Synthesis, characterization and properties of new lauryl amidopropyl trimethyl ammoniums

Article abstract of DOI:10.1007/s11743-012-1350-3

A new lauryl amidopropyl trimethyl ammonium methyl carbonate with the formula CH₃(CH₂)₁₀ CONH(CH₂) ₃N⁺(CH₃)₃CH₃CO ₃^- was synthesized via a high pressure process with tertiary amines and dimethyl carbonate, and its chemical structure was confirmed using ¹H-NMR spectra, mass spectral fragmentation, and FTIR spectroscopic analysis. In addition, several quaternary ammonium salts with new counterions X^- (X^-=HCO₃^-, HCOO ^-, CH₃COO^-, CH₃CH(OH)COO ^-) were also synthesized by the ion exchange reaction of methyl carbonate quaternary ammoniums with corresponding acids. The surface activities of these compounds were measured, including surface tension (γ), critical micelle concentration and minimum surface area (A_min) at 25 °C. Adsorption and micellization free energies of these quaternary ammonium salts in their solutions showed a good tendency towards adsorption at interfaces. The antimicrobial activities are reported for the first time against representative bacteria and fungi for lauryl amidopropyl trimethyl ammoniums. It was found that the antimicrobial potency was Gram-positive bacteria > fungi > Gram-negative bacteria. AOCS 2012.

Full text of DOI:10.1007/s11743-012-1350-3

J Surfact Deterg
DOI 10.1007/s11743-012-1350-3
ORIGINAL ARTICLE
Synthesis, Characterization and Properties of New Lauryl
Amidopropyl Trimethyl Ammoniums
•
Hongqin Liu Fei Li Baocai Xu Guiju Zhang
•
•
•
•
•
•
Fu Han Yawen Zhou Xiulan Xin Bo Xu
Received: 23 December 2011 / Accepted: 27 March 2012
Ó AOCS 2012
Abstract A new lauryl amidopropyl trimethyl ammo-
nium methyl carbonate with the formula CH3(CH2)10
was found that the antimicrobial potency was Gram-posi-
tive bacteria [ fungi [ Gram-negative bacteria.
CONH(CH2)3N?(CH3)3CH3CO3 was synthesized via a
-
high pressure process with tertiary amines and dimethyl
carbonate, and its chemical structure was confirmed using
1H-NMR spectra, mass spectral fragmentation, and FTIR
Keywords Lauryl amidopropyl trimethyl ammonium ꢀ
Dimethyl carbonate ꢀ Surface properties ꢀ
Antimicrobial activity
spectroscopic analysis. In addition, several quaternary
-
ammonium salts with new counterions X- (X-=HCO3
,
HCOO-, CH3COO-, CH3CH(OH)COO-) were also syn-
thesized by the ion exchange reaction of methyl carbonate
quaternary ammoniums with corresponding acids. The
surface activities of these compounds were measured,
including surface tension (c), critical micelle concentration
and minimum surface area (Amin) at 25 °C. Adsorption and
micellization free energies of these quaternary ammonium
salts in their solutions showed a good tendency towards
adsorption at interfaces. The antimicrobial activities are
reported for the first time against representative bacteria
and fungi for lauryl amidopropyl trimethyl ammoniums. It
Introduction
Quaternary ammonium salt cationic surfactants have
attracted considerable attention due to their wide range of
application, rapid development, and good prospects of
valuable research [1–4].
A conventional quaternary
ammonium salt cationic surfactant is always the long-chain
alkyl quaternary ammonium salt and has some toxicity and
poor biodegradability. In addition, the methylating agents
of the synthesis of these compounds are commonly methyl
chloride, methyl bromide, and dimethyl sulfate. They
inevitably contaminate the environment.
In order to obtain cationic surfactants with better
properties, while resolving toxicity and biodegradability,
scientists have done a lot of research [5–7]. Numerous
studies have confirmed that the water-soluble and biode-
gradability could be improved by adding new polar
groups such as an ether, ester, amide, polyoxyethylene
chain imidazoline ring and so on into the molecular
structure of a typical quaternary ammonium cationic
surfactant [8–12].
H. Liu ꢀ F. Li ꢀ B. Xu (&) ꢀ G. Zhang ꢀ F. Han ꢀ Y. Zhou ꢀ
X. Xin
Beijing Key Laboratory of Flavor Chemistry, School of Food
and Chemical Engineering, Beijing Higher Institution
Engineering Research Center of Food Additives and Ingredients,
Beijing Technology and Business University, No. 11 Fucheng
Road, Beijing 100048, People’s Republic of China
e-mail: xubaoc@btbu.edu.cn
In this paper, a new series of quaternary ammonium
salts containing amide groups were synthesized by use of
non-toxic green chemical material, i.e., dimethyl carbon-
ate. The surface activity and antimicrobial activity of these
quaternary ammonium salt compounds were studied.
B. Xu
College of Engineering, University of Illinois
at Urbana-Champaign, Urbana-Champaign,
IL 61801-3636, USA
123

J Surfact Deterg
Experimental Procedures
paper disk diffusion method. Initial screening for antibac-
terial and antifungal activity was performed by impreg-
nating 6-mm sterile filter paper disks with 10 mg/ml of
each substance and dried at 37 °C. Disks were distributed
on the surface of dried agar plates inoculated with the
microorganisms at approximately 106 cfu ml-1. Plates
were incubated at 37 °C for 24 h. Benzalkonium chloride
was used as a reference because it is a common antiseptic
agent. The presence of an absolute inhibition zone around
the disk was used as the diameter of inhibition zones.
Results are summarized in Table 2.
Synthesis of Lauryl Amidopropyl Trimethyl
(Abridged as LAPTM) Ammonium Methyl Carbonate
(LAPTMA-CH3CO3)
Dimethyl carbonate (0.2 mol), lauryl amidopropyl dime-
thyl amine (0.1 mol) and methanol solvent (0.5 mol) were
introduced into a 100-ml stainless steel autoclave reactor
and heated with stirring. At 1.4 MPa, the reaction mixture
was stirred for 10 h at 150 °C. After the reaction, excess
dimethyl carbonate and methanol solvent were vacuum-
stripped in a rotary evaporator. Then the products were
extracted in the water layer through a two-phase extraction
with water and ethyl acetate. Water was removed by vac-
uum distillation and the remaining viscous brown liquid
was purified by silica gel column, using methanol as the
eluent. The final mixture was collected and recrystallized
from acetone to give the compound with a yield of 90 %.
Results and Discussion
Preparation and Spectroscopic Characterization
of the Lauryl Amidopropyl Trimethyl Ammoniums
The general formula and process of the lauryl amidopropyl
trimethyl ammoniums are shown in Scheme 1.
1
The structure of the compound was confirmed by IR, H
NMR and MS.
These compounds were structurally characterized by
1
their IR, H-NMR and MS spectra. The details of these
Synthesis of LAPTM Ammonium
with New Counterions
spectral characterizations were as follows. In all cases, the
spectra acquired were consistent with the assigned struc-
tures of the compounds.
LAPTM ammonium methyl carbonate (0.01 mol), 0.01 mol
of water or organic acids (formic acid, acetic acid and lactic
acid) and methanol solvent (5 ml) were introduced into a
50-ml round-bottomed flask and heated with stirring. The
reaction conditions were as follows: temperature 35 °C,
reaction time 4 h. After the reaction, the mixture was con-
densed under reduced pressure and the crude products were
recrystallized from acetone to give the lauryl trimethyl
quaternary ammonium salts (94 % yields). The structure of
the compound was confirmed by IR and MS.
LAPTMA-CH3CO3: 1H NMR (CDCl3, 300 MHz, d
ppm): 0.84–0.89 (t, 3H, CH3), 1.24 (s, 16H, (CH2)8),
1.60–1.65 (m, 2H, CH2), 2.10–3.37 (m, 2H, CH2-CO),
2.10–3.37 (m, 2H, N-CH2-CH2), 3.28–3.42 (m, 2H, NH-
CH2), 3.28–3.42 (t, 2H, N-CH2), 3.46 (s, 9H, N-CH3), 3.65
(s, 3H, N-CH2), 6.95 (s, H, N–H); Mass Spectra: Cationic
scanning m/e: 299.7, 240.6. 240.6 is the fragment ion of
299.7, its appearance indicated that the DP voltage is too
high to make the parent ion crack in the ion source; Anion
scanning m/e: 74.9; FTIR Spectra: The broad band at
3,416 cm-1 characterized the NH groups. The stretching
band at 2,851 cm-1, 2,920 cm-1 characterized the CH3
and CH2 groups, respectively. The stretching band at
1,654 cm-1, 1,630 cm-1 characterized the C=O groups.
The stretching band at 1,105 cm-1 characterized the
COOCH3 groups.
Analytical Methods
Infrared (IR) spectra were recorded on a Nicolet islo FT-IR
1
spectrometer. H-NMR spectra were acquired on a Bruker
AV-300 NMR spectrometer using CDCl3 as solvent.
Chemical shifts were reported in ppm related to internal
tetramethylsilane. Mass spectra (MS) were performed on
the AB SCIEX API3200LC/MS/MS spectrometer.
The surface tension of aqueous solutions was measured
at 25 °C using a Dataphysics tensiometer DCAT11 by the
Wilhelmy plate method.
LAPTM ammonium formate (LAPTMA-HCOO): Mass
Spectra, Cationic scanning m/e: 299.5; Anion scanning
m/e: 44.9. FTIR Spectra, 1,731 cm-1 characterized the
C=O groups.
LAPTM ammonium acetate (LAPTMA-CH3COO): Mass
Spectra, Cationic scanning m/e: 299.5; Anion scanning
m/e: 58.9. FTIR Spectra, 1,647 cm-1 characterized the
C=O groups.
The antimicrobial activity of the new compounds was
tested against reference strains of Gram-positive (Staphy-
lococcus aureus ATCC 6538) and Gram-negative (Esche-
richia coli ATCC 11105, Pseudomonas aeruginosa
ATCC9027) and fungi (Candida albicans ATCC 10231).
The antimicrobial activity was assessed by using the filter
LAPTM ammonium lactate (LAPTMAMA-CH3CHOH-
COO): Mass Spectra, Cationic scanning m/e: 299.5; Anion
scanning m/e: 88.6. FTIR Spectra, 3,385 cm-1 characterized
the OH groups. 1,648 cm-1 characterized the C=O groups.
123

J Surfact Deterg
Scheme 1 Synthesis of the
lauryl amidopropyl trimethyl
ammoniums
Surface Activity
lauryl amidopropyl trimethyl ammoniums surfactants are
forming micelles. In addition, it is clear that, as the
hydrophilicity of the counterion is decreased, lower con-
centrations of the surfactants are needed to get equivalent
surface tension values (Fig. 1). Furthermore, the results
also showed that the CMC value decreases with decreasing
the hydrophilicity of the counterion (Table 1). This trend
suggests that an increase in the hydrophilicity of the
compounds decreases the efficiency of the surfactant.
The maximum surface excess of the surfactant solution
(Cmax), is defined as the concentration of the surfactant
molecules at the interface near the critical micelle con-
centration. The maximum surface excess of the synthesized
lauryl amidopropyl trimethyl ammoniums was calculated
using the approximate form of the Gibbs adsorption iso-
therm equations:
The minimum surface tension (cCMC) values were acquired
by analyzing the plateau region of the plots. A summary of
the data is compiled in Table 1, which shows that the new
lauryl amidopropyl trimethyl ammoniums surfactants sig-
nificantly reduce the surface tension of the solution at low
concentrations, indicating that these molecules adsorb
strongly at the air/water surface and they are highly effec-
tive aqueous surfactants. From Table 1, we can see that
these synthesized lauryl amidopropyl trimethyl ammoniums
reduced the surface tension of water to a minimum value of
approximately 28 mN m-1 at a concentration of 2.34 9
10-2 mol L-1
.
The critical micelle concentration (CMC) values were
determined using a series of aqueous solutions at various
concentration and estimated from the break point of each
surface tension versus concentration (on log scale) curves.
The relation between the surface tension and the concen-
tration (log c) of the synthesized surfactants at 25 °C is
represented in Fig. 1. The concentration ranges were cho-
sen to cover a large range (from 0.05 to 0.0001 mol/L) to
describe all the expected changes in the behaviors of the
surface tension of the surfactant solutions. As is seen in
Fig. 1, the surface tension-concentration relations are
characterized by two distinguishable regions, one at the
lower concentration range at which the surface tension
values decrease rapidly, the other at higher concentrations
at which the surface tension values remain almost constant.
The dramatic change in slope of the surface tension versus
log surfactant concentration curves suggests that these
ꢀ
ꢁ
1
oc
Cmax ¼ ꢁ
ð1Þ
2:303nRT o log C
T
The minimum surface area (Amin) or the area occupied
by each surfactant molecule at the air/water interface is
calculated according to the formula:
1
Amin
¼
ð2Þ
NACmax
where R = 8.3144 J mol-1 K-1, NA = Avogadro’s num-
ber, Cmax is the maximum surface excess at a constant
temperature. In our solution, we can set n = 2.
The minimum surface area (Amin) appears to be deter-
mined by the area occupied by the hydrated hydrophilic
groups, rather than by the hydrophilic group, because the
Table 1 Surface tension (cCMC), critical micelle concentration (CMC), minimum surface area (Amin), free energy changes of adsorption (DGads
and micellization (DGmic) of the synthesized lauryl amidopropyl trimethyl ammoniums at 25 °C
)
)
Compound
cCMC (mN m-1
)
CMC (mol l-1
)
Amin (A2)
DGmic (KJ mol-1
)
DGads (KJ mol-1
LAPTMA-CH3CO3
LAPTMA-HCOO
29.04
28.15
30.19
33.69
2.24 9 10-2
2.34 9 10-2
2.40 9 10-2
2.57 9 10-2
35.12
28.74
30.59
33.29
-19.37
-19.26
-19.20
-19.03
-28.49
-26.88
-26.94
-26.75
LAPTMA-CH3COO
LAPTMA-CH3CHOHCOO
123

J Surfact Deterg
of the lauryl amidopropyl trimethyl ammonium surfactants
increases as the hydrophilicity of the counterion increases,
indicating that the processes are not thermodynamically
favored.
Thus far, most of the traditional surfactants counterion
have been inorganic ions and there have been many reports
about the study of the changes of surface tension with the
hydrophobic chain length. However, the influence of sur-
factant counterions on the surface tension has been rarely
reported in the literature. The data in Table 1 indicates that
organic counterions have a significant influence on surface
tension. The surface tension variation trend of ammonium
formate, ammonium acetate, and ammonium lactate is
gradually increasing. As the hydrophilicity of the count-
eranion increases, the surface tension value increases. The
same results appeared in our previous studies [13]. We
have also confirmed that the quaternary ammonium salts
with these organic counterions all showed better properties
than the quaternary ammonium salt with Cl- as a coun-
terion [13]. From the above comparison and contrast, one
can safely conclude that the interaction between the
counterion and the cationic charged group has a significant
influence on surface tension.
Fig. 1 Surface tension versus the logarithm of the aqueous molar
concentration (log c) of synthesized lauryl amidopropyl trimethyl
ammoniums at 25 °C
chains in typical ionic or nonionic surfactants with
hydrophilic groups at one end of the molecule do not lie flat
on an interface but rather are somewhat tilted with respect
to it. It is confirmed by the Amin values in Table 1, that the
area occupied by each surfactant molecule of the ammo-
nium formate, ammonium acetate and ammonium lactate
surfactants at the interface increases as the hydrophilicity
of the counterion increases.
Antimicrobial Activity
The results of the disc-diffusion assay (Table 2) show that
all of the synthesized compounds displayed bactericidal
activity slightly less or greater to that of the control on all
four strains tested. On Staphylococcus aureus, all strains
show excellent bactericidal activity to that of the control.
However, on the other strains tested, there were structural
differences in efficacy, with some structures of acetic and
lactic ammoniums showing high efficacy.
The free energies of adsorption (DGads) and micelliza-
tion (DGmic) were calculated according to Rosen’s
methodology:
ꢀ
ꢁ
CMC
DGmic ¼ RT ln
ð3Þ
ð4Þ
55:5
DGads ¼ DGmic ꢁ 6:022ðc0 ꢁ cCMCÞAmin
Sterilization is due to the adsorption and penetration of
surfactant molecules at the microbial surface. The
adsorption and penetration depends on the hydrophobic
chain length, surface activities, and the dosage of these
cationics. With the same hydrophobic chain length and
dosage, compounds which were easily absorbed and per-
meated into the bacterial cell membrane exhibited better
bactericidal properties. The data in Table 1 describe the
where R = 8.3144 J mol-1 K-1, c0 is the surface tension
of the bidistilled water, cCMC is the surface tension at the
CMC. Amin is the area occupied by each surfactant mole-
cule at the air/water interface.
The negative values of DGads and DGmic in Table 1
indicates that both adsorption and micellization are spon-
taneous at 25 °C. The free energy of micellization (DGmic
)
Table 2 Antibacterial and
Compound
Microorganism-inhibition zone diameter (mm)
antifungal in vitro activity of
synthesized surfactants using
the disc-diffusion method at
10 mg/ml
Staphylococcus
aureus
Escherichia
coli
Pseudomonas
aeruginosa
Candida
albicans
LAPTMA-CH3CO3
28.6
35.4
34.7
38.1
21.9
11.0
17.9
23.0
23.3
20.4
13.2
10.9
18.9
19.7
18.5
11.2
31.3
33.7
33.9
20.3
LAPTMA-HCOO
LAPTMA-CH3COO
LAPTMA-CH3CHOHCOO
Benzalkonium chloride
123

J Surfact Deterg
12. Miao ZC, Yang JZ, Wang L (2008) Synthesis of biodegradable
lauric acid ester quaternary ammonium salt and its utilization as
calico softener. Mater Lett 62(19):3450–3452
13. Xu BC, Han F, Shui JH, Zhou YW (2009) Synthesis and char-
acterization of lauryl trimethyl ammonium surfactants with new
counteranion types. J Surf Deterg 12:351–354
adsorption potential of the synthesized compounds at the
interfaces. Formate, acetic, and lactic ammoniums showed
a similar free energy change of adsorption at the interfaces.
However, acetic and lactic ammoniums showed higher
bactericidal activities while formate ammoniums did not. It
is more likely that the penetration of formate ammoniums
is weaker than acetic and lactic ammoniums in some
bacteria.
Author Biographies
Hongqin Liu received a Ph.D. in environmental engineering from the
Beijing Institute of Technology. She is a lecturer with a research field
in synthesis and properties of surfactants.
Acknowledgments We gratefully acknowledge the financial sup-
port of the National Natural Science Foundation of China (20976003,
21176004) and the Funding Project for Academic Human Resources
Development in Institutions of Higher Learning Under the Jurisdic-
tion of the Beijing Municipality (PHR200906109).
Fei Li is a postgraduate student in applied chemistry in Beijing
Technology and Business University. His research interests are
synthesis and properties of surfactants.
References
Baocai Xu received a Ph.D. in applied chemistry from the Beijing
Institute of Technology. He is a professor at the Beijing Key
Laboratory of Flavor Chemistry, Beijing Higher Institution Engi-
neering Research Center of Food Additives and Ingredients, with a
research field in synthesis and properties of surfactants.
1. Tokunaga S (2008) Shampoos containing surfactants and qua-
ternary ammonium salts. Japan Patent 2008069084A
2. Kohno H, Sakai K, Sakai H (2008) The novel method for prep-
aration of titanium dioxide thin film with cationic silane coupling
agent. Mater Technol 26(3):147–153
3. Chandar P, Yang L (2008) Personal care compositions with
enhanced fragrance delivery comprising substituted urea and
quaternary ammonium salt. US Patent 2008299054A1
4. Igarashi T, Ogura N (2008) Textiles treating agent compositions.
Japan Patent 2008297675A
Guiju Zhang received a Ph.D. in organic chemistry from the
Technical Institute of Physics and Chemistry of the Chinese Academy
of Sciences. She is a lecturer with a research field in synthesis and
properties of surfactants.
Fu Han received a Ph.D. in physicochemistry from Wuhan Univer-
sity. He is an associate professor with a research field in synthesis and
properties of surfactants.
5. Zabielska-Matejuk J (2005) The influence of cation and anion
structure of new quaternary ammonium salt on adsorption and
leaching. Holzforschung 59:190–198
6. Jia Z, Shen D, Xu W (2001) Synthesis and antibacterial activities
of quaternary ammonium salt of chitosan. Carbohydr Res
333:1–6
7. Chlebicki J, Wegrzynska J, Maliszewska I (2005) Preparation,
surface-active properties, and antimicrobial activities of bis-
quaternary ammonium salts from amines and epichlorohydrin.
J Surf Deterg 8:227–232
Yawen Zhou received an M.Sc. in applied chemistry from China
Research Institute of Daily Chemical Industry. She is an associate
professor with a research field in synthesis and properties of
surfactants.
Xiulan Xin received a Ph.D. in industrial catalysis from Tianjin
University. She is a professor with a research field in preparation of
new green materials and characterization, the preparation of poly-
merizable surfactant application in emulsion polymerization.
8. Ootawa Y, Kato T, Tomifuji T (2001) Quaternary ammonium
salt. Japan Patent 2001048851
9. Hanada (2005) Cosmetic hair preparation. US Patent 0255074 A1
10. Ootawa Y (2005) Quaternary ammonium salt composition and
method for producing the same. Japan Patent 2005179187
11. Gohl (2005) Laundry rinse aids comprising a propoxylated qua-
ternary ammonium salt. US Patent 6878681 B1
Bo Xu is a freshman at the University of Illinois, Urbana-Champaign.
123