Synthesis of highly fluorinated aryl N -acylsulfamates and evaluation of their surfactant properties

Article abstract of DOI:10.1080/10426507.2012.700355

Reaction of highly fluorinated carboxylic acids with aroxysulfonylisocyanates in the presence of triethylamine allowed the preparation of the corresponding highly fluorinated aroxy-N-sulfonylsulfamates. The reaction proceeds with good yield in toluene at

Full text of DOI:10.1080/10426507.2012.700355

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Phosphorus, Sulfur, and Silicon and the
Related Elements
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Synthesis of Highly Fluorinated Aryl N-
Acylsulfamates and Evaluation of Their
Surfactant Properties
Hassen Sbihi a , Faouzia Ouahmi a , Mohamed Beji a & Ahmed
Baklouti a
a Laboratory of Structural Organic Chemistry, Department of
Chemistry, Faculty of Sciences of Tunis , Tunis , Tunisia
Accepted author version posted online: 22 Jun 2012.Published
online: 31 May 2013.
To cite this article: Hassen Sbihi , Faouzia Ouahmi , Mohamed Beji & Ahmed Baklouti (2013)
Synthesis of Highly Fluorinated Aryl N-Acylsulfamates and Evaluation of Their Surfactant
Properties, Phosphorus, Sulfur, and Silicon and the Related Elements, 188:5, 539-544, DOI:
10.1080/10426507.2012.700355
To link to this article: http://dx.doi.org/10.1080/10426507.2012.700355
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Phosphorus, Sulfur, and Silicon, 188:539–544, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2012.700355
SYNTHESIS OF HIGHLY FLUORINATED ARYL
N-ACYLSULFAMATES AND EVALUATION OF THEIR
SURFACTANT PROPERTIES
Hassen Sbihi, Faouzia Ouahmi, Mohamed Beji,
and Ahmed Baklouti
Laboratory of Structural Organic Chemistry, Department of Chemistry, Faculty of
Sciences of Tunis, Tunis, Tunisia
GRAPHICAL ABSTRACT
O
F—(CF2)n—COOH
Chlorobenzene
F—(CF) —C—NH—SO2—O—R
R—O—SO2—N
C O
R
OH
+
Cl SO2
N
C
O
2
n
Toluene
(C2H5)3N, 60°C
—CO2
130°C
HCl
Abstract Reaction of highly fluorinated carboxylic acids with aroxysulfonylisocyanates in
the presence of triethylamine allowed the preparation of the corresponding highly fluorinated
aroxy-N-sulfonylsulfamates. The reaction proceeds with good yield in toluene at room tem-
perature or more rapidly in the same solvent at 60 ◦C. Surface tension measurement at the
air/water interface showed that these compounds constitute new excellent nonionic surfactants
exhibiting high surface activity in the range of the best nonionic fluoro surfactants, already
described in the literature. The critical micelle concentration (CMC) has been calculated from
the surface tension measurements on surface aqueous solutions.
Keywords Highly fluorinated carboxylic acids; aroxysulfonylisocyanates; highly fluorinated
N-acylsulfamates; surface tension; critical micelle concentration
INTRODUCTION
Aroxysulfonylisocyanates, ROSO2NCO, represent interesting intermediates for syn-
thetic organic chemistry because of their rich and diverse reactivity. They are used as
precursor of chemotherapeutic agents in the pharmaceutical industry as sulfonamides,1
ureas,2 carbamates,3 and antibacterial drugs such as penicillin and cephalosporin.4–6
We have previously reported the reaction of these isocyanates with adamantyl al-
cohols,3 alkyl (aryl) magnesium bromides,7 highly fluorinated alcohols,8 thiols,8 diols,9
aminoalcohols,10 and hydrocarbon acids and diacids, which led to N-acylsulfamates, N,Nꢁ-
diacylsulfamates, and N,Nꢁ-disulfonylureas.11
Sulfamates represent a very interesting family of compounds in organic chemistry
because of their relevance as such or as reaction intermediates with a rich and diverse
Received 16 March 2012; accepted 18 May 2012.
Address correspondence to Hassen Sbihi, Laboratory of Structural Organic Chemistry, Department of
Chemistry, Faculty of Sciences of Tunis, Tunis, Tunisia. E-mail: adam.sbihi@yahoo.com
539

540
H. SBIHI ET AL.
reactivity. Indeed, they are found in many fields ranging from pharmaceuticals to industrials
having a high biological activity.12 We know, moreover, that the introduction of fluorocarbon
chains in a structure gives many physical and chemical properties such as greater chemical
and thermal stability and low surface tension.13–18
Perfluorinated compounds represent a broad class of substances that are used in a
wide variety of industrial and consumer products. But the exposure of even trace amounts
of perfluorinated compounds in open seawater and oceans leads to their accumulation in
wildlife, and many of these compounds exhibit significant negative consequences on aquatic
biota as a result of their persistence in the environment.19,20
In the present work, we extend the reaction of highly fluorinated carboxylic acids
with the same starting sulfonylheterocumulenes in order to develop a new family of highly
fluorinated surfactants derived from F-alkyl-N-acylsulfamates and study their surface prop-
erties.
RESULTS AND DISCUSSION
Synthesis of Highly Fluorinated Aryl N-acylsulfamates
The addition of highly fluorinated carboxylic acids was carried out in toluene in the
presence of triethylamine at 60 ◦C (Schemes 1 and 2). It leads, after decarboxylation of the
intermediates, to the formation of highly fluorinated N-acylsulfamates with good yields.
Chlorobenzene
R
—
O
—
SO2
—
N
C
O
+
HCl
R—
OH
R
+
Cl—
SO2
CH3
—N C O
130°C
a,b
H3C
(a)
Cl
;
(b)
CH3
Scheme 1
O
Toluene
F—
(CF2)n
—
COOH
+
R—O—SO2—N C O
F
—
(CF2)n
—
C
—
NH
Sa n, Sb
—n
—
SO2
—
O
—
R
+
CO2
(C2H5)3N, 60°C
—
n
1,3,7,9
Scheme 2
We noted that for compounds Sa-1, Sa-3, Sa-7, and Sa-9 obtained from the 2,4,6-
trimethylaroxysulfonyl isocyanate (electrodonor ring substituents), the reaction rates were
longer (60 min) and the yields were lower (55–79%) (see Table 1). In contrast, for
compounds Sb-1, Sb-3, Sb-7, and Sb-9 obtained from the 4-chloroaroxysulfonyl isocyanate
(electron-attracting ring substituent), the reaction rates were relatively shorter (20–30 min)
and the yields were higher (82–95%) (see Table 1).

HIGHLY FLUORINATED ARYL N-ACYLSULFAMATES
Table 1 Preparation of highly fluorinated N-acylsulfamates
541
Product
Time (min)
Yield (%)
Sa-1
Sb-1
Sa-3
Sb-3
Sa-7
Sb-7
Sa-9
Sb-9
60
30
60
30
60
30
60
20
79
93
55
85
65
82
70
95
Properties of Aqueous Solutions
Solubility. The solubility of the highly fluorinated N-acylsulfamates in aqueous
alkaline solution (0.05 mol·L−1 NaOH) is high in contrast to pure water in which the lack
of solubility of some members of the series prevents the solutions from reaching the critical
micelle concentration (CMC). As shown in Table 2, the lowest solubility was observed for
Sa-9 (4.82 × 10−3 mol·L−1) and Sb-9 (5 × 10−3 mol·L−1) due to the high hydrophobicity
of the perfluorinated nine carbon chain. In fact, increasing the length of the fluorinated tail
(n) decreases the solubility of these compounds.
Surface Active Properties. The study of the surface tension (γ ) curves plotted
against the logarithm of molar concentration of highly fluorinated N-acylsulfamates re-
vealed that the water surface decreases linearly with increasing logarithm of concentration
and then levels off. The inflection point observed for the compounds corresponds to the
CMC. The CMC values of highly fluorinated N-acylsulfamates are summarized in Table 2
along with the surface tension at the CMC (γ CMC).
An increase of the fluorinated chain length leads to a decrease of the CMC values
as generally found within pure water solutions.21 We detected, for example, a lowering of
the surface tension of water with the compound Sa-9 or Sb-9 from 72 to 18 mN·m−1. The
highest value 27 mN·m−1 was observed for the compound Sa-1 or Sb-1, which is the most
soluble in the alkaline solution.
The examination of data obtained (Table 2) shows also a slight increase in CMC
by comparing the result for Sa-7 (0.21 × 10−4 mol·L−1) and Sa-9 (0.73 × 10−4 mol·L−1).
The CMC results are due to less favorable interactions between the long perfluorinated
Table 2 The physicochemical surface properties of synthesized N-acylsulfamates
Sa-n or Sb-n
Solubility (mol·dm−3
)
104 CMC (mol·dm−3
)
γ CMC (mN·m−1
)
Sa-1
Sb-1
Sa-3
Sb-3
Sa-7
Sb-7
Sa-9
Sb-9
9.8 × 10−3
8.5 × 10−3
6.23 × 10−3
7.07 × 10−3
5.84 × 10−3
5.45 × 10−3
4.82 × 10−3
5 × 10−3
3.92
1.7
2.16
2.8
0.21
0.11
0.73
0.14
26.94
27.08
23.79
23.88
21.06
21.2
18.04
18.4

542
H. SBIHI ET AL.
hydrophobic chain C9F19 of the surfactant and the aromatic hydrocarbon part (2,4,6-
trimethylethyl). This mutual phobicity between hydrocarbons and fluorocarbons affects
the force for micellization in alkaline solution. The size of the hydrophobic segments and
the kind of the hydrophilic groups are important in reducing the water surface tension and
the value of CMC.
EXPERIMENTAL
1
The H NMR (chemical shifts δ measured in deuterated solvents are given in ppm
from tetramethylsilane [TMS] as internal standard), 19F (CFCl3 as internal reference),
and 13C (TMS as internal standard) spectra were recorded on a Bruker AC 300 MHz
spectrometer, using (CD3)2CO as solvent. High-resolution mass spectra (HRMS) were
obtained by negative mode of electrospray ionization (ESI NEG) with a Finningan MAT
SBE spectrometer. Surface tension of alkaline aqueous surfactant solutions was measured at
25 ◦C with an automatic Tensiometer TD 2, using the Wilhelmy plate method. The surfactant
solutions were prepared by using an aqueous alkaline solution (0.05 mol·L−1 NaOH). A
0.1 mol·L−1 surfactant solution was freshly prepared as stock solution and then diluted to
the desired concentration for each measurement. The surface tension was measured twice
at 25 ◦C for each concentration. The CMC were determined from the breakpoint of each
curve obtained for the surface tension as a function of log [concentration]. The melting
points (mp) were determined by using an Electrothermal IA9000 series II apparatus.
Aroxysulfonylisocyanates a and b were prepared (Scheme 1) according to literature
methods.22,23
General Procedure for the Synthesis of Products Sa-n and Sb-n. To a solu-
tion of the fluorinated carboxylic acid (10 mmol) and triethylamine (0.1 mmol) in anhydrous
toluene, 10 mmol of aroxysulfonylisocyanate dissolved in the same solvent were added un-
der argon. The mixture was stirred at 60 ◦C for 20–60 min. After filtration, the solid was
recrystallized from CCl4.
2,4,6-Trimethylphenyl N-(Trifluoroacetyl)sulfamate (Sa-1). Mp: 101 ◦C. 1H
NMR: 2.22 (s, 3H, ArCH3), 2.35 (s, 6H, ArCH3), 6.93 (s, 2H, aromatic H), 10.5–11.5
1
(1H, NH). 13C NMR: 17.19, 20.62 (ArCH3), 115.82 (q, CF3, JC-F = 287 Hz), 137–147
(aromatic C), 155.52 (q, CO, 2JC-F = 41 Hz). 19F NMR: −85.0 (CF3). HRMS (ESI): m/z
(%) = 310.0 (100) [M–1]−.
◦
1
4-Chlorophenyl N-(Trifluoroacetyl)sulfamate (Sb-1). Mp: 95 C. H NMR:
7.4–8.0 (m, 4H, aromatic H), 10.5–11.2 (1H, NH). 13C NMR: 114.38 (q, CF3, JC-F
=
1
287 Hz), 120–150 (aromatic C), 156.72 (q, CO, 2JC-F = 41 Hz). 19F NMR: –81.47 (CF3).
HRMS (ESI): m/z (%) = 301.9 (100) [M–1]−.
2,4,6-Trimethylphenyl N-(2,2,3,3,4,4,4-Heptafluorobutanoyl)sulfamate
◦
1
(Sa-3). Mp: 103 C. H NMR: 2.22 (s, 3H, ArCH3), 2.34 (s, 6H, ArCH3), 6.88 (s, 2H,
aromatic H), 8.0–9.0 (1H, NH). 13C NMR: 17.42, 20.61 (ArCH3), 100–120 (m, C of
2
CF2ou3), 130–147 (aromatic C), 160.90 (q, CO, JC-F = 30 Hz). NMR: −127.86 (CF2β),
-120.40 (CF2α), −81.55 (CF3). HRMS (ESI): m/z (%) = 410 (100) [M–1]−.
4-Chlorophenyl N-(2,2,3,3,4,4,4-Heptafluorobutanoyl)sulfamate (Sb-3).
Mp: 85 ◦C. 1H NMR: 7.3–8.0 (m, 4H, aromatic H), 9.2–10.2 (1H, NH). 13C NMR: 100–120
(m, CF2/3), 120–150 (aromatic C), 156.54 (q, CO, JC-F = 30 Hz). 19F NMR: –127.29
2
(CF2β), -119.50 (CF2α), −80.86 (CF3). HRMS (ESI): m/z (%) = 401.9 (100) [M–1]−.
2,4,6-Trimethylphenyl N-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-Pentadecafluoro-
◦
1
octanoyl)sulfamate (Sa-7). Mp: 87 C. H NMR: 2.23 (s, 3H, ArCH3), 2.35 (s, 6H,

HIGHLY FLUORINATED ARYL N-ACYLSULFAMATES
543
ArCH3), 6.0–6.5 (1H, NH), 6.89 (s, 2H, aromatic H). 13C NMR: 17.41, 20.66 (ArCH3),
2
100–120 (m, C of CF2ou3), 130–147 (aromatic C), 159.53 (q, CO, JC-F = 30 Hz). 19F
NMR: −126.80 (CF2ω), −122.63 (2∗CF2), −121.54 (2∗CF2), −119.42 (CF2α), −81.67
(CF3). HRMS (ESI): m/z (%) = 610.0 (100) [M–1]−.
4-Chlorophenyl N-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-Pentadecafluorooctanoyl)
-sulfamate (Sb-7). Mp: 147 ◦C. 1H NMR: 6.0–6.5 (1H, NH), 7.3–8.0 (m, 4H, aromatic
H). 13C NMR: 100–120 (m, C of CF2ou3), 130–150 (aromatic C), 150.24 (q, CO, 2JC-F
=
30 Hz). 19F NMR: −126.78 (CF2ω), −122.62 (2∗CF2), −121.58 (2∗CF2), −119.43 (CF2α),
−81.65 (CF3). HRMS (ESI): m/z (%) = 601.9 (100) [M–1]−.
2,4,6-Trimethylphenyl
N-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Nona
deca-fluorodecanoyl)sulfamate (Sa-9). Mp: 125 ◦C. 1H NMR: 2.22 (s, 3H, ArCH3),
2.35 (s, 6H, ArCH3), 6.5–7.0 (1H, NH), 6.90 (s, 2H, aromatic H). 13C NMR: 17.16, 20.52
(ArCH3), 100–120 (m, C of CF2/3), 130–148 (aromatic C), 150.24 (q, CO, 2JC-F = 30 Hz).
19F NMR: −126.55 (CF2ω), −122.54 (2∗CF2), −121.56 (4∗CF2), −119.32 (CF2α), −81.67
(CF3). HRMS (ESI): m/z (%) = 710.0 (100) [M–1]−.
4-Chlorophenyl
N-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Nonadeca-
fluoro-decanoyl)sulfamate (Sb-9). Mp: 140 ◦C. 1H NMR: 6.5–7.0 (1H, NH), 7.3–8.0
(m, 4H, aromatic H). 13C NMR: 100–120 (m, C of CF2/3), 120–150 (aromatic C), 155.08
(q, CO, 2JC-F = 30 Hz). 19F NMR: −126.72 (CF2ω), −122.61 (2∗CF2), −121.52 (4∗CF2),
−119.43 (CF2α), −81.63 (CF3). HRMS (ESI): m/z (%) = 701.9 (100) [M–1]−.
CONCLUSION
A new class of highly fluorinated nonionic surfactants based on fluorinated tail groups
as hydrophobic and lipophobic chain linked to hydrophilic O-SO2-NH-CO groups has been
easily prepared by reaction of highly fluorinated carboxylic acids with aroxysulfonyliso-
cyanates with excellent yields. The interfacial behavior of these N-acylsulfamate surfactants
in alkaline aqueous solutions was characterized through surface tension measurements and
CMC. The values obtained show that these compounds are new excellent nonionic surfac-
tants exhibiting high surface activity in the range of the best fluorinated nonionic surfactant,
already described in the literature.24
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