ISSN 1070-3632, Russian Journal of General Chemistry, 2018, Vol. 88, No. 2, pp. 257–261. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © K.A. Plotnikova, T.I. Gorbunova, M.G. Pervova, V.I. Saloutin, O.N. Chupakhin, 2018, published in Zhurnal Obshchei Khimii, 2018,
Vol. 88, No. 2, pp. 279–284.
Features of Sulfonation of Polychlorinated Biphenyl Congeners
K. A. Plotnikova, T. I. Gorbunova, M. G. Pervova*, V. I. Saloutin, and O. N. Chupakhin
Postovskii Institute of Organic Synthesis, Ural Branch, Russian Academy of Sciences,
ul. S. Kovalevskoi/Akademicheskaya 22/20, Yekaterinburg, 620137 Russia
Received August 17, 2017
Abstract—Sulfonation of polychlorinated biphenyls (PCBs) and their commercial mixture (Trichlorobiphenyl)
with oleum has been studied. General sulfonation patterns have been revealed for PCB congeners having no
substituents in the ortho positions. The sulfonation of PCBs with chlorine atoms in only one aromatic ring
gives exclusively the corresponding polychlorobiphenylmonosulfonic acids. The sulfonation of PCBs with
chlorine atoms in both aromatic rings is accompanied by side formation of polychlorodibenzothiophene
Keywords: polychlorinated biphenyls, congeners, electrophilic substitution, sulfonation
Studies on electrophilic substitution reactions in the
series of toxic polychlorinated biphenyls (PCBs) that
are subject to destruction until 2028 are occasional
since introduction of one more substituent into their
molecules with retention of all chlorine atoms does not
favor reduction of potential hazard of the new deriva-
tives. Nevertheless, electrophilic substitution is a classical
reaction of aromatic compounds, whereas such processes
with participation of PCBs remain poorly studied.
We previously studied the reactivity of PCBs in the
bromination  and nitration reactions [2, 3]. It was
shown that the nitration with a mixture of nitric and
sulfuric acids is characterized by 100% conversion of
both individual congeners  and their commercial
mixtures such as Trichlorobiphenyl  and Sovol .
The number of nitro groups introduced into PCB molecule
is inversely proportional to the number of chlorine
atoms in the substrate . The bromination of the same
technical PCB mixtures led to the formation of bromo-
chloro derivatives containing 1 to 5 bromine atoms, whereas
higher chlorinated PCB congeners remained intact .
As concerns sulfonation as a standard electrophilic
substitution reaction of aromatic compounds, there are
only patent data [4–7] related to technical PCB mixtures.
No analysis of the reactivity of individual congeners
constituting commercial products has been performed.
The goal of the present work was to study the
reactivity of PCB congeners in the sulfonation
reaction. Published data on the sulfonation of biphenyl
or its derivatives are few in number. It was found that
jet sulfonation of biphenyl with the system sulfuric
acid–organic solvent–water at a temperature below 50°C
afforded up to 95% of biphenyl-4-sulfonic acid [8, 9].
Treatment of biphenyl with excess 97% sulfuric acid at
25°C also gave biphenyl-4-sulfonic acid . The
reaction with excess sulfuric anhydride at 22°C resulted
in deeper sulfonation, and up to 90% of biphenyl-4,4'-
disulfonic acid was formed in addition to biphenyl-4-
sulfonic acid .
In our study, the progress of the reaction was
monitored, and the sulfonation products were identified,
by gas chromatography/mass spectrometry (GC/MS).
The compositions of the reaction mixtures were
quantitated by the internal normalization of peak areas.
The reaction conditions were selected using unsub-
stituted biphenyl as model substrate; the sulfonation
was carried out with 1.5 equiv of 98% sulfuric acid at
60 or 130°C (4 h) (Scheme 1). The reaction mixtures
were then treated with trimethyl orthoformate to convert
the resulting sulfonic acids into the corresponding methyl
esters for GC/MS analysis. Analogous procedure was
used by us previously to analyze reaction mixtures
obtained in the sulfonation of naphthalene .
It was found that no sulfo derivatives were formed
when the reaction was carried out at 60°C and that the
conversion of biphenyl at 130°C was as low as 15%.