Synthesis and properties of hemifluorinated disodium alkanesulfonates

Article abstract of DOI:10.1016/j.jfluchem.2014.04.003

Perfluorobutyl substituted disodium alkanesulfonates derivatives were synthesized and characterized as alternative substances to perfluorooctanesulfonic acid (PFOS, 1), a well-known surfactant. 1H,1H,2H,2H-nonafluorohexyl iodide, diethyl malonate and sultones were used to prepare disodium sulfonates 2 and 3 in three synthetic steps. The surface tension behavior of 2 and 3 were studied and critical micelle concentration values were noted to be 2025 mg/L and 2052 mg/L, respectively, at room temperature.

Full text of DOI:10.1016/j.jfluchem.2014.04.003

Journal of Fluorine Chemistry 163 (2014) 42–45
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Synthesis and properties of hemifluorinated disodium
alkanesulfonates
V.D. Vijaykumar Bodduri a, Sridhar Chirumarry a, Jae-Min Lim a, Yong-Ill Lee a, Kiwan Jang b,
Bong-In Choi c, Seon-Yong Chung c, Dong-Soo Shin a,
*
a Department of Chemistry, Changwon National University, Changwon, GN 641-773, South Korea
b Department of Physics, Changwon National University, Changwon, GN 641-773, South Korea
c Department of Environmental Engineering, Chonnam National University, Gwangju 500-757, South Korea
A R T I C L E I N F O
A B S T R A C T
Article history:
Perfluorobutyl substituted disodium alkanesulfonates derivatives were synthesized and characterized
Received 29 November 2013
Received in revised form 3 April 2014
Accepted 4 April 2014
as alternative substances to perfluorooctanesulfonic acid (PFOS, 1),
a well-known surfactant.
1H,1H,2H,2H-nonafluorohexyl iodide, diethyl malonate and sultones were used to prepare disodium
sulfonates 2 and 3 in three synthetic steps. The surface tension behavior of 2 and 3 were studied and
critical micelle concentration values were noted to be 2025 mg/L and 2052 mg/L, respectively, at room
temperature.
Available online 18 April 2014
Keywords:
ß 2014 Elsevier B.V. All rights reserved.
Disodium sulfonates
Hemifluorinated surfactants
Alternate PFOS
Surface tension
1. Introduction
been under progress to reduce the hazardous effects of PFOS
derivatives by scientists and some industries all over the globe [7–
Surfactants play major role as wetting, cleaning, foaming and
emulsifying agents in many applications. The conventional
surfactants usually contain one hydrophilic end and one hydro-
phobic group attached to it. These amphiphilic compounds are well
known for their spectacular surface properties, which are
dramatically influenced when attached to a perfluorocarbon chain
as hydrophobic unit. Among which the manmade perfluoroocta-
nesulfonic acid (PFOS, 1) and its derivatives are proven to be most
dependable substrates due to their special physicochemical
properties [1,2]. It has a perfluorooctane chain as hydrophobic
group and sulfonic acid as hydrophilic unit and show low
surface tension as well as critical micelle concentration (CMC)
values. PFOS and its derivatives have been used in stain repellents,
coatings, plane hydraulic fluids, pharmaceuticals and electroplat-
ing, etc., due to their heat, abrasion and chemical resistance [3,4].
Apart from all the advantages and uses of PFOS derivatives, they
are listed under Stockholm convention on persistent organic
pollutants (POPs) owing to their non-biodegradable wastage and
toxic effects in the environment [5,6]. In recent years, efforts have
10]. For instance, 3M company announced voluntary phase out of
PFOS in 2000 and working on alternate surfactants that contain
shorter C4-perfluoro chain derivatives for less bio-accumulative,
less toxic and sustainable substances [11–13].
On the other hand, it is proven that gemini surfactants which
contain more than one hydrophobic as well as hydrophilic
groups show significant effects on surface properties [14–16].
Our interest on making less fluorinated and efficient surfactants to
understand their behavior by structural changes, has come up with
a new design that partly meets the above-mentioned structural
parameters. Thus, we have anticipated two surfactant structures (2
and 3) with two hydrophilic units that are sulfonic acids and one
hemifluorinated hydrophobic tail as shown in Fig. 1.
The process of preparing PFOS related substances involves
electrochemical perfluorination, telomerization of vinylidene
fluoride or by controlled radical copolymerization of vinylidene
fluoride and 3,3,3-trifluoropropene, etc. [9] In continuation of our
efforts toward environmentally friendly PFOS alternatives for
better surface properties [17], we here in present the synthesis and
properties of perfluoroalkyl disulfonate class surfactants. Synthesis
of such skeletons needed a simple route, where the introduction of
perfluorinated alkyl chain must be easily accessible. However, the
synthesis may not be cost-effective for some surfactants as they
*
Corresponding author. Tel.: +82 55 213 3437; fax: +82 55 213 3439.
E-mail address: dsshin@changwon.ac.kr (D.-S. Shin).
http://dx.doi.org/10.1016/j.jfluchem.2014.04.003
0022-1139/ß 2014 Elsevier B.V. All rights reserved.

V.D.V. Bodduri et al. / Journal of Fluorine Chemistry 163 (2014) 42–45
43
80
F F F F F F F F
SO3H
F
2
3
70
60
50
40
30
20
10
F F F F F F F F
1
O
SO3Na
SO3Na
F
F F
F
O n
F
n
F
F F
F
2
(n = 0)
3 (n = 1)
Fig. 1. Structures of PFOS and its proposed alternatives.
would be used as additives to conventional surfactants. As a
preliminary study, the perfluorinated alkyl halide, 1H,1H,2H,2H-
nonafluorohexyl iodide, 4 was used as fluorinated starting material
to synthesize targeted sulfonic acid derivatives mentioned above
in only three synthetic steps (Scheme 1). The other starting
materials include diethyl malonate, 1,3-propanesultone and 1,4-
butanesultone.
0
2000
4000
6000
8000
10000
12000
14000
Concentration (mg/L)
Fig. 2. Surface tension profiles of 2 and 3 in aqueous media.
2. Results and discussion
a base in THF. The propanesultone has given corresponding
disodium sulfonate 2 in 86% yield and butanesultone has afforded
disodium sulfonate 3 in 83% yield. All compounds are completely
characterized by NMR (1H, 13C and 19F), IR and mass spectral data.
After the confirmation of structures and purity by analytical data,
we move forward to the surface characteristics to evaluate
the efficiency of these disodium alkanesulfonates in reducing
the surface tension of water at the liquid–gas interface of their
aqueous solution.
Surface tension measurements of the two disodium sulfonates
(2 and 3) were carried out using Wilhelmy plate tensiometer and a
collective graph plotted between surface tension and concentra-
tion has been shown in Fig. 2. As the concentration increased,
surface tension values were decreased. From the graph, it can be
To make difference from conventional, we report the synthesis
of new hemifluorinated disodium alkanesulfonate compounds.
The synthetic strategy involves a mono alkylation reaction of
diethyl malonate (5) using alkyl halide 4 in the presence of
sodium hydride in dry THF to afford 6 in 89% yield [18].
This reaction was conducted at various conditions (DMF, 0 8C to
rt, 5 h, 68%; DME, 0 8C to reflux, 6 h, 56%; THF, 0 8C to rt, 5 h, 60%;
THF, 0 8C to reflux 3 h, 89%) and standardized to ensure precise
reaction yields of compound 6 in large amounts (50 g). Dibenzyl-
malonate (5a) did not give any better results in increasing the
yields instead decreased to 66% and thus avoided. The purity of
compound 6 has found to be >97% by GC–MS. The 1H NMR of 6
showed a multiplet for the single active proton of malonate around
observed that compounds
2 and 3 have showed excellent
d
3.44–3.40 ppm and corresponding carbon at
d
50.7 ppm in 13C
surfactant activity as they decreased surface tension of water at
low concentrations. The CMC values of the aqueous solutions of 2
and 3 were found to be 2025 mg/L and 2052 mg/L, respectively, at
25 8C, with the error of CMC less than 5% for both the compounds.
The surface tension values of 2 and 3 are observed to be 26.0 mN/m
and 27.4 mN/m, respectively, at their CMC values. Though there is
NMR, confirmed the product. The complete reduction of
mono alkylated diethyl malonate 6 with lithium aluminum
hydride smoothly afforded diol 7 in 91% yield, without affecting
the perfluoroalkyl chain [19]. Further, this diol 7 was subjected to
the nucleophilic ring opening of sultones in the presence of NaH as
Journal of Fluorine Chemistry
COOR
F
F F F
F
F F F
COOR
NaH, THF
6
, LAH, THF
I
F
F
COOR
0 oC to rt, 5 h
0 oC to rt, 10 h
91%
COOR
R = Et
F
F F F
4
F
F F F
5
6
R = Et, 89%
5a
R = Bn
6a
R = Bn, 66%
O
S
8
O
O
SO3Na
SO3Na
O
O
F
F F
F
F
86%
F
F F
F
OH
OH
2
3
F
F F F
NaH, THF
0 oC to rt, 16 h
O
S
O
F
O
O
F
F F F
O
9
SO3Na
SO3Na
F
F F
F
7
F
F
F F
F
83%
Scheme 1. Synthesis of hemifluorinated disodium alkanesulfonates 2 and 3.

44
V.D.V. Bodduri et al. / Journal of Fluorine Chemistry 163 (2014) 42–45
no much difference in the structures of two sulfonates. Moreover, it
is worthy to note that these compounds showed superior
surfactant behavior when compared to that of original PFOS
potassium salt (KPFOS, CMC 4304 mg/L at 80 8C) [20].
tensiometer was used according to the manufacturer’s recom-
mendations.
The biodegradation of surfactants was determined according to
the OECD Test guideline 301 F [22]. This test was conducted by an
Oxitop respirometer to follow the consumption of oxygen during
28 days in a closed flask containing 15–50 mg/L of the test
The structures that have degrading points like ether links and
hydrocarbon chain allow biodegradability by enzymatic cleavage
or chemical treatments to degrade and would be safer ones when
compared to PFOS derivatives. In this purpose, both the disodium
alkanesulfonates (2 and 3) were subjected to biodegradability test
in the presence of inoculums coming from a sewage plant. These
compounds showed moderate biodegradation and were remained
below the 60% level at 28 days. The low level of biodegradation
may be due to the non-biodegradability of perfluorocarbon chain.
However, these two compounds (2 and 3) are biodegradable to
some extent because of hydrocarbon part, and can be considered as
less toxic and sustainable alternatives to non-biodegradable PFOS,
due to inferior fluorine content [7,11,21]. Considering the new
structural features along with good surface tension reduction
properties and environmental aspects, these hemifluorinated
disodium alkanesulfonates may be useful in replacing original
PFOS in industrial and chemical applications. In addition, this work
influences the research toward new design and syntheses of less
perfluorinated surfactants in the aspects of sustainable chemistry.
substance and inoculums coming from
a sewage plant.
The percentage of biodegradation is obtained by dividing the
resulting biological oxygen demand (BOD) by the theoretical
oxygen demand (ThOD) of the test substance [23]. Aniline was
used as a reference.
4.2. Procedures
4.2.1. Diethyl 2-(3,3,4,4,5,5,6,6,6-nonafluorohexyl)malonate (6)
Diethyl malonate (11.5 mL, 75.7 mmol) was added dropwise
to an ice-cold suspension of sodium hydride (60% dispersion in
mineral oil, 2.21 g, 55.4 mmol) in THF (150 mL) at 0 8C during
15 min. The resulting mixture was stirred for 30 min while
allowing the temperature from 0–23 8C. 1H,1H,2H,2H-nonafluor-
ohexyl iodide (9.4 mL, 50.5 mmol) was added slowly to the
reaction and the mixture was heated at reflux for 3 h, and then
was cooled to 23 8C. Water (100 mL) and ethyl ether (100 mL)
were added to it. The aqueous layer was extracted with ethyl
ether (3 ꢀ 80 mL). The combined organic extracts were dried
over sodium sulfate, filtered and concentrated. The residue
was purified by flash column chromatography to afford diethyl 2-
(3,3,4,4,5,5,6,6,6-nonafluorohexyl)malonate (6) as a colorless
3. Conclusions
New disodium sulfonates 2 and 3 were synthesized and
characterized by NMR, IR and mass spectroscopy. The synthesis
of these hemifluorinated disodium alkanesulfonates started from
1H,1H,2H,2H-nonafluorohexyl iodide and diethyl malonate in
three steps in 67–70% overall yields. The surface tension behavior
of 2 and 3 was characterized using Wilhelmy plate method and
critical micelle concentration values were presented. It is
important to note that the CMC values are better when compared
to that of PFOS and thus can be considered as superior surfactants.
The biodegradability test of these sulfonates showed promising
results than non-biodegradable PFOS and can be considered as
environmentally friendly. This study suggests the scope of less
perfluorinated alkanesulfonates in industrial, medicinal and
chemical applications.
liquid (18.2 g, 89%). 1H NMR (400 MHz, CDCl3):
4H), 3.44–3.40 (m, 1H), 2.23–2.13 (m, 4H), 1.30–1.26 (m, 6H).
19F NMR (CDCl3, 376 MHz):
-81.98 (3F, tt, J1 = 11.2 Hz,
d 4.30–4.17 (m,
d
J2 = 3.7 Hz), ꢁ115.37 (2F, quintet, J = 15.0 Hz), ꢁ125.33 to
ꢁ125.36 (2F, m), ꢁ126.89 to ꢁ126.96 (2F, m). 13C NMR
(100 MHz, CDCl3):
d 168.61, 61.90, 50.77, 28.46, 19.77, 14.06;
ESI-MS (m/z): 429 [M+Na]+. Anal. Calcd. for C13H15F9O4: C, 38.44;
H, 3.72. Found: C, 38.12; H, 3.87.
4.2.2. Dibenzyl 2-(3,3,4,4,5,5,6,6,6-nonafluorohexyl)malonate (6a)
By following the same procedure mentioned for compound 6,
except taking dibenzyl malonate (5 g, 17.6 mmol) instead of
diethyl malonate as starting material afforded dibenzyl 2-
(3,3,4,4,5,5,6,6,6-nonafluorohexyl)malonate (6a) (6.16 g, 66%). 1H
4. Experimental
NMR (400 MHz, CDCl3):
5.03–4.98 (m, 4H), 3.44–3.40 (m, 1H), 2.26–2.18 (m, 4H). 19F NMR
(CDCl3, 376 MHz):
ꢁ81.99 (3F, tt, J1 = 11.2 Hz, J2 = 3.7 Hz),
d 7.47–7.45 (m, 4H), 7.39–7.36 (m, 6H),
4.1. General
d
ꢁ115.37 (2F, quintet, J = 15.0 Hz), ꢁ125.34 to ꢁ125.37 (2F, m),
All non-fluorinated starting materials and solvents were
obtained from Sigma–Aldrich (USA). Perfluoroalkyl iodide,
1H,1H,2H,2H-nonafluorohexyl iodide was purchased from Tokyo
Chemical Industries Co. Ltd. (Japan). All reagents were used
without further purification. Melting points were determined on a
digital SMP10 capillary melting point apparatus (SRUAT, UK). NMR
spectra were measured with BRUKER AVANCE 400 (BRUKER,
Germany) spectrometer, IR spectra were recorded on a FT-IR-6300
(JASCO, Japan) spectrometer and MS spectra were obtained from a
Thermo LCQ fleet MS spectrometer (Thermo, USA).
Surface tension was measured according to the American
Society for Testing and Materials ASTM # D1331-56, using the
Wilhelmy plate method on a KRUSS K100 tensiometer (KRUSS,
Germany) in accordance with instructions with the equipment. A
vertical plate of known perimeter was attached to a balance, and
the force due to wetting was measured. Each example to be tested
was added to deionized water by weight based on solids of the
additive in deionized water. Solutions of different concentrations
were prepared and tested 10 times of each dilution. Results were in
mN/m with a standard deviation of less than 1 mN/m. The
ꢁ126.89 to ꢁ126.95 (2F, m). 13C NMR (100 MHz, CDCl3):
d 169.32,
136.82, 128.90, 127.66, 127.14, 66.26, 50.77, 28.46, 19.77; ESI-MS
(m/z): 553 [M+Na]+. Anal. Calcd. for C23H19F9O4: C, 52.05; H, 3.61.
Found: C, 51.90; H, 3.53.
4.2.3. 2-(3,3,4,4,5,5,6,6,6-Nonafluorohexyl)propane-1,3-diol (7)
To a stirred solution of LiAlH4 (3.74 g, 98.5 mmol) in dry
THF (30 mL) under N2 was added dropwise a solution of 6 (10 g,
24.6 mmol) in THF (15 mL). After 48 h at reflux the reaction was
cooled to 0 8C and quenched by careful addition of approx. 40% aq.
KOH. The precipitated aluminum salts were removed by
filtration. The filtrate was concentrated under reduced pressure,
then the residual oil redissolved in Et2O, washed with H2O, dried
(Na2SO4) and evaporated in vacuo to return the 2-substituted
propanediol 7 (7.21 g, 91%) as a viscous solid. 1H NMR (400 MHz,
CDCl3):
d 4.07 (t, J = 5.3 Hz, 2H), 3.74–3.69 (m, 2H), 3.64–3.59 (m,
2H), 2.23–2.10 (m, 2H), 1.74–1.61 (m, 3H). 19F NMR (CDCl3,
376 MHz):
d
ꢁ82.10 to ꢁ82.17 (3F, m), ꢁ114.96 to ꢁ115.08 (2F,
m), ꢁ124.95 to ꢁ124.97 (2F, m), ꢁ126.66 to ꢁ126.73 (2F, m). 13
C
NMR (100 MHz, CDCl3):
d 63.58, 41.76, 28.61, 18.45; ESI-MS

V.D.V. Bodduri et al. / Journal of Fluorine Chemistry 163 (2014) 42–45
45
(m/z): 345 [M+Na]+. Anal. Calcd. for C9H11F9O2: C, 33.55; H, 3.44.
Acknowledgments
Found: C, 33.83; H, 3.75.
This work was supported by the grants from the Ministry of
Environment (KME, 412-111-008), National Research Foundation
(NRF-2009-0094063) and Ministry of Knowledge Economy (MKE,
R0000495), South Korea.
4.2.4. Disodium 3,30-(2-(3,3,4,4,5,5,6,6,6-nonafluorohexyl)propane-
1,3-diyl)bis(oxy)dipropane-1-sulfonate (2)
Compound 7 (3.0 g, 9.3 mmol) pre-dissolved in dry THF (10 mL)
solution was added to suspension of sodium hydride (1.11 g net,
27.9 mmol) at 60 8C. Another dry THF solution (10 mL) containing
propanesultone (3.29 g, 27 mmol) was then added to the reaction
mixture at the same temperature. After 24 h of stirring under
reflux conditions, 20 mL of methanol was added at ambient
temperature to deactivate any excess of sodium hydride. After
evaporation of the reaction mixture, it was subsequently washed
with hexanes (3 ꢀ 10 mL) and ethyl ether (3 ꢀ 10 mL) to remove
the oil impurities as well as excess sultone. The residue was
isolated and purified by silica gel chromatography to afford target
compound 2 (6.70 g, 86% yield) as a pale yellow solid. 1H NMR
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(400 MHz, D2O):
(m, 4H), 2.39–2.21 (m, 2H), 2.08–1.99 (m, 5H), 1.75–1.58 (m, 2H).
19F NMR (CD3OD, 376 MHz):
d 3.69–3.62 (m, 4H), 3.61–3.50 (m, 4H), 3.02–2.95
d
ꢁ81.14 (3F, tt, J1 = 11.2 Hz,
J2 = 3.7 Hz), ꢁ115.00 (2F, quintet, J = 15.0 Hz), ꢁ124.94 to
ꢁ124.96 (2F, m), ꢁ126.65 to ꢁ126.72 (2F, m). 13C NMR
(100 MHz, D2O):
d 70.47, 69.05, 50.55, 40.01, 37.36, 24.15,
14.11; ESI-MS (m/z): 633 [M+Na]+. Anal. Calcd. for
C15H21F9Na2O8S2: C, 29.51; H, 3.47. Found: C, 28.84; H, 3.56.
4.2.5. Disodium 4,40-(2-(3,3,4,4,5,5,6,6,6-nonafluorohexyl)propane-
1,3-diyl)bis(oxy)dibutane-1-sulfonate (3)
Following the same procedure mentioned for compound 2,
butanesultone (4.34 g, 27 mmol) was used to afford target
compound 3 (4.93 g, 83% yield) as a pale yellow solid. 1H NMR
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(400 MHz, D2O):
d
3.66–3.43 (m, 8H), 2.97–2.90 (m, 4H), 2.32–2.11
ꢁ81.11
(m, 2H), 2.05–1.61 (m, 11H). 19F NMR (CD3OD, 376 MHz):
d
to ꢁ81.16 (3F, m), ꢁ114.96 to ꢁ115.08 (2F, m), ꢁ124.95 to ꢁ124.97
(2F, m), ꢁ126.66 to ꢁ126.73 (2F, m). 13C NMR (100 MHz, D2O):
d
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70.36, 70.27, 50.62, 39.47, 37.43, 27.42, 20.86, 13.99; ESI-MS (m/z):
633 [M+Na]+. Anal. Calcd. for C17H25F9Na2O8S2: C, 31.98; H, 3.95.
Found: C, 32.23; H, 3.71.
ˇ
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