Sulfonated surfactants obtained from furfural

Article abstract of DOI:10.1039/c3gc00062a

Furfural obtained from pentose containing biomass such as hemicelluloses is subjected to photooxygenation. The resulting hydroxyfuranone obtained in high yields undergoes acetalization with fatty alcohols. Using NaHSO₃, surfactants are obtained by addition of a sulfonate group to α,β-unsaturated carboxyl or carbonyl compounds. Addition occurred either at the CC double bond (6) or at the aldehyde function (7). Compared to conventional surfactants of this type, the resulting compounds possess similar good detergent properties. In the case of compound family 6 and when compared to the corresponding alkylsulfate and alkylsulfonate surfactants, even lower critical micelle concentrations (CMC) are observed. Biodegradation of the new surfactants was determined according to the OECD Test guideline 301 F. Compounds of family 6 are biodegradable. Biodegradation of compounds of family 7 stopped after 10 days.

Full text of DOI:10.1039/c3gc00062a

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Sulfonated surfactants obtained from furfural
Abdoulaye Gassama,a Cédric Ernenwein,b Ali Youssef,a Mickaël Agach,b
Cite this: DOI: 10.1039/c3gc00062a
Emmanuel Riguet,a Siniša Marinković,*b Boris Estrineb and Norbert Hoffmann*a
Furfural obtained from pentose containing biomass such as hemicelluloses is subjected to photo-
oxygenation. The resulting hydroxyfuranone obtained in high yields undergoes acetalization with fatty
alcohols. Using NaHSO3, surfactants are obtained by addition of a sulfonate group to α,β-unsaturated
carboxyl or carbonyl compounds. Addition occurred either at the CvC double bond (6) or at the alde-
hyde function (7). Compared to conventional surfactants of this type, the resulting compounds possess
similar good detergent properties. In the case of compound family 6 and when compared to the corres-
ponding alkylsulfate and alkylsulfonate surfactants, even lower critical micelle concentrations (CMC) are
observed. Biodegradation of the new surfactants was determined according to the OECD Test guideline
301 F. Compounds of family 6 are biodegradable. Biodegradation of compounds of family 7 stopped
after 10 days.
Received 9th January 2013,
Accepted 9th April 2013
DOI: 10.1039/c3gc00062a
www.rsc.org/greenchem
surfactants possessing two hydrophobic moieties.15 We also
used the photochemically induced radical addition of tertiary
Introduction
The limited resources of fossil hydrocarbons on the one hand amines to the olefinic double bond as a key step.16,17 Such
and the search for new chemical compounds for various appli- photochemical reactions fulfil particularly well requirements
cations on the other focus the interest of chemists on biomass of sustainable chemistry.18,19 A combination of renewable
as a renewable feedstock for fine chemistry.1–5 In this context, resources and sustainable methods for synthesis opens up
carbohydrates play an important role.6 They represent about new prospects in this context. Hitherto, various strategies have
75% of the approximately 180 billion tons of biomass pro- been used to synthesize surfactants from renewable
duced each year by nature. Hemicelluloses and pentoses con- resources.20 In the present article, we focus on the synthesis of
stitute a class of carbohydrates which is now also intensively new families of surfactants carrying a sulfonate group as an
studied as a feedstock for fine chemistry.7
anionic hydrophilic moiety. The major advantage of sulfonates
Thus, furfural obtained from pentose containing biomass is their almost complete dissociation thus leaving a highly
is a valuable synthon for fine chemistry. Currently, about polar anion as the hydrophilic moiety.21–23
300 000 tons per year8 are produced mainly by cyclodehydra-
tion of pentoses.9–12 In the context of process optimisation,
various mechanisms of this dehydration have been
Results and discussion
Synthesis of sulfonate surfactants
reported.9,12–14 Many transformations of furfural into inter-
mediates for the chemical industry have been reported with
the aim to replace fossil based resources.4,6,7,10 In the context
We started our investigations with the photooxygenation of
furfural to 5-hydroxy-2[5H]-furanone 1 (Scheme 1). This reac-
tion is well known and is generally performed in high
of furfural chemistry, we are particularly interested in using
oxidation products of furfural such as furanones (α,β-unsatu-
yields.9,24–26 The transformation is also performed under mild
rated butyrolactones). Recently, we published transformations
reaction conditions with visible artificial or sun light and
of such compounds into zwitterionic surfactants. Michael
oxygen or air is used as an oxidant.19,27 The endoperoxide
addition and condensation with fatty amines and furanones
was applied to the synthesis of a new family of Gemini type
intermediate 2 is generated by addition of singlet oxygen.
Singlet oxygen is produced via photochemical sensitization.28
Due to the low excitation energy of oxygen, the sensitization
can also be performed with visible light using dyes as a sensi-
tizer. This oxygen species is highly polarizible and electro-
aInstitut de Chimie Moléculaire de Reims, UMR 7312 CNRS et Université de Reims
Champagne-Ardenne, Equipe de Photochimie, UFR Sciences, B.P. 1039, 51687 Reims,
France. E-mail: norbert.hoffmann@univ-reims.fr; Fax: +33 (0)3 26 91 31 66;
philic. It easily attacks olefinic double bonds. Generally, the
Tel: +33 (0)3 26 91 33 10
a
perepoxide intermediate is discussed.29
bAgro Industrie Recherches et Développements (ARD), Route de Bazancourt, 51110
Pomacle, France. E-mail: s.marinkovic@a-r-d.fr
formation of
Often, the formation of endoperoxides such as 2 in the
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Scheme 2 Addition of a sulfonate function.
Scheme 1 Synthesis of alkoxyfuranones.
Scheme 3 Addition of a sulfonate function to the α,β-unsaturated aldehyde 5c.
transformation of dienes is in competition with other typical
products from the photooxygenation.30 The perepoxide inter-
mediates may therefore also play a role in the formation of
endoperoxide 2. Since the reaction is carried out in alcohols as
a solvent such as methanol, the addition of a solvent molecule
to the aldehyde function of 2 induces a fragmentation and
hydroxyfuranone 1 and methylformiate are generated. In order
to add a hydrophobic moiety, compound 1 was transformed
with fatty alcohols 3a–c. Thus the 5-alkoxy-2[5H]-furanones 4a–c
were obtained in high yields in an acetalization reaction by
azeotropic destillation.16 This reaction was also performed
with toluene. Prolonged heating under these conditions leads
to the formation of the open form 5a–c possessing an α,β-un-
saturated aldehyde function. In the present study, only com-
pound 5c was isolated while 5a,b were precipitated as bisulfite
adducts (see below).
compounds 5a–c with NaHSO3. Indeed, when compound 5c
was heated for a long period (5 days) in the presence of a
larger excess of NaHSO3 (6 equiv.), compound 8 was formed in
moderate yields (Scheme 3). Obviously, the transformation of
5c into 7c is fast but reversible. In order to maintain a
sufficient stationary concentration of 5c, heating at higher
temperature (80 °C) is necessary (compare Scheme 2). The 1,4-
addition leading to 8 is slower and needs a larger excess of
NaHSO3. This excess is also necessary to compensate the low
stationary concentration of 5c. Further aldehyde chemical
modification in 8 could lead to new families of surfactants
with particular properties.
Determination of physicochemical characteristics
Compounds 4a–c and 5a–c are hydrophobic. In order to
attach a hydrophilic moiety and to confer on them surfactant
properties, we transformed these compounds with NaHSO3
Surfactant properties such as surface tension reduction,
micelles formation (determination of the critical micelle con-
centration (CMC)) or adsorption at the liquid–gas interface
have been studied for compound family 6a,b,c. This study has
been carried out as previously reported for other furfural
derived surfactants.15,16 The results are reported in Table 1.
Due to the Krafft point of the compound 6c, physicochemical
properties were determined at 50 °C. At this point, it has to be
noted that the stability in aqueous solution of compound 6c
has been investigated using NMR spectroscopy. After heating
the solution at 50 °C for one hour, no product degradation was
detected.
−
(Scheme 2). In a Michael reaction the HSO3 was added to the
α,β-unsaturated lactone.22,31,32 Thus, compounds 6a–c have
been obtained in good yields. When the open ring derivatives
5a–b were treated under similar conditions, 1,2-addition of the
−
HSO3 anion to the aldehyde function of the α,β-unsaturated
carbonyl compound occurred and the resulting hydroxyl sulfo-
nates 7a–c were isolated in good yields. Such compounds are
generally obtained as a precipitate. In contrast to the previous
1,4-addition of bisulfite, the latter reaction has frequently been
reported in the literature.33
This latter reaction is reversible and in the case of trans-
formations of α,β-unsaturated aldehydes, the concomitant 1,4-
addition (Michael reaction) was studied.32 We wonder whether
this competition plays a role in the transformations of
The surfactant concentration at which micellization starts
is known as the critical micelle concentration. This value is
one of the most important properties of surfactant solutions,
because the micelle formation affects both the surface or
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Table 1 Surfactant properties of furfural derived anionic sulfonates 6a,b,c (Scheme 2) at pH 7
Entry
Compound
n
T [°C]
CMC [mM]
pC20
γCMC [mN m−1
]
A [Å2]
Krafft point [°C]
1
2
3
6a
6b
6c
6
8
10
25
25
50
28.72
5.81
0.81
2.562
3.224
3.935
29.1
29.0
28.1
89.0
80.6
65.8
Nd
31
43–45
interfacial tension reduction and the properties of the surfac-
Although the value of 0.388 found for B is slightly high, it is
tants such as the solubilization and detergency. The CMC was still in accordance with the general rule (B = log 2) for the
detected by the break of the curve of the surface tension with ionic surfactants. Moreover, the value of 1.59 found for A is
the concentration of the surfactant in solution, measured by also in accordance with the value obtained for other anionic
the Wilhelmy plate method.34 The efficiency of a surfactant in surfactants.21
reducing surface tension is measured by the C20 value, the sur-
In the same manner, it was shown that the efficiency factor
factant concentration needed to reduce the surface tension by pC20 is a linear function of the number of carbon atoms in a
20 mN m−1, and the CMC values. The pC20 (negative loga- straight-chain hydrophobic group, increasing as the number of
rithm), rather than the concentration itself is most often used carbon atoms increases (Fig. 2).21
since these values can more easily be related to the corre-
It is important to point out the high effectiveness of this
sponding standard free enthalpy ΔG0 needed for the transfer family of surfactants as interesting surface tension reductions
of the surfactant from the bulk liquid phase to the interphase. were observed at the CMC in the same range as those observed
The effectiveness is also measured by the surface tension for conventional anionic surfactants.21 These results indicate
reached at the CMC.21 The Gibbs equation (eqn (1)) shows an efficient adsorption at the interface. The area per molecule
the relationship between the surface excess (Γ in mol m−2
and the slope of the plot of the surface tension (γ in N m−1
)
)
at surface saturation decreases with increasing length of the
hydrophobic chain of the surfactants and is particularly pro-
versus the logarithm of the surfactant concentration. In our nounced for the compound 6c. The physicochemical character-
case, the ionic surfactant in the absence of any other solutes istics of compounds 6a,b,c were compared to anionic
in the solution was studied. Then a multiplying factor 2 in the surfactants such as sodium alkylsulfate, sodium alkylsulfonate
denominator was added to the Gibbs equation,21
and sodium alkylbenzenesulfonate.21 Table 2 describes the
properties of these conventional surfactants. First, we observe
that compounds 6a,b,c have lower CMC than the correspond-
ing alkylsulfate and alkylsulfonate surfactants (Table 1, entry 1
and Table 2, entries 1 and 6; Table 1, entry 2 and Table 2
entries 2 and 7; Table 1 entry 3 and Table 2 entries 3 and 8)
confirming that the lactone ring behaves as a part of the
hydrophobic tail. Indeed, taking into consideration the four
additional carbons of the lactone ring, the CMC values
measured for compounds 6a,b,c were in the same range than
the values of the corresponding alkylsulfate and alkylsulfonate
surfactants (Table 1, entry 1 and Table 2, entries 3 and 8;
Table 1, entry 2 and Table 2 entries 4 and 11; Table 1 entry 3
and Table 2 entries 5 and 12). Despite the presence of oxygen
atoms, we conclude that the lactone ring is more hydrophobic
ꢀ
ꢁ
1
dγ
Γ ¼ ꢀ
ð1Þ
T
2RT d ln C
The reciprocal of this value gives the surface area occupied by
a mole of adsorbed molecules. Division by Avogadro’s number
converts this into the area per molecule at the interface.
As expected, the CMC decreases 102 times with increasing
the length of the hydrophobic chain of the surfactants by
4 methylene groups. We have also validated that this family of
surfactants follows the well known empirical equation
observed by Klevens (eqn (2)) between the log CMC and the
number of carbon atoms n in the hydrophobic chain (Fig. 1).35
log CMC ¼ A ꢀ Bn
ð2Þ
Fig. 1 Log(CMC) as a function of the number of carbon atoms in the hydro-
Fig. 2 pC20 as a function of the number of carbon atoms in the hydrophobic
phobic chain.
chain.
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Table 2 Physicochemical properties of conventional anionic surfactants
Entry
Family
Molecular structure
C8H17SO3Na
Temperature [°C]
CMC [mM]
pC20
Γm [mol cm−2 10−10
]
A [Å2]
1
2
Sodium alkylsulfonate
40
25
40
25
40
40
50
40
27
40
25
40
25
25
25
40
40
25
35
50
70
60
70
160
43
40
12.4
11.4
2.5
0.7
140
—
—
—
—
52
54
57
60
—
—
—
57
—
53
—
57
63
56
—
—
55
—
—
43
—
45
C10H21SO3Na
1.69
1.66
2.36
2.33
—
—
—
1.89
—
2.51
—
2.75
2.92
3.1
—
3.70
—
—
—
2.53
—
3.10
3.22
3.05
2.93
2.73
—
—
—
2.9
—
3.16
—
2.92
2.62
3.0
—
—
3.0
—
—
3.9
—
3
C12H25SO3Na
4
5
6
7
C14H29SO3Na
C16H33SO3Na
C8H17SO4Na
C10H21SO4Na
Sodium alkylsulfate
33
8
C12H25SO4Na
8.2
8.6
3.9
2.9
2.1
2.2
0.58
—
15
3.1
—
1.2
—
9
10
11
C12H25(OC2H4)1SO4Na
C12H25(OC2H4)2SO4Na
C14H29SO4Na
12
13
C16H33SO4Na
p-C8H17C6H4SO3Na
Sodium alkylbenzene sulfonate
14
15
p-C10H21C6H4SO3Na
p-C12H25C6H4SO3Na
3.7
than the corresponding sulfated ethoxylates (Table 1, entry 3 close to those observed for a similar polar head surfactant 6b
and Table 2, entries 5, 8, 9, 10 and 12). Moreover, we noticed that was built up with the same hydrophobic chain. However,
that CMC of compounds 6a,b,c were in the same range as the we observed a striking difference between the two molecules
values of alkylbenzenesulfonate with the same number of as 7b possesses an area per molecule of 182 Å2. This probably
carbon atoms in the hydrophobic chain (Table 1, entry 1 and means that 7b is spreading out while absorbing at the
Table 2, entry 13; Table 1, entry 2 and Table 2, entry 14; interface.
Table 1, entry 3 and Table 2, entry 15).
We also studied physicochemical behavior of compounds of
Biodegradability of the surfactants
family 7. Unfortunately, the more hydrophobic one 7c was not
Biodegradability is an important item in the field of surfac-
stable in warm water. The reversible addition of the bisulfite
tants and standards have been defined by international insti-
tutions such as the OECD. The biodegradation of our
surfactants was determined according to the OECD Test guide-
function to aldehyde may explain the weak chemical stability
of compound 7c. Thus we only focused our investigation on
compounds 7a and 7b (Fig. 3).
line 301 F36 which is particularly demanding. This test uses a
It is first important to point out that in the range of concen-
manometric respirometer to follow the consumption of oxygen
trations studied here, the shorter tailed surfactant did not
during 28 days in a closed flask containing 30 to 60 mg l−1 of
the test substance and inoculums coming from a sewage
aggregate. This behavior is typical for hydrotrope surfactants.
For compound 7b, we observed a CMC of 5.76 mM and a
plant. The percentage of biodegradation is obtained by divid-
surface tension at CMC of 28.8 mN m−1. These values are very
ing the resulting biological oxygen demand (BOD) by the
theoretical oxygen demand (ThOD) of the test substance. As in
one of our previous studies15 on zwitterionic compounds,
three replicates were performed for each surfactant. The
results are presented in Table 3. According to the E.U. directive
(Commission Regulation (EC) No. 907/2006 of 20 June 2006),37
surfactants of the family 6 are considered as biodegradable as
degradation reaches 60% after 28 days. Thus, all compounds
6a,b,c are classified as biodegradable. We notice that surfac-
tants of the family 6 show better biodegradation than conven-
tional linear alkylbenzene sulfonate (LAS) (Table 3, entry 7).7,38
Significant biodegradation is already observed after 10 days.
Moreover, the short latency during the biodegradation of com-
pounds 6a,b,c compared to conventional surfactants may indi-
cate a low toxicity of these molecules. For compounds of
family 7, the biodegradation remained below the 60% level at
Fig. 3 Evolution of surface tension as a function of ln(C) for compounds 7a
and 7b.
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Table 3 Biodegradation according to the OECD Test guideline 301 F36
Entry
Surfactants
n
Biodegradation after 28 days [%]
Biodegradation after 10 days [%]
Latency (<10%) [days]
1
2
3
4
5
6
7
6a
6b
6c
7a
7b
7c
6
8
10
6
8
10
12
74
78
67
37.5
50
26
60
49
56
52
33
41
26
20
2
2
2
2
2
3
8
LAS
28 days. It is also important to point out that for 7c, the biode- Synthesis of alkoxyfuranones 4a–c16
gradation process seems to stop after 10 days. We actually
Compound 4a. A solution of 5-hydroxy-2[5H]-furanone 1
(10 g, 0.1 mol), 1-octanol 3a (13.6 g, 0.105 mol) and p-toluene-
sulfonic acid (570 mg, 3 mol%) in chloroform (50 ml) was
heated under reflux for 1 h. After evaporation of the solvent,
the residue was neutralized with a saturated Na2CO3 solution.
The alkoxyfuranone 4a was extracted with CH2Cl2. The organic
solution was dried with MgSO4. After evaporation of the
solvent, the residue was distilled under high vacuum. Yield:
15.7 g (74%).
question the potential antimicrobial effect of these com-
pounds. The unsaturated bond of the polar head or the
possible toxicity of metabolites generated during the biodegra-
dation might explain the low biodegradation level.
Furthermore, α,β-unsaturated aldehydes are formed during
degradation. These compounds formed by the release of
HSO3− anions may be toxic (see above).
1H NMR (250 MHz, CDCl3): δ = 7.18 (dd, J = 4.6, 1.5 Hz,
1H), 6.19 (dd, J = 4.5, 1.4 Hz, 1H), 5.89 (d, J = 1.2 Hz, 1H),
2.59–3.88 (m, 2H), 1.55–1.66 (m, 2H), 1.24 (m, 10H), 0.83 (dt,
J = 4.8, 6.8 Hz, 3H) ppm; 13C NMR (62 MHz, CDCl3): δ =
170.66, 150.50, 125.03, 103.49, 70.74, 31.84, 29.53, 29.34,
29.25, 25.93, 22.70, 14.15 ppm.
Compound 4b. This compound was synthesized following
the same procedure as for compound 4a at the same molar
scale. Yield: 17.1 g (71%).
Conclusions
Starting from furfural obtained from pentose containing
biomass, we have developed a synthetic approach to new
families of sulfonate containing surfactants. The ecologically
friendly photooxygenation of furfural with air is used as a key
step. In particular, the introduction of the sulfonate group is
carried out under mild conditions, either by Michael addition
of HSO3− to α,β-unsaturated lactones or by addition to an alde-
hyde function. The resulting compounds of family 6 possess
interesting surfactant activities when compared to convention-
al compounds such alkyl sulfates or alkyl sulfonates. These
compounds are also biodegradable.
1H NMR (250 MHz, CDCl3): δ = 7.20 (d, J = 5.6 Hz, 1H), 6.22
(d, J = 5.6 Hz, 1H), 5.91 (s, 1H), 3.85 (ddd, J = 8.8, 6.6, 2.2 Hz,
1H), 3.65 (ddd, J = 9.1, 6.8, 2.3 Hz, 1H), 1.61 (m, 2H), 1.25 (m,
14 H), 0.86 (dt, J = 4.8, 6.8 Hz, 3H) ppm; 13C NMR (62 MHz,
CDCl3): δ = 170.61, 150.49, 124.98, 103.47, 70.68, 31.92, 29.56,
29.51 (2×), 29.34 (2×), 25.90, 22.71, 14.14 ppm.
Compound 4c. This compound was synthesized following
the same procedure as for compound 4a at the same molar
scale. Yield: 20.91 g (78%).
In perspective, avoiding purification by chromatography or
extraction with halogenated solvents will increase the sustain-
ability of the synthesis.
1H NMR (250 MHz, CDCl3): δ = 7.19 (dd, J = 5.7, 0.9 Hz,
1H), 6.21 (dd, J = 5.7, 1.0 Hz, 1H), 5.91 (d, J = 1.0 Hz, 1H), 3.84
(ddd, J = 9.2, 6.6, 2.5 Hz, 1H), 3.65 (ddd, J = 9.1, 6.7, 2.4 Hz,
1H), 1.62 (qint, J = 6.7 Hz, 2H), 1.24 (m, 18H), 0.86 (dt, J = 4.8,
6.1 Hz, 3H) ppm; 13C NMR (62 MHz, CDCl3): δ = 170.62,
150.48, 125.01, 103.47, 70.71, 31.97, 29.69 (2×), 29.63 (2×),
29.58, 29.52, 29.38, 25.92, 22.74, 14.17 ppm.
Experimental part
General
NMR spectra were recorded with a Bruker AC 250 (250 MHz for
1H and 62 MHz for 13C). Chemical shifts are given in ppm rela-
tively to TMS using residual solvent signals as secondary refer-
ences. IR spectra were recorded on a Nicolet AVATAR 320 FT-IR.
MS and HRMS were obtained on a hybrid tandem quadrupole/
time-of-flight (Q-TOF) instrument, equipped with a pneumati-
cally assisted electrospray (Z-spray) ion source (Micromass,
Synthesis of α,β-unsaturated aldehydes 5a–c
Manchester, UK) operated in positive mode (EV = 30 V, 80 °C, The α,β-unsaturated aldehydes 5a–c were obtained when the
flow of injection 5 ml min−1). Atom absorption spectroscopy acetalization of 5-hydroxy-2[5H]-furanone 1 was performed in
was carried out with a Variant Liberty 2 (ICPAES). Preparative toluene instead of chloroform and upon prolonged heating
chromatography was carried out with silica gel 60A from Carlo (compare Scheme 1). The aldehydes were not isolated and the
Erba Reactifs-SDS. TLC was carried out with Kieselgel 60F254 yields were determined by spectroscopy. They have been trans-
plates from Merck. 5-Hydroxy-2[5H]-furanone 3 has been syn- formed in situ into the bisulfite adducts 7a–c (see below,
thesized as previously described.26
compare Scheme 2).
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Compound 5c was also prepared separately. A solution of
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Compound 6c. A solution of alkoxyfuranone 4c (4.6 g,
5-hydroxy-2[5H]-furanone 1 (15 g, 0.15 mol), 1-dodecanol 3c 17.2 mmol) in isopropanol (77 ml) is added to a solution of
(29.5 g, 0.158 mol) and p-toluenesulfonic acid (285 mg, 1 mol NaHSO3 (3.58 g, 34.4 mmol) in water (57 ml). The resulting
%) in chloroform (70 ml) was heated under reflux for 1 h mixture was heated at 50 °C for 28 h. After evaporation of the
using a Dean–Stark distilling trap. After evaporation of the solvent, the residue was subjected to flash chromatography
solvent, the residue was neutralized with a saturated Na2CO3 (eluent: ethyl acetate–methanol 90/10). Yield: 4.5 g (71%);
solution. The alkoxyfuranone 3a was extracted with CH2Cl2. mp. 237–238 °C.
The organic solution was dried with MgSO4. After evaporation
of the solvent, the residue was distilled under high vacuum. J = 9.4, 6.3, 3.0 Hz, 2H), 3.10 (dd, J = 9.5, 0.8 Hz, 1H), 2.90 (dd,
1H NMR (250 MHz, [d6]DMSO): δ = 5.52 (s, 1H), 3.58 (ddd,
Yield: 14.5 g (36%); mp. 29–30 °C.
J = 18.4, 9.5 Hz, 1H), 2.49 (dd, J = 18.4, 2.5 Hz, 1H), 1.50 (m,
1H NMR (250 MHz, CDCl3): δ = 9.76 (d, J = 7.5 Hz, 1H), 6.85 2H), 1.23 (m, 16H), 0.85 (t, J = 6.7 Hz, 3H) ppm; 13C NMR
(dd, J = 15.9, 7.5 Hz, 1H), 6.71 (d, J = 15.9 Hz, 1H), 4.22 (t, J = (62 MHz, [d6]DMSO): δ = 175.43, 105.07, 68.85, 59.21, 31.32,
6.6 Hz, 2H), 1.68 (quin, J = 6.4 Hz, 2H), 1.25 (m, 18H), 0.86 (dt, 30.41, 29.03 (4×), 28.95, 28.74 (2×), 25.43, 22.12, 13.96 ppm; IR
J = 5.4, 6.7 Hz, 3H) ppm; 13C NMR (62 MHz, CDCl3): δ = (KBr): ν = 3593, 3455, 3007, 2955, 2918, 2851, 1769, 1636 cm−1
;
192.63, 165.02, 140.41, 139.61, 66.03, 32.03, 29.74 (2×), 29.67, Elemental analysis: calcd (%) for C16H29NaO6S (372.45):
29.61, 29.46, 29.32, 28.59, 25.98, 22.81, 14.24 ppm; IR (film): C 51.60, H 7.85, S 9.61; found: C 49.56, H 7.96, S 8.95;
ν = 2957, 2926, 2856, 2732, 1730, 1703 cm−1; Elemental analy- TOFMSES− [M − Na+] = 349.1684 (calcd 349.1685).
sis: calcd (%) for C16H28O3 (268.20): C 71.60, H 10.52; found: C
Synthesis of hydroxysulfonates 7a–c
71.40, H 10.66; TOFMSES+ [M + Na+] = 291.1936 (calcd
291.1936).
Compound 7a. A mixture of ethyl acetate (38 ml), ethanol
(23 ml), water (7.5 ml), NaHSO3 (5.0 g, 47.8 mmol) and 5a/4a
in a ratio of 4 : 1 (11.34 g, 53.5 mmol) was heated to 40 °C for
Synthesis of sulfonates 6a–c
Compound 6a. A solution of alkoxyfuranone 4a (14.8 g, 2 h. The mixture was filtered and the solid was washed with
70 mmol) in isopropanol (310 ml) is added to a solution of ethanol and dried at air. Yield 9.5 g (70%) Compound 4a
NaHSO3 (14.5 g, 140 mmol) in water (230 ml). The resulting (2.2 g) was recovered from the liquid phase.
mixture was heated at 50 °C for 28 h. After evaporation of the
1H NMR (250 MHz, [d6]DMSO): δ = 6.83 (dd, J = 15.9, 5.1
solvent, the residue was subjected to flash chromatography Hz, 1H), 5.83 (m, 2H), 4.51 (s, broaden, 1H), 3.87 (t, J = 6.8 Hz,
(eluent: ethyl acetate–methanol 90/10). Yield: 19.53 g (88%); 2H), 0.81 (m, 12H), 0.65 (t, J = 6.9 Hz, 3H) ppm; 13C NMR
mp. 236–237 °C.
(62 MHz, [d6]DMSO): δ = 166.21, 146.51, 120.61, 83.18, 64.19,
1H NMR (250 MHz, [d6]DMSO): δ = 5.53 (s, 1H), 3.58 (ddd, 31.61, 29.01 (2×), 28.57, 25.82, 22.47, 14.33 ppm; IR (KBr): ν =
J = 9.6, 6.5, 3.0 Hz, 2H), 3.11 (dd, J = 9.3, 1.3 Hz, 1H), 2.90 (dd, 3513, 2957, 2923, 2853, 1716, 1176 cm−1; Elemental analysis:
J = 18.4, 9.5 Hz, 1H), 2.50 (dd, J = 18.2, 2.4 Hz, 1H), 1.51 (m, calcd (%) for C12H21NaO6S (316.35): C 45.56, H 6.69, S 10.14;
2H), 1.24 (m, 10H), 0.84 (dt, J = 5.6, 6.7 Hz, 3H) ppm; 13C NMR found: C 32.28, H 4.80, S 15.86 (the sample contained NaHSO3
(62 MHz, [d6]DMSO): δ = 175.43, 105.06, 68.85, 59.21, 31.25, which was added in excess to the reaction mixture); TOFMSES+
30.40, 28.94, 28.73, 28.66, 25.43, 22.10, 13.98 ppm; IR (KBr): [M + Na+] = 339.08.
ν = 3598, 3461, 3010, 2956, 2956, 2854, 1768, 1636 cm−1
;
Compound 7b. A mixture of ethyl acetate (46 ml), ethanol
Elemental analysis: calcd (%) for C12H21NaO6S (316.35): (27 ml), water (9 ml), NaHSO3 (6.0 g, 57.4 mmol) and 5b/4b in
C 45.56, H 6.69, S 10.14; found: C 44.25, H 6.86, S 10.58; a ratio of 6 : 1 (15.42 g, 64.2 mmol) was heated to 40 °C for
TOFMSES− [M − Na+] = 293.1049 (calcd 293.59).
2.5 h. The mixture was filtered and the solid was washed with
Compound 6b. A solution of alkoxyfuranone 4b (15.3 g, ethanol and dried at air. Yield 12.7 g (71%). Compound 4b
64 mmol) in isopropanol (285 ml) is added to a solution of (2.0 g) was recovered from the liquid phase.
NaHSO3 (13.3 g, 127 mmol) in water (210 ml). The resulting
1H NMR (250 MHz, [d6]DMSO): δ = 7.08 (dd, J = 15.6, 5.1
mixture was heated at 50 °C for 28 h. After evaporation of the Hz, 1H), 6.19 (m, 2H), 4.73 (d, broaden, J = 5.1 Hz, 1H), 4.10
solvent, the residue was subjected to flash chromatography (t, J = 6.7 Hz, 2H), 1.12 (m, 16H), 0.89 (t, J = 6.7 Hz, 3H) ppm;
(eluent: ethyl acetate–methanol 90/10). Yield: 13.77 g (63%); 13C NMR (62 MHz, [d6]DMSO): δ = 166.22, 146.01, 120.54,
mp. 236–237 °C.
83.21, 64.18, 31.67, 29.34 (2×), 29.07, 28.57, 25.81, 22.49,
1H NMR (250 MHz, [d6]DMSO): δ = 5.52 (s, 1H), 3.58 (ddd, 14.34 ppm; IR (KBr): ν = 3449, 2957, 2922, 2850, 1717,
J = 9.6, 6.6, 3.0 Hz, 2H), 3.11 (dd, J = 9.4, 1.1 Hz, 1H), 2.90 (dd, 1175 cm−1; Elemental analysis: calcd (%) for C14H25NaO6S
J = 18.4, 9.5 Hz, 1H), 2.50 (dd, J = 18.1, 2.4 Hz, 1H), 1.51 (m, (344.40): C 48.82, H 7.32, S 9.31; found: C 37.31, H 5.30,
2H), 1.24 (m, 14H), 0.85 (t, J = 6.7 Hz, 3H) ppm; 13C NMR S 13.93 (the sample contained NaHSO3 which was added in
(62 MHz, [d6]DMSO): δ = 175.43, 105.06, 68.85, 59.21, 31.32, excess to the reaction mixture); TOFMSES+ [M + Na+] = 367.11.
30.40, 28.99 (2×), 28.77 (2×), 28.73, 25.44, 22.13, 13.99 ppm; IR
(KBr): ν = 3597, 3460, 3011, 2955, 2922, 2852, 1768, 1636 cm−1
Compound 7c. A mixture of ethyl acetate (32 ml), ethanol
(19 ml), water (6 ml), NaHSO3 (4.16 g, 40.0 mmol) and 5c/4c in
;
Elemental analysis: calcd (%) for C14H25NaO6S (344.40): a ratio of 4 : 3 (12.0 g, 44.7 mmol) was heated to 40 °C for
C 48.82, H 7.32, S 9.31; found: C 46.79, H 7.15, S 8.91; 2.5 h. The mixture was filtered and the solid was washed with
TOFMSES− [M − Na+] = 321.1372 (calcd 321.1370).
ethanol and dried at air. Yield 5.25 g (94%). Compound 4b
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2C þ 0:5ðH ꢀ Cl ꢀ 3NÞ þ 3S þ 2:5P þ 0:5Na ꢀ O
(5.6 g) and dodecanol 3c (2.4 g) were recovered from the liquid
phase after evaporation and flash chromatography (eluent:
ethyl acetate–ethanol 3/7).
ThOD ¼
ꢁ 16
ð3Þ
MW
1H NMR (250 MHz, [d6]DMSO): δ = 7.30 (dd, J = 15.8, 5.1
Hz, 1H), 6.40 (m, 2H), 4.94 (s, broaden, 1H), 4.32 (t, J = 6.0 Hz,
2H), 1.32 (m, 20H), 1.10 (t, J = 6.3 Hz, 3H) ppm; 13C NMR
(62 MHz, [d6]DMSO): δ = 163.86, 144.25, 118.19, 80.87, 61.82,
29.35, 26.06 (3×), 26.77 (2×), 26.73, 26.24, 23.47, 20.15,
11.99 ppm; IR (KBr): ν = 3499, 2956, 2921, 2849, 1717,
1175 cm−1; Elemental analysis: calcd (%) for C16H29NaO6S
(372.45): C 51.60, H 7.85, S 9.61; found: C 40.71, H 6.07,
S 13.11; (the sample contained NaHSO3 which was added
in excess to the reaction mixture); TOFMSES− [M + Na+] =
395.1484 (calcd 395.1481).
The biological oxygen consumption (BOC) was determined
by means of an IBUK respirometer, which identifies the
oxygen consumption all along the degradation process. Exper-
iments were conducted at 20 °C over a period of 28 days in a
medium containing various mineral substances (sodium and
potassium phosphates, ammonium, calcium and iron chlo-
rides, magnesium sulfate) and bacteria collected from a local
wastewater treatment plant. The starting pH was 7.4. The per-
centage of biodegradation or biodegradability (B [%]) values is
obtained according to the subsequent equation (eqn (4)):
BOC
B½%ꢂ ¼
ꢁ 100
ð4Þ
ThOD
Synthesis of sulfonate 8
The reliability of the experiment depends on 3 parameters.
The first one is the degradation of the reference molecule
(sodium acetate). Its degradation has to reach 60% after 14
days. Secondly, the mineral medium has to exhibit oxygen con-
A solution of α,β-unsaturated aldehyde 5c (268 mg, 1.0 mmol)
in isopropanol (4.5 ml) is added to a solution of NaHSO3
(624 mg, 6.0 mmol) in water (3 ml). The resulting mixture was
heated at 80 °C for 5 days. After evaporation of the solvent, the
residue was subjected to flash chromatography (eluent: ethyl
acetate–methanol 95/5). Yield: 100 mg (27%); mp. 228–229 °C.
1H NMR (250 MHz, [d6]DMSO): δ = 9.72 (s, 1H), 4.40 (m,
1H), 4.17 (m, 2H), 3.34 (m, 2H), 1.61 (m, 2H), 1.25 (m, 18H),
0.86 (dt, J = 5.5, 6.5 Hz, 3H) ppm; 13C NMR (62 MHz, [d6]-
DMSO): δ = 201.14, 168.52, 64.20, 59.53, 43.24, 31.37, 29.09
(3×), 28.79 (2×), 28.13, 25.37, 25.03, 22.18, 13.99 ppm; IR (KBr):
ν = 3437, 2958, 2924, 2853, 1724, 1642 cm−1; Elemental ana-
lysis: calcd (%) for C16H29NaO6S (372.45): C 51.60, H 7.85,
S 9.61; found: C 51.46, H 7.54, S 9.23; TOFMSES− [M + Na+] =
395.1488 (calcd 395.1481).
sumption below 60 mg l−1 (ideally between 20 and 30 mg l−1
)
after 28 days. Finally, after 28 days the pH should be between 6
and 8.5.
Acknowledgements
We are grateful to ADEME/AGRICE (Project 0601C0022) and to
the Région Champagne-Ardenne (Project Agrosolvants) for
financial support.
Physicochemical characterizations
Notes and references
Solution preparation and materials. All solutions were pre-
pared using water that was completely deionized (Millipore)
and filtered (0.22 mm). Hydrochloric acid, 0.1 N in solution,
was supplied by VWR (France) and sodium hydroxide (0.1 N)
by Labosi (France).
Surface tension, CMC and area/molecule. The plot of the
surface tensions (γ) against ln C of aqueous surfactant solu-
tions was recorded by a Wilhelmy-type surface balance (Krüss
K100MK2) equipped with a dosimeter (700 dosino, Metrohm).
Measurements were conducted at 25 0.5 °C.
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