ISSN 1070-4280, Russian Journal of Organic Chemistry, 2013, Vol. 49, No. 9, pp. 1291–1299. © Pleiades Publishing, Ltd., 2013. Original Russian Text © I.V. Kapitanov, I.A. Belousova, A.E. Shumeiko, M.L. Kostrikin, T.M. Prokop’eva, A.F. Popov, 2013, published in Zhurnal Organicheskoi Khimii, 2013, Vol. 49, No. 9, pp. 1308–1316.
Supernucleophilic Systems Based on Functionalized Surfactants in the Decomposition of 4-Nitrophenyl Esters Derived from Phosphorus and Sulfur Acids: I. Reactivity of a Hydroxyimino Derivative of Gemini Imidazolium Surfactant I. V. Kapitanov, I. A. Belousova, A. E. Shumeiko, M. L. Kostrikin, T. M. Prokop’eva, and A. F. Popov Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, ul. R. Lyuksemburg 70, Donetsk, 83114 Ukraine e-mail:
[email protected] Received March 20, 2013
Abstract—A new functionalized gemini surfactant, 3,3′-[2-(hydroxyimino)propane-1,3-diyl]bis(1-dodecyl-1Himidazol-3-ium) dichloride, and its non-micelle-forming methyl analog, were synthesized. Nucleophilicity of the oximate group in these compounds in the decomposition of 4-nitrophenyl esters derived from phosphorus and sulfur acids follows Brønsted relations for monomeric functionalized surfactants and non-micelle-forming oximes. As compared to the single-chained analog, the gemini surfactant ensured the same observed rate of substrate decomposition at lower concentration and lower pH. Micellar effects of the gemini surfactant in these reactions attain a value of ~10 3 and are determined mainly by substrate concentration in the micellar pseudophase.
DOI: 10.1134/S1070428013090091 Functionalization of surfactants with reactive fragments gives rise to unique enzyme-like reagents whose action combines several factors of different natures (concentration effect, variation of microenvironment, etc.), which ensure significant increase of observed reaction rates [1–6]. For instance, introduction into a surfactant molecule of a covalently bonded oxime fragment exhibiting anomalously high reactivity in acyl group transfer processes afforded efficient systems for the decomposition of toxic phosphorus and sulfur acid esters [1, 3–6] (Scheme 1). A distinguishing feature of oxime-modified surfactants is anomalous relation between the basicity of the functional fragment and its reactivity in acyl transfer
processes: the Brønsted plots for functionalized surfactants are characterized by a bend at pKa of the oxime group 8.5–9.0 and are analogous to those typical of non-micelle-forming oximes [5, 7, 8], for which the sensitivity of the reaction rate to the basicity of the functional group (βN) at pKa ≥ 9.0 is close to zero and βN > 0.3–0.5 at pKa ≤ 9.0 [7, 8]. Factors responsible for such shape of the Brønsted plot were discussed in detail in [5–8]; one of the main factors determining the kinetic relations is differences in the solvation of weakly and strongly basic oximes. The fact that these differences are retained in microheterogeneous systems based on surfactants functionalized with oxime group [5, 6] is nontrivial, and it is likely to indicate
Scheme 1. NOH R1
R2 OxH
pKa –H+ H+
NO– R1
NOX
4-O2NC6H4OX (I–III)
R2
+ R1
R2
4-O2NC6H4O–
Ox–
I, X = EtO(Et)P(O); II, X = (EtO)2P(O); III, X = 4-MeC6H4SO2.
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similarity of the effects of the medium in aqueous solution and microheterogeneous organized systems based on functionalized surfactants. The reactivity relations found for single-chained (i.e., containing one hydrophobic and one hydrophilic fragment) functionalized surfactants [5, 6] made it possible to contemplate ways of purposeful modification of surfactant structure for the design of new supernucleophilic microorganized systems for decomposition of acyl-containing ecotoxicants. The bend on the Brønsted plot at pKa 8.5–9.0 indicates that compounds characterized by just the same acid ionization constants are most attractive as reagents. In this case, substrate decomposition should occur under relatively mild conditions (pH ≤9.5) while the reactivity should be retained at a level comparable with that of strongly basic oximes. Insofar as the synthesis of weakly basic oximes is based on introduction of electron-withdrawing substituents into nucleophile molecule [7], reagents with pKa ~9.0 were obtained by modification of strongly basic oxines IV and V via introduction of one more N-alkylimidazolium fragment (compounds VI and VII). The pKa values of IV and V are lower approximately by 2 log units [4, 5, 9] than that of acetone oxime (pKa 12.6 [8]). Therefore, there are reasons to believe that the pKa values of oximes VI and VII containing two N-alkylimidazolium fragments will range from 8.5 to 9.0. In the present article we describe a procedure for the synthesis of oxime VI and oxime-functionalized gemini surfactant VII. The reactivity of compound VI and microorganized system based on oxime VII in the decomposition of 4-nitrophenyl esters I–III was studied and compared with the reactivity of their strongly basic single-chained analogs IV and V. Ketone oximes IV–VII are functionalized analogs of ionic liquids; the latter constitute a unique class of compounds that attract undoubted interest from the practical viewpoint [1, 10, 11]. In addition, gemini NOH Alk
N
Me
N
Cl–
IV, V
Cl– N
Alk
Cl–
NOH N
N
N
Alk
VI, VII
IV, VI, Alk = Me; V, VII, Alk = C12H25.
surfactant VII containing two hydrophobic and two hydrophilic fragments connected through a spacer were expected to be characterized by anomalously low critical micelle concentration (CMC) as compared to single-chained surfactant V [12]. Therefore, the same micellar effects in nucleophilic substitution reactions should be attained at a gemini surfactant concentration lower by an order of magnitude (and more) than the concentration of microorganized systems based on single-chained surfactants [11, 12]. The dependence of the observed pseudofirst-order rate constants (kobs, s–1) on the analytical concentration of non-micelle-forming nucleophile VI ([OxH]0, M) is typical of processes involving oximate ion (Ox–) as reactive species. The reaction rate increases in parallel with both pH and nucleophile concentration. The observed relations are described by the following equation [8]: kobs = kwOH– aOH– + k2w[OxH]0 Ka/(Ka + aH+) = kwOH– aOH– + kw2 [Ox–].
Here, the first term reflects the contribution of alkaline hydrolysis, Ka is the acid ionization constant of oxime, and k2w (l mol–1 s–1) is the second-order rate constant characterizing nucleophilicity of oximate ion in water. The ratio Ka/(Ka + aH+) = α is the degree of nucleophile ionization. In the determination of nucleophilicity, the pKa value was preliminarily estimated by potentiometry or spectrophotometry (Fig. 1); the k2w values were then determined from the kobs—[OxH]0 dependence (Fig. 2, Table 1) assuming complete ionization of oxime ([Ox – ] ≈ [OxH]0 ). The acid ionization constant of oxime VI falls into the range corresponding to the bend on the Brønsted plot, and its reactivity is comparable to the reactivity of strongly basic oximes, i.e., the kinetic behavior of oxime VI shows no anomaly (Fig. 3). The kinetic relations for the decomposition of substrates I–III in a microorganized system based on gemini surfactant VII are analogous to those found for functionalized surfactant V [4, 5, 9]. The observed rate constant (kobs, s–1) increases as the acidity of the medium decreases (c0 = const; c0, M, is the analytical surfactant concentration), as well as the surfactant concentration increases, the pH value remaining unchanged. Acceleration of the reaction with rise in pH indicates that, as with non-micelle-forming oxime VI, the reactive species is oximate ion (Fig. 4). Increase of kobs
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SUPERNUCLEOPHILIC SYSTEMS BASED ON FUNCTIONALIZED SURFACTANTS ... I.
Quantitative parameters of the behavior of the microorganized system based on surfactant VII were analyzed in terms of the pseudophase distribution model which implies that a substrate (S) is rapidly distributed between two phases, micellar pseudophase (m) and aqueous phase (w) (Scheme 2) and that its equilibrium distribution is controlled by the partition coefficient PS = [S]m/[S]w, while the chemical reaction itself does not affect the thermodynamics of substrate distribution [13].
D 1.6
pH 11.00
1.2 0.8
0.4 pH 7.00 0.0 200
220
240
(S)m
+
Ox–
PS Water
(S)w
12
Products
+
OH–
Products
Then the experimentally observed pseudofirst-order rate constant (kobs, s–1) in the system under study is given by Eq. (1): (k2m/Vm)KS c + kwOH– aOH– Ka, app kobs = . 1 + KS c Ka, app + aH+
(1)
Here, k2m (l mol–1 s–1) is the second-order rate constant characterizing the nucleophilicity of the oximate fragment, Vm (l mol–1) is the partial molar volume of surfactant, c (M) is the concentration of the micellized surfactant (c = c0 – CMC, M), KS = (PS – 1) Vm (l/mol) is the equilibrium substrate binding constant, and Ka, app is the apparent acid ionization constant of the functional fragment [4–6]. The Ka, app value for the oxime group in VII was determined by spectrophotometry (Table 1), as well as by analysis of the kinetic dependence k obs —pH (Fig. 4). Under the conditions approaching complete binding of the substrate, the pH profile of the reaction is described by the equation [4] kobs = km Ka, app/(Ka, app + aH+)
or kobs = km – kobs aH+/(1/Ka, app),
0
1
10
w
kOH
kobs × 104, s–1
Micellar pseudophase
280
300
λ, nm
Fig. 1. UV spectra of oxime VI at different pH values; [VI] 0 = 1.3 × 10 –4 M, water, μ = 1.0 (KCl), 0.01 mol/l of KH2PO4, 25°C; pKa was determined by spectrophotometry.
Scheme 2. m k2
260
[OxH]0 × 102, M 2
3
4
I
II
8
12 10 8
III
6
6
4
4
2
2
0
0
2
4 6 [OxH]0 × 102, M
8
10
kobs × 104, s–1
upon variation of c0 at pH = const reflects increase in the substrate concentration in micelles formed by oxime VII (Figs. 5, 6). Almost complete binding may be attained for the most hydrophobic substrate III, as follows from the presence of a plateau on the kobs—c0 plot (Fig. 6).
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0
Fig. 2. Plots of the observed rate constants (kobs, s–1) for the decomposition of esters I–III versus concentration of VI ([OxH]0, M) at pH 10.70; water, μ = 1.0 (KCl), 0.01 mol/l of KH2PO4, 25°C.
where km = k2m/Vm (s–1) is the reduced pseudofirst-order rate constant corresponding to the reaction of VII with substrate within surfactant micelles. This equation may be used to process the obtained data and determine Ka, app value. The character of variation of acid–base properties in going from methyl analog VI to surfactant VII is similar to that observed for compound V and the corresponding methyl derivative IV [4, 5, 9]. Replacement of methyl groups in positions 3 and 3′ of the imidazole rings in VI by dodecyl groups (compound VII) does not lead to an appreciable change of acid–base properties of the oxime fragment (cf. pKa of VI and pKa, app of VII in Table 1). As might be expected, the pK a
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Table 1. Physicochemical properties and nucleophilic reactivity of compounds IV–VII in the decomposition of esters I–III in water at 25°C Comp. no. IV V VI VII
a b
c d
Ethyl 4-nitrophenyl ethylphosphonate (I)
a
pKa
km, s–1 10.67 ± 0.06 (p) 010.5 ± 0.1 (sp) 010.1 ± 0.1 (kin) 09.00 ± 0.07 (p) 009.2 ± 0.1 (sp) 008.9 ± 0.1 (sp) 008.8 ± 0.1 (kin)
– 0.18
Diethyl 4-nitrophenyl phosphate (II)
KS, l/mol k2m,b l mol–1 s–1 (CMC) 0.09 [4] 0.09 [9]
–
0.046
0.40
0.20
km, s–1
KS, l/mol k2m,b l mol–1 s–1 (CMC)
– – 091 0.008 (3.0 × 10–3) – – 155 –c
0.0084 0.0040 0.0110
0.034
4-Nitrophenyl 4-methylbenzenesulfonate (III) km, s–1
k2m,b l mol–1 s–1
KS, l/mol (CMC)
– 0.038
0.015 0.019
–
00.0096
– 1240 (2.7 × 10–3) –
– 110 (3.3·10–3) –
0.0170
175 –c
0.031 0.028d
d
0.016 0.014d
d
1700 1700d (2.0 × 10–5) d
The pKa values were determined by (p) potentiometry, (sp) spectrophotometry, or (kin) from the kinetic data. While estimating k2m for V and VII, the Vm value was assumed to be equal to 0.5 l/mol [5, 9, 15]; for methyl analogs IV and VI, the corresponding kw2 values are given in this column. CMC was not determined from the kinetic data. Calculated by analysis of the kobs—pH plot.
values of VI and VII are lower by ~1.5 log unit than those of IV and V (Table 1), and they fit the desired range (8.5–9.0). The concentration dependences shown in Figs. 5 and 6 are appropriately described in terms of the pseudophase distribution model [Eq. (1)]. The nucleophilicity of the oximate group in VII (k2m, Table 1) is similar to that of its methyl analog VI (the k2m/k2w log k2 0.0
log k2 –0.5 –1.0
I
–1.5
III
–2.5 –3.0 –3.5 –4.0
6
8
10 pKa
12
kobs × 102, s–1 3.0
–0.5
2.5
–1.0
2.0
–1.5
1.5
–2.0
1.0
–2.5
0.5
–3.0 14
0.0
II
–2.0
ratio for the reaction with I is ~4, and the corresponding ratio for the reactions with II and III is ~1.5). The log k2m values for the examined substrates conform to the Brønsted plots for oxime-functionalized singlechained surfactants (Fig. 7). The relations found indicate that (1) factors determining the reactivity of functional group in single-chained (V) and gemini surfactants (VII) are likely to be similar and (2) the
Fig. 3. Brønsted plots for the decomposition of esters I–III with non-micelle-forming oximes. Dark points correspond to oxime VI; the data for the other oximes were taken from [8].
8
9
10 pH
11
12
Fig. 4. Plot of the observed rate constants (kobs, s–1) for the decomposition of ester III with surfactant VII versus pH; [VII]0 = 0.0103 M, water, 25°C.
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kobs × 102, s–1 4
2 1 0.15
3
0.10
2
0.05
1
0.00 0.0
III
II
0.2
0.4
0.6
0.8
1.0
0 0.0
0.4
2
0.8
1.2
2
c0 × 10 , M
c0 × 10 , M
Fig. 5. Plot of the observed rate constants (kobs, s–1) for the decomposition of ester I versus concentration of VII (c0, M) at pH (1) 9.20 and (2) 10.0; water, 25°C.
Fig. 6. Plots of the observed rate constants (kobs, s–1) for the decomposition of esters II and III versus concentration of VII (c0, M); pH 10.99 (II), 10.94 (III); water, 25°C.
polarity of the micelle region responsible for chemical reaction is comparable with the polarity of water. Thus, taking into account similarity in the variation of nucleophilicity of the oximate fragment in the above systems, it becomes possible to purposefully modify the structure of surfactants and predict their properties in the design of weakly basic functionalized gemini surfactants.
the variation of CMC radically differs from that found for trialkylammonium gemini surfactants [12, 15]. Presumably, this is related to the rigid planar structure of the imidazolium head groups, which hampers packing of the spacer as its length increases [12, 14]. It should also be taken into account that micellization of
Critical micelle concentration (CMC) is one of the key parameters largely determining the magnitude of micellar effects of surfactants. The CMC of VII estimated on the basis of the kinetic data (from the concentration dependences for the decomposition of ester III; Table 1) turned out to be considerably lower than CMC of cationic gemini surfactants VIII (CMC 5.5 × 10 –4 M, n = 2; 7.2 × 10 –4 M, n = 4 [11]). The observed variation of CMC depending on the spacer length is likely to be reasonable for imidazolium geminis. The CMC values of geminis IX are the lowest at n = 3 (CMC 3.4 × 10–5 for n = 2, 4.8 × 10–6 for n = 3, and 2.22 × 10–5 M for n = 4 [14]), and the tendency in Hlg Alk
–
Hlg N
N
( )n
N
N
–
Alk
VIII, IX
VIII, Alk = C12H25; IX, Alk = C16H33.
log k2 0.0
log k2 –0.5
–0.5
–1.0
–1.0
–1.5
–1.5
–2.0
I
–2.0
–2.5
–2.5 –3.0
–3.0
III II 7
8
9 pKa
10
–3.5 11
Fig. 7. Brønsted plots for the decomposition of esters I–III in micelles of oxime-functionalized surfactants. Dark points correspond to oxime VII; the data for the other oximes were taken from [5, 6].
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Scheme 3. N
Alk
N
NO –
–H+
NOH N
N
Alk
H+
functionalized gemini surfactants is largely affected not only by hydrophobic but also by electrostatic interactions which should be fairly strong for covalently bound cationic centers [12]. The CMC of VII was determined under the conditions implying that micellization involved its zwitterionic form (Scheme 3) which is potentially more prone to aggregation as compared to the cationic form [12, 16]. Considerable differences in CMC values were also noted for zwitterionic forms of functionalized single-chained surfactants and their cationic analogs. For example, the CMC of V with almost completely ionized functional group is ~3 × 10–3 M [9] (Table 1), whereas its cationic analog, 1-dodecyl-1-methylimidazolium bromide, has a critical micelle concentration of 1.09 × 10–2 M [11]. Comparison of the nucleophilic reactivities of the oximate fragments in VI and VII, which are characterized by the second-order rate constants, does not allow us to estimate micellar effects in going from water to micellar pseudophase. It should be kept in mind that micellar effects of surfactants are determined
Alk
N
N
N
N
Alk
not only by variation of the nucleophilicity and change of the acid ionization constant but also by substrate concentration in surfactant micelles. Table 2 compares the observed rate constants for decomposition of esters I–III with oxime VI and gemini surfactant VII at similar pH values and concentrations c 0 . Substrate decomposition in micelles formed by VII is faster by almost three orders of magnitude. As we noted above, variation of the reactivity of the functional group in going from non-micelle-forming oxime VI to surfactant VII is not large (cf. k2m/k2w ratios for VI and VII; Table. 2). There is almost no effect of “shift” of the acid ionization constant upon complete ionization of the functional fragment (rH > 10) at virtually equal pKa, app and pKa values in going from water to micellar pseudophase (Table 1); this effect is characterized by the ratio [K a, app(K a + a H +)]/[K a(K a, app + a H+)] ≈ 1 [4, 5]. Therefore, the main contribution to micellar effects of VII is that provided just by substrate concentration in the micellar pseudophase. Micellar effects of VII in reactions with phosphorus esters I and II exceed those of single-chained
Table 2. Micellar effects of oxime-functionalized surfactants V and VII in the decomposition of esters I–III in water at 25°C Compound no.
pH
c0, M
kobs, s–1
k2m/k2w
kmobs/kwobs
–
–
Ethyl 4-nitrophenyl ethylphosphonate (I) IV V VI VII
11.87
8.14 × 10–3
7.39 × 10–4
11.40
8.14 × 10
–3
4.30 × 10
–2
1.0
1.03 × 10
–3
04.6 × 10
–5
–
1.03 × 10
–3
04.5 × 10
–2
4.2
10.20 10.00
~60 – ~103
Diethyl 4-nitrophenyl phosphate (II) IV V VI VII
12.00
4.20 × 10–2
03.5 × 10–4
11.42
4.20 × 10
–2
7.56 × 10
–3
0.5
1.34 × 10
–2
1.47 × 10
–5
–
1.34 × 10
–2
1.38 × 10
–2
1.5
10.94 10.94
–
– ~22 – ~103
4-Nitrophenyl 4-methylbenzenesulfonate (III) IV V VI VII
12.00
04.8 × 10–3
7.20 × 10–5
11.35
04.8 × 10
–3
2.46 × 10
–2
1.3
1.03 × 10
–3
9.88 × 10
–6
–
–
1.03 × 10
–3
2.02 × 10
–2
1.6
~2 × 103
10.99 10.99
–
– ~340
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(kobs/α) × 102, s–1 2.5 VII
VII
0.30
2.0 0.25 1.5
0.20 0.15
1.0
V
V
0.10 0.5
0.05 0 0
0.5
1.0
1.5
2.0
0
2.5
0
2
1
c0 × 102, M
3
c0 × 102, M
Fig. 8. Plots of kobs/α for the decomposition of ethyl 4-nitrophenyl ethylphosphonate (I) versus concentration of surfactants V and VII; α is the degree of ionization of the oxime group; water, 25°C.
Fig. 9. Plots of kobs/α for the decomposition of diethyl 4-nitrophenyl phosphate (II) versus concentration of surfactants V and VII; α is the degree of ionization of the oxime group; water, 25°C.
surfactant V throughout the examined range of concentrations (Figs. 8, 9). Here, higher kobs values for the reactions of substrates I and II with surfactant VII ensue from both higher nucleophilicity of the latter (cf. k2m for V and VII; Table 1) and more efficient substrate binding* (cf. KS for V and VII; Table 1). As concerns 4-nitrophenyl 4-methylphenylsulfonate (III), its high hydrophobicity (K S; Table 1) ensures a degree of binding to micelles of surfactants V and VII of no less than 80% even at a concentration c0 of ~0.006 M; at higher concentrations, difference in the kobs values results mainly from different nucleophilicities of surfactants V and VII [the k2m(V)/k2m(VII) value for the reaction with III is about 1.2; Table 1]; this is responsible for fairly similar efficiencies in the decomposition of highly hydrophobic compound III after its almost complete binding by micelles of V and VII (Fig. 10). It should be specially noted that micellar effects of VII should appear at a concentration lower by two orders of magnitude than the corresponding concentration of V (cf. CMC of V and VII; Table 1). This is a quite valuable advantage, for a high rate of substrate decomposition may be attained at a lower surfactant concentration. Thus our results not only indicate prospects of the proposed mode of structural modification of surfac-
tants via functionalization with an oxime group but also provide the possibility for purposeful design of supernucleophilic microheterogeneous systems via enhancement of hydrophobic properties of the N-alkyl substituent. Undoubtedly, structural variation in this
* The degree of substrate binding by surfactant micelles was estimated by the formula αS = KS c/(1 + KS c) [4, 5].
(kobs/α) × 102, s–1 4 V
VII
3
2
1
0
0
0.8
0.4
1.2
2
c0 × 10 , M Fig. 10. Plots of k obs/α for the decomposition of 4-nitrophenyl 4-methylbenzenesulfonate (III) versus concentration of surfactants V and VII; α is the degree of ionization of the oxime group; water, 25°C.
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line should ensure more efficient substrate concentration in micellar pseudophase and more significant micellar effects of surfactants. EXPERIMENTAL The 1H NMR spectra were recorded on a Bruker Avance II 400 spectrometer at 400 MHz using tetramethylsilane as internal reference. Esters I and III were prepared as reported in [4, 8]. Commercial ester II (Aldrich, ≥90%) and inorganic reagents of analytical or ultrapure grade were used without additional purification. Solutions were prepared using doubly distilled water. 1,3-Dichloropropan-2-one oxime was synthesized according to the procedure described in [17]. n D30 = 1.5041; published data [17]: nD30 = 1.5044. 1H NMR spectrum (CDCl3), δ, ppm: 4.29 s (2H, CH2), 4.41 s (2H, CH2), 7.91 br.s (1H, NOH). Found, %: C 25.40; H 3.52; Cl 49.91; N 9.89. C3H5Cl2NO. Calculated, %: C 25.38; H 3.55; Cl 49.94; N 9.86. 3,3′-[2-(Hydroxyimino)propan-1,3-diyl]bis(1-methyl-1H-imidazol-3-ium) dichloride (VI). A solution of 1.9 g (0.014 mol) of 1,3-dichloropropan2-one oxime in 10 ml of anhydrous THF was added in portions to a solution of 2.0 g (0.025 mol) of 1-methyl1H-imidazole (Aldrich, ≥99%) in 10 ml of anhydrous THF. The mixture was kept for 15 h at 5–10°C, and the precipitate was filtered off and washed with THF. Yield 3.0 g (50%), mp 221–222°C (decomp.). 1H NMR spectrum (DMSO-d6), δ, ppm: 3.88 s (6H, CH3), 5.15 s (2H, CH2), 5.24 s (2H, CH2), 7.72 s (2H, Harom), 7.73 s (1H, H arom), 7.76 s (1H, H arom), 9.29 s (1H, H arom), 9.35 s (1H, H arom), 12.23 s (1H, NOH). Found, %: C 43.12; H 5.58; Cl 23.19; N 22.90. C11H17Cl2N5O. Calculated, %: C 43.15; H 5.60; Cl 23.16; N 22.87. 1-Dodecyl-1H-imidazole. A mixture of 4.1 g (0.06 mol) of imidazole, 14.4 ml (0.06 mol) of 1-bromododecane (Aldrich, ≥97%), and 3.9 (0.07 mol) of thoroughly ground potassium hydroxide in 60 ml of anhydrous acetone was heated for 8 h under reflux. The mixture was evaporated on a rotary evaporator, and the residue was distilled under reduced pressure. Yield 13.0 g (92%), bp 165–170°C (0.5–0.8 mm). 1 H NMR spectrum (CDCl3), δ, ppm: 0.88 t (3H, CH3, J = 6.8 Hz), 1.19–1.40 m [18H, (CH2)9], 1.71–1.81 m (2H, CH2), 3.92 t (2H, CH2N, J = 7.2 Hz), 6.90 s (1H, Harom), 7.05 s (1H, Harom), 7.48 s (1H, Harom). Found, %: C 76.24; H 11.92; N 11.83. C15H28N2. Calculated, %: C 76.21; H 11.94; N 11.85. 3,3′-[2-(Hydroxyimino)propan-1,3-diyl]bis(1-dodecyl-1H-imidazol-3-ium) dichloride (VII).
A solution of 1.0 g (7 mmol) of 1,3-dichloropropan-2one oxime in 10 ml of acetonitrile was added in small portions over a period of 5 h at room temperature to a solution of 3.3 g (14 mmol) of 1-dodecyl-1H-imidazole in 10 ml of acetonitrile. The precipitate was filtered off and thoroughly washed with acetonitrile. Yield 4.2 g (98%), mp 186–190°C (decomp.). 1 H NMR spectrum (CDCl3), δ, ppm: 0.88 t (6H, CH3, J = 6.7 Hz), 1.20–1.44 m [36H, (CH2)9], 1.84–1.98 m (4H, CH 2 ), 4.18–4.27 m (4H, CH 2 N +), 5.43 s (2H, CH2N+), 5.62 s (2H, CH2N+), 7.33 s (1H, Harom), 7.54 s (1H, H arom), 7.87 s (1H, H arom), 8.05 s (1H, H arom), 10.07 s (1H, Harom), 10.14 s (1H, Harom). Found, %: C 64.45; H 10.02; Cl 11.51; N 11.38. C33H61Cl2N5O. Calculated, %: C 64.47; H 10.00; Cl 11.53; N 11.39. The kinetics of decomposition of substrates I–III were studied by spectrophotometry (Genesys 10S UVVis, Thermo Electron Corp., 25°C), following accumulation of 4-nitrophenoxide ion at λ 400–420 nm. The acidity of the medium was monitored using a Metrohm 744 pH meter. The procedures for kinetic experiments and calculation of the observed pdeudofirst-order rate constants (kobs, s–1) were described in [3–5, 8]. The critical micelle concentrations were determined on the basis of the kinetic data: the CMC values corresponded to the bend on the kobs—c0 plot [4]. The error in the determination of k 2m from the kinetic data did not exceed 10%, and in the determination of KS and CMC, 20%. The pK a values were determined by spectrophotometry from variation of the UV spectra versus pH (Fig. 1) according to the equation pKa = pHi + log[(Dmax – Di)/(Di – Dmin),
where Dmax and Dmin are, respectively, the maximum and minimum optical densities at a given wavelength, and Di is the optical density at the same wavelength at pHi. The analytical wavelength was selected so that to ensure the maximum difference between Dmax and Dmin [3, 18]. REFERENCES 1. Popov, A.F., Pure Appl. Chem., 2008, vol. 80, p. 1381. 2. Morales-Rojas, H. and Moss, R.A., Chem. Rev., 2002, vol. 102, p. 2497. 3. Kivala, M., Cibulka, R., and Hampl, F., Collect. Czech. Chem. Commun., 2006, vol. 71, p. 1642. 4. Simanenko, Yu.S., Karpichev, E.A., Prokop’eva, T.M., Latt, A., Popov, A.F., Savelova, V.A., and Belousova, I.A., Russ. J. Org. Chem., 2004, vol. 40, p. 206. 5. Kapitanov, I.V., Belousova, I.A., Turovskaya, M.K., Karpichev, E.A., Prokop’eva, T.M., and Popov, A.F., Russ. J. Org. Chem., 2012, vol. 48, p. 651.
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SUPERNUCLEOPHILIC SYSTEMS BASED ON FUNCTIONALIZED SURFACTANTS ... I. 6. Prokop’eva, T.M., Karpichev, E.A., Belousova, I.A., Turovskaya, M.K., Shumeiko, A.E., Kostrykin, M.L., Razumova, N.G., Kapitanov, I.V., and Popov, A.F., Theor. Exp. Chem., 2010, vol. 46, p. 94. 7. Terrier, F., Rodriguez-Dafonte, P., Le Guevel, E., and Moutiers, G., Org. Biomol. Chem., 2006, vol. 4, p. 4352; Buncel, E., Um I.-H., and Terrier, F., The Chemistry of Hydroxylamines, Oximes, and Hydroxamic Acids, Rappoport, Z. and Liebman, J.F., Eds., Chichester, Wiley, 2009, vol. 2, chap. 17, p. 818. 8. Prokop’eva, T.M., Simanenko, Yu.S., Suprun, I.P., Savelova, V.A., Zubareva, T.M., and Karpichev, E.A., Russ. J. Org. Chem., 2001, vol. 37, p. 655. 9. Belousova, I.A., Kapitanov, I.V., Shumeiko, A.E., Anikeev, A.V., Turovskaya, M.K., Zubareva, T.M., Panchenko, B.V., Prokop’eva, T.M., and Popov, A.F., Theor. Exp. Chem., 2010, vol. 46, p. 225. 10. Welton, T., Chem. Rev., 1999, vol. 99, p. 2071; Kustov, L.M., Vasina, T.V., and Ksenofontov, V.A., Ross. Khim. Zh., 2004, vol. 48, no. 6, p. 13; Kamboj, R., Singh, S., Bhadani, A., Kataria, H., and Kaur, G., Langmuir, 2012, vol. 28, p. 11 969. 11. Ao, M., Huang, P., Xu, G., Yang, X., and Wang, Ya., Colloid Polymer Sci., 2009, vol. 287, p. 395; Ao, M., Xu, G., Zhu, Y., and Bai, Y., J. Colloid Interface Sci.,
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