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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
123
Han, Fu
