration for Trial 1, first run using ~0.2 M NaOH with 0.1000 M HCl.

Run 2

Acid

Volume of 0.1000 M HCL (mL)

20.0

Base

Initial reading (mL)

4.6

Final reading (mL)

15.0

Amount added (mL)

10.4

Indicator

Drops of phenolphthalein

Table 9. Titration for Trial 1, second run using ~0.2 M NaOH with 0.1000 M HCl.

Trial 2 (~0.3M)

Run 1

Acid

Volume of 0.1000 M HCL (mL)

19.2

Base

Initial reading (mL)

20.0

Final reading (mL)

26.5

Amount added (mL)

6.5

Indicator

Drops of phenolphthalein

Table 10. Titration for Trial 2, first run using ~0.3 M NaOH with 0.1000 M HCl.

Run 2

Acid

Volume of 0.1000 M HCL (mL)

19.2

Base

Initial reading (mL)

26.5

Final reading (mL)

33.1

Amount added (mL)

6.6

Indicator

Drops of phenolphthalein

Table 11. Titration for Trial 2, second run using ~0.3 M NaOH with 0.1000 M HCl.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Trial 3 (~0.4M)

Run 1

Acid

Volume of 0.1000 M HCL (mL)

20.0

Base

Initial reading (mL)

0.4

Final reading (mL)

5.6

Amount added (mL)

5.2

Indicator

Drops of phenolphthalein

Table 12. Titration for Trial 3, first run using ~0.4 M NaOH with 0.1000 M HCl.

Run 2

Acid

Volume of 0.1000 M HCL (mL)

20.0

Base

Initial reading (mL)

5.7

Final reading (mL)

10.8

Amount added (mL)

5.1

Indicator

Drops of phenolphthalein

Table 13. Titration for Trial 3, second run using ~0.4 M NaOH with 0.1000 M HCl.

Errors

Despite efforts to completely clear out the capillary tubes before the experiment, small pockets of water sometimes remained in the tube during the procedure. The additional weight of the water would have counteracted the hydrostatic force caused by the reaction, potentially slowing the volumetric expansion.

Additionally, as the NaOH was poured into the reaction vessel, some leaked out through the gap between the mouth of the vessel and the funnel. This error would affect the accuracy of our concentration values, ultimately affecting the accuracy of our rate constant.

Another potential error comes from leaks in the reaction vessel’s seal. The reaction vessel is sealed in two ways: a rubber washer between the cap and the vessel and a tight fitting between the capillary tube and the cap. To check for leaks in either of the seals, the vessel was filled with water and overturned. Although no leaks were observed, this does not mean that there would not be any leaks during the reaction when the pressure in the vessel was higher. To check for leaks during the reaction, the top of the reaction vessel could be wetted with water: if air can be seen bubbling out through the water, there is a leak. A preventative measure that was taken involved pulling up on the capillary tube to ensure that the rubber washer was adequately lodged in the space between the capillary and the cap.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Titration

Trial 1

Run

Concentration (M)

Average concentration (M)

0.19048

0.19140

0.19231

Trial 2

Run

Concentration (M)

Average concentration (M)

0.29538

0.29315

0.29091

Trial 3

Run

Concentration (M)

Average concentration (M)

0.38462

0.38838

0.39216

Table 14. Calculated sodium hydroxide solution concentrations and their averages.

Graphs

Determining the Order of DAA

As trial 2 had the highest quality of data, it was used to determine the order of the diacetone alcohol.

0th Order

Figure 2. A linear fit on the scatter plot of Trial 2 plotting the change in height in the capillary vs time in minutes.

The trendline is not the best as R2 = 0.733.

1st Order

Figure 3. A linear fit on the scatter plot of Trial 2 plotting ln(change in height in capillary) vs time in minutes.

The trendline is a good fit as R2 = 0.986. This is the best trendline.

2nd Order

Figure 4. A linear fit on the scatter plot of Trial 2 plotting 1/(change in height) vs time in minutes.

The trendline is not a good fit as R2 = 0.583.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

First order fits

Trial 1

Figure 5. A linear fit on the scatter plot of Trial 1 plotting ln(change in height in capillary) vs time in minutes.

kobs = 0.131. The trendline is a good fit as R2 = 0.968.

Trial 2

Figure 6. A linear fit on the scatter plot of Trial 2 plotting ln(change in height in capillary) vs time in minutes.

kobs = 0.133. The trendline is a good fit as R2 = 0.986.

Trial 3

Figure 7. A linear fit on the scatter plot of Trial 3 plotting ln(change in height in capillary) vs time in minutes.

kobs = 0.152. The trendline is a good fit as R2 = 0.986.

Discussion

General

Catalysts are used in chemical reactions to reduce the activation energy of the reaction. An essential characteristic of catalyzed reactions is that the catalyst is always regenerated when the reaction comes to completion. In acid-base catalysis, H+ protons and OH- ions are used as the catalysts, respectively 10. The reaction observed during this experiment is a base catalysis, and therefore it involves the OH- ion as a catalyst. The mechanism of the reaction can be found in the figure below.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Figure 8. Mechanism for DAA depolymerization (p. 119) 11.

As discussed in the introduction, a reaction goes to completion according to its rate law, as shown below: 𝑟𝑎𝑡𝑒=𝑘[𝐶6𝐻12𝑂2]𝑎[𝑂𝐻−]𝑏

Equation 6. General DAA and OH- rate law

In order to isolate the effects of DAA, the reaction vessel was flooded with OH-: 100 mL of NaOH was mixed with 1 mL of DAA. This practice permitted the rate law to be changed, namely that 𝑘[𝑂𝐻]−was absorbed into kobs. Thus, the rate law became 𝑟𝑎𝑡𝑒=𝑘𝑜𝑏𝑠[𝐶6𝐻12𝑂2]𝑎.

Equation 7. Rate law with observed k

The results of our calculations showed that the reaction is a first-order reaction with respect to DAA. This was determined by calculating the change in capillary height at every 2-minute interval, which is directly proportional to the concentration. This data alone was sufficient to determine the value of kobs and the order of the reaction with respect to DAA. The relations in Table 1 were plotted, and the most linear relation determined the overall order of the reaction. The relation 𝑙𝑛(𝛥ℎ)∶ 𝑡𝑖𝑚𝑒had a strong linear fit with an R squared > 0.96. Thus, the reaction is first order with respect to DAA. To determine kobs, the negative of the slope of the linear regression was taken, according to the relation 𝑙𝑛[𝐷𝐴𝐴]= −𝑘𝑜𝑏𝑠𝑡. The average of the 3 trials produced a kobs of 0.1387, and with a standard deviation of 0.0116, the data is of high quality.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Calculations

Preparation of a 0.2 M NaOH solution

To make 300 mL of 0.2 M NaOH solution one needs: (0.2 𝑚𝑜𝑙𝐿)(0.300 𝐿) = 0.06 𝑚𝑜𝑙 𝑜𝑓 𝑁𝑎𝑂𝐻

If the starting solution is 0.3 M NaOH one needs: (0.06 𝑚𝑜𝑙) (0.3 𝑚𝑜𝑙𝐿)−1 = 0.2 𝐿 𝑜𝑓 0.3 𝑀 𝑁𝑎𝑂𝐻

The difference in volume of solution needed and used is the amount of distilled water that needs to be added. 0.3 𝐿 − 0.2 𝐿 = 0.1 𝐿 = 100 𝑚𝐿

Hence to make 300 mL of 0.2 M NaOH solution one needs to add 100 mL of distilled water to 200 mL of 0.3 M NaOH solution.

A titration was performed afterwards to determine the exact concentration.

Titration

Concentration (C) of HCl (M)

0.1000

Volume (VAcid) of HCl used (mL)

20.0

Volume (VBase) of NaOH used (mL)

10.4

Table 15. Values used in sample calculation of base molarity from titration. 𝐶𝐴𝑐𝑖𝑑𝑉𝑎𝑐𝑖𝑑=𝐶𝐵𝑎𝑠𝑒𝑉𝐵𝑎𝑠𝑒

Equation 8. Concentration by volume is constant for any solute. (0.1000 𝑀)(20.0 𝑚𝐿) =𝐶𝐵𝑎𝑠𝑒(10.4 𝑚𝐿) 𝐶𝐵𝑎𝑠𝑒=0.192 𝑀

Volume to Density correlation

As the reaction progresses, the level of liquid in the column of the capillary increases. This increase occurs because acetone is being generated from diacetone alcohol. Acetone is less dense than DAA. The density of diacetone alcohol is 0.9306 g/mL at 25 °C 5,12,13. The density of acetone is 0.7845 g/mL at 20 °C 14–16. The density of DAA divided by the density of acetone yields 1.186. This means that every 1 mL of DAA converted to acetone will occupy in 1.19 mL, or a 0.19 mL increase in volume.

Knowing that the internal diameter of the capillary tube is 1 mm one can calculate the moles of acetone being produced. This, however, is not necessary as one can simply plot the change in height of the liquid in the capillary to find the relation to reaction rate, and order of

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

DAA. This simplification is possible because the operations done on the change in height are all linear, and when plotting, the natural logarithm is used, and so the units do not matter.

Change in height

The change in height is simply the difference between the current height and the final height. The final height is taken to be the height as time approaches infinity. As an example, the final height for one of the trials was 34 cm. The height at time of 2 minutes is 46 cm. Thus, according to the equation 𝛥ℎ=ℎ𝑡→∞−ℎ𝑡, the final height is 𝛥ℎ=34−26 = 8 𝑐𝑚.

Reaction rate constant

The following is a demonstration of the calculation of the rate constant k, or kreal. This value should be identical for all three trials and not be dependent on the concentration of the hydroxide ion nor the concentration of DAA. The rate constant is temperature dependent 17.

Using the equation 𝑙𝑛 𝑘𝑜𝑏𝑠 = 𝑙𝑛 𝑘 + 𝐴 𝑙𝑛[𝑂𝐻−]

Equation 9. Equation used to find ln(k).

Where ‘A’ denotes the order of the hydroxide ion in the rate law equation.

Using the goal seek function of excel, the cells for LHS-RHS were set to zero while modifying ln(k). This was done for every trial. The standard deviation of the ln(k) values are shown, and colour coded based on a conditional formatting where the lowest number is the best.

Assume [OH-] order is zero

Trial

K_obs

[OH-]

ln(k_obs)

ln[OH]

ln(k)

RHS

LHS-RHS

0.131

0.19140

-2.032557956

-1.6533898

-2.032557956

0.133

0.29315

-2.017406151

-1.227070856

-2.017406151

0.152

0.38838

-1.883874758

-0.945771037

-1.883874758

Average ln(k)

-1.977946288

0.138353083

St.dev 0.066805608

Table 16. Rate constant calculation if order of hydroxide is zero.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Assume [OH-] order is one

Trial

K_obs

[OH-]

ln(k_obs)

ln[OH]

ln(k)

RHS

LHS-RHS

0.131

0.19140

-2.032557956

-1.6533898

-0.379168156

-2.032557956

0.133

0.29315

-2.017406151

-1.227070856

-0.790335295

-2.017406151

0.152

0.38838

-1.883874758

-0.945771037

-0.938103721

-1.883874758

Average ln(k)

-0.702535724

0.495327696

St.dev 0.236479478

Table 17. Rate constant calculation if order of hydroxide is one.

Assume [OH-] order is two

Trial

K_obs

[OH-]

ln(k_obs)

ln[OH]

ln(k)

RHS

LHS-RHS

0.131

0.19140

-2.032557956

-1.6533898

1.274221644

-2.032557956

0.133

0.29315

-2.017406151

-1.227070856

0.43673556

-2.017406151

0.152

0.38838

-1.883874758

-0.945771037

0.007667316

-1.883874758

Average ln(k)

0.57287484

1.773357851

St.dev 0.525953353

Table 18. Rate constant calculation if order of hydroxide is two.

Conclusion

The order of the hydroxide concentration is zero (0); the standard deviation in the natural logarithm of the real reaction constant is the lowest, therefore the standard deviation in the real reaction constant will be lower too. The real reaction constant is there for 0.13835 and the order of DAA is one (1).

The standard deviation in the natural logarithm of the found k values is 7.9 greater in the assumption for the order of the hydroxide being two (2) compared to the order zero (0).

Questions

1. What is the rate law when hydroxide ions are present in excess? −𝜕𝑥𝜕𝑡=𝑘 [𝐶6𝐻12𝑂2]𝑛 [𝑂𝐻−]𝑚

Equation 10. General rate equation for reaction of DAA and OH-. −𝜕𝑥𝜕𝑡=0.138 [𝐶6𝐻12𝑂2]1 [𝑂𝐻−]0

Equation 11. Solution to general rate equation for reaction of DAA and OH-.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

When the hydroxide ions are in excess, the change in the OH- ions is considered negligible and constant from the beginning to the end of the reaction. And so, the observed k is one that includes the concentration of [OH-]

2. Write a simple expression for the hydroxyl-dependent rate constant kobs. 𝑘𝑜𝑏𝑠=𝑘[𝑂𝐻−]𝑚

3. What rate law results if you assume the reaction is first order with respect to diacetone alcohol. −𝜕𝑥𝜕𝑡=𝑘 [𝐶6𝐻12𝑂2]1 [𝑂𝐻−]𝑚

4. Give the integrated rate law of the pseudo-first-order rate law determined in question three:

ln[DAA]=-kt

5. How can you determine the value of kobs?

Having the initial volume, and densities, we can attribute the change in volume to the density change caused by the generation of acetone. From that we can determine the mass, and then the moles of acetone produced. This can be used to calculate the final concentration of DAA/

6. What calculations or graphical analysis are required to determine the rate constant k and the order of the reaction with respect to [OH-]?

A plot of ln (x) versus time would have a slope of -k{obs}. where x is the concentration of DAA at the specific time. This concentration is calculated as the remainder of DAA in the dilatometer as acetone is being produced. The amount of acetone produced is found from the change in volume and the relation with the densities of the DAA and acetone.

7. How can you determine the rate of the depolymerization of the diacetone alcohol given the available materials and equipment listed above? Which physical property could you monitor? (Hint: consider the reaction stoichiometry too).

The height of the liquid in the capillary could be measured to study the rate, as it is directly proportional to the concentration. If the actual rate in moles per minute is needed, the following conversion could take place: 𝛥ℎ𝜋(0.001 𝑚)2[𝑣𝑜𝑙𝑢𝑚𝑒]∗𝑔𝐿[𝑑𝑒𝑛𝑠𝑖𝑡𝑦]∗𝑚𝑜𝑙𝑒𝑠𝑔[𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠]=𝑚𝑜𝑙𝑒𝑠

Equation 12. Solution to question seven (7).

Finally, divide moles by time.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

8. How can you determine what volumes of NaOH and diacetone alcohol to mix in order for the reaction to be complete in about two hours? (Hint: remember that the reaction mixture must contain a large excess of NaOH). In which order should you mix the reagents?

To determine the good amount, several pre-trials could be performed in which the apparatus is set up with several different mixtures, the reaction is observed for several minutes, and the results are extrapolated to determine roughly if the solution is appropriate (of course, it is possibly incorrect to assume that the reaction will take place linearly, but this will at least give a rough idea of the appropriateness of the mixture)

The best way to mix the reagents is to put the NaOH in the vessel first then add the DAA.

9. Give the volumes of NaOH and diacetone alcohol that you have determined to satisfy the above conditions:

100 mL NaOH & 1 mL DAA.

10. Do you need to know the change in concentration with time of the alcohol to determine the rate constant kobs or can you use another variable that is directly proportional to this concentration and more straightforward? If you need to know the actual concentrations, how

will you determine them? What experimental data must you obtain and what calculations or

graphical analysis are necessary? (Hint: refer to your answer to question 7).

The change in height can be used to determine the kobs. The following reaction could take place: 𝛥ℎ𝜋(0.001 𝑚)2[𝑣𝑜𝑙𝑢𝑚𝑒]∗𝑔𝐿[𝑑𝑒𝑛𝑠𝑖𝑡𝑦]∗𝑚𝑜𝑙𝑒𝑠𝑔[𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠]=𝑚𝑜𝑙𝑒𝑠

Equation 13. Solution to question ten (10).

The experimental data needed will include the liquid capillary height at two-minute intervals, titration data for each NaOH solution. In terms of graphical analysis, [DAA]=kobst,

𝑙𝑛[𝐴]=−𝑘𝑜𝑏𝑠𝑡, and 1/[𝐴]=𝑘𝑜𝑏𝑠𝑡would be plotted to determine kobs.

11. The thermostated bath temperature is set at 25°C. Why is it important to maintain the temperature of the reaction constant?

Temperature affects rate of reaction, thus, to isolate the effects of concentration on rate, the temperature must remain constant.

12. What NaOH concentrations could be used to determine the rate constant and order of the reaction?

0.2 M, 0.3 M, and 0.4 M could be used.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

13. How frequently and for long should you monitor the reaction?

The reaction should be monitored every 2 minutes, and it should be monitored until the reaction reaches equilibrium (i.e. the height stops changing)

14. In your procedure, what should you be particularly careful about in order to obtain accurate and reproducible results?

Care should be taken to ensure that there is a good seal in the top of the reaction vessel, that there is no contamination between the NaOH and the DAA before the apparatus is set up, and that the thermostated bath functions properly.

Conclusion

The overall order of the reaction of depolymerization of diacetone alcohol with sodium hydroxide solution was found to be one (1), with the orders for the concentrations of diacetone alcohol and hydroxide ion being one (1) and zero (0) respectively. The rate constant at 25 °C was found to be 0.13835 min-1.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Bibliography

(1) Pseudo-first Order Kinetics – Determination of a rate law http://sitesmedia.s3.amazonaws.com/chem/files/2012/08/Pseudo_first_order_Primer.pdf (accessed Feb 20, 2019).

(2) Keillor, J. W. Experimental Kinetics: Enzyme Kinetics.

(3) Chembase. Sodium oxidanide http://en.chembase.cn/substance-371462.html (accessed Feb 25, 2019).

(4) ChEBI. CHEBI:17883 - hydrogen chloride https://www.ebi.ac.uk/chebi/searchId.do?chebiId=17883 (accessed Feb 25, 2019).

(5) PubChem Compound Database. Compound Summary for CID 31256 4-Hydroxy-4-methyl-2-pentanone https://pubchem.ncbi.nlm.nih.gov/compound/31256 (accessed Feb 25, 2019).

(6) PubChem Compound Database. Compound Summary for CID 4764 Phenolphthalein https://pubchem.ncbi.nlm.nih.gov/compound/4764 (accessed Feb 25, 2019).

(7) Monument Chemical. Diacetone Alcohol Safety Data Sheet; Vol. 77, No. 58; MSDS; 2018.

(8) Fisher Science Education; AquaPhoenix Scientific. Phenolphthalein Indicator; MSDS; 2015.

(9) ChemBuddy. Laboratory volumetric glassware used in titration: ASTM E287-02 standard specification http://www.titrations.info/pipette-burette (accessed Feb 25, 2019).

(10) Khan Academy. Types of catalysts https://www.khanacademy.org/science/chemistry/chem-kinetics/arrhenius-equation/a/types-of-catalysts (accessed Feb 25, 2019).

(11) Moriyoshi, T. Effects of Pressure on Organic Reactions IV: The Base-Catalyzed Decomposition of Diacetone Alcohol in Aqueous Ethanol Mixtures. Phys.-Chem. Soc. Jpn. 1971, 40 (2), 102–121.

(12) The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 11th ed., centennial ed.; Budavari, S., Ed.; Merck: Rahway, N.J., U.S.A, 1989.

(13) NIH U.S. National Library of Medicine. HSDB: 4-HYDROXY-4-METHYL-2-PENTANONE CASRN: 123-42-2 http://toxnet.nlm.nih.gov/cgi-bin/sis/search2/r?dbs+hsdb:@term+@DOCNO+1152 (accessed Feb 25, 2019).

(14) PubChem Compound Database. Compound Summary for CID 180 Acetone https://pubchem.ncbi.nlm.nih.gov/compound/180 (accessed Feb 25, 2019).

(15) NIH U.S. National Library of Medicine. HSDB: ACETONE CASRN: 67-64-1 http://toxnet.nlm.nih.gov/cgi-bin/sis/search2/r?dbs+hsdb:@term+@DOCNO+41.

(16) CRC Handbook of Chemistry and Physics: A Ready-Reference Book of Chemical and Physical Data; Haynes, W. M., Ed.; CRC Press LLC: New York, 2014.

(17) de Dios, A. C. Temperature dependence of rates constants https://bouman.chem.georgetown.edu/S02/lect4/lect4.htm (accessed Feb 25, 2019).

(18) Pseudo-1st-order reactions https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/Reaction_Rates/Second-Order_Reactions/Pseudo-1st-order_reactions (accessed Feb 22, 2019).

(19) Åkerlöf, G. Decomposition Of Diacetone Alcohol By Sodium Hydroxide In Water Mixtures Of Organic Solvents. J. Am. Chem. Soc. 1928, 50 (5), 1272–1275. https://doi.org/10.1021/ja01392a006.

(20) French, C. C. Basic Catalysis in the Decomposition of Diacetone Alcohol. J. Am. Chem. Soc. 1929, 51 (11), 3215–3225. https://doi.org/10.1021/ja01386a005.

(21) Hewett, D. Kinetics Study of Base Catalysed Diacetone Alcohol Depolymerisation. Simon Langton Grammar. Sch. Boys 2015, 57. https://doi.org/https://www.pdf-archive.com/2015/09/16/project-latex/project-latex.pdf.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Schedule I

Works consulted but not cited 18–21. These added to our understanding but were not used directly in the writing of this paper.

Schedule II

Figure 9. Slide 33 of Experimental Kinetics by Keillor for CHM 8304† 2

Schedule III

The following is the Bibliography but in APA to make finding sources easier

Åkerlöf, G. (1928). Decomposition of Diacetone Alcohol by Sodium Hydroxide in Water Mixtures Of Organic Solvents. Journal of the American Chemical Society, 50(5), 1272–1275. https://doi.org/10.1021/ja01392a006

Budavari, S. (Ed.). (1989). The Merck index: An Encyclopedia of Chemicals, Drugs, and Biologicals (11th ed., centennial ed). Rahway, N.J., U.S.A: Merck.

ChEBI. (n.d.). CHEBI:17883 - hydrogen chloride. Retrieved February 25, 2019, from https://www.ebi.ac.uk/chebi/searchId.do?chebiId=17883

Chembase. (n.d.). Sodium oxidanide. Retrieved February 25, 2019, from http://en.chembase.cn/substance-371462.html

ChemBuddy. (2009, June 17). Laboratory volumetric glassware used in titration: ASTM E287-02 standard specification. Retrieved February 25, 2019, from http://www.titrations.info/pipette-burette

de Dios, A. C. (n.d.). Temperature dependence of rates constants. Retrieved February 25, 2019, from https://bouman.chem.georgetown.edu/S02/lect4/lect4.htm

† Accessible on: https://mysite.science.uottawa.ca/jkeillor/English/Teaching_files/Experimental%20kinetics.pdf.

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

Fisher Science Education, & AquaPhoenix Scientific. (2015). Phenolphthalein Indicator (MSDS). Retrieved from https://beta-static.fishersci.com/content/dam/fishersci/en_US/documents/programs/education/regulatory-documents/sds/chemicals/chemicals-p/S25467.pdf

French, C. C. (1929). Basic Catalysis in the Decomposition of Diacetone Alcohol. Journal of the American Chemical Society, 51(11), 3215–3225. https://doi.org/10.1021/ja01386a005

Haynes, W. M. (Ed.). (2014). CRC handbook of chemistry and physics: a ready-reference book of chemical and physical data. New York: CRC Press LLC.

Hewett, D. (2015). Kinetics Study of Base Catalysed Diacetone Alcohol Depolymerisation. Simon Langton Grammar School for Boys, 57. https://www.pdf-archive.com/2015/09/16/project-latex/project-latex.pdf

Keillor, J. W. (n.d.). Experimental Kinetics: Enzyme Kinetics. Presented at the CHM 8304, University of Ottawa. Retrieved from https://mysite.science.uottawa.ca/jkeillor/English/Teaching_files/Experimental%20kinetics.pdf

Khan Academy. (n.d.). Types of catalysts. Retrieved February 25, 2019, from https://www.khanacademy.org/science/chemistry/chem-kinetics/arrhenius-equation/a/types-of-catalysts

Monument Chemical. (2018). Diacetone Alcohol Safety Data Sheet (MSDS). Retrieved from https://monumentchemical.com/uploads/files/SDS/DAA-SDS%20(US)-NEW.pdf

Moriyoshi, T. (1971). Effects of pressure on organic reactions IV: the base-catalyzed decomposition of diacetone alcohol in aqueous ethanol mixtures. The Physico-Chemical Society of Japan, 40(2), 102–121. Retrieved from http://hdl.handle.net/2433/46954

NIH U.S. National Library of Medicine. (1991, May 8). HSDB: 4-HYDROXY-4-METHYL-2-PENTANONE CASRN: 123-42-2. Retrieved February 25, 2019, from http://toxnet.nlm.nih.gov/cgi-bin/sis/search2/r?dbs+hsdb:@term+@DOCNO+1152

NIH U.S. National Library of Medicine. (2015, May 14). HSDB: ACETONE CASRN: 67-64-1. Retrieved from http://toxnet.nlm.nih.gov/cgi-bin/sis/search2/r?dbs+hsdb:@term+@DOCNO+41

Pseudo-1st-order reactions. (2016, June 16). Retrieved February 22, 2019, from https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/Reaction_Rates/Second-Order_Reactions/Pseudo-1st-order_reactions

Pseudo-first Order Kinetics – Determination of a rate law. (n.d.). Retrieved February 20, 2019, from http://sitesmedia.s3.amazonaws.com/chem/files/2012/08/Pseudo_first_order_Primer.pdf

PubChem Compound Database. (n.d.-a). Compound Summary for CID 180 Acetone. Retrieved February 25, 2019, from https://pubchem.ncbi.nlm.nih.gov/compound/180

PubChem Compound Database. (n.d.-b). Compound Summary for CID 4764 Phenolphthalein. Retrieved February 25, 2019, from https://pubchem.ncbi.nlm.nih.gov/compound/4764

PubChem Compound Database. (n.d.-c). Compound Summary for CID 31256 4-Hydroxy-4-methyl-2-pentanone. Retrieved February 25, 2019, from https://pubchem.ncbi.nlm.nih.gov/compound/31256

DEPOLYMERIZATION OF DIACETONE ALCOHOL Amini & Audet

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