SPECIAL REPORT 97-5

Investigation of the Kinetics and

Products Resulting from the

Reaction of Peroxone with

Aminodinitrotoluenes

Ronald J. Spanggord, David Yao, and Theodore Mill February 1997
Abstract: The reaction between peroxone and two isomers of aminodinitrotoluene (ADNT) was studied with

respect to kinetics of reaction and the products

formed. The ADNTs react rapidly with ozone and

hydroxyl radical, the principal components of peroxone. At fairly high ADNT concentrations (ppm), the reHow to get copies of CRREL technical publications:

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action of ADNT is primarily with ozone. At lower ADNT

concentrations (ppb), hydroxyl radical competes with

ozone in pure water systems. Reactions of both the 2-

and 4-ADNT isomers result in the formation of pyruvic

acid, nitrate ion, and nitrite ion. A reaction mechanism

consistent with these products is proposed.
Special Report 97-5

Investigation of the Kinetics and

Products Resulting from the

Reaction of Peroxone with

Aminodinitrotoluenes

Ronald J. Spanggord, David Yao, and Theodore Mill February 1997

Approved for public release; distribution is unlimited.

US Army Corps

of Engineers

Cold Regions Research &

Engineering Laboratory

®
PREFACE

This report was prepared by Dr. Ronald J. Spanggord, Director, Bio-Analytical

Chemistry Program, Life Sciences Division, and by Dr. David Yao, Research

Chemist, and Dr. Theodore Mill, Senior Scientist, Chemistry Laboratory, Physical

Sciences Division, SRI International, Menlo Park, California. Funding was provided by the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL)

and the U.S. Army Engineer Waterways Experiment Station (WES), Thomas F. Jenkins (CRREL) and Elizabeth Fleming (WES), Project Monitors, under the Strategic

Environmental Research and Development Program (SERDP).

The authors gratefully acknowledge Daniel Leggett and Thomas F. Jenkins,

CRREL, for their technical review of this manuscript, and Dr. Mark Zappi of Mississippi State University (formerly of WES) for initiating financial support for this

research.

This publication reflects the personal views of the authors and does not suggest

or reflect the policy, practices, programs, or doctrine of the U.S. Army or Government of the United States. The contents of this report are not to be used for advertising or promotional purposes. Citation of brand names does not constitute an

official endorsement or approval of the use of such commercial products.

ii
iii

CONTENTS

Preface ............................................................................................................................................ ii

Introduction and background .................................................................................................... 1

Objectives ....................................................................................................................................... 2

Experimental methods................................................................................................................. 2

Ozone oxidations ..................................................................................................................... 2

Hydroxyl radical oxidations .................................................................................................. 3

Peroxone treatment system oxidations ................................................................................ 3

Results ............................................................................................................................................ 3

Direct ozonation rate constant............................................................................................... 3

Direct hydroxyl radical rate constant ................................................................................... 4

Oxidation in peroxone oxidizing system ............................................................................. 4

Transformation products ........................................................................................................ 6

Material balance ....................................................................................................................... 8

Discussion ...................................................................................................................................... 9

Conclusions ................................................................................................................................... 13

Literature cited .............................................................................................................................. 13

Abstract .......................................................................................................................................... 15

ILLUSTRATIONS

Figure

1. Measured ozone rate constants for 2-ADNT and 4-ADNT against the reference

chemical, nitrite............................................................................................................ 4

2. Measured hydroxyl radical rate constants for 2-ADNT and 4-ADNT against the

reference chemical, p-nitroacetophenone ................................................................ 5

3. Oxidation stoichiometry of 4-ADNT and 2-ADNT in the peroxone, ozone alone,

and ozone with scavenger systems .......................................................................... 5

4. HPLC profile of carbonyl-containing products from the ozonation of 2-ADNT ...... 6

5. HPLC profile of carbonyl-containing products from the ozonation of 4-ADNT ...... 6

6. UV spectral data for 4-ADNT compared to glyoxal and pyruvic aldehyde ............. 7

7. Quantitative determination of 2,4-dinitrophenylhydrazone derivatives of

products from 2-ADNT and 4-ADNT ........................................................................... 7

8. HPLC profile of carboxylic acids formed from the ozonation of 4-ADNT and

2-ADNT using UV detection at 210 nm.................................................................... 8

9. HPLC profile of carboxylic acids generated from the ozonation of 2-ADNT

and 4-ADNT using conductivity detection.............................................................. 8

10. Carbon balance and product distribution from the ozonation of 2-ADNT................ 9

11. Carbon balance and product distribution from the ozonation of 4-ADNT................ 9

12. Plots of nitrite and nitrate formation as a function of 2-ADNT and 4-ADNT loss ... 10

13. HPLC profile of nitrite and nitrate formation in 2-ADNT oxidation by ozone......... 10

TABLES

Table

1. Loss of 2-ADNT and 4-ADNT with ozone in the presence of resorcinol and nitrite

reference chemicals ..................................................................................................... 4

2. Loss of ADNTs in the presence of hydroxyl radical ...................................................... 4
INTRODUCTION AND BACKGROUND

The U.S. Army is interested in using Advanced Oxidation Technologies (AOTs) for the treatment of wastes, residues, and contaminated groundwater resulting from past and present military

manufacturing and chemical handling practices. One AOT of interest is the use of peroxone. Peroxone is a mixture of ozone (O3) and hydrogen peroxide (H2O2) that, when mixed together at a 1:1

ratio at pH > 7, generates hydroxyl radical (HO•), which is a powerful oxidant. Ozone is also a

strong oxidant of organic molecules in aqueous solution and offers competitive oxidative pathways in a peroxone system. Hydrogen peroxide may contribute to some oxidation of organics, but

because of the reactivity of ozone with hydrogen peroxide, ozone and hydroxyl radical will dominate the oxidative process.

TNT (2,4,6-trinitrotoluene) is a major land contaminant at military installations, including TNT

manufacturing sites and load and pack (LAP) facilities. Once introduced into the soil, TNT can

undergo both aerobic and anaerobic microbial transformations that lead to 4-amino-2,6-dinitrotoluene (4-ADNT) and 2-amino-4,6-dinitrotoluene (2-ADNT). The structures of these chemicals are

shown below.

4-amino-2,6-dinitrotoluene 2-amino-4,6-dinitrotoluene

These compounds are currently being found in groundwater at munitions facilities. The use of an

AOT technology will involve the oxidation of TNT transformation products. It therefore becomes

important to understand oxidation rates, pathway, and stable end-products to make an assessment of the safety of peroxone treatment of ADNT-contaminated waters.

Oxidation rates can be described by simple second-order rate expressions. The kinetic rate expressions for oxidation by ozone and hydroxyl radical processes are shown in eq 1 and 2. The

overall loss can be described by eq 3.

k1

ADNT + O3 —————> Products d[ADNT]/dt = k1[ADNT][O3] (1)

 k2

ADNT + HO• ————> Products d[ADNT]/dt = k2[ADNT][HO•] (2)

d[ADNT]/dt = k1[ADNT][O3] + k2[ADNT][HO•] = (k1[O3] + k2[HO•]) [ADNT] (3)

Equation 3 shows that [O3] and [HO•] and the rate constants (k1 and k2) will control the rate of

ADNT disappearance.

CH3

O2N NO2

NH2

CH3

O2N NH2

NO2

Investigation of the Kinetics and Products Resulting from

the Reaction of Peroxone with Aminodinitrotoluenes

RONALD J. SPANGGORD, DAVID YAO, AND THEODORE MILL
The rate constants for oxidizing ADNTs are not known, but their range can be estimated from

known compounds and structure activity relationships (SARs). For example, the rate constant for

the reaction of aniline with ozone is 9 × 107 M–1 s–1 (Buxton and Greenstoch 1988). ADNT has two

electron-withdrawing nitro groups and one electron-donating methyl group, so a rate constant for

ozone oxidation of ADNT should be in the 104 to 107 M–1 s–1 range. Estimation of the hydroxyl

radical oxidation rate constant is possible because the related compound, p-nitroaniline, is known

to have a hydroxyl radical rate constant of 1010 M–1 s–1 (Buxton and Greenstoch 1988). Therefore,

the rate constant for ADNT oxidation by hydroxyl radical is expected to be in the 109 M–1 s–1 range.

In peroxone oxidizing systems, oxidant concentrations range from 10–4 M for ozone to 10–14 M for

hydroxyl radical. We have used these values as a guide for our rate determination experiments.

When rate constants exceed 104 M–1 s–1, half-lives become extremely short (≈ 1 s) and it is difficult to measure oxidant and substrate loss. This problem can be solved by competitive oxidation

of the substrate (S) in the presence of a reference compound (R) with a known rate constant for

oxidation by a specific oxidant. In this case, the rate constant for the oxidation of the substrate is

kS = kR × ln [(So)/(St)]/ln [(Ro)/(Rt)] (4)

where kS and kR are the rate constants for the substrate and reference chemicals, respectively. For

this study, we have used this approach to measure rate constants for the oxidation of 2-ADNT and

4-ADNT.

OBJECTIVES

The objectives of this study were to examine the kinetics of oxidative transformation of 4-

ADNT and 2-ADNT by the peroxone advanced oxidation process, identify stable end-products,

and attempt to understand the oxidative pathway. We are interested in establishing rates of transformation and stable end-products resulting from the process and the mechanism by which these

transformations occur.

EXPERIMENTAL METHODS

Ozone oxidations

Ozone oxidations were conducted in aqueous solutions adjusted to pH 5.0 with phosphate

buffer. Because the acid dissociation constants (pKas) of 2-ADNT and 4-ADNT are 1.23 and 0.59

(Glover et al. 1977), respectively, the amines are in their free form at this pH. To inhibit concurrent

hydroxyl radical transformations, some studies were conducted in the presence of t-butyl alcohol

as a hydroxyl radical scavenger (Hoigne and Bader 1983). Ozone was generated from a Welsbach

ozone generator and bubbled into water. Ozone concentration was determined by a standard colorimetric technique with indigo (Bader and Hoigne 1981).

An ozone stock solution was added in 20-μM increments to a rapidly stirred stock solution of

ADNT (150 μM) and a reference chemical (nitrite or resorcinol). After each addition, the ADNT

and resorcinol were analyzed by high-performance liquid chromatography (HPLC), and nitrite

and nitrate by ion chromatography (Thayer and Huffaker 1980). Aldehydes and ketones were

analyzed as their 2,4-dinitrophenylhydrazones according to the methods of Kieber and Mopper

(1990). Carboxylic acids were analyzed by ion chromatography with a conductivity detector and

by ion chromatography with UV detection as described below.

Ion chromatography with UV detection

Instrument: HP1081B liquid chromatograph

Column: Supelcogel C-610H (sulfonated polystyrene divinylbenzene), 7.8 × 300 mm

2
Solvent: 1% H3PO4 in water

Flow rate: 0.5 mL/min

Detector: UV @ 210 nm

Ion chromatography with conductivity detection

Instrument: Dionex ion chromatograph

Column: PAX-500

Solvent: A = 200 mM NaOH; B = 0.6 mM NaOH; C = 5% methanol

Gradient: T = 0 to 10 min: 0/25/75 (A/B/C)

T = 10 to 15 min: 10/65/25

T = 15 to 30 min: 30/45/25

T = 30 to 40 min: 30/45/25

T = 40 to 45 min: 0/75/25

Flow rate: 1.0 mL/min

Anion suppressor: 27 mM H2SO4

Detector: Conductivity

Hydroxyl radical oxidations

Hydroxyl radicals were generated using Fenton’s system, where Fe+2 is oxidized to Fe+3 in the

presence of hydrogen peroxide to generate hydroxyl radical as shown below.

Fe+2 + H2O2 ————> Fe+3 + HO• + –OH

In this system, hydrogen peroxide is incrementally added in the dark to freshly prepared 0.88 M

Fe(ClO4)2 solution containing the ADNT and p-nitroacetophenone (PNAP, internal reference chemical). The solution was stirred for 20 min and the ADNT and PNAP were analyzed directly by

HPLC.

Peroxone treatment system oxidations

The efficiency of peroxone oxidations compared to oxidations by other potential oxidants in the

peroxone system was determined in three experiments: one with ozone and 1.9 mM t-butyl alcohol

as a HO• scavenger; one using ozone alone; and one using ozone with 117 μM hydrogen peroxide.

In each of these experiments, ozone was added at 0, 39, 82, or 182 μM to stirred solutions of the

ADNT. After each ozone addition, samples were removed for analysis of the ADNT by HPLC and

remaining hydrogen peroxide by the titanium sulfate method (Setterfield and Bonnel 1955).

RESULTS

Direct ozonation rate constant (kO3

)

Two reference chemicals, resorcinol and nitrite ion, with reported rate constants of 9.4 × 104

M–1 s–1 and 3.5 × 105 M–1 s–1, respectively (Buxton and Greenstoch 1988), were selected for competitive kinetic studies with 2-ADNT and 4-ADNT. Both ADNTs disappeared in the presence of ozone;

the data appear in Table 1.

First-order plots of 2-ADNT and 4-ADNT loss and reference compound loss (nitrite) appear in

Figure 1. From eq 4 the rate constant for 2-ADNT loss was calculated to be 1.4 × 105 M–1 s–1 with

resorcinol as a reference and 5.3 × 105 M–1 s–1 with nitrite as a reference. For 4-ADNT, the rate constants were 1.5 × 105 M–1 s–1 and 1.9 × 105 M–1 s–1.

Because the reaction of ozone with the ADNTs could generate hydroxyl radical, identical experiments were performed in the presence of twentyfold excess t-butyl alcohol as a hydroxyl radical

scavenger. The loss of ADNTs was not affected (see “Oxidation in peroxone oxidizing system,”

3
below), which indicates that hydroxyl radical

plays an insignificant role in the oxidation of

ADNTs by ozone.

Direct hydroxyl radical rate constant (kHO)

Most organics are oxidized by hydroxyl

radical with rate constants in the range of 109

to 1010 M–1 s–1 (Buxton and Greenstoch 1988).

We selected PNAP as a reference compound

with an average hydroxyl radical rate

constant of 3.1 × 109 M–1 s–1 (Buxton and

Greenstoch 1988). Average data (two determinations) for the loss of 2-ADNT and

4-ADNT with respect to PNAP are shown in

Table 2.

Plots of the loss of ADNTs and PNAP

appear in Figure 2. From eq 4, hydroxyl radical rate constants were calculated to be 1.6 ×

109 M–1 s–1 and 1.9 × 109 M–1 s–1 for 2-ADNT

and 4-ADNT, respectively.

Oxidation in peroxone oxidizing system

The reactions of the ADNTs with peroxone

(O3/H2O2), ozone, and ozone with t-butyl

alcohol are depicted graphically in Figure 3.

These linear plots of ADNT consumed versus

ozone utilized indicate that hydroxyl radical, hydrogen peroxide, or the hydroxyl radical scavenger (t-butyl alcohol) have little effect in the peroxone oxidation. These data suggest that the direct

oxidation by ozone controls the oxidative process. In studying the stoichiometry of the transformation in the above three systems, we found that each mole of 2-ADNT consumes 2.5 moles of

ozone. For 4-ADNT, the ratio was found to be similar: 2.7 moles ozone for each mole of 4-ADNT. If

we consider that one mole of ADNT will react with one mole of ozone, then ≈ 60% [(2.5–1.0)/2.5 ×

100] of the ozone is used to oxidize secondary products generated in the transformation, and these

products are more reactive than the ADNT.

Table 1. Loss of 2-ADNT and 4-ADNT (μM) with

ozone in the presence of resorcinol and nitrite

reference chemicals.

Rate Rate

Resorcinol constant 2-ADNT Nitrite constant

(μM) (M–1 s–1 )(μM) (μM) (M–1 s–1)

2-ADNT

10.5 15.5 200 200

8.0 11.8 148 164

5.8 8.2 120 142

4.0 5.0 93.4 122 5.3 × 105

2.7 3.0 1.4 × 105

4-ADNT

11.0 14.5 300 300

9.4 11.8 267 265

8.3 9.9 233 183

6.1 6.0 1.5 × 105 192 139 1.9 × 105

Figure 1. Measured ozone rate constants for 2-ADNT and 4-

ADNT against the reference chemical, nitrite.

Table 2. Loss of ADNTs in the presence of hydroxyl

radical.

Rate Rate

2-ADNT PNAP constant 4-ADNT PNAP constant

(μM) (μM) (M–1 s–1 )(μM) (μM) (M–1 s–1)

20.0 37.2 20.0 37.2

18.7 31.5 18.8 33.1

16.7 24.9 17.3 28.9

14.9 20.0 15.6 22.2

13.7 17.4 13.6 19.3

12.6 14.7 1.9 × 109 12.4 16.6 1.6 × 109

4

2–ADNT

4–ADNT

–1.2

–1.0

–0.8

–0.6

–0.4

–0.2

0

0.2

0 –0.2 –0.4 –0.6 –0.8

ln[NO2]/[NO2]0

ln[ADNT]/[ADNT]0
Figure 2. Measured hydroxyl radical rate constants for 2-ADNT

and 4-ADNT against the reference chemical, p-nitroacetophenone

(PNAP).

0 20 100

40

30

20

10

40 60 80

O3 (μM)

∆4-ADNT (μM)

O3 and Scavenger

O3 and H2O2

O3 Alone

0 20 100

40

30

20

10

40 60 80

O3 (μM)

∆2-ADNT (μM)

O3 and t-BuOH

O3 and H2O2

O3 Alone

Figure 3. Oxidation stoichiometry of 4-ADNT and 2-ADNT

in the peroxone, ozone alone, and ozone with scavenger (tbutyl alcohol) systems.

a. 4-ADNT.

b. 2-ADNT.

5

0

0.1

0

–0.1

–0.2

–0.3

–0.4

–0.5

–0.6 –0.8

ln [PNAP]/[PNAP]o

ln [ADNT]/[ADNT]o

2-ADNT

4-ADNT

–0.2 –1 –0.4 –0.6
Transformation products

The identification of transformation products involved those that had UV spectral and chromatographic properties identical to authentic standards. Aldehydes and ketonic intermediates

were identified as their 2,4-dinitrophenylhydrazones by high-performance liquid chromatography and diode array UV spectral data. Products resulting from 2-ADNT include glyoxylic acid,

pyruvic acid, glyoxal, and pyruvic aldehyde. The structures of these components are shown below.

Glyoxylic acid Pyruvic acid Pyruvic aldehyde Glyoxal

The chromatographic profile for 2-ADNT of the 2,4-dinitrophenylhydrazones appears in Figure 4.

There are still numerous products that have not been identified based on the lack of available

reference standards.

The 4-ADNT showed a similar set of carbonyl-containing products, but glyoxal was not observed (Fig. 5). In place of glyoxal was another derivative that is believed to contain multiple

carbonyl-containing groups based on its chromatography and UV spectral properties (Fig. 6). It

appears that these products, although small in concentration, possess multifunctional carbonyl

moieties in their structures.

The formation (and decline) of the major known components for 2-ADNT and 4-ADNT are

shown in Figure 7 as a function of exposure time to ozone. The aldehyde and ketonic intermediates account for approximately 30% of the carbon material balance.

Carboxylic acids, chromatographed on the Supelcogel 610H column and detected at 210 nm,

6

0 35

0

4

8

12

16

20

24

28

32

36

5 10 15 20 25 30

AU

Time (min)

2, 4-Dinitrophenylhydrazine

Glyoxylic

Acid

Pyruvic

Acid

Glyoxal Pyruvic

Aldehyde

Figure 4. HPLC profile of carbonyl-containing

products from the ozonation of 2-ADNT.

0

0

0.02

0.04

0.06

0.08

0.10

0.12

5 10 15 20 25 30 35

AU

Time (min)

2, 4-Dinitrophenylhydrazine

Glyoxylic

Acid

Pyruvic

Acid

Pyruvic

Aldehyde

?

Figure 5. HPLC profile of carbonyl-containing

products from the ozonation of 4-ADNT.

O

HOOC – CH = O CH – CCOOH CH C – CH = O O = CH – CH = O 3 3

O
confirmed the generation of pyruvic acid as a stable end-product. Based on chromatographic retention times, glycolic acid (HOCH2COOH) and acetic acid were also identified. Other acids appeared in the profile, but their retention times could not be matched with authentic standards.

Oxalic acid eluted near the dead volume and was masked by the large amounts of nitrate ion

generated during ozonation. A comparison of acids generated from 2-ADNT and 4-ADNT is

shown in Figure 8 and indicates the direct difference in product compositions for identical ozonation times.

Using anion exchange with conductivity detection, nitrate ion could be resolved from oxalic

acid and other carboxylic acids. Formic, malonic, oxalic, and acetic acids were observed. The tentative identifications of acids observed by this technique are shown in Figure 9 for 2-ADNT and 4-

ADNT. The product profile was found not to agree with that observed on the Supelcogel column

(with UV detection), especially with respect to formic and pyruvic acids. These results indicate

that other methods of confirmatory analysis need to be addressed for the carboxylic acid fraction.

7

200 300 400 500 600

0

0.02

0.04

0.06

0.08

AU

Wavelength (nm)

4-ADNT Product

Glyoxal

Pyruvic Aldehyde

209.7nm

219.1 nm

209.7 nm

369.4 nm

422.4 nm

432.0 nm

436.9 nm

1

0

2

3

4

5

40 80 120 160 200

Time (min)

Carbonyl Compound (PPM)

Glyoxylic

Pyruvic

Glyoxal

Pyruvalde

0

1

2

3

40 80 120 160 200

Time (min)

Carbonyl Compound (PPM)

4-Glyoxylic

4-Pyruvic

4-Derivative

4-Pyruvalde

Figure 7. Quantitative determination of 2,4-dinitrophenylhydrazone derivatives of products from 2-ADNT

and 4-ADNT.

Figure 6. UV spectral data for 4-ADNT product compared to glyoxal

and pyruvic aldehyde.

a. 2-ADNT. b. 4-ADNT.
8

Material balance

A material balance of carbon and

nitrogen was estimated based on analytical results of samples subjected to

ozonation. Total organic carbon analyses of samples before and after ozonation showed a 120% recovery of

available carbon, suggesting that little

mineralization of carbon (i.e., production of CO2) occurs during ozonation. A

combined product quantitation and

graph for 2-ADNT and 4-ADNT appear

in Figures 10 and 11. The data indicate

that 35% of the available carbon can be

accounted for by identified products.

For nitrogen, 85% of the available

nitrogen was accounted for by nitrite

and nitrate. Other nitrogen-containing

species such as NO and NO2 gases were

not detected. Plots of nitrite and nitrate

formation as a function of ADNT conPyruvic

Acid

Glycolic

Acid

4-ADNT

0 10 15 20 25 30 35 5

Time (min)

Relative Intensity

Pyruvic

Acid

Glycolic

Acid

0 5 10 15 20 25 30 35

Time (min)

Relative Intensity

2-ADNT

Figure 8. HPLC profile of carboxylic acids formed from the ozonation of 4-ADNT and 2-ADNT using UV

detection at 210 nm.

a. 4-ADNT. b. 2-ADNT.

0 20

30

40

50

60

5 10 15 20 25

S

Glycolate

Acetate

Formate

Glyoxylic

Acid

Nitrate

Malonic

Acid

Oxalic

Acid

Time (min)

0 20

30

40

50

70

60

5 10 15 20 25 30

Glycolate

Acetate

Formate

Glyoxylic

Acid

Nitrate

Malonic

Acid

Oxalic 

Acid

Figure 9. HPLC profile of carboxylic acids

generated from the ozonation of 2-ADNT

(top) and 4-ADNT (bottom) using conductivity detection.

μS μS
9

sumed appear in Figure 12. Initially, nitrite concentrations are higher than nitrate; however, nitrite

will compete with the ADNT for ozone, resulting in its conversion to nitrate. A typical chromatogram for nitrite and nitrate appears in Figure 13.

DISCUSSION

ADNTs react rapidly with ozone and hydroxyl radical oxidants in aqueous systems. The peroxone treatment of ADNTs will be controlled by ozone oxidation based on the measured rate constants and relative oxidant concentrations in peroxone systems. Because of the magnitude of the

rate constants (105 M–1 s–1 for ozone and 109 M–1 s–1 for hydroxyl radical), competitive oxidation

kinetics offers a convenient method to study the reaction kinetics.

The rate constants for the oxidation of 2-ADNT and 4-ADNT by ozone were calculated to be 5.3

× 105 M–1 s–1 and 1.9 ×105 M–1 s–1, respectively, when nitrite was used as a reference chemical. The

rate constants for the oxidation of 2-ADNT and 4-ADNT by hydroxyl radical were calculated to be

0

400

800

1200

4000 8000 12000

Time (s)

Concentration (μM of carbon)

Glycolate

Acetate

Formate

Oxalate

Glyoxylic

Pyruvic Acid

Unknown 1

Pyruvaldehyde

4-ADNT

C Balance

0

400

800

1200

4000 8000 12000

Time (s)

Concentration (μM of carbon)

Glycolate

Acetate

Formate

Oxalate

Glyoxylic Acid

Pyruvic Acid

Glyoxal

Pyruvaldehyde

2-ADNT

C Balance

Figure 11. Carbon balance and product distribution from the ozonation

of 4-ADNT.

Figure 10. Carbon balance and product distribution from the ozonation of

2-ADNT.
1.6 × 109 M–1 s–1 and 1.9 ×109 M–1 s–1, respectively, when p-nitroacetophenone was used as a reference chemical. If we assume an ozone concentration of 1× 10–4 M (4.8 mg/L), we can estimate the

hydroxyl radical concentration necessary to make the hydroxyl radical rate (RHO•) competitive

with ozone (RO3) by using eq 5 and 2-ADNT as an example:

 RO3/RHO• = kO3(O3)/kHO•[OH•] (5)

 = 5.3 × 105 M–1s–1 (1 × 10-4 M) / 1.6 × 109 M–1s–1 [HO•]

 = 3.3 × 10–8 M/[HO•]

If RO3/RHO• = 1, then [HO•] = 3.3 × 10–8 M.

Because hydroxyl radical concentration is usually in the 10–11 to 10–14 M range, this oxidative pathway cannot compete with ozone for ADNTs in pure water systems. However, when ADNT concentrations become extremely low (ppb range), the reaction of ozone with hydrogen peroxide will

dominate the loss of ozone (compared to the reaction with ADNT) and lead to an increase in the

loss of ADNT by the hydroxyl radical pathway.

10

0

20

10

30

50

40

60

40 50 60 70 80 90

μMoles 4-ADNT Consumed

μMoles Nitrite or Nitrate Formed

Nitrite-4

Nitrate-4

NO2

NO3

–

–

NO2

NO3

2-ADNT

–

–

0 5 10 15 20

Relative Intensity

Time (min)

Figure 13. HPLC profile of

nitrite and nitrate formation in 2-ADNT oxidation

by ozone.

Figure 12. Plots of nitrite and nitrate formation as a function of

2-ADNT and 4-ADNT loss.

a. 2-ADNT.

b. 4-ADNT.

20

0

20

40

60

80

30 40 50 60 70 80 90

μMoles 2-ADNT Consumed

μMoles Nitrite or Nitrate Formed

Nitrite-2

Nitrate-2

NO2

–

NO3

–
11

The speed of the reaction of ADNTs with ozone and the accompanying reactivity of suspected

intermediate products make the study of the mechanistic degradation pathway a challenging endeavor. With the information gained in this study and the current understanding of the chemistry

of ozone in aqueous solution, one approach to evaluate pathways is to examine stable end-products and assess how these products may arise.

Pyruvic acid is generated as a major stable end-product from both 2–ADNT and 4-ADNT. The

most direct route of formation involves cleavage around the aromatic methyl group as shown

below. We propose an ozone-amine adduct as an initial binding step, which ruptures the ring at

the 2-3 carbon bond. In a series of steps, nitrite is produced, which is observed early in the oxidations. This pathway would generate pyruvic aldehyde (a found intermediate), which undergoes

further oxidation with ozone to produce pyruvic acid.

Cleavage on the right side of the carbon atom bearing the methyl group could also lead to pyruvic

acid.

At this time, the behavior of the nitro intermediate (I) is not clear. While hydrolysis is expected,

reduction, leading to pyruvic aldehyde and nitrate, cannot be ignored as an alternate route of

transformation.

In the current investigation, a potential transformation product studied was oxalacetic acid.

This acid formed a 2,4-dinitrophenylhydrazone derivative that could not be found in ozonized

solutions. However, on standing, this derivative was converted to pyruvic acid. Therefore, it cannot be ruled out that oxalacetic acid is a precursor to pyruvic acid.

CH3

NH2

NO2

O2N CH3

O

O

O2N

CH3

O

O

HO

O3 H2O

+ HNO3

(I)

CH3

O

O

O

N

H NO2

O2N

H

H CH 3

O

O

NO2

O2N

H

H

CH C 3 C=O

O

H

CH C 3 C=O

O

OH

O + 2 

O3

- + + NO2

–

(I)

CH3

O

O

O2N

CH3

O

O

HO

CH 3

O

O

H + HNO3

+ HNO2

H2O

(Hydrolysis)

(Oxidation/Reduction)

H2O
The presence of oxalacetic acid may be derived from the reaction of an isomeric form of the

ADNTs.

Oxidation at the three double bonds of the isomeric form of 4-ADNT could lead to oxalacetic acid.

Intermediate aldehydes are possible that also undergo oxidation to the acids with ozone. Thus, it

appears that multiple sources of pyruvic acid are possible in the oxidation of ADNTs by ozone.

Glyoxylic acid was observed and confirmed (HPLC retention time and UV spectrum) by the

DNPH assay technique as a major transformation product; however, it was not observed in the

carboxylic acid profile (UV method), although the reference chemical possesses good chromatographic properties. This suggests that the derivatization conditions, although mild (low pH, room

temperature), convert a precursor product to glyoxylic acid. Glyoxylic acid was observed by the

conductivity method and its formation could result as shown below.

12

CH 3

NO 2

NH 2

O2N

CH 3

NO 2

NH

O2N

CH 3

NO 2

NH

O2N

CH 3

NO2

NH

O2N O

O

O

NO2

H

O

O

O

OH

HO

O3

H2O

O3

Oxalacetic acid

H

CH3

O

O

NO2

O2N

H

H

H

O

O

O2N

H

O

O

HO

H

O

O

 Glyoxal 

Glyoxylic Acid

Hydrolysis

HO C

O

CH2 C

O

COOH HO C

O

CH2 C

DNPH

COOH

CH3 C

DNPH

CO COOH 2 +

+ DNPH

Oxalacetic acid 

Oxalacetic acid

Dinitrophenylhydrazone 
Glyoxal could also be derived by this pathway by an oxidation/reduction process. Both of these

compounds would be precursors to oxalic and formic acids.

Differences in carboxylic acid content observed by the UV method and the conductivity method

(for example, formic acid and glyoxylic acid) suggest that positive identifications must be addressed by additional techniques.

CONCLUSIONS

In conclusion, the laboratory oxidation of ADNTs by peroxone AOT proceeds rapidly to primarily innocuous products. Ozone in the peroxone system appears to dominate the ADNT loss process. Product studies indicate that the ring is ruptured readily with the release of nitrite and nitrate

ions.

LITERATURE CITED

Bader, H., and J. Hoigne (1981) Determination of ozone in water by the indigo method. Water

Research, 15: 448–456.

Buxton, G.V., and C.L. Greenstoch (1988) Critical reviews of rate constants for reactions of hydrated

electrons, hydrogen atoms and hydroxyl radicals (.

OH/.O–) in aqueous solution. Journal of Physical

and Chemical Reference Data, 17: 513–886.

Glover, D.J., J.C. Hoffsommer, and D.A. Kubose (1977) Analysis of mixtures of 2-Amino-4,6-

dinitrotoluene and 4-Amino-2,6-dinitrotoluene, 2,4-Diamino-6-nitrotoluene, and 2,6-Diamino-4-

nitrotoluene. Analytica Chemica Acta, 88: 381–384.

Hoigne, J., and H. Bader (1983) Rate constants of reactions of ozone with organic and inorganic

compounds in water. Water Research, 17: 173–183.

Kieber, R.J., and K. Mopper (1990) Determination of picomolar concentrations of carbonyl compounds in natural waters, including seawater, by liquid chromatography. Environmental Science

and Technology, 24(10): 1477–1481.

Setterfield, C.N., and A.H. Bonnel (1955) Interferences in the titanium sulfate method for hydrogen

peroxide. Analytical Chemistry, 27: 1174.

Thayer, J.R., and R.C. Huffaker (1980) Determination of nitrate and nitrite by high-performance

liquid chromatography: Comparison to other methods for nitrate determination. Analytical Biochemistry, 102(1): 110–119.

13
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Investigation of the Kinetics and Products Resulting from the

Reaction of Peroxone with Aminodinitrotoluenes

Ronald J. Spanggord, David Yao, and Theodore Mill

U.S. Army Cold Regions Research and Engineering Laboratory

Hanover, New Hampshire 03755-1290 Special Report 97-5

U.S. Army Cold Regions Research U.S. Army Engineer Waterways

and Engineering Laboratory Experiment Station

Hanover, New Hampshire Vicksburg, Mississippi

Approved for public release; distribution is unlimited.

Available from NTIS, Springfield, Virginia 22161.

advanced oxidation

aminodinitrotoluene

hydrogen peroxide

The reaction between peroxone and two isomers of aminodinitrotoluene (ADNT) was studied with respect to

kinetics of reaction and the products formed. The ADNTs react rapidly with ozone and hydroxyl radical, the

principal components of peroxone. At fairly high ADNT concentrations (ppm), the reaction of ADNT is

primarily with ozone. At lower ADNT concentrations (ppb), hydroxyl radical competes with ozone in pure

water systems. Reactions of both the 2- and 4-ADNT isomers result in the formation of pyruvic acid, nitrate

ion, and nitrite ion. A reaction mechanism consistent with these products is proposed.

hydroxyl radical

ozone

peroxone

 19

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