Reduction of mono-and dichlorobiphenyls with sodium-naphthalene complex

Article abstract of DOI:10.1134/S1070363210040201

Reactivity of low-chlorinated congeners of polychlorinated biphenyls in relation to sodiumnaphthalene complex in THF was studied. It was shown that the rate of reduction of these substrates weakly depended on their structure. The regioselectivity of the first stage of reduction of dichlorobiphenyls may be caused by relative stability of the intermediately formed aryl radicals. Kinetic analysis of the processes taking place in the system showed that sodium-naphthalene complex alongside with one-electron reduction of dichlorobiphenyls is involved also in the multi-electron reduction leading directly to biphenyl avoiding the stage of formation of monochlorobiphenyl. Pleiades Publishing, Ltd., 2010.

Full text of DOI:10.1134/S1070363210040201

ISSN 1070-3632, Russian Journal of General Chemistry, 2010, Vol. 80, No. 4, pp. 800–808. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © V.P. Boyarskii, M.V. Sangaranarayanan, T.Sh. Khaibulova, I.A. Boyarskaya, 2010, published in Zhurnal Obshchei Khimii, 2010,
Vol. 80, No. 4, pp. 639–647.
Reduction of Mono- and Dichlorobiphenyls
with Sodium-Naphthalene Complex
a
b
a
a
V. P. Boyarskii , M. V. Sangaranarayanan , T. Sh. Khaibulova , and I. A. Boyarskaya
a
St. Petersburg State University, Universitetskii pr. 26, St. Petersburg, 198504 Russia
e-mail: vadimpb@yahoo.com
b
Indian Technological Institute of Madras, Chennay, 600036 India
Received September 5, 2009
Abstract—Reactivity of low-chlorinated congeners of polychlorinated biphenyls in relation to sodium-
naphthalene complex in THF was studied. It was shown that the rate of reduction of these substrates weakly
depended on their structure. The regioselectivity of the first stage of reduction of dichlorobiphenyls may be
caused by relative stability of the intermediately formed aryl radicals. Kinetic analysis of the processes taking
place in the system showed that sodium-naphthalene complex alongside with one-electron reduction of
dichlorobiphenyls is involved also in the multi-electron reduction leading directly to biphenyl avoiding the
stage of formation of monochlorobiphenyl.
DOI: 10.1134/S1070363210040201
One of the results of rapid development of chemical
industry in the middle of the XX century is the
problem of elimination of the stable organic cont-
aminants disastrous for human beings in the environ-
ment. To this group belong 12 types of chemical
substances including polychlorinated biphenyls con-
taining from one to ten atoms of chlorine in the
molecule. Commercial polychlorinated biphenyls are
complex mixtures consisting of 50–70 individual
compounds, the so-called congeners. Mullins et al. [1]
identified all 209 possible congeners. Their physico-
chemical properties such as thermostability, high
boiling point, non-flammability, stability to chemical
decomposition, low solubility in water, miscibility
with organic solvents and plastics determined the
application of polychlorinated biphenyls in various
branches of industry [2–4]. Nowadays production of
these substances is cut off, but because of leakages
from various technical devices they continue to cont-
aminate the environment.
appearing in waste water are concentrated in the
bottom deposits. Hence, their natural biodegradation
takes place mainly under the anaerobic conditions
characteristic of bottom deposits. It proceeds ac-
cording to the pathway of reductive dechlorination
with the successive formation of less chlorinated
congeners [7]. Highly chlorinated polychlorobiphenyls
are destructed in the same manner, moreover, their
reactivity is higher as compared to that of low chlori-
nated congeners [7].
As is known [8], many microorganisms can
assimilate the chlorinated compounds enzymatically
transferring electrons to these substances. For example,
Desulfomonile tiedjei obtain ATP necessary for their
growth using the reductive hydrodechlorination as the
source of energy [9].
Considerable part of methods of reprocessing of
polychlorinated biphenyls and some other stable
organic contaminants based on the reactions of
substitution of chlorine atoms with hydrogen or any
functional group include the stage of electron transfer.
First of all it is the reductive dechlorination of
polychlorobiphenyls by alkali metals (for example,
sodium) in the presence of compounds characterized as
good hydrogen donors (hexane, cyclohexane) [10–13].
Note further the reduction of polychlorinated biphenyls
Natural decomposition of polychlorinated bi-
phenyls proceeds by different pathways under the
aerobic as well as anaerobic conditions. Only low
chlorinated congeners are oxidized by microorganisms
under the aerobic conditions [5, 6], but their content in
technical mixtures is usually low. Besides because of
low solubility in water polychlorinated biphenyls
800

REDUCTION OF MONO- AND DICHLOROBIPHENYLS
801
under the action of alkali metals in the presence of
such solvents as ammonia, amines, alcohols or esters
insufficiently [17]. That is why it seems important to
study the hydrodechlorination of polychlorinated bi-
phenyl congeners.
(
the so-called “solvated electron” technology) [14].
And finally, it is a recently developed method of
carbonylation of polychlorobiphenyls using the effect-
tive catalytic systems on the basis of the epoxide-
modified cobalt carbonyl in the alkaline ethanol me-
dium [15, 16].
Hence, the key stage of a series of methods of
reprocessing of polychlorobiphenyls is the radical
anion activation of these inert molecules.
No less important for biodegradation of the
compounds under study taking place in the nature is
the stage of electron transfer. It explains the interest to
establishing the laws of the radical anion reactions in
the series of polychlorobiphenyls. At the same time the
data on the intersubstrate selectivity in the radical
anion reduction of polychlorinated biphenyls is prac-
tically absent, and the positional selectivity is studied
In this work the hydrodechlorination of low
chlorinated congeners, mono- and dichlorobiphenyls,
is studied. In this case comparatively simple mixtures
of the products are formed considerably facilitating the
establishment of the reaction rules. The reduction with
the alkali metal–naphthalene complex was chosen as
the most widespread (alongside with the reduction with
a solution of sodium in liquid ammonia) chemical
method of one-electron reduction of organic halides [17].
1. Studies of relative reactivity of polychlorinated
biphenyls. The first step in solving the problem under
investigation was the evaluation of relative reactivity
of monochlorobiphenyls and some of dichlorobi-
phenyls in the reduction with sodium–naphthalene
complex dissolved in THF. This reaction proceeds
according to the following scheme (Scheme 1) [18]:
Scheme 1.
+
nf
+SolvH
_Solv
_
Cl−
_nf
Clx
Clx
Clx−1
Clx−1
+
nf
Clx−1
nf is naphthalene.
If the concentration of naphthalene radical anions in
the solution is very small, the formation of the
reduction products may proceed by the abstraction of
the hydrogen atom from the solvent. When THF is
used as a solvent this stage is quick because THF is a
good donor of hydrogen atom for the aryl radical [19].
At the significant concentrations of naphthalene radical
anions in solution aryl radical undergoes the preferable
reduction to aryl anion because the transfer of electron
from the naphthalene anion radical to the aryl radical
proceeds with the diffusion rate [20]. Aryl anion may
further form the reaction product by the abstraction of
a proton from the solvent during the workup of the
reaction mixture or may undergo further reduction.
naphthalene complex took place in situ at the excess of
sodium and naphthalene in THF (procedure I). In the
second one solution of substrate in THF was treated
with the previously prepared solution of sodium-
naphthalene complex in THF (procedure II). In the
third case solution of the substrate in 1,2-
dimethoxyethane was treated with the previously
prepared solution of lithium–naphthalene complex
dissolved in 1,2-dimethoxyethane (procedure III). The
data obtained are listed in Table 1.
While using the previously prepared sodium-
naphthalene (procedure II) or lithium-naphthalene
complex (procedure III) reaction with aryl halides
proceeds very fast (in several seconds after mixing of
solutions). It is accompanied by the disappearance of
the intense dark-green color of the solution of the
The reaction was carried out at 20–22°C by three
methods. In the first one the formation of sodium-
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8
02
BOYARSKII et al.
Table 1. Dependence of composition of the reaction mixture
in hydrodechlorination of 3,4-dichlorobiphenyl on the
experimental conditions (molar % according to GLC, for
procedures and relative error see Experimental)
Table 2. Relative rate constants of the reduction of mono-
and dichlorobiphenyls with sodium-naphthalene complex,
procedure I
Substrate
(kobs
)
rel
–E1/2,a V [22]
Component of the
reaction mixture
Procedure I Procedure II Procedure III
2-Chlorobiphenyl
1.0
2.092
3
4
2
2
2
3
4
-Chlorobiphenyl
0.79±0.04
1.09±0.03
0.90±0.05
1.14±0.05
1.17±0.06
0.95±0.02
1.11±0.04
2.108
3
3
,4-Dichlorobiphenyl
-Chlorobiphenyl
68
93
0.4
94
0.3
-Chlorobiphenyl
2.056
1.956
1.983
1.942
1.871
2.000
7
,3-Dichlorobiphenyl
,4-Dichlorobiphenyl
,5-Dichlorobiphenyl
,4-Dichlorobiphenyl
,4'-Dichlorobiphenyl
4
-Chlorobiphenyl
<0.01
<0.01
4.7
<0.01
5.2
Biphenyl
2
5
complex. The analysis of samples taken at different
times after the addition of reagent to the substrate
showed that the conversion achieved during the first
a
Half-wave potentials of polarographic reduction against the
standard calomel electrode.
2
0–30 seconds did not increase later. While using the
excess of sodium and naphthalene with respect to alkyl
chloride and the formation of complex in situ
In its turn the rate of fragmentation of the radical anion
depends on its energy of formation in a complex
manner. Standard reducing potential of the aryl halide
may be used as its quantitative characteristic. On the
one hand, a less negative value of the reducing
potential of substrate, the aryl halide, corresponds to a
higher concentration of radical anion, and due to that
to the increase in the rate of its fragmentation. On the
other hand, the fragmentation of the radical anion
having lower energy of formation under the equal
condition must proceed slower according to the Bell-
Evans-Polanyi principle. Such dependence of the rate
constant of fragmentation of radical anions on the
energy of its formation was really observed for the
series of aryl halides [23, 24].
Evidently just the opposite trend in the two above-
mentioned factors leads to the fact that for mono- and
dichlorobiphenyls under study relative reactivity of
substrates in the reduction with sodium-naphthalene
complex occurs to be equal and independent of the
reducing potential of the aryl halide. It is somehow
unusual for the radical anion reactions.
2. Regioselectivity of fragmentation of radical
anions of dichlorobiphenyls. Similar reactivity of
mono- and dichlorobiphenyls under investigation in
the reactions of the one-electron reduction gives no
opportunity to establish how the position of chlorine
atom in the molecule of aryl halide affects the rate of
fragmentation of the radical anion. It compelled us to
develop an approach to the investigation of the
regioselectivity problem of this reaction from another
side. It is evident that while using as the substrate the
(
procedure I) the conversion of the substrate increases
in the course of several hours what agrees with the
reported data on the rate of formation of the complex
[
21]. In this case the last process determines evidently
the rate of reduction of aryl chloride. The resemblance
of the results obtained while using a solution of
sodium-naphthalene complex in THF and a solution of
lithium-naphthalene complex in dimethoxyethane
(
known as better chelating agent in relation to lithium
cations) (procedure III) shows that the variation in the
complex solvation under the reaction conditions does
not affect its reducing properties.
By the method of competing reactions the relative
rates of consumption of substrates were evaluated. The
studies were carried out according to the procedure I
because this method of evaluation requires a
significant (more than 30%) conversion. Obtained
(
k ) values are listed in Table 2 together with the
obs rel
reported data on the values of the reducing potentials
of the corresponding aryl halides.
It may be suggested that the rate of one-electron
reduction of the aryl halides under the reaction
conditions is determined by the rate of the formation
and fragmentation of the radical anion, and the
abstraction of hydrogen atom from the molecule of
solvent by the aryl radical (the last stage in the Scheme 1)
is fast. In the opposite case by-products of recom-
bination of the aryl radicals or of their reaction with
naphthalene should have formed, but no such data was
obtained. Material balance was preserved even at the
significant conversion of substrate (Table 1, procedure I).
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REDUCTION OF MONO- AND DICHLOROBIPHENYLS
803
unsymmetrically substituted dichlorobiphenyl the
abstraction of chloride anion from two different
positions of the radical anion is possible. The greatest
interest presents the reduction of polychlorobiphenyls
having one chlorine atom in ortho-position in relation
to the C–C bond between the phenyl rings (Scheme 2).
Scheme 2.
Cl
Cl
_Cl−
_
Cl−
Cl
Cl
A
B
The radicals A and B abstract hydrogen atom from
the molecule of solvent and give a mixture of
monochlorobiphenyls, the products of the one-electron
reduction of the starting substrate. Monochloro-
biphenyls formed in their turn may take part in the
reduction leading finally to biphenyl.
The assumed kinetic scheme of reduction of the
unsymmetrically substituted dichlorobiphenyl without
the consideration of possible formation of the aryl
anion is presented below for the case of 2,3-
dichlorobiphenyl (Scheme 3):
products of its one-electron reduction will be present in
the reaction mixture. In this case the regioselectivity of
fragmentation of the radical anion will be quanti-
tatively characterized by the ratio of concentrations of
monochlorobiphenyls formed.
For the evaluation of regioselectivity of the process
of one-electron reduction a series of dichlorobiphenyls
was reduced to a small conversion (5–6%) using the
procedure II. The results obtained are presented in
Table 3. It follows from these data that even at a small
(<5%) conversion of starting substrate the system in all
the cases together with monochlorinated substances
contains significant amount of unsubstituted biphenyl
exceeding the amounts of monochlorobiphenyls. This
fact together with the data on relative reactivity of
mono- and dichlorobiphenyls in the reduction with
sodium-naphthalene complex disagree with the above-
presented kinetic scheme.
Scheme 3.
Cl
Cl
k
(2,3)
obs
This contradiction can be eliminated by an as-
sumption that alongside the one-electron reduction the
multi-electron reduction process takes place.
Cl
Cl
+
–
·
·
–
Ar
2
Cl
2
→ (Ar
Cl
2 2
) → (Ar
2
Cl) → (Ar
2
Cl) → … → Ar
2
H
2
Such multi-electron processes are well known for
k
(2)
k
(3)
obs
obs
the electrochemical reduction [20] when the radical
formed by fragmentation has no time to leave the
cathode space and is reduced further to monoanion or
even dianion in the case of the presence in it of several
functional groups.
In this case considering the above-presented
experimental data on the relative reactivity of mono-
and dichlorobiphenyls kinetic scheme of the process
may be descibed as follows (by an example of 2,3-
dichlorobiphenyl, Scheme 4).
Here k is the observed rate constant of reduction of
obs
this congener.
In agreement with the Scheme 3 and basing on the
data on the relative reactivity of various mono- and
dichlorobiphenyls (Table 2) it could be expected that
in the early stages of the reaction when the
concentration of starting dichlorobiphenyl exceeds
significantly the concentrations of monochlorobi-
phenyls formed only the starting substrate and the
It follows from Scheme 4 and the data presented in
the Tables 2, 3 that practically all biphenyl under the
conditions of the experiment (conversion of starting
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8
04
BOYARSKII et al.
Table 3. Composition of the reaction mixture of
hydrodechlorination of some dichlorobiphenyls at low
conversions (mol %, GLC data)
Constants k and k are diffusion constants [20], that
5
6
is why in this case k = k . Considering the correction
5
6
taking into account the part of multi-electron process
and regarding the constants k and k as close in value
3
4
Product of one-electron
Substrate
reductiona
Biphenyl
we evaluated the regioselectivity of the one-electron
reduction by the kinetic Scheme 4 and the data of the
Table 3 (see Table 4).
2
2
2
,3-Dichlorobiphenyl
,4-Dichlorobiphenyl
,5-Dichlorobiphenyl
3-Chlorobiphenyl (2.8)
4-Chlorobiphenyl (1.0)
3-Chlorobiphenyl (0.6)
3.2
3.8
3.6
From the data presented it is evident that for all
dichlorobiphenyls having one chlorine atom in the
ortho-position to the C–C bond between two aromatic
rings (mono-ortho-substituted dichlorobiphenyls) the
fragmentation by this position is preferred. The
regioselectivity of hydrodechlorination in this case
may be affected by different stability of the products
formed in the stage of fragmentation, that is, of aryl
radicals, connected with the specific features of their
spatial arrangement. Possible pathways of fragmenta-
tion of radical anion formed from mono-ortho-
substituted dichlorobiphenyl are shown in Scheme 2.
The quantum chemical calculation of geometry of
starting dichlorobiphenyl molecules and the aryl
radicals formed from them (Gaussian 03 program [25])
was carried out by the density functional DFT
a
In all cases only one monochlorobiphenyl was found. Second
possible product, 2-chlorobiphenyl, was absent. Detection limit
was 0.007–0.01 mol % with respect to the taken dichloro-
biphenyl as was evaluated specially by addition of the given
amount of 2-chlorobiphenyl to the reaction mixture.
2
,3-dichlorobiphenyl < 5–6%) is formed by multi-
electron reduction of dichlorobiphenyl. Hence, the
contribution of the multi-electron reduction expressed
as the ratio of the amount of biphenyl obtained to the
summary conversion of substrate in the course of
hydrodechlorination with sodium–naphthalene complex
in THF solution is sufficiently high (Table 4).
Scheme 4.
Cl
Cl
_nf
+
nf
Cl
Cl
k
k
2
1
Cl
Cl
Cl
k
k
4
+
nf
3
+
nf
Cl
k
k
6
5
Cl
Cl
+
nf
+
nf
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 4 2010

REDUCTION OF MONO- AND DICHLOROBIPHENYLS
805
Table 4. The contribution of the process of multi-electron
reduction and regioselectivity of one-electron reduction of
dichlorobiphenyls in the hydrodechlorination with sodium-
naphthalene complex
Table 5. Values of dihedral angles, deg., between the planes
of phenyl rings in the radicals formed during the
decomposition of radical anions of dichlorobiphenyls, and
difference in energies of these radicals according to the data
of calculations by the density functional method DFT
B3LYP/6-31+G(d,p) (Gaussian-03 [25])
Part of multi-electron
а
Substrate
k
1
/k
2
reduction, %
53
2
2
2
,3-Dichlorobiphenyl
,4-Dichlorobiphenyl
,5-Dichlorobiphenyl
<0.0035
<0.010
<0.017
φ, deg
ΔEA–B
,
Dichlorobiphenyl
79
86
–1
Radical of Radical of kJ mol
type А
type B
2
2
2
,3-Dichlorobiphenyl
,4-Dichlorobiphenyl
,5-Dichlorobiphenyl
25
56
16
13
14
a
k
2
is the rate constant of fragmentation of dichlorobiphenyl
radical anion by the C–Cl bond located in ortho-position to the
27
28
56
57
bond between the phenyl rings, k is the rate constant of
1
fragmentation of dichlorobiphenyl radical anion by the
alternative C–Cl bond.
B3LYP/6-31+G(d,p). The results obtained are listed in
Table 5. If in mono-ortho-chlorosubstituted dichlorobi-
phenyls dihedral angles between the planes of aromatic
rings are sufficiently large and reach 56°–60°, in the
corresponding radicals A (Scheme 2) this parameter
decreases to 25°–28°. It improves significantly the
conjugation of π-orbitals of aromatic rings that sig-
nificantly stabilizes radical A as compared to the
radical B.
fragmentation of one radical anion according to
different pathways in several tens times even at the
#
unlimitedly large ΔG . At the decrease in the internal
0
barrier the difference will increase still more. Besides,
#
ΔG will also decrease with the decrease in energy of
0
the aryl radical formed in the course of fragmentation.
Hence, the preferred fragmentation of the chloride ion
from the position 2 of mono-ortho-substituted di-
chlorobiphenyl arises from the lower energy of the
corresponding aryl radical.
The energy gain during the abstraction of chloride
ion from the position 2 of the radical anion of mono-
ortho-substituted dichlorobiphenyls compared to the
alternative pathway according to our calculations is
On the whole the studies performed showed that the
intersubstrate selectivity in the reactions of mono- and
dichlorobiphenyls with sodium-naphthalene complex
in THF is not high. At the same time the region-
selectivity of the reduction for all mono-ortho-sub-
stituted dichlorobiphenyls is significant. The abstract-
tion of the chlorine atom located in the ortho-position
to the C–C bond between two aromatic rings is preferred.
Note also that sodium-naphthalene complex is not
only the one-electron reducing agent as it was con-
sidered before. In the reduction of polychlorobiphenyls
together with the one-electrion reduction the multi-
electron process takes place, and its contribution is
rather large.
–
1
about 13–14 kJ mol . That is why in the fragmentation
of radical anion formed from mono-ortho-substituted
dichlorobiphenyl the abstraction of chloride ion from
the position 2 is preferred.
For the reaction of fragmentation of radical anions
of the aryl halides the Markus-Hush model [24,26,27]
#
connecting the activation energy ΔG with the reaction
energy ΔG [Eq. (1) in the Scheme 5] is applicable.
0
Scheme 5.
–
·
·
–
RX → R + X ,
2
(
1
ΔG
0
)
ΔG
0
#
#
0
EXPERIMENTAL
ΔG =
+
+ ΔG
.
(1)
#
6ΔG
0
2
GLC analysis was carried out on a Chrom-5
chromatograph equipped with the flame-ionization
#
Here ΔG is the internal barrier of free energy equal to
–1
0
detector, carrier gas argon, flow rate 20–30 ml min .
–
–
(
D
RX
)/4; D
is the energy of dissociation of the
RX
Two types of glass columns were used, 2500×3 mm
filled with 10% of SE-30 on Chromaton N-Super (80–
100 mesh), and 2500×3 mm filled with 5% of OV-225
on Chromaton N-Super. Evaporator temperature 200°C,
oven temperature 200°C.
carbon-halogen bond in the radical anion.
It follows from Eq. (1) that the established dif-
–
1
ference in the reaction energy (13–16 kJ mol ) must
lead to the difference in the rate constants of
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BOYARSKII et al.
Calculation of concentrations of the aryl chlorides
and biphenyl was carried out according to the formula
cooled to room temperature to give the solution 1 with
–1
the calculated concentration of complex 0.10–0.13 mol l .
C
X
0
S
Х
/
b. Performing the reduction. A solution of 0.08–
,
0
=
(2)
0
0
.12 g of dichlorobiphenyl and the internal GLC
C
X
S
X
/Sst
standard (docosane) in 2 ml of THF was prepared in a
10 ml Schlenk flask equipped with a magnetic stirrer,
and the apparatus was flushed with argon. A 1.0 ml
sample of solution (1) (sodium–naphthalene complex
content 0.10–0.13 mmol) was added at 20-22°C under
argon to the reaction mixture. One minute after
addition of sodium-naphthalene complex a sample was
taken and treated according to the general procedure.
Procedure III. Reduction with the preliminary
formed lithium-naphthalene complex (shortage of
complex). a. Preparing the solution of lithium-
naphthalene complex. 1,2-Dimethoxyethane, 12 ml,
0
where CX and C are the concentrations of the
X
evaluated substance after performing the reaction and
0
0
the initial one respectively, S and S , S and S are
X
X
st
st
the areas of peaks of the evaluated substance and the
internal standard (docosane) after performing the
reaction and the initial ones. Each probe was analyzed
three times and the mean square deviation of the
evaluated square ratio was established. In the case of
square deviation being more than 2% the sample was
analyzed several times more until the achievement of
the above-mentioned value of deviation. Hence,
relative deviation of analysis in all the cases was no
more than 8% at the exclusion of the specially marked
ones.
1
50–210 mg of naphthalene, and 30–40 mg of lithium
were placed in a 25 ml Schlenk flask equipped with a
magnetic stirrer and a reflux condenser. The reaction
mixture was flushed with argon and heated to boiling.
The appearance of dark green color marked the
beginning of the formation of lithium–naphthalene
complex [solution (1)]. Reaction mixture was refluxed
for 2 h and cooled to room temperature (concentration
General Procedures of Reduction
Procedure I. Reduction with sodium-naphthalene
complex formed in situ. THF, 2 ml, 500 mg of
naphthalene, and 30 mg of sodium were placed in a
5
ml Schlenk flask equipped with a magnetic stirrer
–
1
of complex 0.10–0.13 mol l ).
and a reflux condenser. The flask was flushed with
argon and heated to boiling. Dark green color marked
the beginning of formation of sodium–naphthalene
complex. After that the mixture was cooled to 20–22°C
b. Performing the reduction. A solution of 0.08–
0.12 g of dichlorobiphenyl and the internal GLC
standard (docosane) in 2 ml of 1,2-dimethoxyethane
was prepared in a 10 ml Schlenk flask equipped with a
magnetic stirrer and flushed with argon. Solution (1),
1 ml (lithium–naphthalene complex content 0.10–
0.13 mmol) was added under argon to the reaction
mixture. After 1 min a sample of the reaction mixture
was taken and treated according to the general
procedure.
1
and a solution of 0.4–0.6 mmol of substrate and the
internal GLC standard (docosane) in 2 ml of THF was
added. Reaction was carried out until the 30–70%
conversion. Reaction progress was controlled by the
analysis of samples taken each 5–10 min.
Procedure II. Reduction with the preliminary
formed sodium-naphthalene complex (shortage of
complex). a. Preparing the solution of sodium-
naphthalene complex. THF, 12 ml, 150–210 mg of
naphthalene, and 50–60 mg of sodium were placed in a
Procedure for Preparing GLC Samples
A sample of the reaction mixture, 0.2–0.3 ml, was
added to 3 ml of the hexane–water mixture. The
mixture obtained was shaken intensely, and after the
separation of layers the organic layer was taken for
analysis.
2
5 ml Schlenk flask equipped with a magnetic stirrer
and a reflux condenser. The flask was flushed with
argon and heated to boiling. The appearance of the
dark green color marked the beginning of formation of
sodium–naphthalene complex [solution (1)]. Reaction
mixture was refluxed for 2 h. Under these conditions
the conversion of naphthalene to the sodium complex
was complete [21, 28]. The reaction mixture was
Evaluation of Relative Rates
of the Reduction of Polychlorobiphenyls
Evaluation of relative rates of the reduction of
polychlorobiphenyls was carried out by the competing
reactions method according to the procedure I.
Calculation of the rate constant values was carried out
1
In concurrent reactions two substrates were used in a ratio about
:1.
1
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 4 2010

REDUCTION OF MONO- AND DICHLOROBIPHENYLS
807
Table 6. Evaluation of relative rate constant of reduction for the pair 2-chlorobiphenyl–3-chlorobiphenyl
Amounts loaded, mmol
0
1
0
2
а
C
1
/С
C
2
/С
(kobs
)
2
/(kobs
)
1
1
2
internal standard docosane)
0.15
2
-chloro biphenyl
3-chloro biphenyl
0
.25
0.26
0.64
.58
.53
0.63
.56
.43
0.72
0.65
0.60
0.70
0.61
0.53
0.74
0.79
0.80
0.77
0.85
0.77
0
0
0
.30
0.28
0.16
0
0
а
(
k
obs
)
2
/(kobs) = 0.79±0.04.
1
on the basis of consumption of starting substrates
according to the formula:
3. Kannan, N., Schulz-Bull, D.E., Petrick, G., and
Duinker, J.C., Intern. J. Environ. Anal. Chem., 1992,
vol. 47, p. 201.
0
2
0
1
(
k
obs
)
rel = (kobs
)
2
/(kobs
)
1
= ln (C
2
/C
)/ln (C
1
/C
),
4
. Safe, S., Critical Rev. Toxicol., 1984, vol. 13, p. 319.
where (k ) and (k ) are the rate constants of
5. Triska, J., Kuncova, G., Mackova, M., Novakova, H.,
Paasivirta, J., Lahtipera, M., and Vrchotova, N.,
Chemosphere, 2004, vol. 54, p. 725.
obs 1
obs 2
0
0
reduction of polychlorobiphenyls, C and C are con-
1
2
centrations of polychlorobiphenyls at the initial
moment, C and C are their concentrations in the
6. Havel, J. and Reineke, W., FEMS Microbiol. Lett.,
1
2
1
991, vol. 78, p. 163.
sample.
7
. Tiedje, J.M., Quesen, J.F., and Chee-Sanford, J.,
Following pairs of substrates were used: 2-chloro-
biphenyl and 3-chlorobiphenyl, 2-chlorobiphenyl and
Biodegradation, 1993, vol. 4, no. 7, p. 231.
8
9
. Dolfing, J., Arch. Microbiol., 1990, vol. 153, p. 264.
4
-chlorobiphenyl, 2-chlorobiphenyl and 3,4-dichloro-
. Mohn, W.W. and Tiedje, J.M., Arch. Microbiol., 1991,
biphenyl, 2-chlorobiphenyl and 4,4'-dichlorobiphenyl,
vol. 157, p. 1.
2
,4-dichlorobiphenyl and 3,4-dichlorobiphenyl, 2,5-
1
0. Ariizumi, A., Otsuka, T., Kamiyama, M., and Hosomi, M.,
dichlorobiphenyl and 3,4-dichlorobiphenyl, 2,3-di-
chlorobiphenyl and 3,4-dichlorobiphenyl. Evaluation
of the relative rate constant was carried out twice for
each pair of polychlorobiphenyls. In each experiment
J. Environ. Chem., 1997, vol. 7, p. 793.
1
1
1. Suzuki, H., Environ. Manag., 1997, vol. 33, p. 889.
2. Noma, Y., Mitsuhara, Y., Matsuyama, K., and Sakai, S.,
Organohalogen Compounds, 2003, vol. 63, p. 280.
3. Miyoshi, K., Nishio, T., Yasuhara, A., and Morita, M.,
Chemosphere, 2000, vol. 41, p. 819.
3
-4 samples were taken and the relative rate constant
1
was evaluated for each sample independently.
In the Table 6 an example of evaluation of the
relative rate constant for the pair 2-chlorobiphenyl–3-
chlorobiphenyl is presented.
14. Pittman, C.U. and He, J., J. Hazard. Mater., 2002,
vol. 92, no. 1, p.51.
15. Boyarskii, V.P., Zhesko, T.E., Lanina, S.A., and
Tereshchenko, G.F., Zh. Prikl. Khim., 2007, vol. 80,
no. 7, p. 1120.
ACKNOWLEDGMENTS
1
6. Lanina, S.A., Boyarskii, V.P., Zhesko, T.E., Nikifo-
rov, V.A., and Bart, T.Ya., Zh. Obshch. Khim., 2008,
vol. 78, no. 1, p. 127.
The work was carried out with the financial support
of Russian Fundation for Basic Research (grant no. 08-
03-91301-IND_a).
17. Hawari, J., J. Organomet. Chem., 1992, vol. 437,
nos. 1–2, p. 91.
REFERENCES
18. Sargent, G.D., Tetrahedron Lett., 1971, vol. 12, no. 35,
p. 3279.
1
. Mullins, M.D., Pochini, C.M., Mc-Crindle, S., Romkes, M.,
Safe, S.H., and Safe, L.M., Environ. Sci. Technol.,
984, vol. 18, no. 6, p. 468.
. Ivanov, V. and Sandell, E., Environ. Sci. Technol.,
992, vol. 26, no. 10, p. 2012.
19. Jing, L., Nash, J.J., and Kenttmaa, H.I., J. Am. Chem.
Soc., 2008, vol. 130, no. 52, p. 17697.
1
2
0. Amatore, C., Combellas, C., Lebbar, N.-E., Thiebault, A.,
and Verpeaux, J.-N., J. Org. Chem., 1995, vol. 60,
p. 18.
2
1
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 4 2010

8
2
08
BOYARSKII et al.
1. Scott, N.D., Walker, J.F., and Hansley, V.L., J. Am.
Chem. Soc., 1936, vol. 58, no. 12, p. 2442.
2. Farwell, S.O., Beland, F.A., and Geer, R.D., Anal.
Cammi, R., Pomelli, C., Ocherski, J.W., Ayala, P.Y.,
Morokuma, K., Voth, G.A., Salvador, P., Dannenberg, J.J.,
Zakrzewski, V.G., Dapprich, A.D., Daniels, M.C.,
Strain, O., Farkas, D.K., Malick, S., Rabuck, A.D.,
Raghavachari, K., Forsmann, J.B., Ortiz, J.V., Cui, Q.,
Baboul, A.G., Clifford, S., Cioslowski, J., Stefanov, B.B.,
Liu, G., Liashenko, A., Piskorz, P., Komaromi, I.,
Martin, R.L., Fox, D.J., Keith, T., Al-Lacham, M.A.,
Peng, C.Y., Nanayakkara, A., Challacombe, M.,
Gill, P.M.W., Johnson, B., Chen, W., Wong, M.W.,
Gonsalez, C., and Pople, J.A., Gaussian03, Ver.5,
Gaussian Inc., Pittsburg P.A., 2003.
2
2
Chem., 1975, vol. 47, p. 895.
3. Enemaerke, R.J., Christinsen, T.B., Jensen, H., and
Daasbjerk, K., J. Chem. Soc., Perkin Trans. 2, 2001,
no. 9, p. 1620.
2
2
4. Saveant, J.M., J. Phys. Chem., 1994, vol. 98, no. 14,
p. 3716.
5. Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuce-
ria, G.E., Robb, M.A., Cheeseman, J.R., Montgomery, J.A.,
Vreven, Jr.T., Kudin, K.N., Burant, J.C., Millam, J.M.,
Iyengar, S.S., Tomasi, J., Barone, V., Menucci, B.,
Cossi, M., Scalmani, G., Rega, N., Petersson, G.A.,
Nakatsuji, H., Hada, M., Ehara, M., Toyota, K., Fukuda, R.,
Hasegawa, J., Ishida, M., Nakajima, T., Honda, Y.,
Kitao, O., Nakai, H., Klene, M., Li, X., Knox, J.E.,
Hratchian, H.P., Cross, J.B., Adamo, C., Jaramillo, J.,
Gomperts, R., Stratmann, R.E., Yazyev, O., Austin, A.J.,
2
2
2
6. Takeda, N., Poliakov, P.V., Cook, A.R., and Miller, J.R.,
J. Am. Chem. Soc., 2004, vol. 126, no. 13, p. 4301.
7. Prasad, M.A. and Sangaranarayanan, M.V., Chem.
Phys. Lett., 2006, vol. 421, p. 193.
8. Sargent, G.D., Cron, J.A., and Bank, S., J. Am. Chem.
Soc., 1966, vol. 88, no. 22, p. 5363.
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