Synthesis and properties of sodium mono-alkylamide phthalate surfactants

Article abstract of DOI:10.1007/s11743-011-1325-9

The synthesis of a series of sodium monoalkylamide phthalate surfactants is described, and the surface activity properties of the surfactants are reported. The mono-alkylamide phthalic acids were synthesized by amidation using primary aliphatic amines (lauryl, myristyl, cetyl) and phthalic anhydride as starting material. They were structurally characterized by IR, ¹H NMR and MS. The sodium mono-alkylamide phthalate surfactants were prepared by neutralization of the precursor acids with sodium hydroxide. They reduced the surface tension of water to 30-38 mN m^-1 at concentration levels of 10^-4 mol L^-1. AOCS 2012.

Full text of DOI:10.1007/s11743-011-1325-9

J Surfact Deterg (2012) 15:445–448
DOI 10.1007/s11743-011-1325-9
ORIGINAL ARTICLE
Synthesis and Properties of Sodium Mono-Alkylamide Phthalate
Surfactants
•
Fu Han Bao-cai Xu Zhi-qiang Qu
•
•
•
Ya-wen Zhou Gui-ju Zhang
Received: 14 October 2011 / Accepted: 22 December 2011 / Published online: 6 January 2012
Ó AOCS 2012
Abstract The synthesis of a series of sodium mono-
alkylamide phthalate surfactants is described, and the sur-
face activity properties of the surfactants are reported. The
mono-alkylamide phthalic acids were synthesized by ami-
dation using primary aliphatic amines (lauryl, myristyl,
cetyl) and phthalic anhydride as starting material. They
emulsifying capacity and foam capacity [1–9]. However,
the ester group in the molecular structure of the surfactants
hydrolyzes more easily at high temperature with an acid or
base that affects the performance of stability in their
application.
The stability could be improved by using an amide
group instead of an ester group. The sodium mono-al-
kylamide phthalate surfactants are useful in a variety of
technical applications, such as fastbreak emulsifiers in
personal care products, domestic fabric softening agents,
foodstuff emulsifiers, various domestic detergents and hard
surface cleaners, emulsifiers for Portland cement and
concrete, enhanced oil recovery additives, compatibilizers/
surfactants for polyurethane/isocyanurate foam systems,
wood pulping additives, and other similar uses. However, it
has been rarely reported [10].
1
were structurally characterized by IR, H NMR and MS.
The sodium mono-alkylamide phthalate surfactants were
prepared by neutralization of the precursor acids with
sodium hydroxide. They reduced the surface tension
of water to 30–38 mN m-1 at concentration levels of
10-4 mol L-1
.
Keywords Phthalate ꢀ Alkylamide ꢀ Synthesis ꢀ
Characterization
In this paper, we report the preparation of the sodium
mono-alkylamide phthalate surfactants and the study of the
surface activity of these compounds by measuring the
equilibrium surface tensions of the dilute aqueous solu-
tions. The parameters studied include CMC (critical
micelle concentration), cCMC (the surface tension at the
CMC), Cmax (the maximum surface excess concentration at
the air/water interface), asm (the minimum area per sur-
factant molecule at the air/water interface), DG (the stan-
dard free energy of micellization).
Introduction
It is well known that carboxylate surfactants possess good
properties and extensive uses. In recent years the sodium
monoester phthalate surfactants have attracted considerable
interest because of their many technical applications. The
sodium monoester phthalates are synthesized by etherifi-
cation using fatty alcohol and phthalic anhydride and
neutralization with sodium hydroxide. They have superior
surface properties such as low surface tension, strong
Experimental Procedures
Preparation of Sodium Mono-Alkylamide Phthalate
Surfactants
F. Han (&) ꢀ B. Xu (&) ꢀ Z. Qu ꢀ Y. Zhou ꢀ G. Zhang
School of Food and Chemical Engineering, Beijing Technology
and Business University, No. 11 Fucheng Road, Haidian District,
Beijing 100048, People’s Republic of China
Firstly, 16.3 g (0.11 mol) of phthalic anhydride, 0.04 g
(6.5 9 10-4 mol) of boracic acid (catalyst) and 100 mL
e-mail: hanricher@gmail.com
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J Surfact Deterg (2012) 15:445–448
dichloromethane (solvent) were introduced into a 500-mL
reaction vessel. Then 0.1 mol of the primary aliphatic
amine (dodecylamine, myristyl amine, cetylamine) dis-
solved in dichloromethane (40 mL) was added slowly
dropwise with rapid stirring at 35 °C. After the completion
of addition, stirring was continued for 15 min at 35 °C. The
crude product was cooled for 2–3 h and the white crystals
were precipitated. After being filtered under reduced pres-
sure, the crystals were recrystallized from dichloromethane
to give the mono-alkylamide phthalic acid with a yield of
81.8, 85.7 and 76.5%, a purity of 97.0, 98.0 and 98.5%,
respectively (Agilent 1200 high-performance liquid chro-
matography). The structures of the compounds were con-
firmed by IR, 1H NMR and MS. An equal molar quantity of
NaOH solution was added to neutralize the mono-alkyla-
mide phthalic acid and the corresponding sodium salts were
obtained.
Results and Discussion
Preparation and Spectroscopic Characterization
of the Sodium Mono-Alkylamide Phthalate Surfactants
The general formula and process of the sodium mono-
alkylamide phthalate surfactants is shown in Scheme 1.
Herein, the mono-alkylamide phthalic acids were prepared
by amidation using the primary aliphatic amine and
phthalic anhydride as starting materials. The boracic acid
was added, which restrained the reaction of carboxylic acid
and primary aliphatic amine [11].
These compounds were structurally characterized by
their IR, 1H-NMR and MS spectra. In all cases, the spectra
acquired were consistent with the assigned structures of the
compounds.
Mono-Laurylamide Phthalic Acid
Characterization of the Sodium Mono-Alkylamide
Phthalate Surfactants and Surface Activity
Measurements
Yield, 81.8%; IR (KBr, t, cm-1): 3243 (N–H), 3075 (O–
H), 1709 (C = O in –COOH), 1642 (C = O in –NHCO–);
1H NMR (CDCl3, 300 MHz, d ppm): 0.87 (t, 3H, CH3),
1.25 (m, 18H, (CH2)9), 1.60 (m, 2H, CH2), 3.42 (t, 2H,
CH2), 6.40 (s, 1H, N–H), 7.52–8.06 (m, 4H, benzene ring),
9.60 (s, 1H, O–H); MS: m/z = 334 ([M ? 1]? of mono-
laurylamide phthalic acid).
The proton nuclear magnetic resonance (1H NMR) spectra
were acquired on a 300 MHz Bruker DRX-300 NMR
spectrometer. Samples were prepared in 5-mm OD tubes
with deuterated solvents CDCl3. Chemical shifts were
referenced to tetramethylsilane. The infrared (IR) spectra
were recorded on an Avater FT-IR Spectrometer Tensor
370 (KBr). The mass spectra (MS) were scanned on a
Quattro Micro instrument at 70 eV.
Mono-Myristyl Amide Phthalic Acid
Yield, 85.7%; IR (KBr, t, cm-1): 3308 (N–H), 3092 (O–
H), 1711 (C = O in –COOH), 1645 (C = O in –NHCO–);
1H NMR (CDCl3, 300 MHz, d ppm): 0.89 (t, 3H, CH3),
1.28 (m, 22H, (CH2)11), 1.57 (m, 2H, CH2), 3.38 (t, 2H,
CH2), 6.41 (s, 1H, N–H), 7.49–8.11 (m, 4H, benzene ring),
9.62 (s, 1H, O–H); MS: m/z = 362 ([M ? 1]? of mono-
myristyl amide phthalic acid).
Aqueous solution equilibrium surface tension values
were obtained by the Wilhelmy plate method using a
Dataphysics tensiometer, model DCAT11. The CMC value
was taken at the intersection of the linear portions of the
plots of the surface tension against the logarithm of the
surfactant concentration. Surfactant solutions were pre-
pared with distilled, de-ionized water. The sample tem-
perature was kept at 25 0.2 °C. Prior to measurements
on surfactant solutions, the surface tension of the distilled,
de-ionized water was measured. These water values were
in the range of 72.3 0.3 mN m-1. Samples were aged
15 min prior to the surface tension measurement.
Mono-Cetyl Amide Phthalic Acid
Yield, 76.5%; IR (KBr, t, cm-1): 3307 (N–H), 3099 (O–
H), 1710 (C = O in –COOH), 1647 (C = O in –NHCO–);
1H NMR (CDCl3, 300 MHz, d ppm): 0.88 (t, 3H, CH3),
O
O
O
O
O
OH
ONa
CH3(CH2)nNH2
NaOH
O
boracic acid,
dichloromethane
(CH2)nCH3
N
H
(CH2)nCH3
N
H
O
n=11,13,15
Scheme 1 The general process of the sodium mono-alkylamide phthalate surfactants
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447
1.26 (m, 26H, (CH2)13), 1.54 (m, 2H, CH2), 3.42 (t, 2H,
CH2), 6.48 (s, 1H, N–H), 7.48–8.00 (m, 4H, benzene ring),
10.11 (s, 1H, O–H); MS: m/z = 390 ([M ? 1]? of mono-
cetyl amide phthalic acid).
Inspection of the data in Table 1 shows that the sodium
mono-alkylamide phthalate surfactants significantly reduce
the surface tension of the solutions at low concentrations,
indicating that these molecules adsorb strongly at the air/
water surface and that they are highly effective aqueous
surfactants.
Equilibrium Surface Tension Measurements
The sodium mono-alkylamide phthalate surfactants
solutions were aged a week and their surface tensions at
different concentrations did not increase, indicating that
these surfactants are stable in water.
The equilibrium surface tensions of dilute aqueous solu-
tions of the sodium mono-alkylamide phthalate surfactants
were measured. The minimum surface tension (cCMC
)
values were acquired by analyzing the plateau region of the
plots. The critical micelle concentrations (CMC) of the
surfactants were acquired by analyzing the intersection
point of the plateau region and the steeply downward
sloping portion of the plots. The surface excess concen-
tration (Cmax) and the surface area per molecule (asm) were
acquired by analyzing the application of the Gibbs equation
to the steeply downward sloping section of the plots. A
summary of the data is compiled in Table 1 and in Fig. 1.
These surfactants all reduced the surface tension of water
to a minimum value of approximately 30–38 mN m-1 at
A dramatic change in slope of the surface tension versus
log surfactant concentration curves is generally interpreted
as the onset of surfactant aggregation into micelles in bulk
aqueous solution. By use of these criteria, inspection of
the curves in Fig. 1 suggests that the species of the
sodium mono-alkylamide phthalate surfactants are forming
micelles.
The sodium mono-alkylamide phthalate surfactants
show small CMC values. This indicates that these com-
pounds aggregate easily. Micellization takes place at a
concentration of about 10-4 mol L-1. The CMC values
decrease as the length of their carbon chains increase
because the hydrophobic interaction increase between the
surfactants as the length of their carbon chains increase.
The saturation adsorption values, Cmax, at the air/water
interface and the minimum area per surfactant molecule,
asm, at the air/water interface were obtained from the slope
of the surface tension versus log concentration plots
(Fig. 1) by using the approximate form of the Gibbs
adsorption isotherm equations (Eqs. 1 and 2).
concentrations of 10-4 mol L-1
.
Table 1 Aqueous surface activity of the sodium mono-alkylamide
phthalate surfactants
Compounds
Laurylamide
Myristyl amide Cetyl amide
CMC (mol L-1
)
7.25 9 10-4
38.19
3.24 9 10-4
36.06
3.11 9 10-4
cCMC (mN m-1
Cmax (lmol m-2
)
30.28
2.48
)
-1
1.10
1.19
2
asm (A molecule
)
150.96
139.54
66.96
˚
ꢀ
ꢁ
1
oc
DG (KJ mol-1
)
-27.88
-29.87
-29.98
Cmax ¼ ꢁ
ð1Þ
2:303nRT o log C
T
1016
ams
¼
ð2Þ
ð3Þ
75
70
65
60
55
50
45
40
35
30
25
NACmax
ꢀ
ꢁ
CMC
DG ¼ RT ln
55:5
where R = 8.3144 J mol-1K-1, NA = Avogadro’s num-
ber, Cmax is in 107 lmol m-2, and asm is in 102 nm2 mol-
ecule-1. In our solution, we were able to set n = 2 [12].
It was to be expected, and was confirmed by the
asm values in Table 1, that the surface area per molecule
(asm) (Eq. 2) of the sodium mono-alkylamide phthalate
surfactants at the interface decrease as the length of their
carbon chain increases. The surfactants at the interface can
be packed much tighter as the hydrophobic interaction
increase between the surfactants, and the asm would be
smaller.
10-6
10-5
10-4
10-3
10-2
10-1
Concentration (mol·L-1)
The free energy of micellization (DG) (Eq. 3) of the
sodium mono-alkylamide phthalate surfactants decreases
as the length of their carbon chain increases, indicating that
the processes are thermodynamically favored.
Fig. 1 Plots of equilibrium surface tensions of aqueous solutions of
the sodium mono-alkylamide phthalate surfactants versus log moles
concentration. Filled squares, laurylamide; Filled circles myristyl
amide; Filled triangles, cetyl amide
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J Surfact Deterg (2012) 15:445–448
Acknowledgments The financial support of the Natural Science
Foundation of China (No. 20976003 and 21176004) and the Research
Program of Beijing Municipal Commission of Education (No.
KM201010011003) are gratefully acknowledged.
12. Rosen M (2004) Surfactants and interfacial phenomena, 3rd edn.
John Wiley, New Jersey
Author Biographies
References
Fu Han received a B.Sc. in chemical engineering from the East China
University of Technology, an M.Sc. in physicochemistry from the
China Research Institute of Daily Chemical Industry, and a Ph.D. in
physicochemistry from Wuhan University. His research interests are
synthesis and properties of novel surfactants.
1. Zhou Y, Zhou W, Han F et al (2010) Synthesis and properties of
sodium mono-fatty alcohol phthalate. Fine Chem 27:429–432
2. Li S, Ding L (2010) Studies on synthesis and properties of sodium
phthalate of alkylpolyglycoside. Huaxue Shiji 32:921–924
3. Sun D, Hu P (2006) Synthesis of the sodium phthalate of mono
lauryl alcohol. J Southwest University Natl 32(1):93–95
4. Fan Y, Chen H, Huang Y et al (2005) Synthesis of sodium
monolauryl alcohol polyoxyethylene (9) ether o-phthalate. Adv
Fine Petrochem 6:38–41
Bao-cai Xu received a B.Sc. and an M.Sc. in applied chemistry from
the Beijing Technology and Business University, and a Ph.D. in
applied chemistry from the Beijing Institute of Technology. His
research interests are synthesis and properties of novel surfactants.
5. Liu Y, Pu W, Yang Y et al (2004) Study on a new anionic
surfactant PS in laboratory. Adv Fine Petrochem 5:31–34
6. Ge H, Wang J, Xu P et al (2002) Study on synthesis of sodium
mono lauryl alcohol polyoxyethylene(3) ether o-phthalate and its
surfactancy. Speciality Petrochem 19(2):4–6
7. Ishiguro Hitoshi (2001) Composition containing phthalic acid
monoester with good stability and flowability. World Patent
2,001,007,395
8. Tapnikar S, Bhagade S, Jadhav R (1997) Selective catalytic
esterification of phthalic anhydride to monoesters. Indian Patent
178,729
9. Lv T, Li W (1998) Study on synthesis of monoester surfactant of
alcohol ether. Speciality Petrochem 15:15–18
Zhi-qiang Qu received a B.Sc. and an M.Sc. in applied chemistry
from the Beijing Technology and Business University. His research
interests are synthesis and properties of surfactants.
Ya-wen Zhou received a B.Sc. in organic chemistry from the
Yaiyuan University of Technology and an M.Sc. in applied chemistry
from the China Research Institute of Daily Chemical Industry. Her
research interests are synthesis and properties of surfactants.
Gui-ju Zhang received a B.Sc. and an M.Sc. in applied chemistry
from the Beijing Technology and Business University, and a Ph.D. in
organic chemistry from the Technical Institute of Physics and
Chemistry of the Chinese Academy of Sciences. Her research
interests are synthesis and properties of surfactants.
10. Goze J, Bernhardt R, Hartlage J et al (1991) Surfactants com-
prising salts of phthalamic acid derivatives and their preparation
and use. World Patent 9,101,970
11. Dolzhenko A, Kolotova N, Kotegov V et al (2005) Synthesis and
biological activity of substituted tetrachlorophthalic acid
monoamides. Pharm Chem J 39:409–412
123