Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 7, pp. 992−996.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © T.I. Gorbunova, D.N. Bazhin, A.Ya. Zapevalov, V.I. Saloutin, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 7,
ORGANIC AND PETROCHEMICAL
Inhibitory Activity of Fluorine-containing Quaternary
Ammonium Salts Comprising an N-Methylpiperazinyl Moiety
T. I. Gorbunova, D. N. Bazhin, A. Ya. Zapevalov, and V. I. Saloutin
Postovskii Institute of Organic Synthesis, Ural Division, Russian Academy of Sciences, Yekaterinburg, Russia
Received May 18, 2013
Abstract—New ﬂ uorine-containing quaternary ammonium salts comprising an N-methylpiperazinyl moiety, which
exhibited a high inhibiting capacity against hydrochloric acid corrosion of low-carbon steel, were synthesized.
The polarization-resistance method was applied to determine the uniform corrosion rate of steel-3 in relation to
the structure and concentration of the ﬂ uorine-containing substituents in the salts. It was found that the structure
of the ﬂ uorine-containing moiety of the quaternary ammonium salts does not signiﬁ cantly inﬂ uence the corrosion
N-Methylpiperazine is one of the intermediates
in production of drugs, including commonly known
ﬂ uoroquinolone antibiotics, anthelmintics, neuroleptics,
etc. . Also, N-methylpiperazine was used for
synthesizing compounds having antiarrhythmic  and
anticancer activity . However, its application is not
limited to the synthesis of biologically active compounds.
The presence in the molecule of N-methylpiperazine
of two heteroatoms suggests its suitability as an
independent agent for inhibition of corrosion processes
and for synthesis of nitrogen-containing corrosion
Semiempirical quantum chemical calculations 
showed that, when N-methylpiperazine acts as inhibitor
of steel corrosion in acid medium, both its nitrogen atoms
initially undergo double protonation. During subsequent
physical adsorption on the negatively charged metal
surface, the piperazinyl moieties can assume two types of
orientation with respect to the substrate, with adsorption
occurring via both nitrogen sites or via one of them.
In the former case, the piperazinyl framework should
adopt a “chair” conformation (ﬂ at-lying adsorption). In
the latter case, it is attached vertically via the N4 atom
(vertical adsorption), because speciﬁ cally this nitrogen
atom has the largest positive charge, as shown by
PM3 calculations. In both cases, the orientation of the
piperazinyl derivatives is followed by deprotonation.
It was shown  that medicines, in particular
ﬂ uoroquinolone antibiotics, hold promise as corrosion
inhibitors. Nonconventional use of pharmaceutical
products has become the focus of attention of researchers
who are looking for corrosion-resistant materials unable
of inﬂ icting major environmental damage. Most drugs
typically undergo biodegradation under environmental
Here, we synthesized ﬂ uorine-containing quaternary
ammonium salts comprising an N-methylpiperazinyl
moiety and examined their inhibition effect against low-
carbon steel corrosion in hydrochloric acid.
The choice of ﬂ uorinated quaternary ammonium salts
(F-QASs) as the subjects of our study was dictated by the
following reasons: enhanced, in many cases, solubility
of organic and more hydrophobic organoﬂ uorine
compounds in aqueous media due to the presence of a
quaternary nitrogen atom [13, 14], better performance
characteristics compared to nonﬂ uorinated analogs [15–
17], and the possibility to achieve the desired effect with
low-concentration solutions .
To study the inhibitory effect, reactions of
esters of perﬂ uorocarboxylic acids Ia–Id, or of
2,3,4,5-tetraﬂ uorobenzoic acid chloride Ie, with