Acid-base properties and nucleophilicity of o-aminomethylphenols in aqueous micellar solutions and microemulsions

Article abstract of DOI:10.1007/s11172-006-0488-4

The pK _a values and constants of tautomeric equilibrium of several o-aminomethylphenols with different hydrophilic-lipophilic ability were measured in aqueous micellar solutions and in direct microemulsions based on cetyltrimethylammonium bromi

Full text of DOI:10.1007/s11172-006-0488-4

Russian Chemical Bulletin, International Edition, Vol. 55, No. 10, pp. 1788—1793, October, 2006
1788
Acidꢀbase properties and nucleophilicity of oꢀaminomethylphenols
in aqueous micellar solutions and microemulsions
A. B. Mirgorodskaya,ꢀ N. S. Erzikova, L. A. Kudryavtseva, and A. I. Konovalov
A. E. Arbuzov Institute of Organic and Physical Chemistry,
Kazan Research Center, Russian Academy of Sciences,
8 ul. Akad. Arbuzova, 420088 Kazan, Russian Federation.
Fax: +7 (843 2) 73 2253. Eꢀmail: mirgorod@iopc.knc.ru
The pKa values and constants of tautomeric equilibrium of several oꢀaminomethylphenols
with different hydrophilic—lipophilic ability were measured in aqueous micellar solutions and
in direct microemulsions based on cetyltrimethylammonium bromide. The kinetics of hydrolyꢀ
sis of pꢀnitrophenyl acetate at different pH and concentrations of aminomethylphenol and
surfactant was studied.
Key words: micelles, microemulsions, oꢀaminomethylphenols, acidꢀbase properties, tauꢀ
tomerism, pꢀnitrophenyl acetate, kinetics.
In highly organized media based on surfactants, the
In the present work, to reveal specific features of the
effect of microdispersion media on the reaction behavior
of AMPs, we studied their acidꢀbase properties and
nucleophilicity in systems based on cetyltrimethylammoꢀ
nium bromide (CTAB) and decaoxyethylated oleyl alcoꢀ
hol (Brijꢀ97). The AMPs with different hydrophilic—lipoꢀ
philic ability were used: R = H (AMPꢀ1), Me (AMPꢀ2),
and isoꢀC9H19 (AMPꢀ3). The kinetics of hydrolysis of
pꢀnitrophenyl acetate (PNPA) in the presence of these
compounds was studied in molecular solutions and aqueꢀ
ous micellar systems, and direct microemulsions with varyꢀ
ing pH and concentrations of the reactants and surfactants.
interface sorbs selectively particles participating in acidꢀ
base equilibria. The sorption shifts pK of solubilized subꢀ
stances relative to the values in molecular solutions and
changes their reactivity.1—6 The effect depends on the
surfactant nature, the structure of a microaggregate and
its surface potential, and the properties of the substance
under study. The presence of two ionogenic groups of
different nature in oꢀaminomethylphenols (AMPs) creꢀ
ates a complicated system of acidꢀbase equilibria with
proton transfer involving the formation of zwitterions
(Scheme 1) and preꢀdetermines their reactivity in chemiꢀ
cal reactions.7,8
Experimental
Scheme 1
Commercial CTAB and Brijꢀ97 (Sigma) containing ~99%
of the major substance were used; AMPs were synthesized and
purified according to Ref. 9, and PNPA was recrystallized using
standard procedures. Aqueous systems with a surfactant conꢀ
centration of 0—0.015 mol L–1 and microemulsions containing
a surfactant (9.4 g), butanol (9.4 g), hexane (2.0 g), and water
(79.2 g) (volume fraction of water 0.74) were used as media.
The pK1 and pK2 values were determined by the potentioꢀ
metric titration of AMPs and the corresponding phenoxides
(CAMP = 0.005—0.01 mol L–1) with a 0.1 M solution of HCl
using a pHꢀ340 instrument. The values averaged over results of
three experiments were used, the reproducibility being 0.05
logarithmic units. Spectra of AMPs were recorded on a Specord
UV—Vis spectrophotometer in 1ꢀcm quartz cells in the waveꢀ
length range from 250 to 400 nm. Molar absorptivities (ε) were
determined from the absorbance values, which were measured
at the absorption maxima of the anionic and zwitterionic forms.
The changes in ε for AMPꢀ2 at different pH in different media
are presented in Table 1 as an example.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1724—1729, October, 2006.
1066ꢀ5285/06/5510ꢀ1788 © 2006 Springer Science+Business Media, Inc.

Acidꢀbase properties and nucleophilicity
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 10, October, 2006
1789
Table 1. Molar absorption coefficients of AMPꢀ2 in different
media
were determined by potentiometric titration. The acidꢀ
base properties of these compounds are virtually the same
in the absence of a surfactant in molecular solutions
(Table 2). A different situation is observed in CTABꢀbased
micellar solutions, where changes in pKа show the effect
of selective sorption of ionic forms of the AMPs by the
positively charged micellar surface. The pK1 values of
waterꢀsoluble AMPꢀ1 and AMPꢀ2 in the presence of the
surfactants change almost similarly (see Table 2). The
pK2 value that characterizes proton abstraction changes
more remarkably (∆pK = 0.5—1.1). For AMPꢀ3 in a miꢀ
cellar solution of CTAB, the pK2 values are close to pK2
of the hydrophilic homologs, whereas pK1 are substanꢀ
tially lower. Probably, the shift of pKа for AMPꢀ3 is deterꢀ
mined by contributions of both electrostatic and hydroꢀ
phobic interactions of a micelle and each AMP form inꢀ
volved in acidꢀbase equilibrium.
Water
Micellar solution
(CCTAB = 5 mmol L–1
Microemulsion
based on CTAB
)
pH ε (302 nm)
pH
ε (306 nm)
pH
ε (305 nm)
13.0
12.4
12.0
11.5
11.0
10.5
3400
3310
3200
3000
2830
2700
13.0
11.0
10.5
10.0
9.4
3270
3050
2750
2300
1800
1400
13.0
12.5
12.0
11.5
11.0
10.5
3600
3350
2800
1750
1050
500
9.0
The reaction kinetics was studied in freshly prepared microꢀ
dispersion media by spectrophotometry on a Specord UV—Vis
instrument at 25 °C under the pseudoꢀfirst reaction conditions.
The reaction progress was monitored by a change in the absorꢀ
bance of solutions at the wavelength 400 nm (formation of
pꢀnitrophenoxide anion); the initial concentration of the subꢀ
strate being 5•10–5 mol L–1, and conversion more than 90%.
The apparent pseudoꢀfirst order rate constants (kapp) were deꢀ
termined from the plot log(D∞ – Dt) = –0.434kappt + const,
where Dt and D∞ are the absorbancies of solutions at the moment
t and after reaction completion, respectively. The kapp values
were calculated by the leastꢀsquares method.
In a CTABꢀbased microemulsion, differences in the
acidꢀbase properties of the AMPs are aligned. This can
be due to a decrease in the role of electrostatic interacꢀ
tions in these systems compared to micellar solutions:
for direct CTAB micelles the surface potential (ψ) is
120—140 mV,10,11 whereas for oil—water microemulsions
based on this surfactant ψ ≈ 30 mV.12,13 The systems based
on nonionic surfactants for which ψ ≈ 0 have no contribuꢀ
tion of electrostatic interactions, and the pKа value is
affected by the hydrophobic effect, which is most signifiꢀ
cant for AMPꢀ3 (see Table 2).
The formation of the hydrolysis product in microdispersion
media was confirmed by the yield of the reaction products in
experiment with an equimolar amount of PNPA and AMP. The
concentration of acetic acid that formed was measured by poꢀ
tentiometric titration, and that of pꢀnitrophenol was measured
spectrophotometrically. Equal amounts of these substances were
found to form in the reaction. For instance, in a 0.01 M soluꢀ
tion of CTAB at a concentration of AMPꢀ1 and PNPA of
0.008 mol L–1, in 10 min after the beginning of the reaction the
concentrations of acetic acid and pꢀnitrophenol were 0.0033
and 0.0036 mol L–1, respectively, whereas after 30 min the conꢀ
According to the earlier proposed procedure,14 we calꢀ
culated the constant of tautomeric equilibrium (Kt) for
the AMPs by the equation
centrations were 0.0056 and 0.0055 mol L–1
.
using combined data of potentiometric titration and UV
spectroscopy when the molar absorption coefficients (εm)
were measured at constant pH of the medium.
Results and Discussion
The UV spectra in a range of 290—310 nm contains no
absorption of the cationic (D) and neutral (A) forms of
the AMPs, i.e., εm(А) = 0. In this region, the molar abꢀ
The pKа values characterizing the proton addition
(pK1) and abstraction (pK2) for the AMPs under study
Table 2. Constants of acidꢀbase and tautomeric equilibria of AMPs in different media (CAMP = 2.5 mmol L–1
)
Medium
AMPꢀ1
AMPꢀ2
AMPꢀ3
pK1
pK2
Kt
pK1
pK2
Kt
pK1
pK2
Kt
Water
Water—ethanol (1 : 1)*
ЦТАБ (0.01 mol L–1
Microemulsion (CTAB)
Brijꢀ97 (0.01 mol L–1
8.45
8.20
8.24
8.30
8.4
10.90
11.60
10.45
11.0
2.5
8.75
8.45
8.60
8.1
11.40
11.75
10.25
11.45
11.3
3.5
—
—
—
~0
0.3
~0
~0
~0
1.1
~0
~1
~0
1.3
~0
1.4
8.20
6.50
7.20
6.4
11.65
10.0
11.65
10.8
)
)
10.95
8.7
* In these media, the pH value in the halfꢀneutralization point detected with a pHꢀmeter was accepted as pKа. This
effective value makes it possible to compare the properties of AMPs depending on their structure within the same
system; however, in this case, it is incorrect to discuss the effect of the medium on pKа.

1790
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 10, October, 2006
Mirgorodskaya et al.
Table 3. Partial constants of acidꢀbase equilibria of AMPs in
water and aqueous micellar solutions of surfactants*
sorption coefficients of their anionic (C) and zwitterꢀ
ionic (B) species are equal.
The data obtained (see Table 2) show that for the
AMPs the Kt value decreases on going from aqueous to
micellar solutions. This indicates preferential solubilizaꢀ
tion of the neutral AMP form by micelles compared to the
zwitterionic form. In a microemulsion, as well as in an
aqueousꢀalcohol solution, equilibrium is virtually shifted
completely to the neutral form; the AMPs are located in a
microdroplet regardless of the hydrophobic properties.
Probably, the AMPs nonionized by the external effect of
acid or alkali are located in a microregion with a lower
polarity, which is the interphase layer and, the more so,
the core of the microaggregate, rather than in the aqueous
volume phase. The medium is insufficiently polar to favor
intramolecular proton transfer and zwitterion formation.
We observed15 the same effect of the medium on AMP
tautomerism in acetonitrile—water solutions with a variꢀ
able ratio of the components.
AMP
Medium
pK1´
pK1″
pK2´
pK2″
AMPꢀ1
Water
CTAB
Brijꢀ97
Water
CTAB
Brijꢀ97
CTAB
8.6
8.62
8.7
8.86
8.85
8.95
7.14
9.0
8.65
8.7
9.40
8.96
9.05
6.62
10.75
10.12
10.65
11.29
10.0
10.36
10.06
10.65
10.74
9.90
AMPꢀ2
AMPꢀ3
10.8
9.37
10.65
9.9
* CCTAB = 0.01 mol L–1; CBrijꢀ97 = 0.01 mol L–1
.
affect the reactivity of these compounds, in particular,
their nucleophilicity during interaction with PNPA.
It is known16,17 that the zwitterionic and anionic AMP
forms are reactive in nucleophilic substitution reactions.
The anionic form exists at high pH and, in this case, the
hydroxide ion competes with AMP. The neutral form also
manifests nucleophilicity due to the formation of an inꢀ
tramolecular hydrogen bond resulting in an increase in
the electron density on the oxygen atom.
According to published data,14 the partial constants of
acidꢀbase equilibria can be calculated for the media where
zwitterionic AMP forms are formed
K1 = K1´ + K1″; K2 = K2´K2″/(K2´ + K2″);
K1´ = K1Kt/(1 + Kt); K1″ = K1/(1+ Kt);
K2´ =K2(1 + Kt)/Kt; K2″ = K2(1 +Kt).
A possible general mechanism of the reaction is shown
in Scheme 2.
In the case of AMPs, intermediate products of transꢀ
esterification of PNPA are rapidly hydrolyzed due to inꢀ
tramolecular catalysis with the aminomethyl group, which
was confirmed by the yields of acetic acid and pꢀnitroꢀ
phenol in the reaction. Unlike simple phenols forming
rather stable transesterification products,8,18 these comꢀ
pounds are characterized by hydrolysis catalyzed via the
nucleophilic mechanism at the concerted action of the
amino group and phenolic hydroxyl group.
Based on analysis of the partial constants (Table 3),
we can conclude a relative ability of different forms of
AMPꢀ1 and AMPꢀ2 to solubilization by CTAB micelles.
The ability increases in the order: cation ≈ zwitterꢀ
ion < neutral molecule < anion. Considerable differences
between the partial constants of AMPꢀ3 and the correꢀ
sponding values for its waterꢀsoluble analogs indicate a
strong effect of hydrophobic interactions on the physicoꢀ
chemical properties of this compound in micellar soluꢀ
tions. The ratio of the AMP forms in solutions should
Under the conditions of changing pH of the medium,
the regions of existence of different AMP forms are deterꢀ
Scheme 2

Acidꢀbase properties and nucleophilicity
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 10, October, 2006
1791
kapp/s–1
kapp/s–1
0.05
0.004
0.003
0.002
0.001
0.04
0.03
0.02
0.01
1
2
3
2
1
0
9
10
11
pH
7
8
9
10
11
pH
Fig. 1. Effect of pH on the apparent rate constant of PNPA
hydrolysis in an aqueousꢀalcohol (1 : 1) solution in the presence
of AMPꢀ3 (1) and AMPꢀ2 (2); CAMP = 2.5 mmol L–1, 25 °C.
Fig. 2. Effect of pH on the apparent rate constant of PNPA
hydrolysis in a micellar solution of CTAB (0.01 mol L–1) in the
absence of AMP (1) and in the presence of AMPꢀ2 (2) and
AMPꢀ3 (3); CAMP = 2.5 mmol L–1, 25 °C.
mined by the pKа values, which is reflected by their reacꢀ
tion behavior. In the absence of surfactants in molecular
solutions, for instance, in an aqueousꢀalcohol medium,
the acidꢀbase properties of the AMPs under study are
virtually the same (see Table 2). An aqueousꢀalcohol meꢀ
dium manifests no substantial differences in their interacꢀ
tion with PNPA: the plots of the apparent reaction rate
constant (kapp) vs. pH in alkaline and weakly alkaline
media for AMPꢀ2 and AMPꢀ3 are described by the single
curve (Fig. 1).
kapp/s–1
0.025
4
1, 5´´
2
0.020
3, 5´
4, 5
A different pattern is seen when studying the properꢀ
ties of the AMPs in micellar systems based on cationic
surfactants. The plots of the apparent rate constant for the
reactions of the AMPs with PNPA vs. pH of the medium
for AMPꢀ2 and AMPꢀ3 in a micellar solution of CTAB
(0.01 mol L–1) at 25 °C are shown in Fig. 2. According to
pK1 at pH of the medium <7.5, AMPꢀ2 is almost comꢀ
pletely transformed into the inactive cationic form and
the kapp value coincides with that for substrate hydrolysis
(see Fig. 1); AMPꢀ3 is rather reactive under these condiꢀ
tions. The difference in kapp for the both AMPs decreases
gradually with an increase in pH and accumulation of the
reactive forms. At high pH in the region where the comꢀ
pounds under study exist predominantly in the anionic
form, their reactivities toward PNPA are close.
3
0.015
0.010
0.005
0
2
1
5, 5´, 5´´
0.004 0.008 0.012
CCTAB/mol L–1
Fig. 3. Apparent rate constant of PNPA hydrolysis at pH = 10.0
as a function of the CTAB concentration in the absence of
AMP (1) and in the presence of AMPꢀ1 (2), AMPꢀ2 (3), and
AMPꢀ3 (4) and as a function of the Brijꢀ97 concentration in the
absence of AMP (5) and in the presence of AMPꢀ1 (5´) and
AMPꢀ3 (5″); CAMP = 2 mmol L–1, 25 °C.
When studying the kinetics of the reaction of the AMPs
with PNPA with changing CTAB concentration at conꢀ
stant pH (data obtained at pH 10.0 are presented as an
example in Fig. 3), much higher kapp values were revealed

1792
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 10, October, 2006
Mirgorodskaya et al.
kapp/s–1
for AMPꢀ3 compared to other AMPs, which can be
a consequence of high affinity of this compound to the
micellar pseudoꢀphase and a possibility of forming mixed
aggregates.
Quantitative characteristics that reflect the interaction
of the substrate with a micelle can be obtained by analysis
of the experimental kinetic data in the framework of
the pseudoꢀphase model of micellar catalysis using the
equation19
0.04
0.03
0.02
0.01
kapp = (kmKsCdet + k0)/(1 + KsCdet),
where Cdet is the surfactant concentration corrected to the
critical micelle concentration (CMC); k0 and km are the
rate constants in the aqueous medium and micellar phase,
respectively; Ks is the binding constant of the substrate.
As can be seen from the results obtained in Table 4, an
increase in the concentration of the anionic AMP form in
a micellar solution of CTAB facilitates micelle formation
decreasing the CMC, decreases binding of PNPA with a
micelle, and enhances the micellar catalytic effect. The
higher effect (up to 23 times) is observed for AMPꢀ3,
which can be due to the content of the anionic form for
this compound at pH 10.0 exceeding those for AMPꢀ1
and AMPꢀ2 (see Tables 2 and 3). A small fraction of the
anionic AMP form in solutions of Brijꢀ97 results in the
situation when at pH 10.0 no differences between AMPꢀ1
and AMPꢀ3 are seen and the main direction of ester bond
cleavage is alkaline hydrolysis in solutions (see Fig. 3).
Thus, the micellar catalytic effect of PNPA hydrolysis in
the presence of the AMPs is related first of all to the
influence of the medium on the acidꢀbase properties
of AMP.
1
2
9
10
11
pH
Fig. 4. Effect of pH on the apparent rate constant of PNPA
hydrolysis in a direct CTABꢀbased microemulsion in the presꢀ
ence of AMPꢀ1 (1) and AMPꢀ3 (2); CAMP = 0.05 mol L–1, 25 °C.
lated and kapp increases (Fig. 4). The plot of kapp vs. AMP
concentration at constant pH in microemulsions is linear
(Fig. 5). Based on these data and taking into account pK1
kapp/s–1
1
0.010
In the case of CTABꢀbased microemulsions at
pH < (pK1 + pK2)/2, the neutral AMP form is reactive in
the reactions with PNPA. With an increase in the basicity
of the system, the more reactive anionic form is accumuꢀ
2
0.008
3
Table 4. Parameters of micelleꢀcatalyzed PNPA hydrolysis in
weakly alkaline solutions of CTAB in the presence of AMPs
(C = 2 mmol L–1, 25 °C)
0.006
km/s–1
Ks
CMC
/mol L–1
km/k0
**
Nucleoꢀ pH*
phile
/L mol–1
0.004
AMPꢀ1
AMPꢀ2
AMPꢀ3
9.2
10.0
9.2
10.0
9.2
0.0035
0.011
0.004
0.017
0.007
0.035
780
450
750
300
650
250
0.0007
0.00012
0.0007
0.00011
0.0004
0.00010
4
7
5
11
10
23
4
0.002
10.0
0
0.01
0.02
0.03
CAMP/mol L–1
* To maintain pH, a buffer solution of sodium tetraborate
(0.05 mol L–1, pH 9.2) was used as a basis, adding a 0.1 M
solution of sodium hydroxide and monitoring the pH value with
a pHꢀmeter.
Fig. 5. Apparent rate constant of PNPA hydrolysis as a function
of the AMP concentration in a direct CTABꢀbased microꢀ
emulsion: AMPꢀ2 (1) and AMPꢀ3 (2) at pH = 10.6; AMPꢀ2 (3)
and AMPꢀ3 (4) at pH = 10.0.
** The km/k0 ratio is a measure of the micellar catalytic effect.

Acidꢀbase properties and nucleophilicity
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 10, October, 2006
1793
Table 5. Secondꢀorder rate constants of PNPA hydroꢀ
lysis in the presence of the neutral and anionic AMP
forms in the CTABꢀbased microemulsion (volume
fraction of water 0.74) at 25 °C
3. D. M. Vriezema, M. C. Aragones, J. A. A. W. Elemans, J. L.
M. Cornelisstn, A. E. Rowan, and R. J. M. Nolte, Chem.
Rev., 2005, 105, 1445.
4. K. K. Ghosh, D. Sinha, M. L. Satnami, D. K. Dubey,
P. RodriguezꢀDafonte, and G. L. Mundhra, Langmuir, 2005,
21, 8664.
5. K. M. Solntsev, S. A. AlꢀAinain, Y. V. Il´ichev, and M. G.
Kuzmin, J. Phys. Chem., A, 2004, 108, 8212.
6. M. Arias, L. GarciaꢀRio, J. S. Mejuto, P. Rodriguezꢀ
Dafonte, and J. SimalꢀGandara, J. Agric. Food. Chem., 2005,
53, 7172.
Compound
AMPꢀ1
Form
k2/L mol–1 s–1
Neutral
Anionic
Neutral
Anionic
0.1
1.2
AMPꢀ3
0.05
0.8
7. R. A. Shagidullina, I. S. Ryzhkina, A. B. Mirgorodskaya,
L. A. Kudryavtseva, and V. E. Bel´skii, Izv. Akad. Nauk
SSSR, Ser. Khim., 1994, 1215 [Russ. Chem. Bull., 1994, 43,
1149 (Engl. Transl.)].
8. A. B. Teitel´baum, I. S. Ryzhkina, L. A. Kudryavtseva, V. E.
Bel´skii, and B. E. Ivanov, Izv. Akad. Nauk SSSR, Ser. Khim.,
1983, 1016 [Bull. Acad. Sci. USSR, Div. Chem. Sci., 1983, 32,
918 (Engl. Transl.)].
9. B. Reichert, Die Mannich Reaction, Springer Verlag,
Berlin—Gottingen—Heidelberg, 1959, 192.
10. L. Ya. Zakharova, F. G. Valeeva, A. V. Zakharov, A. R.
Ibragimova, L. A. Kudryavtseva, and H. E. Harlampidi,
J. Colloid Interface Sci., 2003, 263, 597.
11. A. B. Mirgorodskaya, L. A. Kudryavtseva, L. Ya. Zakharova,
and V. E. Bel´skii, Izv. Akad. Nauk, Ser. Khim., 1998, 1333
[Russ. Chem. Bull., 1998, 47, 1296 (Engl. Transl.)].
12. A. B. Mirgorodskaya and L. A. Kudryavtseva, Zh. Obshch.
Khim., 2002, 72, 1343 [Russ. J. Gen. Chem., 2002, 72 (Engl.
Transl.)].
and pK2 of the compound under study and the alkaline
hydrolysis rate constant (k0), which is determined as
a section cut on the ordinate of the kapp = f(CAMP) plot,
we determined the secondꢀorder rate constants for the
neutral and anionic forms of the AMPs (Table 5).
The obtained data show that the nucleophilicity of the
anionic AMP form is approximately an order of magniꢀ
tude higher than that of the neutral form. In the microꢀ
emulsion under study (unlike micellar solutions), the
hydrophobic AMPs are less reactive than the hydroꢀ
philic AMPs. This is probably due to the fact that a conꢀ
siderable volume of the oil phase in microemulsions proꢀ
vides more possibilities for localization of reactants than
micelles do. A hydrophobic compound can immerse into
the oil phase. This shifts the zone of reactant interaction
to the region of lower polarity exerting an unfavorable
effect on the reaction rates.
13. R. A. Mackay and C. Hermansky, J. Phys. Chem., 1981,
85, 739.
Thus, using as an example hydrolysis of esters of carbꢀ
oxylic acids in the presence of the AMPs in surfactantꢀ
based microdispersion media, one can monitor a combiꢀ
nation of possibilities of homogeneous bifunctional and
micellar catalysis. The specific reaction behavior of the
AMPs is due to the presence of two nonionogenic groups
of different nature, which creates a complicated system of
acidꢀbase equilibria of proton transfer including the forꢀ
mation of zwitterions and provides prerequisites for the
concerted effect of the functional groups similar to the
effect of active centers in enzymes. Selective sorption of
the ionic AMP forms by the positively charged interface is
the main reason for the catalytic effect of microdispersion
media on PNPA hydrolysis in the presence of the AMPs.
14. A. B. Teitel´baum, K. A. Derstuganova, N. A. Shishkina,
L. A. Kudryavtseva, V. E. Bel´skii, and B. E. Ivanov, Izv.
Akad. Nauk SSSR. Ser. Khim., 1980, 803 [Bull. Acad. Sci.
USSR, Div. Chem. Sci., 1980, 29, 558 (Engl. Transl.)].
15. A. B. Teitel´baum, L. A. Kudryavtseva, V. E. Bel´skii, and
B. E. Ivanov, Izv. Akad. Nauk SSSR, Ser. Khim., 1980, 2253
[Bull. Acad. Sci. USSR, Div. Chem. Sci., 1980, 29, 1571 (Engl.
Transl.)].
16. I. S. Ryzhkina, L. A. Kudryavtseva, K. M. Enikeev, V. I.
Morozov, G. A. Boss, and Yu. I. Sal´nikov, Izv. Akad. Nauk,
Ser. Khim., 2000, 1355 [Russ. Chem. Bull., Int. Ed., 2000,
49, 1349].
17. R. A. Shagidullina, L. A. Kudryavtseva, A. B. Mirgorodskaya,
L. Ya. Zakharova, and B. E. Ivanov, Izv. Akad. Nauk SSSR,
Ser. Khim., 1990, 1126 [Bull. Acad. Sci. USSR, Div. Chem.
Sci., 1990, 39, 1010 (Engl. Transl.)].
18. J. F. Kirsh and W. P. Jencks, J. Am. Chem. Soc., 1964,
86, 837.
References
19. E. J. Fendler and J. H. Fendler, Adv. Phys. Org. Chem.,
1970, 8, 271.
1. I. V. Berezin, K. Martinek, and A. K. Yatsimirskii, Usp.
Khim., 1973, 42, 1729 [Russ. Chem. Rev., 1973, 42, 1343
(Engl. Transl.)].
2. K. Holmberg, Current Opinion in Colloid Interface Sci.,
2003, 8, 187.
Received March 21, 2006;
in revised form June 23, 2006