Reductive Dehalogenation of Monobromo- and Tribromoacetic Acid by Sodium Borohydride Catalyzed by Gold Nanoparticles Entrapped in Sol–Gel Matrices Follows Different Pathways

Article abstract of DOI:10.1002/ejic.201700069

An efficient, green, and reusable system comprising gold nanoparticles entrapped in an organically modified sol–gel silica matrix was found to catalyze the reduction of monobromo- and tribromoacetic acid by NaBH₄. Interestingly, the reduction of tribromoacetic acid yielded succinic acid along with acetic acid, whereas monobromoacetic acid was reduced only to acetic acid. The relative yields of succinic acid and acetic acid depended on the rate of addition of BH₄^–. Slow addition resulted in the formation of succinic acid as the major product. A variable product distribution was achieved as a result of the different pathways for dehalogenation.

Full text of DOI:10.1002/ejic.201700069

A Journal of
Accepted Article
Title: The Reductive De-halogenations of Mono and Tribromo Acetic
Acids by NaBH4 Catalysed by Gold Nanoparticles Entrapped in
Sol-Gel Matrices Follow Different Pathways
Authors: Jaydeep Adhikary, Michael Meistelman, Ariela Burg, Dror
Shamir, Dan Meyerstein, and Yael Albo
This manuscript has been accepted after peer review and appears as an
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of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
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content of this Accepted Article.
To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.201700069
Link to VoR: http://dx.doi.org/10.1002/ejic.201700069

10.1002/ejic.201700069
European Journal of Inorganic Chemistry
COMMUNICATION
The Reductive De-halogenations of Mono and Tribromo Acetic
Acids by NaBH4 Catalysed by Gold Nanoparticles Entrapped in
Sol-Gel Matrices Follow Different Pathways
Jaydeep Adhikary,[a] Michael Meistelman,[b] Ariela Burg,[c] Dror Shamir,[d] Dan Meyerstein,[a,e] and Yael
Albo*[b]
compounds from drinking water.[8] Only few examples have been
Abstract: An efficient, green and reusable gold nano-particles
entrapped in an organically modified sol-gel silica matrix catalyses
the reduction of monobromo and tribromoacetic acids by NaBH4.
Interestingly, the reduction of tribromoacetic acid yields succinic acid
along with acetic acid while monobromoacetic acid is reduced to
merely acetic acid. The relative yields of succinic acid and acetic
found where de-halogenation of BDBP have been studied and in
those cases they used zero valent iron, silver catalyst, iron
based bimetallic catalysts and UV irradiation.[9]
De-halogenations of other halo-organic compounds
were studied previously by many groups. [10] Most of them used
TiO2 and Pd based catalysts for the de-halogenation. However
the exceptionally effective catalytic species, [11] Au° nanoparticles
(Au°-NPs), were used only rarely for the de-halogenation
process.[10e] The catalysis, by Au°-NPs, of the de-halogenation
of haloacetic acids has not been reported up to date. Therefore,
TBAA and MBAA have been chosen as substrates in the
-
acid depend on the rate of addition of the BH4 . In slow addition,
succinic acid is obtained as the major product. The variable product
distribution is achieved due to the different pathways of the de-
halogenation.
Introduction
Chlorine disinfection is being used in the provision of safe
-
present study for the reductive de-halogenation using BH4
[1]
drinking water
and is widely used in disinfection of
catalysed by sol-gel entrapped Au°-NPs.
wastewater.[2] However, these disinfection processes result in
the production of several toxic by-products due to the reaction
between chlorine and organic matter in water.[3] It was reported
Herein, are reported the synthesis and structural
investigation of Au°-NPs sol-gel entrapped in the mesopores of
organically modified sol-gel silica (ORMOSIL) matrices. To the
best of our knowledge, only two applications of Au°-NPs
entrapped in organically modified silica (ORMOSIL) were
reported. [12,13] Ramaraj et. al. encapsulated Au°/Ag° bimetallic
NPs in methyl-modified silica for electrocatalytic reduction and
sensing of H2O2 and Pagliaro et. al. reported ORMOSIL-
entrapped gold nanoparticles applied for 1-phenylethanol
oxidation. In the present study, the matrices have been
employed in the de-halogenation of MBAA and TBAA using
NaBH4 as the reducing agent. It was previously reported that
TBAA is consecutively de-brominated to dibromoacetic acid
(DBAA) then to MBAA and finally into acetic acid (AA) (Scheme
1).[14] Surprisingly, the results reported herein point out that Au°-
NPs catalyse the de-bromination of TBAA via a different
pathway yielding succinic acid (SA) as the major product.
However, the reduction of MBAA proceeds via the literature
reported mechanism (Scheme 2). Furthermore, even the rate of
the addition of the reducing agent, NaBH4, affects the relative
yields of the products during TBAA reduction.
[2]
that some brominated disinfection by-products (BDBP) are
also produced during chlorine disinfection processes due to
bromide traces.[4] The presence of trace concentrations of
bromide ion in drinking water has major implications regarding
health effects associated with disinfection by products. It has
been shown that often BDBP represent higher developmental
toxicity and growth inhibition than their chlorinated analogues.[5,6]
Tribromoacetic acid (TBAA) and monobromoacetic acid (MBAA)
are typical BDBP, with high toxicity, genotoxicity, and
carcinogenicity.[7] An effective treatment of BDBP which will
provide some guidance for the provision of safe drinking water is
thus urgently needed. In most of the examples in the literature,
chlorinated disinfection by products were taken as the
substrates for studies on the removal of halo-organic
[a] Dr. Jaydeep Adhikary, Prof. Dan Meyerstein
Chemical Sciences Dep., Ariel University, Ariel, Israel.
[b] Michael Meistelman, Dr. Yael Albo
Chemical Engineering Dep., Ariel University, Ariel, Israel. E-mail:
yaelyt@ariel.ac.il
[c] Dr. Ariela Burg
Succinic acid and its derivatives are widely used in
Chemical Engineering Dep., Sami Shamoon College of Engineering, Beer-
Sheva, Israel.
industry as specialty chemicals with applications in polymers,
foods, pharmaceuticals and cosmetics. In addition, succinic
acid has also some biological importance. There are three
possible metabolic pathways leading towards succinate: the
[d] Dr. Dror. Shamir
Chemistry Dep., Nuclear Research Centre Negev, Beer-Sheva, Israel.
[e] Prof. Dan Meyerstein
Chemistry Dep., Ben-Gurion University, Beer-Sheva.
Supporting information for this article is given via a link at the end of
the document.
1
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10.1002/ejic.201700069
European Journal of Inorganic Chemistry
COMMUNICATION
oxidative part of the citric acid cycle, the reductive part of the
citric acid cycle, and the glyoxylate bypass.[15] Nowadays,
succinic acid is manufactured biochemically from glucose using
several bacteria like an engineered Anaerobiospirillum
succiniciproducens, an engineered Eschericia coli, and most
recently via an engineered Mannheimia succiniciproducens.[16] In
that consequence, our green and reusable gold catalyst could
play an imperative role in producing SA.
gold demonstrates four diffraction peaks attributable to Au°-
NPs, with face-centered cubic phase at 2 = 38.27, 44.40, 64.68
and 77.55° that can be perfectly related to the (111), (200), (220)
and (311) crystal planes, respectively. Only two peaks at 2 =
38.17 and 44.30 were observed in the case of 0.054 mol% of
gold, Au-cat. The other two peaks at higher two theta were not
observed probably due to the low concentration of Au°-NPs in
Au-cat. The broad band for the (111) and (200) reflections for
the Au°-NPs, indicates that the size of the particles is in the
nanometer range after immobilization without any aggregation.
[17,18] The particle size of Au°-NPs in Au-cat was calculated using
the Debye-Scherer equation and was found to be 6.3 ± 0.2 nm.
The results for the (111) plane were used for this calculation as
this peak is stronger than the others. Such a crystalline phase
could not be detected in the PXRD spectrum of the blank matrix
i.e. characteristic to amorphous silica (not presented here). With
the increase in Au° loading, the colour of the matrices changes
from light pink to ruby (Figure S1).
Br-
2e- + H+
O
2e- + H+
2e- + H+
Br-
Br-
O
O
O
Br3C
OH
Br2HC
OH
BrH2C
OH
H3C
OH
TBAA
AA
DBAA
MBAA
Scheme 1. The proposed pathway for the degradation of TBAA according to a
literature report. [14]
Au-cat,
NaBH4(slow addition)
(65%)
BrCH2COOH
Br3CCOOH
CH3COOH
(AA)
(i)
H2O, 5h, stir
Au-cat,
NaBH4(slow addition)
(15%) COOHCH2CH2COOH (80%)
(SA)
CH3COOH
(AA)
(ii)
H2O, 5h, stir
+ BrCH2COOH(5%)
(MBAA)
Blank matrix
Au-cat
4
Scheme 2. Au°-NPs entrapped in ORMOSIL catalysed de-halogenation of
2
MBAA and TBAA.
2910 cm-1
0
1628 cm-1
1280 cm-1
2973 cm-1
934 cm-1
785 cm-1
Results and Discussion
3472 cm-1
3500
1100 cm-1
1418 cm-1
2000
-1
4000
3000
2500
1500
1000
500
As Au°-NPs entrapped within the pores of a gel cannot be
accessed by HRTEM, the prepared matrices were characterized
by FTIR, PXRD and UV-vis spectroscopy. The identification of
the possible functional groups present in the blank and Au-cat
matrices was achieved by FTIR spectroscopy (Figure 1). The
broad band with a peak at 3472 cm-1 is assigned to the
stretching vibrations of –OH groups present in the silica matrix.
(HOH) band at 1628 cm-1 is due to adsorbed water since both
the matrices are hydrophilic in nature. The bands at 2973 and
2910 cm-1 are assigned to the stretching modes (anti symmetric
and symmetric, respectively) of the Si-CH3 bond. The
corresponding deformation modes appear at 1418 and 1280
cm-1, respectively. The asSi-O-Si band is broad with unresolved
components and a maximum absorption around 1100 cm-1. The
sSi-O-Si band overlaps with the (Si)-CH3 mode detected at
785 cm-1. The band at 934 cm-1 is assigned as Si-OH. All the
important bands of the blank silica matrix are also found in the
matrix after entrapping the Au°-NPs, indicating that incorporation
of the Au°-NPs does not alter the internal structure of the matrix.
Figure 2 shows the PXRD patterns of gold matrices
containing 0.27 and 0.054 mol% gold (mol of gold vs. mol of
silicone) The PXRD pattern of the sample with 0.27 mol% of
cm
Figure 1. FTIR spectra of blank matrix and Au-cat.
(111)
Au matrix (0.27 mol% of Au NPs)
Au-cat(0.054 mol% of Au NPs)
800
600
400
200
0
(200)
(200)
(220)
(311)
(111)
40
50
60
70
80
2degree
Figure 2. PXRD pattern of the matrices having 0.054 mol%(Au-cat) and 0.27
mol% of Au°-NPs.
UV-vis spectrum of the Au-cat was taken in sol condition
and is represented in the supplementary file (Figure S2). A
sharp peak at 515 nm. indicates that the size of Au°-NPs is ~ 10
nm. as reported earlier.[19]
MBAA and TBAA were chosen as substrates to study the
reductive de-halogenation. Details of the catalytic procedure are
reported in the experimental section. The gold matrices
prepared from 100% Tetraethyl orthosilicate (TEOS) had poor
catalytic activity, probably due to the small porosivity of such
2
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10.1002/ejic.201700069
European Journal of Inorganic Chemistry
COMMUNICATION
matrices.[20] Therefore matrices consisting of different ratios of
Trimethoxymethylsilane (MTMOS) and TEOS were prepared. It
was found that gold catalyst (Au-cat) with 30% MTMOS and
70% TEOS worked superiorly to the other matrices.
Consequently, all the reported results are for matrices with this
composition. The effect of the load of Au°-NPs, 0.027 to 0.27
mol%, (mol of gold vs. mol of silicone) into the matrix was
studied. It was observed that the matrix consisting 0.054 mol%
worked commandingly. Further increase in the gold
concentration did not affect the yield of the products.
Figure 3b. Effect of the molar ratio of TBAA and NaBH4 on the products
distribution. Aqueous NaBH4 solution was added dropwise over a period of 3.5
h.
-
Au°-NPs are known to catalyse the reaction of BH4
[21]
with water to form H2 and borate
and the reduction of p-
nitrophenol to form p-aminophenol.[22] The first step in these
processes clearly is:
H2O
(1) (Au°-NP) + nBH4-  {(Au°-NP)-H4n}-4n+ nB(OH)3
Clearly this is a complex process and some partially
oxidized BH4- are formed as intermediates. In aqueous solutions,
First, Au-cat catalysed reductive de-halogenation of
this reaction is probably followed by:
MBAA by NaBH4 was studied. It was found that at 1:4 ratio of
MBAA to NaBH4 (optimized), 100% MBAA was converted into
acetic acid. However, slow addition of the same amount of
NaBH4 resulted in 65% conversion of MBAA to AA.
(2) {(Au°-NP)-H4n}-4n + mH3O+ {(Au°-NP)-H4n+m m-4n + mH2O
}
The equilibrium constant of reaction (2) depends on
the the pH of the solution. If the redox potential is below the
over-potential for H2 release from the Au°-NPs then reaction (2)
will be followed by either:
Surprisingly, acetic and succinic acid are formed in the
Au-cat catalysed de-halogenation of TBAA (Figure 3). However,
in the analogous reduction of trichloroacetic acid (TCAA) the
only product is acetic acid. Four other experimental observations
shed light on the plausible mechanisms of Au°-NPs catalysed
(3) {(Au°-NP)-H4n+m
}
m-4n  {(Au°-NP)-H4n+m-2
}
m-4n + H2
or by:
(4) {(Au°-NP)-H4n+m
}
m-4n + H3O+/H2O
-
{(Au°-NP)-H4n+m-1}
m+1-4n + H2 + H2O/OH-
de-halogenation by BH4 :
1. The relative yields of succinic acid and acetic acid
In the presence of CH3-kBrkCO2H the {(Au°-NP)-
-
m-4n might react via one of the following mechanisms:
depend on the rate of addition of BH4 to the
H4n+m
}
suspension (Figure 3).
(5) {(Au°-NP)-H4n+m
{(Au°-NP)-H4n+m-1
m-4n+1 + CH4-kBrk-1CO2H + Br-
(6) {(Au°-NP)-H4n+m
m-4n + CH3-kBrkCO2H 
{(Au°-NP)-H4n+m
m-4n+1 + .CH3-kBrk-1CO2H + Br-
(7) {(Au°-NP)-H4n+m
m-4n + CH3-kBrkCO2H 
{(Au°-NP)-H4n+m-1
m-4n + .CH3-kBrk-1CO2H + H+ +Br-
}
m-4n + CH3-kBrkCO2H 
2. The total degree of de-halogenation depends on
}
-
the amount and the rate of addition of BH4 (Figure
}
3).
}
3. No (-CBr2COOH)2 or (-CHBrCOOH)2 are observed
as intermediates.
}
}
4. Also in the reduction of CHBr2COOH succinic acid
is a major product.
Reaction (5) is a hydride transfer reaction, such reactions
were proposed in the Au°-NPs catalysed reduction of p-
TBAA
- [23]
DBAA
nitrophenol by BH4 .
This type of reaction cannot lead to the
Substrate : NaBH4=1:10
MBAA
SA
formation of dimers, i.e. succinic acid. Reaction (6) is an electron
transfer process whereas reaction (7) is a bromide abstraction
by a hydrogen atom bound to the surface of the Au°-NPs. Both
these reactions were not observed up to date, but in the case of
CBr3CO2H one of them, at least, should occur as only the
radicals formed in these reactions might yield succinic acid as a
final product.
AA
Substrate : NaBH4=1:6
Substrate : NaBH4=1:4
Substrate : NaBH4=1:2
No NaBH4
0
10
20
30
40
50
60
70
80
90
100
110
% Yield
Figure 3a. Effect of the molar ratio of TBAA and NaBH4 on the products
distribution. Aqueous NaBH4 solution was added in one time.
The radicals formed in reaction (6) & (7) are formed
near the surface of the nano-particles and are therefore
TBAA
DBAA
MBAA
SA
AA
Substrate : NaBH4=1:10
expected to react with them via:
Substrate : NaBH4=1:6
Substrate : NaBH4=1:4
Substrate : NaBH4=1:2
No NaBH4
m-4n
(8) {(Au°-NP)-H4n+m
}
m-4n+1/{(Au°-NP)-H4n+m-1
}
+
.CH3-kBrk-
1CO2H

{(Au°-NP)-H4n+m-CH3-kBrk-1CO2H}m-4n+1/{(Au°-NP)-
H4n+m-1-CH3-kBrk-1CO2H}m-4n
in analogous reactions to those of other alkyl radicals with Au°-
NPs.[24] Alternatively they might react via:
0
10
20
30
40
50
60
70
80
90
100
110
% Yield
3
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10.1002/ejic.201700069
European Journal of Inorganic Chemistry
COMMUNICATION
m-4n
(9) {(Au°-NP)-H4n+m
}
m-4n+1/{(Au°-NP)-H4n+m-1
}
+
.CH3-kBrk-
pollutants using a green approach is proposed. Of special
interest are the observations that:
m-4n
1CO2H  {(Au°-NP)-H4n+m-1
}
m-4n+1/{(Au°-NP)-H4n+m-2
}
+ CH4-
1. Radicals are intermediates in the catalytic de-
halogenation process.
kBrk-1CO2H
i.e. via hydrogen atom abstraction, the rate constants of such
reactions are not known but recent results for M°-NPs, including
Au°-NPs, suggest that they are fast.[25]
2. The detailed mechanism of the process differs for
different substrates.
-
3. The rate of addition of the reducing agent, BH4 ,
Succinic acid will be formed via dimerization of two radicals on
the surface of the nanoparticles in analogous to the formation of
has a major effect on the detailed mechanism of
the de-halogenation of TBAA. The slower the
addition the higher the yields of the desired
products. This is probably correct for other
ethane in recation of methyl radicals on the surface of Au°-NPs:
[24a]
(10){(Au°-NP)-H4n+m-(CH3-kBrk-1CO2H)l}m-4n+1/{(Au°-NP)-H4n+m-1
(CH3-kBrk-1CO2H)l}m-4n
-
-
reductions by BH4 .

{(Au°-NP)-H4n+m-(CH3-kBrk-1CO2H)l-2}m-4n+1/{(Au°-NP)-H4n+m-1
(CH3-kBrk-1CO2H)l-2}m-4n + (-CH3-kBrk-1CO2H)2
-
4. The total degree of de-halogenation depends on
NaBH4 dosage. A similar result was reported for
-
the bromate reduction by BH4 catalysed by a
metal – organic framework. [27]
followed by de-bromination of these dimers. Clearly the {(Au°-
NP)-H4n+m-(CH3-kBrk-1CO2H)l}m-4n+1/{(Au°-NP)-H4n+m-1-(CH3-kBrk-
1CO2H)l}m-4n intermediates can also decompose via:
(11){(Au°-NP)-H4n+m-(CH3-kBrk-1CO2H)l}m-4n+1/{(Au°-NP)-H4n+m-1
(CH3-kBrk-1CO2H)l}m-4n
-
Experimental Section

{(Au°-NP)-H4n+m-1-(CH3-kBrk-1CO2H)l-1}m-4n+1/{(Au°-NP)-H4n+m-2
(CH3-kBrk-1CO2H)l-1}m-4n +CH4-kBrk-1CO2H
-
Physical Methods and Materials: Infrared spectra (4000–
400 cm-1) were recorded at room temperature using a Perkin Elmer
Spectrum One spectrometer in transmittance mode with KBr pellets
containing 1% in weight powder samples. Powder X-ray diffraction
(PXRD) was measured using a X’Pert Pro diffractometer using the CuK
radiation ( = 0.154 nm). The scanning for PXRD was made for a 2
angle from 20 to 1000, with a step time of 2s. UV-vis spectrum was
measured using an Agilent 8453 diode-array spectrophotometer. The de-
halogenation of the halo-acetic acids was monitored by applying an
HPLC system (Jasco) with a UV/Vis detector (= 210 nm) along with a
HPLC column of Agilent (Eclipse XDB-C18, 5 µm) with a dimension of
4.6×150 mm. The eluent: H2O : CH3CN = 98:2 with 0.2 % H3PO4, pH 2.0,
flow 1.0 mL/min.
i.e. via a combination between the bound alkyl radical and a
bound hydrogen atom.
At present the relative rate constants of reactions (5)-
(7), (8)-(9) and (10)-(11) are unknown and therefore there is no
answer to the question why succinic acid is not formed in the de-
bromination of MBAA. It seems reasonable to assume that the
difference stems from the difference between the properties of
the radicals: .CH2CO2H and .CBr2CO2H. This could be due to the
electron withdrawing properties of Br vs. H. The latter
suggestion is clearly not the source of the observed effect as the
de-chlorination of CCl3CO2H does not yield succinic acid.
Tribromoacetic acid, dibromoacetic acid, monobromoacetic
acid,
trichloroacetic
acid,
Trimethoxymethylsilane
and
(3-
-
However probably when the BH4 is added slowly the
Aminopropyl)trimethoxysilane were obtained from Alfa Aesar.
Tetraethylorthosilicate and gold(iii) chloride trihydrate were purchased
from Aldrich. NaBH4 was bought from Strem Chemicals.
number of hydrogen atoms/hydrides, (4n + m)/(4n + m -1) bound
at steady state to the Au°-NPs is smaller. Therefore the
competition between reactions (3) and/or (4) with reactions (5)-
(7) will favour the latter, as observed. This will also favour
reaction (8) over reaction (9) and reaction (10) over reaction (11)
and thus explain why the yield of succinic-acid is larger when the
BH4- is added slowly to the solution.
Syntheses: Synthesis of Au-cat with the composition of 30 mol %
MTMOS and 70 mol % TEOS has been achieved by adopting a slightly
modified procedure of that reported previously. [13] Briefly, 90 µL of HCl
was added to 6.0 mL of ice cold water and the mixture was poured into a
solution containing 2.5 mL of Trimethoxymethylsilane (MTMOS) 8.8 mL
of Tetraethylorthosilicate (TEOS) and 13.3 mL of ethanol. The mixture
was stirred in an ice bath for 10 minutes. 125 µL (3-
Aminopropyl)trimethoxysilane (APS) was then added to the mixture. 5.0
Conclusions
.
mL of ice cold aqueous solution of 3×10-3 M HAuCl4 3H2O was then
The results reported herein point out that Au°_NPs entrapped in
silica sol-gel matrices can be used as catalysts for the de-
halogenation of halo-organic compounds and not only for the
reduction of p-nitrophenol.[22,23,26] Thus a process for removal of
added drop wise. The reduction of Au(III) was done by the addition of 5.0
mL of an aqueous solution of 3×10-2 M NaBH4. 5.0 mL of 2.8% NH3 was
added to the mixture for the conversion of the sol to gel. The final
solution was then stirred for another 15 minutes for complete gelation.
The solid gel was kept for 7 days for ageing and drying. After one week,
4
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10.1002/ejic.201700069
European Journal of Inorganic Chemistry
COMMUNICATION
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the solid matrix was well crashed and washed with water for several
times. The washed matrix was then dried and used for the catalytic
processes. Blank matrix with same composition was prepared as
explained in case of Au-cat. Here, 10.0 mL of ice-cold water was added
.
in place of the 5.0 mL of the solutions of HAuCl4 3H2O and NaBH4.
Catalytic tests: TBAA, DBAA, MBAA and TCAA were taken as model
substrates to study the catalytic activity of our purposely synthesised Au°
materials towards reductive de-halogenation. In a typical catalytic run,
3.5 mL of 0.010 M halo-acetic acid was added to the suspension of 0.50
g (0.054 mol %) of the Au-cat taken in 18 mL of deionised water in a 50
mL beaker kept at room temperature. The mixture was then stirred for
few minutes. 3.5 mL of 0.040 M of aqueous NaBH4 (for MBAA) or 0.060
M of aqueous NaBH4 (for TBAA) was then added. The resulting solution
was stirred for 5 h. After completion of the reaction the catalyst was
recovered by filtration and the filtrate was analysed by HPLC. HPLC
chromatogram highlighting acetic and succinic acid are presented in the
supporting information file (Figures S3-S4). The catalyst was washed
extensively with water, dried in a desiccator and reused as such in
subsequent reaction runs under the same conditions. The yields in each
cycle were not significantly different, implying the stability of our catalyst
(Figures S5).
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Acknowledgements
This study was supported in part by a grant from the Pazy
Foundation.
Keywords: Sol-gel processes . gold nanoparticle .
dehalogenation . radicals . succinic acid
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Entry for the Table of Contents
COMMUNICATION
Sol-gel entrapped gold nanoparticles
catalyse the de-halogenation of mono
and tribromoacetic acids by NaBH4 via
different pathways and depend on the
rate of addition of the reducing agent.
Jaydeep Adhikary, Michael Meistelman,
Ariela Burg, Dror Shamir, Dan
Meyerstein, and Yael Albo*
Page No. 1 – Page No.5
The Reductive De-halogenations of
Mono and Tribromo Acetic Acids by
NaBH4
Catalysed
by
Gold
Nanoparticles Entrapped in Sol-Gel
Matrices Follow Different Pathways
7
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