Synthesis and inhibiting capacity of new fluorine-containing quaternary ammonium salts

Article abstract of DOI:10.1134/S1070427211060127

New fluorine-containing quaternary ammonium salts exhibiting a high inhibiting capacity against hydrochloric acid corrosion of low-carbon steels were synthesized. The polarization resistance method was used to determine the uniform-corrosion rates of steel-3 and steel-35 in relation to the structure of fluorine-containing moieties of quaternary ammonium salts and their concentration.

Full text of DOI:10.1134/S1070427211060127

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 6, pp. 972–977. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © T.I. Gorbunova, D.N. Bazhin, A.Ya. Zapevalov, V.I. Saloutin, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 6,
pp. 948–953.
APPLIED ELECTROCHEMISTRY
AND CORROSION PROTECTION OF METALS
Synthesis and Inhibiting Capacity
of New Fluorine-containing Quaternary Ammonium Salts
T. I. Gorbunova, D. N. Bazhin, A. Ya. Zapevalov, and V. I. Saloutin
Postovskii Institute of Organic Synthesis, Ural Branch, Russian Academy of Sciences, Yekaterinburg, Russia
Received May 5, 2010
Abstract—New fluorine-containing quaternary ammonium salts exhibiting a high inhibiting capacity against
hydrochloric acid corrosion of low-carbon steels were synthesized. The polarization resistance method was
used to determine the uniform-corrosion rates of steel-3 and steel-35 in relation to the structure of fluorine-
containing moieties of quaternary ammonium salts and their concentration.
DOI: 10.1134/S1070427211060127
Nitrogen-containing corrosion inhibitors of organic
nature are efficient protective means for precluding
wear of metallic parts of equipment employed in
corrosive media [1]. The protection efficiency of
inhibitors depends on the nature of a metal being pro-
tected and on the type of a corrosive medium, tem-
perature and duration of exposure, presence of
impurities both in the medium and in the corrosion
inhibitor, and structure of a protecting compound and
its concentration [2].
have been little studied. However, there exist
numerous prerequisites for a study of the inhibiting
activity of F-QASs: unique properties of the fluorine
atom and polyfluorinated groups in organic com-
pounds (hydrophobicity, stability in corrosive media,
decrease in the surface energy of solutions) [18, 19],
accessibility of raw material resources, possible
synthesis of water-soluble organofluorine materials,
and the resulting better performance, compared with
hydrocarbon analogs. In particular, gravimetric cor-
rosion tests of low-carbon steel-3 in a 10% solution of
HClconc at temperatures of 20 and 50°C, with addition
of an F-QAS of formula RFCONH(CH2CH2OH)X–
(RF = C6F13, C8F17; X = Cl, Br, I) in an amount of
0.1 wt % demonstrated a 91–98% degree of protection
of the metal [20].
A most important class of N-containing inhibitors is
constituted by quaternary ammonium salts (QASs),
which are used to protect metals from acid [3–12] and
mineralized [13–17] media and belong to cationic
inhibitors with a general formula R1R2R3R4N+A–,
where R1, R2, R3, and R4 are organic moieties, and A–
is an anion.
The present study is concerned with the inhibiting
properties of new F-QASs against the hydrochloric
acid corrosion of low-carbon steels (steel-3, steel-35).
Application of QASs for corrosion protection of
metals does not require any special technique and
consists in their dissolution in corrosive aqueous
media. It is the solubility parameters of QASs that
primarily predetermine use of these salts in an
individual form [3, 14–17] or in a multicomponent
mixture [4–13] that contains auxiliary materials that
facilitate solubility of QASs and variously affect the
corrosion of metals.
As objects of study served F-QASs IVa, IVb, Va,
and VIII whose synthesis is based on quaternization of
fluorine-containing tertiary amines with alkyl iodides
(Schemes 1, 2). Two approaches were used to obtain
the corresponding tertiary amines IIa, IIb, IIIa, and
VII. The first of these consists in that fluoroglycidyl
esthers synthesized from readily available reagents,
telomeric alcohol and hexafluoropropylene oxide
(HFPO) trimer are reacted with secondary amines
(Scheme 1). In this case, the oxirane ring is region-
Most of QASs studied with regard to their
corrosion-protection activity contain hydrocarbon sub-
stituents, there fluorine-containing analogs (F-QAS)
972

SYNTHESIS AND INHIBITING CAPACITY
973
Scheme 1.
Me
N +
I_
O
RFO
RFO
RFO
RFO
N
iii
i
OH
OH
O
IVa, IVb
IIa, IIb
RFO
Ia, Ib
O
+
ii
iii
NEt2Me
NEt2
I_
OH
Va
OH
IIIa
RF = (a) H(CF2)2CH2 and (b) C3F7OCF(CF3)CF2OCF(CF3)CH2; i: NH(CH2CH2)2O, 100°C; ii: HNEt2, 70°C; iii: MeI,
acetone, bp.
Scheme 2.
i
ii
+
RFCONH(CH2)2NMe2
RFCOOMe
RFCONH(CH2)2NMe2Et,
I_
VII
VI
VIII
RF = C3F7OCF(CF3)CF2OCF(CF3); i: H2N(CH2)2NMe2, 100°C; ii: EtI, acetone, bp.
selectively opened under the action of an appropriate
Analysis of the graphical data (Figs. 1, 2) shows
that the F-QASs (IVa, IVb, Va, VIII) strongly affect
the Kn of both steels. All the four F-QASs under study
(IVa, IVb, Va, VIII), which contain the same counter
ion (I–), can be divided, as regards the degree of
corrosion protection of low-carbon steels, into two
groups of compounds, depending on the structure of
the polyfluoroalkyl substituent: the first group is
constituted by compounds IVa and Va, and the
second, by IVb and VIII, with their corrosion-protect-
N-nucleophile [18, 22–25]. In the second approach, an
amide is formed from methyl ether IV, also produced
from an HFPO trimer and N,N-disubstituted ethylene-
diamine (Scheme 2).
The thus synthesized F-QASs IVa, IVb, Va, and
VIII differ in the nature of a fluoroalkyl moiety and in
the structure of the hydrocarbon part adjacent to the
ammonium group. These F-QASs have a high solub-
ility in water and their structural formulas show hydro-
phobicity breaks by polar oxygen-containing moieties
[26].
The uniform corrosion rates Kn of low-carbon steels
and the inhibiting activities of F-QASs IVa IVa, IVb,
Va, and VIII were studied in a 1 M solution of HClconc
at room temperature by the polarization-resistance
method.
The data obtain in blank runs (without introduction
of F-QASs into solution) for determining Kn of the
steels in a 1 M solution of HClconc are presented in Fig. 1,
and Fig. 2 shows Kn data for the steels at F-QAS (IVa,
IVb, Va, and VIII) concentration of 1.2 × 10–4 M.
Four parallel measurements were made for each value
of Kn in Figs. 1–3, with the root-mean-square deviation
not exceeding 3%.
τ, min
Fig. 1. Uniform corrosion rate Kn vs. the time τ in a 1 M
hydrochloric acid solution for (1) steel-3 and (2) steel-35.
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974
GORBUNOVA et al.
(a)
(b)
τ, min
τ, min
Fig. 2. Uniform corrosion rate Kn of (a) steel-3 and (b) steel-35 vs. the time τ in a 1 M hydrochloric acid solution in the presence of
1.2 × 10–4 M of an F-QAS. Compound: (1) IVa, (2) Va, (3) IVb, and (4) VIII.
(a)
(b)
τ, min
τ, min
Fig. 3. Uniform corrosion rate Kn of (a) steel-3 and (b) steel-35 vs. the time τ in a 1 M hydrochloric acid solution at various
concentrations of F-QAS VIII. Concentration (M): (1) 2.4 × 10–4, (2) 1.2 × 10–4, (3) 6 × 10–5, and (4) 6 × 10–6.
tion activity being nearly independent of the nature of
the hydrocarbon moieties. The strongest inhibiting
effect is observed forF-QASs IVb and VIII, which
contain a long polyfluoro-ether-alkyl substituent of
iso-structure. It is noteworthy that, despite the different
values of Kn for the steels (Fig. 1), their corrosion in
the presence of F-QASs IVa, IVb, Va, and VIII is
about the same and proceeds to nearly equal levels
within the groups specified above, which is the most
clearly pronounced with F-QASs IVb and VIII.
presumably due to the possibility of deformation of
long alkyl moieties, with the result that the positively
charged nitrogen atom is closer to the electrode
surface, compared with QASs possessing shorter
hydrocarbon chains [1]. At the same time, QASs with
hydrocarbon moieties of iso-structure show a lower
inhibiting activity, compared with QASs containing
the same radicals, but with normal structure.
Compounds IVa, IVb have the same hydrocarbon
substituents, and F-QASs Va and VIII, hydrocarbon
moieties with similar structures. However, these F-
QASs exhibit different levels to which the Kn of both
steels are reduced within groups of compounds IVa,
It is known that, with increasing length of the
hydrocarbon chain of substituents in QASs, the
inhibiting capacity of these salts grows [1, 27]. This is
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SYNTHESIS AND INHIBITING CAPACITY
975
IVb, Va, and VIII. Consequently, the key factor
determining the activity of the corrosion inhibitors, F-
QAS groups of compounds IVa, IVb, Va, and VIII, is
the size of the fluoroalkyl moiety. On the one hand, the
chain of the fluoroalkyl substituent in compounds IVb,
VIII is longer and contains moieties of iso-structure.
On the other hand, the electron-acceptor effect of
fluoroalkyl groups in compounds IVb, VIII exceeds
that for F-QASs IVa and Va: in the first case, the
positive charge on the nitrogen atom exceeds that for
salts IVa, Va. Hence follows that that highest
inhibiting activity must be observed for salts IVb and
VIII, whose nitrogen atom exhibits a higher activity in
the formation of an electric double layer, compared
with F-QASs IVa and Va.
Ekspert-004 versatile automated corrosimeter and a
two-electrode measuring sensor (manufactured by
Ekoniks-Ekspert Limited-Liability Company). The
electrodes were made of steel-3 (composition, %: Si
0.05–0.15, Mn 0.40–0.65, P ≤ 0.04, Cr ≤ 0.30, S, ≤
0.05) and steel-35 (composition, %: Si 0.17–0.37, Cu ≤
0.25, As ≤ 0.08, Mn 0.50–0.80, Ni ≤ 0.25, P ≤ 0.035,
Cr ≤ 0.25, S ≤ 0.04); the area of each electrode was
0.00078 m2.
IR spectra were recorded with a Perkin–Elmer
Spectrum One spectrophotometer in Vaseline oil, and
1H and 19F NMR spectra, with a Bruker DRX 400
spectrometer at working frequencies of 400.1 (1H) and
376.5 MHz (19F) with, respectively, Me4Si and C6F6 as
internal standards. An elemental analysis was made
with a Perkin–Elmer CHN PE 2400 automated analyzer.
A most important characteristic of the inhibiting
activity of QASs is their minimum concentration
required for effective suppression of the corrosion of
metals in solutions. Analysis of the scientific literature
shows that the minimum concentration of QASs used
to inhibit the corrosion of metals is chosen individually
and depends on numerous factors, some of which were
mentioned above. The concentrations of QASs actually
Fluorine-containing glycidyl ethers were obtained
as described in [21]. Methyl ether of the HFPO trimer
was synthesized by the method reported in [28].
General procedure for synthesis of compounds
IIa, IIb, IIIa, and VIII. To 0.3 mol of an amine was
added, in the course of 1 h, 0.1 mol of ether Ia, Ib) and
VI at a temperature of 70°C under vigorous agitation.
The mixture was kept for 2 h. The excess amount of
the amine was evaporated and the residue was distilled
in a vacuum.
used in Russia are in the range from 10–1 to 10–5
[3–17].
M
An optimization of this parameter for F-QAS VIII
demonstrated that, on passing from a salt concentration
of 1.2 × 10–4 to 6 × 10–5 M (a 20 times decrease in the
content of F-QAS VIII in solution), the electro-
chemical corrosion of steels remains insensitive for
both steel-3 and steel-35 (Figs. 3a and 3b). A tenfold
dilution of the last solution (F-QAS VIII concentration
6 × 10–6 M) leads to a pronounced increase in Kn for
both steels.
1-(Morpholin-4-yl)-6,6,7,7-tetrafluoro-4-oxahep-
tan-ol-2 (IIa). Colorless fluid, yield 88%, bp 158–
160°C/30 Torr. 1H NMR spectrum [(CD3)2CO, δ, ppm;
J, Hz]: 2.40 m (4Н, 2NCH2СН2), 2.49 m (2Н,
CHCH2N), 3.58 m (4H, 2CH2СН2O), 3.60 m (2H,
CH2CHOH), 3.90 m (1H, CHОН), 3.98 t.t (2Н,
3
4
3
CF2CH2, JHF 13.1, JHF 1.7), 6.31 t.t (1Н, HCF2, JHF
53.2, 4JHF 4.6). 19F NMR spectrum [(CD3)2CO, δ, ppm;
J, Hz]: 21.50 m (2F, HCF2), 36.08 m (2F, CF2CH2).
Found, %: С 43.56, Н 6.19, F 27.57, N 5.02.
C10H17F4NO3. Calculated, %: С 43.64, Н 6.23, F
27.61, N 5.09.
Consequently, F-QAS VIII is indeed an effective
corrosion inhibitor used in aqueous-acid solutions
without auxiliary materials; its minimum concentration
providing a positive effect of corrosion inhibition of
low-carbon steels is on the order of 10–5 M.
1-(Morpholin-4-yl)-6,8,8,9,11,11,12,12,13,13,13-
undecafluoro-6,9-bis(trifluoromethyl)-4,7,10-trioxa-
tridecanol-2 (IIb). Colorless fluid, yield 72%, bp
The results of this study confirm that F-QAS are
promising because the uniform corrosion rate of low-
carbon steels decreases in their presence and the
desired effect is obtained at substantially lower con-
centrations of F-QASs introduced into solution.
1
179–181°C/30 Torr. H NMR spectrum [(CD3)2CO, δ,
ppm; J, Hz]: 2.47 m (4Н, 2NCH2СН2), 2.78 m (2Н,
CHCH2N), 3.58 m (4H, 2CH2СН2O), 3.72 m (2H,
OCH2CH), 3.97 m (1H, CHOH), 4.08 d (2Н, CFCH2,
3JHF 11.2). 19F NMR spectrum [(CD3)2CO, δ, ppm]:
18.78 m [1F, OCF(CF3)], 29.19 m (1F, CFCH2), 34.23
m (2F, CF3CF2), 78.71 m (2F, CFCF2O), 80.50 m (2F,
EXPERIMENTAL
The uniform corrosion rate of low-carbon steels
was studied in a 1 M solution of HClconc with an
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 6 2011

976
GORBUNOVA et al.
CF2CF2O), 80.61 m (3F, CF3CF2), 82.02 m (6F,
2CF3CF). Found, %: С 30.68, Н 2.49, F 51.50, N 2.09.
C16H16F17NO5. Calculated, %: С 30.73, Н 2.58, F
51.65, N 2.24.
2CF3CF). Found, %: С 26.51, Н 2.35, F 42.01, N 1.72.
C17H19F17INO5. Calculated, %: С 26.61, Н 2.50, F
42.10, N 1.83.
N-Methyl-N-[2-hydroxy-6,6,7,7-tetrafluoro-4-oxa-
heptyl]morpholinium iodide (IVb). Yellow oil, yield
Diethyl(2-hydroxy-6,6,7,7-tetrafluoro-4-oxahep-
tyl)amine (IIIa). Colorless fluid, yield 83%, bp 123–
125°C/30 Torr. 1H NMR spectrum [(CD3)2CO, δ, ppm;
1
95%. Н NMR spectrum [(CD3)2CO, δ, ppm; J, Hz]:
3.67 s (3H, CH3), 3.81–3.95 m (8H, 4СН2О), 3.98 m
(2Н, CF2CH2), 4.10–4.20 m (6H, 3NCH2), 4.40 m (1Н,
2
J, Hz]: 1.03 t (6Н, 2 CH3, JHH 7.1), 2.52 m (6Н,
3
4
2NCH2), 3.58 m (2H, CH2СН), 3.76 m (2H, CHOH),
CHОН), 6.65 t.t (1Н, HCF2, JНF 53.2, JНF 4.6). 19F
NMR spectrum [(CD3)2CO, δ, ppm]: 21.79 m (2F,
HCF2), 36.65 m (2F, CF2CH2). Found, %: С 31.49, Н
4.74, F 18.05, N 3.28. C11H20F4INO3. Calculated, %: С
31.67, Н 4.83, F 18.22, N 3.36.
3
3.93 m (2Н, CF2CH2), 5.95 t.t (1Н, HCF2, JHF 53.2,
4JHF 4.6). 19F NMR spectrum [(CD3)2CO, δ, ppm; J,
3
Hz]: 21.86 d.m (2F, HCF2, JHF 53.2), 36.35 m (2F,
CF2CH2). Found, %: С 45.72, Н 7.16, F 28.83, N 5.29.
C10H19F4NO2. Calculated, %: С 45.97, Н 7.33,
F 29.09, N 5.36.
N,N-Dimethyl-N-methyl-N-[2-hydroxy-6,6,7,7-
tetrafluoro-4-oxaheptyl]ammonium iodide (Va).
1
2,4,4,5,7,7,8,8,9,9,9-Undecafluoro-3,6-bis-(tri-
fluoromethyl)-N-[2-(dimethylamino)-ethyl]-3,6-
dioxanonamide (VII). To 0.1 mol of methyl ether of
NFPO was added 0.1 mol N,N-dimethylethylene-
diamine, and the reaction mixture was boiled at 100°C.
The product was distilled in an oil-pump vacuum to
give a colorless fluid, yield 89%, bp 105–107°C/
Yellow oil, yield 96%. Н NMR spectrum [(CD3)2CO,
δ, ppm; J, Hz]: 1.03 t (6Н, 2CH3, 2JHH 7.1), 3.67 s (3H,
CH3), 3.81–3.95 m (8H, 4СН2О), 3.98 m (2Н,
CF2CH2), 4.02–4.20 m (6H, 3NCH2), 4.40 m (1Н,
3
4
CHОН), 6.65 t.t (1Н, HCF2, JНF 53.2, JНF 4.6). 19F
NMR spectrum [(CD3)2CO, δ, ppm]: 21.79 m (2F,
HCF2), 36.65 m (2F, CF2CH2). Found, %: С 32.51, Н
5.27, F 18.67, N 3.29. C11H22F4INO2. Calculated, %: С
32.77, Н 5.50, F 18.85, N 3.47.
1
10 Torr. Н NMR spectrum [CDСl3, δ, ppm; J, Hz]:
2.25 s (6Н, 2CH3), 2.47 t [2Н, CH2N(CH3)2, 3JHH 5.9],
3.42 m (2H, NHCH2), 7.2 m (1H, NH). 19F NMR
spectrum (CDСl3, δ, ppm): 16.52 m [1F, OCF(CF3)],
29.35 m (1F, CFCH2), 32.26 m (2F, CF3CF2), 79.40 m
(2F, CFCF2O), 80.48 m (2F, CF2CF2O), 80.48 m (3F,
CF3CF2), 81.84 m (6F, 2CF3CF). Found, %: С 27.37,
Н 1.79, F 56.87, N 4.78. C13H11F17N2O3. Calculated,
%: С 27.58, Н 1.96, F 57.04, N 4.95.
N,N-Dimethyl-N-ethyl-2-{[2,4,4,5,7,7,8,8,9,9,9-
undecafluoro-2,5-bis(trifluoromethyl)-3,6-oxanon-
anoyl]amino}ethaneammonium iodide (VIII). Red
1
oil, yield 98%. Н NMR spectrum [(CD3)2SO, δ, ppm;
J, Hz]: 1.31 s (3Н, CH3, 3JHH 7.2), 3.16 s [6Н, N(CH3)2],
3.49 m [4H, N(CH2)2], 3.73 m (2H, NHCH2), 9.80 m
(1H, NH). 19F NMR spectrum [(CD3)2SO, δ, ppm]:
17.32 m [1F, OCF(CF3)], 30.25 m (1F, CFCH2), 32.89
m (2F, CF3CF2), 80.52 m (2F, CFCF2O), 81.23 m (2F,
CF2CF2O), 81.48 m (3F, CF3CF2), 82.45 m (6F,
2CF3CF). Found, %: С 24.73, Н 2.04, F 44.52, N 3.69.
C15H16F17IN2O3. Calculated, %: С 24.95, Н 2.23, F
44.72, N 3.88.
General procedure for synthesis of compounds
IVa, IVb, Va, VIII. A single-necked vessel with a
reflux was charged with a mixture of 0.10 mol of an
amine IIa, IIb, IIIa, VIII and 0.15 mol of CH3I (or
C2H5I) in 40 mol of acetone, and the mixture was
boiled for 1 h. The solvent and the excess amount of
CH3I (or C3H5I) was evaporated and the residue was
vacuum treated.
CONCLUSIONS
N-Methyl-N-[2-hydroxy-6,8,8,9,11,11,12,12,13,13,-
13-undecafloro-6,9-bis(trifluoromethyl)-4,7,10-
trioxatridecyl]morpholinium iodide (IVa). Yellow
oil, yield 98%. 1Н NMR spectrum [(CD3)2CO, δ, ppm]:
3.67 s (3H, CH3), 3.83–3.94 m (8H, 4СН2О), 4.02 m
(2Н, CFCH2), 4.08–4.20 m (6H, 3NCH2), 4.40 m (1Н,
CHОН). 19F NMR spectrum [(CD3)2CO, δ, ppm]:
18.80 m [1F, OCF(CF3)], 29.21 m (1F, CFCH2), 34.23
m (2F, CF3CF2), 78.71 m (2F, CFCF2O), 80.50 m (2F,
CF2CF2O), 80.61 m (3F, CF3CF2), 82.02 m (6F,
(1) Fluorine-containing quaternary ammonium salts
have structures differing in the nature of the
fluoroalkyl moiety and structure of the hydrocarbon
part adjacent to the ammonium group. The salts are
characterized by high solubility in water, and their
structural formulas, by a break in hydrophobicity by
polar oxygen-containing moieties.
(2) Fluorine-containing quaternary ammonium salts
are promising as corrosion inhibitors. In their presence,
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SYNTHESIS AND INHIBITING CAPACITY
977
14. RF Patent 2141948.
15. RF Patent 2168498.
16. RF Patent 2168499.
17. RF Patent 2265676.
the uniform corrosion rate of low-carbon steels de-
creases, with the desired effect obtained at a sub-
stantially lower concentration of salts introduced into
solutions.
18. Szonyi, F. and Cambon, A., New J. Chem., 1993,
ACKNOWLEDGMENTS
vol. 17, pp. 425–434.
19. Zaggia, A., Conte, L., Padoan, G., and Bertani, R.,
The study was financially supported by the Ural
Branch of the Russian Academy of Sciences (project
no. 09-M-13-2001).
J. Surfact. Deterg., 2010, vol. 13, pp. 33–40.
20. Zotikov, V.S., Ryabinin, N.A., Gankin, E.A., et al.,
Abstracts of Papers, IV Vsesoyuznaya konferentsiya po
khimii ftororganicheskikh soedinenii (IV All-Union
Conf. on Chemistry of Organofluorine Compounds),
Tashkent, 1982, p. 5.
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