Transcript FinalPresentation_Johnston_H

DETERMINING REACTION RATES OF
NITROAROMATIC REDUCTION REACTIONS
Hayley Johnston
Mentor: Ali Salter-Blanc
Tratnyek Lab
Summer 2013
Background
• Release of energetic munitions
compounds into the environment
leads to contamination
• Water
• Soil
• Sediments
• Selection of new energetic
compounds
• Less shock sensitive (safer)
• Toxicity
• Environmental persistance
Objectives
• Determine the reaction rate of various nitroaromatic
compounds in reducing conditions
• Formulate quantitative structure activity relationships
(QSARs)
• Predict the behavior of current and future ammunitions
contaminants in the environment
2,4-dinitroanisole
nitrobenzene
2,4,6-trinitrotoluene
2,4-dinitrotoluene
4-chloro-1-nitrobenzene
1,3-dinitrobenzene
Reduction of Nitroaromatic Compounds (NACs)
• Reduction: an electron transfer reaction where the
product gains electrons
• Overall Reaction
• 1st Step
• Reduction by electron shuttle (mediator)
High rate
Moderate rate
Kinetics
log(NAC)
• Generally assumed to be pseudo-first-order
• Reaction is second order in [Fe(II)P] and [NAC] rate=
kFeP[Fe(II)P][NAC]
• [Fe(II)P] is constant so it can combine with the kFeP to get the kobs
rate= kobs [NAC]
7
6
5
4
3
2
10
7
6
5
1
2
3
4
Time (h)
• Obtain second order rate constant (kFeP) from
3.0
kobs
kobs = kFeP [FeP]
2.0
1.0
0.0
0
5
10
15
20
[FeP]
25
30 35x10-6
Methods
• 60mL Reaction Vial containing:
• 25-400μL of 4.29mM iron(III) porphine (FeP)
• 1mL of 0.25M cysteine (to generate Fe (II))
• 49mL Sodium Phosphate Buffer pH 7.0
• 50μL 0.1M nitroaromatic compound (NAC)
• 25O water bath
• HPLC detection @ 254nm or
220nm
• Sampling frequency based on
half life of NAC
Reduction Rates of 2,4-dinitrotoluene (DNT) by increasing concentrations of FeP
100
9
8
log(Concentration of DNT (uM))
7
6
5
Slope values are the
observed reaction rate (kobs)
for each reaction
4
3
2
4.29uM FeP
8.58uM FeP
12.87uM FeP
17.16uM FeP
25.74uM FeP
34.32uM FeP
10
9
0
2
4
6
8
10
1.6
Time (h)
1.4
The kobs values are plotted
against the concentration of
FeP to obtain the kFeP value
of each NAC
kobs (1/h)
1.2
1.0
0.8
0.6
0.4
0.2
0.0
kFeP=49,135
-0.2
0
5
10
15
20
[FeP] M
25
30
-6
35x10
25.74uM FeP
Complications
• Autocatalytic reaction?
A→B
A+B→C
log(Concentration DNAN)
100
• New fit parameters
9
8
7
6
5
4
3
2
10
9
0.0
0.2
0.4
0.6
0.8
Time (h)
1.0
1.2
25.74uM
25.74uM FeP
FeP
100
100
DNANuM)
log(Concentration DNANuM)
log(Concentration
log(Concentration DNANuM)
Trial 1
Trial 2
Trial 3
Trial 4
10
10
10
11
1
Trial
Trial 11
Trial
Trial 33
Trial
Trial 55
NP
NP
NP
0.1
0.1
0.0
0.0
0.5
0.5
0.5
1.0
1.0
1.5
1.5
Time
Time(h)
(h)
2.0
2.0
2.0
2.5
2.5
2.5
1.4
Results
• First order fit is good up until ≈10μM NAC
• This enables me to obtain second order rate constants for
each compound
TNT
NACs
1,3-DNB
DNAN
2,4-DNT
4-ClNB
NB
0.5
1.0
log(kFeP)
1.5
2.0
Acknowledgements
I would like to extend many thanks to:
Ali Salter-Blanc
Paul Tratnyek
Vanessa Green
Oregon Health and Science University (OHSU)