Synthesis of novel quaternary ammonium surfactants containing adamantane

Article abstract of DOI:10.1016/j.cclet.2012.04.002

A series of novel quaternary ammonium surfactants containing adamantane were designed and synthesized from 1-adamantanecarboxylic acid. The structures of target surfactants were confirmed by ¹H NMR, elements analysis and FTIR. Surface properties of these surfactants were investigated. Due to the lipophilicity of adamantane, the critical micelle concentration (CMC) and C ₂₀ values of the synthesized quaternary ammonium surfactants are lower than that of conventional quaternary ammonium surfactants.

Full text of DOI:10.1016/j.cclet.2012.04.002

Available online at www.sciencedirect.com
Chinese Chemical Letters 23 (2012) 653–656
www.elsevier.com/locate/cclet
Synthesis of novel quaternary ammonium surfactants
containing adamantane
*
Jian Wei Guo , Xing Zhong, Hua Zhu, Li Juan Feng, Ying De Cui
Faculty of Chemical Engineering & Light Industry, Guangdong University of Technology, Guangzhou 510006, China
Received 9 January 2012
Available online 14 May 2012
Abstract
A series of novel quaternary ammonium surfactants containing adamantane were designed and synthesized from 1-adamanta-
necarboxylic acid. The structures of target surfactants were confirmed by 1H NMR, elements analysis and FTIR. Surface properties
of these surfactants were investigated. Due to the lipophilicity of adamantane, the critical micelle concentration (CMC) and C20
values of the synthesized quaternary ammonium surfactants are lower than that of conventional quaternary ammonium surfactants.
# 2012 Jian Wei Guo. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Adamantane; Synthesis; Quaternary ammonium surfactants; 1-(Alkyldimethylammoniamethyl) adamantane bromide
Quaternary ammonium compounds (QACs) are an important branch of surfactants that have unique qualities that
make them attractive for investigation. QACs have been proved to be useful in a variety of applications, including the
following: such as detergents, disinfectants, antistatic agents and fabric softeners [1–3]. Benzalkonium bromide
(dodecyldimethylbenzylammonium bromide), for example, is currently utilized for disinfectants in hospital and a
high-efficiency algaecide in seawater [4–5].
Adamantane (tricyclo[3.3.1.13,7]decane) is a very symmetric tricyclic hydrocarbon with three fused chair-form
cyclohexane rings in a diamond lattice structure. The particular structure of adamantane imparts many useful chemical
and physical properties, such as extreme lipophilicity, good thermal and oxidative stabilities, low surface energy, and
innocuity, etc. [6–8]. Amino derivatives of adamantane, such as aminoadamantanes which are known to have
interesting biological properties, are used medically to treat influenza [9]. Incorporation of adamantyl groups into the
molecular structure of surfactants will take advantage of the special properties of the adamantane structure. The
benefits of adamantane lipophilicity may exhibit low CMC value [10–12]. However, nowadays a little study focuses on
the surfactants containing adamantane.
In this paper, we successfully synthesized a series of quaternary ammonium surfactants containing adamantane,
1-(alkyldimethylammoniamethyl) adamantane bromide from 1-adamantanecarboxylic acid. The synthetic procedure
sketch is shown in Scheme 1.
Firstly, 1-adamantanyl-N,N-dimethylcarboxamide (2) was synthesized by modification of published literature
procedures [13]. The mixture of 1-adamantanecarbonxylic acid (56 mmol) and SOCl2 (80 mmol) was stirred for 3 h at
* Corresponding author.
E-mail address: doctorgjw@163.com (J.W. Guo).
1001-8417/$ – see front matter # 2012 Jian Wei Guo. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
http://dx.doi.org/10.1016/j.cclet.2012.04.002

654
J.W. Guo et al. / Chinese Chemical Letters 23 (2012) 653–656
HCl
N
R
Br-
N
N
N
O
COOH
COCl
a
d
e
c
b
5a-5d
3
2
4
1
Scheme 1. The synthesis of compounds 5a–5d. Condition and regent: (a) SOCl2, 80 8C, 3 h, 99%; (b) TEA, HN(CH3)2.HCl, CH2Cl2, r.t., 12 h, 79%;
(c) i: LiAlH4, dry THF, reflux, 20 h, ii: 2 mol/L HCl, 77% in two steps; (d) 2 mol/L NaOH; and (e) RBr, isopropanol, reflux, 48 h, 26À43%.
80 8C, and became transparent. The excess SOCl2 was removed by distilling to give compound 1. Then to a stirring
suspension of dimethyl amine hydrochloride salt (86 mmol) and triethylamine (TEA) (180 mmol) in CH2Cl2 (50 mL)
was added into the solution of the compound 1 (55 mmol) in CH2Cl2 (25 mL) at 0 8C. The resulting solution was
stirred at r.t. for 12 h, and then the solution was washed by dilute hydrochloric acid and brine. The combined organic
layers were dried (MgSO4), and concentrated to give a light yellow crystalline solid. The solid was purified by column
chromatography (ethyl acetate:hexanes = 1:1) to give compound 2 as a colorless crystalline solid. 1H NMR (300 MHz,
CDCl3): d 1.717 (br s, 6H), 2.019 (br s, 9H), 3.053 (br s, 6H).
N,N-Dimethyl-1-aminomethyladamantane hydrochloride (3) was synthesized by the reduction of compound 2
using LiAlH4 in dry THF and then hydrochlorination with ice cold 2 mol/L HCl. Compound 3 was recrystallized from
1
methanol/acetone to give white crystals, H NMR (300 MHz, D2O): d 1.546–1.554 (m, 6H), 1.591–1.691 (m, 6H),
1.931 (br s, 3H), 2.832 (s, 6H), 2.865 (m, 2H). Then compound 3 was neutralized by 2 mol/L NaOH (25 mL) to give
compound 4 as a colorless transparent liquid.
Finally, a series of 1-(alkyldimethylammoniamethyl) adamantane bromide (5a–5d) were synthesized by
quaternization of compound 4 with n-bromoalkanes. For instance, the 1-(octyldimethylammoniamethyl) adamantane
bromide was synthesized as follows. The solution of 1-bromooctane (13 mmol) in isopropanol was added to a stirred
solution of compound 4 (10 mmol) in isopropanol, the mixture was refluxed for 48 h. Then the resulting mixture was
concentrated. The residue was washed several times with diethyl ether (3 Â 30 mL) to give a colorless crystalline
solid. Then the solid was recrystallized from THF and purified by column chromatography (dichloromethane:-
methanol:ammonia = 15:1:0.01) to give compound 5a as colorless crystals. 5b, 5c and 5d were synthesized via similar
procedures. The results of compounds 5a–5d are listed in Table 1.
Table 1
The results of compounds 5a–5d.
Compound
R
Yield 1H NMR (300 MHz, CDCl3): d
Elements analysis (%, calcd.)
FTIR (KBr, cmÀ1): n
5a
–C8H17
43%
0.858–0.902 (t, 3H), 1.269–1.362 (m, 10H),
1.702–1.725 (m, 8H), 1.828–1.835 (m, 6H),
2.053 (br s, 3H), 3.324 (s, 2H), 3.482 (s, 6H),
3.619–3.676 (t, 2H)
C, 65.27(65.09); H, 10.43(10.48); 2904, 2848, 1632, 1486,
Br, 20.68(20.55); N, 3.62(3.88). 1469, 1458, 1105, 933.
5b
5c
5d
–C10H21 39%
–C12H25 35%
–C16H33 26%
0.855–0.900 (t, 3H), 1.258–1.361 (m, 14H),
1.713–1.733 (m, 8H), 1.810–1.833 (m, 6H),
2.061 (br s, 3H), 3.320 (s, 2H), 3.476 (s, 6H),
3.615–3.671 (t, 2H)
C, 66.64(66.90); H, 10.70(10.63); 2904, 2849, 1631,
Br, 19.28(19.05); N, 3.38(3.42).
1477 1469, 1457,
1103, 932.
0.854–0.898 (t, 3H), 1.250–1.366 (m, 18H),
1.712–1.731 (m, 8H), 1.808––1.834 (m, 6H),
2.059 (br s, 3H), 3.314 (s, 2H), 3.470 (s, 6H),
3.609–3.664 (t, 2H)
C, 67.85(67.98); H, 10.93(10.87); 2905, 2849, 1631,
Br, 18.05(17.87); N, 3.16(3.28).
1477 1469, 1457,
1103, 984.
0.854–0.898 (t, 3H), 1.250–1.358 (m, 26H),
1.699–1.722 (m, 8H), 1.769–1.832 (m, 6H),
2.052 (br s, 3H), 3.322 (s, 2H), 3.482 (s, 6H),
3.615–3.672 (t, 2H)
C, 69.85(70.08); H, 11.32(11.27); 2916, 2849, 1631,
Br, 16.02(15.71); N, 2.81(2.94). 1469, 1457, 1103, 984.

J.W. Guo et al. / Chinese Chemical Letters 23 (2012) 653–656
655
DTAB
65
60
55
5a
5b
5c
5d
50
CMC
45
40
-4.0
-3.5
-3.0
-2.5
-2.0
-1.5
Log C
Fig. 1. Surface tension of aqueous 5a–5d and DTAB solutions at 25 8C.
Table 2
Value of the CMC, gCMC and C20 for surfactants 5a–5d.
Surfactants
CMC (mol/L)
gCMC (mN/m)
C20 (mol/L)
5a
5b
12 Â 10À3
8 Â 10À3
4 Â 10À3
2 Â 10À3
16 Â 10À3
43.053
40.953
38.906
37.902
38.894
5.62 Â 10À3
2.40 Â 10À3
5.01 Â 10À4
2.24 Â 10À4
6.61 Â 10À3
5c
5d
C12H25N+(CH3)3 BrÀ (DTAB)
1. Surface tension and CMC
The surface tension of aqueous solutions (g) was measured by KSV Sigma 700 tensiometer at 25 8C. This
tensiometer works based on the Wilhelmy plate method. The surface activity of target compounds 5a–5d has been
compared with conventional surfactant DTAB (dodecyltrimethylammonium bromide), which was purchased from
Aladdin-reagent (China). Fig. 1 shows the surface tension of aqueous solutions of 5a–5d and DTAB. The critical
micelle concentration (CMC) and surface tension at the CMC (gCMC) were determined from the break point of the
surface tension versus logarithm of concentration curve. The concentration values of the surfactants in the aqueous
phase that produces a 20 mN/m reduction in the surface tension of the solvent (C20) were got from Fig. 1. The results
were showed in Table 2. The CMC and gCMC of DTAB were 16 Â 10À3 mol/L and 38.894 mN/m, which were similar
with literature [14]. Compared with DTAB, the surfactants 5a–5d have lower CMC and C20 values, which may be
resulting from the lipophilicity of adamantane.
In summary, a series of novel quaternary ammonium surfactants containing adamantane can be synthesized from 1-
adamantanecarboxylic acid. These surfactants exhibit the lower CMC and C20 values.
Acknowledgment
The authors greatly appreciate the financial support by the Major Program of Guangdong University of Technology
(No. 405095220).
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