Changes in the relative contribution of specific and general base catalysis in cationic micelles. The cyclization of substituted ethyl hydantoates

Article abstract of DOI:10.1021/jo001759w

The rate-surfactant profiles for the HO^-- and AcO^--catalyzed ring closure of two ethyl hydantoates, E2 and E3, to hydantoins with three cetyltrimethylammonium salts (CTAX, X = Br^-, Cl^-, or AcO^-) are m

Full text of DOI:10.1021/jo001759w

J . Org. Chem. 2001, 66, 2123-2130
2123
Ch a n ges in th e Rela tive Con tr ibu tion of Sp ecific a n d Gen er a l
Ba se Ca ta lysis in Ca tion ic Micelles. Th e Cycliza tion of Su bstitu ted
Eth yl Hyd a n toa tes
,
†
†
‡
,‡
Iva B. Blagoeva,* Maria M. Toteva, Nadia Ouarti, and Marie-Fran c¸ oise Ruasse*
Institute of Organic Chemistry, Bulgarian Academy of Sciences, ul. Acad. G. Bonchev bl.9, Sofia 1113,
Bulgaria, and Institut de Topologie et de Dynamique des Syst e` mes de l’Universit e´ Paris 7-Denis Diderot,
associ e´ au CNRS, UPRESA 7086, 1, rue Guy de la Brosse, 75005 Paris, France
ruasse@paris7.jussieu.fr
Received December 19, 2000
-
-
The rate-surfactant profiles for the HO - and AcO -catalyzed ring closure of two ethyl hydantoates,
-
-
-
E2 and E3, to hydantoins with three cetyltrimethylammonium salts (CTAX, X ) Br , Cl , or AcO )
are measured in 0.02 and 0.2 M acetate buffers 50% base with starting pH 4.65. Marked
accelerations associated with large pH increases are found in 0.02 M buffered CTAOAc. Smaller
accelerations and smaller pH changes are observed in 0.2 M buffered CTAOAc and CTACl. From
these profiles, the micellar rate constants for the specific base- and general base-catalyzed reactions,
-
-
HO
AcO
w
k2 and k2,m , respectively, of E2 and E3 are obtained separately. The resulting values of k2,m/k ,
,m
E2/E3 rate constant ratios, and kinetic solvent isotope effects, KSIEs, are consistent with a strong
-
predominance of the HO reaction in the dilute buffer, while in the more concentrated buffer, specific
a n d general catalysis compete for the two substrates. This result is in sharp contrast with that
observed in water in which the reaction of E2 is almost exclusively specifically catalyzed. The
increase in the general base-catalyzed pathway for E2 is attributed not to an increase in the rate
constant for this pathway in micelles but to a smaller decrease than that for the specific catalysis
w
(k2,m/k ) 0.2 and 0.4 for the specific and general catalysis, respectively). The different responses
of the rate constants to the micellar media are interpreted as a larger effect of the interfacial polarity
on the specific than on the general catalysis. The apparent contradiction between the rate constant
decreases and the marked accelerations in micellar media is discussed in terms of pH changes,
-
i.e., [HO ] changes, and of acetate inclusion via ion exchanges at micellar interfaces.
Micellar systems provide models for understanding the
ways by which changes in the microenvironment can
affect rates of reactions of bioorganic interest. Contrary
Sch em e 1
1
to nucleophilic substitutions and specific acid-base-
catalyzed reactions, general acid-base catalysis, which
plays an important role in the accelerations of enzyme-
catalyzed reactions,2 has not been widely studied in
micellar systems. This is due to numerous drawbacks of
both conceptual and experimental origins.1
a,3,4
General
catalysis has been most convincingly identified in cases
of mixed micelles containing covalently bound catalyst
or on the basis of structure-reactivity relationships and
kinetic solvent isotope effects (KSIE).5
A suitable reaction for investigating general acid-base
catalysis in micelles is the ring closure of sterically
strained ethyl hydantoates to hydantoins (Scheme 1).
This reaction has been extensively studied as a model
reaction for the carboxylation of biotin.7
,6
*
To whom correspondence should be addressed. (M.-F.R.) Tel.: +33
1
44 27 68 42. Fax: +33 1 44 27 68 14. (I.B.) E-mail: iva@orgchm.bas.bg.
Some of the model compounds react at convenient rates
by hydroxide and general base-catalyzed reactions at pH
values below 7,7 which provides a unique opportunity
to investigate catalysis by weak bases such as acetate
ion in micellar media at low pH. We expected to maximize
catalysis at the micellar interface by using a surfactant
†
Bulgarian Academy of Sciences.
Institut de Topologie et de Dynamique des Syst e` mes de l’Universit e´
‡
d,e
Paris 7-Denis Diderot.
1) (a) Bunton, C. A.; Savelli, G. Adv. Phys. Org. Chem. 1986, 22,
13. (b) Menger, F. M. Angew. Chem., Int. Ed. Engl. 1991, 30, 1086.
c) Ta sˇ cio gˇ lu, S. Tetrahedron 1996, 34, 11113. (d) Dugas, H.; Penney,
(
2
(
C. In Bioorganic Chemistry; Springer-Verlag: New York, Heidelberg,
Berlin, 1981. (e) Perrin, C. L.; Chen, J .-H.; Ohta, B. K. J . Am. Chem.
Soc. 1999, 121, 2448. (f) Bunton, C. A.; Yatsimirsky, A. K. Langmuir
2
000, 16, 5921.
(6) Rav-Acha, Ch.; Ringel, I.; Sarel, S.; Katzhendler, J . Tetrahedron
1988, 44, 5879.
(2) Kirby, A. J . Acc. Chem. Res. 1997, 30, 290.
(
3) J encks, W. P. In Catalysis in Chemistry and Enzymology;
(7) (a) Blagoeva, I. B.; Pojarlieff, I. G.; Kirby, A. J . J . Chem. Soc.,
Perkin Trans. 2 1984, 745. (b) Knowles, J . R. Annu. Rev. Biochem.
1989, 58, 195. (c) Blagoeva, I. B. J . Chem. Soc., Perkin Trans. 2 1987,
127. (d) Blagoeva, I. B.; Tashev, D.; Kirby, A. J . J . Chem. Soc., Perkin
Trans. 1 1989, 1157. (e) Atay, E.; Blagoeva, I. B.; Kirby, A. J .; Pojarlieff,
I. G. J . Chem. Soc., Perkin Trans. 2 1998, 2289.
McGraw-Hill: New York, 1969.
4) Romsted, L. S.; Bunton, C. A.; Yao, J . Curr. Opin. Colloid
Interface Sci. 1997, 2, 622.
5) Froehner, S. J .; Nome, F.; Zanette, D.; Bunton, C. A. J . Chem.
Soc., Perkin Trans. 2 1996, 673.
(
(
1
0.1021/jo001759w CCC: $20.00 © 2001 American Chemical Society
Published on Web 02/20/2001

2
124 J . Org. Chem., Vol. 66, No. 6, 2001
Blagoeva et al.
Sch em e 2
Sch em e 3
effect of CTAX micelles on these two reactions are
expected because of favorable electrostatic interactions
between the two anionic catalysts and the cationic
surfactant headgroups. In this paper, we show that the
relative contribution of the specific and general catalysis
is different in micellar systems because of a different
sensitivity of their rate constants to the change in the
polarity of the reaction medium.
with the same reactive counterion as the studied general
base. Cetyltrimethylammonium acetate is a good candi-
date for an efficient micellar general base catalysis on
these substrates.
Exp er im en ta l Section
We report now results on the rates of ring closure of
two ethyl hydantoates to hydantoins (E2, R ) H and E3,
R ) Me) with three cetyltrimethylammonium salts
Ma ter ia ls. Inorganic reagents and buffer components were
of analytical grade and used without further purification.
Buffer solutions were prepared with CO
2
-free distilled water.
-
-
-
D
2
O, 99.99 atom % D, was from Aldrich. Cetyltrimethyl-
(
CTAX, X ) Br , Cl , or AcO ) in acetate buffers.
ammonium chloride, CTACl, 25 wt % solution in water, was
from Aldrich and used without further purification. Cetyltri-
methylammonium bromide, CTABr, from Merck was used
after recrystallization from ethanol. Cetyltrimethylammonium
The model compounds E2 and E3 were chosen because
their base-catalyzed reactions proceed by different mech-
anisms in water. The extra methyl group of E3 changes
-
10
the mechanism of the HO -catalyzed reaction (Scheme
acetate, CTAOAc, was prepared according to Sepulveda et al.
2
) from specific base-catalyzed formation of the tetrahe-
and purified by several recrystallizations from methanol/ether
1:20. The purity of the product was checked by titration with
HCl of the acetate ions in 90:10 (v/v) ethanol/water. Purity
was ca. 98%. The preparation of ethyl hydantoates E2 and E3
was described previously.11
Kin etic Mea su r em en ts. Rate constants were determined
at 25.0 ( 0.01 °C under pseudo-first-order conditions in the
thermostated cell compartment of a Unicam SP-800 or Carl
-
dral intermediate T (step 2 for E2) to its general acid-
catalyzed breakdown by water (step 3 for E3) by slowing
the proton transfer involved in the decomposition of T .
General catalysis by buffer bases, A , also goes via
different mechanisms for E2 and E3. The acetate-
catalyzed reaction of E2 (A ) AcO , Scheme 3) does not
involve any prior proton removal from SH but the direct,
rate-determining formation of T . In other terms, the E2
reaction with A consists of a true general base catalysis.
-
7e
-
8
-
-
Zeiss J ena spectrophotometer. Reactions were initiated by
-
injecting 20-50 µl of 1 × 10-2 M stock solution of the substrate
-
in THF into 2.7 mL of preheated buffer solution containing
the surfactant. The rates for cyclization of the substituted
esters were followed at 238 nm by monitoring the decrease of
the absorbance due to the phenylureido group. Pseudo-first-
In contrast, the general base-catalyzed reaction of E3
(
Scheme 4) goes through the kinetically equivalent
specific base and general acid catalysis, with rapid
deprotonation of SH and rate-limiting decomposition of
T
order rate constants, kobs, were obtained by nonlinear regres-
sion fitting to the equation A ) A e-kobst + A where A , A
t
0
∞
t
0
-
catalyzed by AH (acetic acid).
∞
and A are the absorbances at time t, zero, and infinity,
In water, the pseudo-first-order rate constants, k
w
′, are
respectively; kobs values were found to be reproducible within
%.
p H Mea su r em en ts. pH values were measured directly
5
described by eq 1 in which all rate constants (k with
superscripts referring to the several catalysts) have been
measured previously7 (see footnotes of Table 1):
after each kinetic run using a Radiometer pH M 84 research
pH meter, with a GK 2401 C electrode standardized at pH
e,9
6
.87 and 4.01.7c The electrode standardization was checked
-
-
H2O
HO
-
AcO
-
kw′ ) k
+ kw [HO ] + kw [AcO ] +
after each series of runs and found not affected by the
2
surfactant solutions studied. Experiments in D O and H O
AcOH
2
k
[AcOH] (1)
w
solutions were run simultaneously in the multicell compart-
ment of the spectrophotometer. pD values were obtained by
-
The two substrates have the particularity of different
reactivity ratios E2/E3 (kE2/kE3) for the hydroxide- and
acetate-catalyzed reactions.7 At pH values above 4
adding 0.4 to the pH meter readings. To convert pH to [OH ]
-
and pD to [OD ], pK
w
of 14.0 and of 14.86 were taken,
respectively.12
a,e
2
where these two catalysts compete and where the H O
Resu lts a n d Discu ssion
and AcOH reactions can be neglected, E2 is more reactive
-
-
HO
than E3, with kw
HO
w
for E2 4.4 times larger than k
for
The extent of micellar catalysis was determined from
experimental rate-surfactant profiles (Figures 1 and 2)
-
AcO
E3, while the second-order rate constant kw
is two
times smaller for E2 than for E3. Significant kinetic
(
10) Sepulveda, L.; Gabrera, W.; Gamboa, C.; Meyer, M. J . Colloid
(
8) Blagoeva, I. B.; Kirby, A. J .; Koedjikov, A. H.; Pojarlieff, I. G.
Can. J . Chem. 1999, 77, 849.
9) Catalysis by acetic acid could not be detected for E2, and catalysis
Interface Sci. 1987, 117, 460.
(11) Pojarlieff, I. G.; Blagoeva, I. B.; Kirby, A. J .; Mikhova, B. P.;
Atay, E. J . Chem. Res., Synop. 1997, 220.
(
by acetate ions is weaker for this substrate (ref 7e). In any case, as a
result of the favorable electrostatic effect, we expect only catalysis by
anionic species to be significant at the interface of cationic micelles.
(12) (a) Covington, A. K.; Robinson, R. A.; Bates, R. G. J . Phys.
Chem. 1966, 70, 3820. (b) Fishbein, J . C.; J encks, W. P. J . Am. Chem.
Soc. 1988, 110, 5075.

Specific and General Base Catalysis in Micelles
J . Org. Chem., Vol. 66, No. 6, 2001 2125
Sch em e 4
Sch em e 5
-
The ring closure of E2 and E3 is first order in [HO ]
in the investigated pH region.7d In acetate buffers, as
shown in Scheme 5, hydroxide- and acetate-catalyzed
reactions are expected to take place in both micellar and
aqueous pseudophases.
F igu r e 1. Dependence of the observed rate constants for ring
closure of E2 and E3 at 25 °C in micelles of CTACl in acetate
buffers on the concentration of surfactant. O, E2 in 0.02 M
buffer; 0, E3 in 0 02 buffer; b, E2 in 0.2 M buffer; 9, E3 in
In the pseudophase model1 the observed rate constant,
a
k
obs, is described by eq 2, in which k are second-order rate
0
.2 M buffer. The curves are calculated with the rate constants
kobs
k
)
from Tables 1 and 2 (see text).
HO-
AcO-
-
-
AcO
[HO-] + kw [AcO-] + {kM [HO-] + kM [AcO ] }K
HO
-
w
w
w
M
M
S
1
+ K ([D] - cmc)
S
T
(2)
constants, with concentrations in square brackets refer-
ring to molarity in the total solution volume. The
subscripts w and M refer to water and micellar reactions,
-
-
respectively, and the superscripts HO and AcO to the
catalysts. K is the binding constant of the substrate, [D]
is the surfactant concentration, and cmc is the critical
S
T
-
1
-1
micelle concentration. In eq 2, k
w
are in units of M
s ,
-
1
and k are in s units. To obtain the second-order rate
constants, k2,m, for the reaction in the micellar phase, k
M
M
1
a
is multiplied by the micellar volume, V
m
(k2,m ) k
M m
V ).
1
4
In the usual pseudophase ion exchange (PIE) model,
the ion concentrations in both phases are obtained from
F igu r e 2. Dependence of the observed rate constants for ring
closure of E2 and E3 at 25 °C in micelles of CTAOAc in acetate
buffers on the concentration of surfactant. O, E2 in 0.02 M
buffer; 0, E3 in 0.02 M buffer; b, E2 in 0.2 M buffer; 9, E3 in
-
the equilibrium constants for exchange of anions Y from
-
the aqueous phase for surfactant counterions X :
-
-
0
.2 M buffer. The curves are calculated with the rate constants
[
Y ] [X ]
M
-
w
Y
from Tables 1 and 2 (see text).
Kex ) K
)
(3)
X-
-
-
[
Y ] [X ]
w
M
with cetyltrimethylammonium salts in the 0-0.1 M
range. The standard aqueous medium for the rate-
surfactant profiles is 0.02 M acetate buffer 50% base with
pH 4.65 at [CTAX] ) 0. The effect of increasing the
concentration of the buffer to 0.2 M is also measured,13
as well as the kinetic solvent isotope effects at both buffer
concentrations.
-
In the case of parallel base-catalyzed reactions, [HO ]
M
-
and [AcO ]
two concentrations are interdependent. Therefore, [AcO ]
is first obtained from the pH dependence on the surfac-
M
cannot be determined separately since these
-
M
-
tant concentration (vide infra). [HO ]
from the previously measured K
M
is then calculated
exchange constant.
Consequently, the pH changes of the buffer solutions
provoked by the surfactant addition are analyzed to
obtain the micellar catalyst concentrations at every
-
HO
AcO
-
(13) In accordance with the procedure usually adopted in work on
micellar reactivity, the ionic strength of the water phase is not
controlled by addition of any salt to avoid additional ion exchanges.
The underlying assumptions of this procedure (negligible changes in
pH, pK, and k in the water pseudophase as compared to aqueous buffer
solutions) have been widely discussed and its reliability fairly well
established (ref 1f and references therein).
(14) (a) Bunton, C. A.; Nome, F.; Quina, F. H.; Romsted, L. S. Acc.
Chem. Res. 1991, 24, 357. (b) Romsted, L. S. Surfactants in Solution;
Mittal, K. L., Lindman, B. Eds; Plenum Press: New York, 1984; Vol.
1, p 1015.

2
126 J . Org. Chem., Vol. 66, No. 6, 2001
Blagoeva et al.
-
pH ) pH + log{[AcO ] + cmc + R([D] - cmc)} -
0
0
T
log[AcOH]0 (6)
We obtain R ) 0.48 ( 0.01 and cmc ) (0.0004 ( 0.0002)
M using least-squares nonlinear regression fit of the data
for 0.02 M buffer. The corresponding â value of 0.52 is
1
8
in the range of published values for CTAOAc. The cmc
-
-
-
18
values of CTAX (X ) AcO , Cl , and Br ) in pure water
-
3
are in the range of 1-1.5 × 10 M, but the cmc values
of CTACl in the presence of 0.1 and 0.01 M buffers are
-
4
-4
in the range of 2 × 10 to 6 × 10 M, whatever the
buffer concentration.19
If the R value of 0.48, obtained in 0.02 M buffer, is
applied to the pH data in 0.2 M buffer, the calculated
pH of a 0.1 M solution of CTAOAc is only 0.17 pH units
higher than that of the pure aqueous buffer. The experi-
mental increase is, however, 0.30 pH units and would
correspond to R ) 0.8, which value is highly unlikely.
Most likely, this additional pH increase arises, in contrast
to an earlier assumption,20 from an intake of acetic acid
in the micelles from the buffer, since the concentration
of the acid in the concentrated buffer is very large (0.1
F igu r e 3. Dependence of pH values of acetate buffers 50%
base on the concentration of CTAOAc and CTACl. Open
symbols, 0.02 M buffer; closed symbols, 0.2 M buffer; circles,
CTAOAc; squares, CTACl.
surfactant concentration, before applying eq 2 to the rate
data for calculating k .
M
pH Ch an ges with Su r factan t Con cen tr ation . When
the surfactant counterion is identical to that of the buffer
-
base (CTAOAc in acetate buffer), the [AcO ]
w
/[AcOH]
w
M).
AcOH
buffer ratio changes as a result of the dissociation of the
The association constant, KS
, for incorporation of
surfactant.1
a,14
The pH changes of acetate buffers with
acetic acid in cetyltrimethylammonium micelles can be
-1
increasing surfactant concentrations are shown in Figure
estimated as 1.7 M from the linear solvation free energy
relationship proposed by Quina et al.21 With this value
we calculate that up to 14.5% of the acetic acid of the
buffer is incorporated at the maximum concentration of
3
0
. In the case of 0.02 M buffer, the pH increases up to
.8 pH units with the addition of 0.1 M surfactant, while
in the more concentrated (0.2 M) buffer, where the
amount of acetate ions released by the surfactant is less
significant as compared to the buffer acetate ions, the
pH changes only by 0.3 pH units.
-
2
CTAOAc ([AcOH]M ) 1.45 × 10 M for [CTAOAc] ) 0.1
M). Accordingly, eq 6 is transformed in eq 7 in which the
In CTACl and CTABr the pH values decrease with
addition of surfactant as a result of opposite changes in
-
pH ) pH + log{[AcO ] + cmc + R([D] - cmc)} -
0
0
T
the buffer ratio.1
5,16
-
[AcOH]0
w
[AcO ] decreases since chloride and
log
(7)
bromide surfactant counterions exchange for acetate ions
from the buffer. The observed decreases of pH are in
these cases not larger than 0.2 pH units.
{
AcOH
}
1
+ KS ([D] - cmc)
T
concentration term for the acetic acid in the water phase
is calculated by means of KS
acetate buffer from eq 7 is now 0.48 ( 0.02, in agreement
with that found from 0.02 M buffer22 in which the
micellar inclusion of acetic acid can be neglected ([AcO-
r, Degr ee of Micelle Dissocia tion , in CTAOAc
Bu ffer ed Solu tion s. These pH data (Figure 3) allow for
the calculation of the degree of CTAOAc dissociation.
Micelle dissociation is characterized by the parameter R,
while â represents the fraction of counterions bound to
AcOH
. The value of R in 0.2 M
-
3
-1
1
a
H]
M
) 1.5 × 10 M only for [CTAOAc] ) 10 M).
the micelle :
Ra te-Su r fa cta n t P r ofiles. The dependences of the
rate constants for ring closure of E3 and E2 in 0.02 and
AcO-]
[
w
0
.2 M acetate buffers on the concentration of CTACl are
R ) (1 - â) )
(4)
(
[D] - cmc)
shown in Figure 1. The maxima in the rate profiles are
consistent with second-order micelle-mediated ion-
molecule reactions.1 The experimental first-order rate
constants, kobs, increase with increasing [CTACl] and
then decrease. The largest accelerations in 0.02 M buffer
T
a
of acetic acid13,17 and
a
When it is assumed that the pK
the concentration of acetic acid in the water phase of the
diluted buffer remain unchanged (eq 5 with [AcOH]
AcOH] , index 0 indicating initial concentrations of
w
)
w
for E3 and E2 (expressed as kmax/k ) are 10 and 4,
[
0
respectively. In 0.2 M buffer, the rate constants are
surprisingly smaller (vide infra), but the decrease at high
surfactant concentrations due to dilution of the reagents
in the micellar phase is very small.
buffer species), R is calculated from the pH change via
eq 6, pH
0
being the value in the absence of surfactant.
-
pH ) pH + log[AcO ] - log[AcOH]
(5)
0
w
w
(
18) Gallion, L.; Hamidi, M.; Lelievre, J .; Gaboriaud, R. J . Chim.
(
15) Ouarti, N.; Marques, A.; Blagoeva, I.; Ruasse, M.-F. Langmuir
000, 16, 2157.
16) (a) Quina, F. H.; Politi, M. J .; Cuccovia, I. M.; Baumgarten, E.;
Martins-Franchetti, S. M.; Chaimovich, H. J . Phys. Chem. 1980, 84,
61. (b) Romsted, L. S. J . Phys. Chem. 1985, 89, 5107, 5113.
17) pK in the micellar phase is about the same as that in bulk
Phys. 1997, 94, 707.
(19) Unpublished measurements by tensiometry and spectrofluo-
rometry.
(20) Toullec, J .; Couderc, S. Langmuir 1997, 13, 1918.
(21) Quina, F. H.; Alonso, E. O.; Farah, J . P. S. J . Phys. Chem. 1995,
99, 11708.
2
(
3
(
a
water. (El Seoud, O. A. Adv. Colloid Interface Sci. 1989, 30, 1. Berthold,
A.; Saliba, C. Analusis 1985, 13, 437.)
(22) Soldi, V.; Keiper, J .; Romsted, L. S.; Cuccovia, I. M.; Chaimov-
ich, H. Langmuir 2000, 16, 59.

Specific and General Base Catalysis in Micelles
J . Org. Chem., Vol. 66, No. 6, 2001 2127
Ta ble 1. Equ ilibr iu m a n d Ra te Con sta n ts for Rin g Closu r e of E2 a n d E3 a t 25 °C in Micelles of CTAX in 0.02 M Aceta te
Bu ffer s 50% Ba sea
-
AcO-
, s-1 i
M
substrate
surfactant
Ks, M -
1 f
k × M 10-5, s-1 f
HO
k2m/kwg
KSIE
E2/E3h
k
k2m/kw
E2/E3j
b
E2
E2
E2
E2
CTAOAc
CTACl
CTABr
50 ( 6
47 ( 5
55 ( 7
57 ( 7
13.7 ( 0.5
9.71 ( 0.67
11.2 ( 1.0
17.8 ( 0.7
0.2
1.9
2.1
1.2
0.0304
0.0248
0.0274
12
10
11
1.7
2.1
1.4
b
0.14
0.16
0.17
b
c
CTAOAc/D2O
0.78 ( 0.06
1.5 ( 0.1
d
E3
E3
E3
E3
CTAOAc
CTACl
CTABr
58 ( 5
7.06 ( 0.19
4.68 ( 0.56
9.17 ( 0.6
4.58 ( 0.3
0.45
0.30
0.59
0.53
0.0181
0.0118
0.0198
3.7
2.4
4.1
d
74 ( 14
39 ( 4
36 ( 6
d
e
CTAOAc/D2O
HO-
HO
Cl
-
HO
Br
-1
-
AcO
Cl
-
AcO
Br
-
a
-4
Calculated from eq 2 (see text), with KAcO
M, âCTAOAc ) 0.52, âCTACl ) 0.6, âCTABr) 0.7.
-
) 0.49, K
-
) 0.25, K
-
) 0.048, K
-
) 0.50, K
-
) 0.098 from ref 10, cmc ) 4 × 10
-
-
b
HO
5
s-1; kw
AcO
) 3.53 × 10 M-1
-4
-1
-5 -1
k
) 9.51 × 10
M
s
; kH O ) 1.43 × 10
s
; from ref
w
2
-
-
-
-
c
DO
w
6
-1 -1
AcO
-4
-1 -1
-6 -1
d
HO
5
-1
-1; kw
AcO
7
×
e.
10-
k
4
) 1.42 × 10
M
s
; kw
) 1.18 × 10
M
s
; kD O ) 7 × 10
s
; from ref 7e.
k
) 2.17 × 10
M
s
) 6.77
2
w
-
-
-1 -1
; kH2O ) 1.68 × 10 s-1; k
-5
AcOH
-4
-1 -1
; from ref 7e. e
DO
w
5
-1 -1
AcO
w
) 3.3 × 10 M-1
-3
-1
M
s
) 2.27 × 10
M
s
k
) 1.21 × 10 M
s
; k
s
h
;
w
-
-
6
-1
AcOH
w
) 1.1 × 10 M-1
-4
-1
from ref 7e. From eq 2 with the term kM omitted. g With Vm ) 0.14 M , ref 1a. In
omitted. j In water E2/E3 ) 0.52.
f
AcO
-1
kD O ) 8.5 × 10
s
; k
s
2
-
i
HO
water E2/E3 ) 4.4. From eq 2 with the term k
M
The rate profiles in CTABr for both substrates (Figure
S1, Supporting Information) parallel those in CTACl. The
reaction in CTABr micelles is not markedely slower than
in water, [AcO-]
obtained from the quadratic eq 11, which describes the
w
, at each surfactant concentration, is
-
2
w
-
-
that in CTACl micelles, the accelerations, kmax/k
w
, being
[AcO ] (K - 1) + [AcO ] {[AcO ] (2 - K ) +
ex
w
0
-
ex
-
about 6 and 3 at small and large buffer concentrations,
respectively.
Figure 2 shows the rate-surfactant profiles for ring
closure of E3 and E2 in CTAOAc. As opposed to the
profiles in CTACl, the reaction in CTAOAc micelles
exhibits no maximum but a continuous increase in kobs
â([D] - cmc)(K - 1)} - [AcO ] {[AcO ] -
T
ex
0
0
â([D] - cmc)} ) 0 (11)
T
change in [AcO-]
its dependence on Kex. [AcO ]
with the surfactant concentration and
w
-
0
is the initial concentration
of acetate ions in the buffer, and Kex is the constant for
w
with [CTAOAc]. The largest accelerations, kmax/k , in 0.02
-
-
the exchange of Cl or Br for acetate ions. â and Kex are
M buffers are now very large, 60 and 25 for E3 and E2,
respectively. As in the case of the two other surfactants,
the accelerations are significantly larger for E3 than for
E2. This is in accordance with the expectations for
micellar catalysis by acetate ions, since general base
catalysis by acetate ions in water is more important for
ester E3. However, these accelerations in CTAOAc mi-
celles cannot be straightforwardly attributed to an in-
crease in the total concentration of micellized acetate
ions, since the associated increases in pH values indicate
large increases in micellized hydroxide ions also. The
rate-surfactant profiles in the more concentrated 0.2 M
acetate buffer show again a decrease in the reaction
rates, as compared to the less concentrated buffer.
However, the reaction takes place at much lower pH
values, and this effect probably overcomes the effect of
increasing concentrations of micellized acetate ions.
Micella r Ra te Con sta n ts of th e Hyd r oxid e-Ca ta -
lyzed Rea ction . Table 1 lists the rate and association
constants calculated (eq 2) by nonlinear fits of the rate-
surfactant profiles in CTAX micellar solutions in 0.02
optimized until the sum of the differences between
-
experimental and calculated values of [AcO ]
w
obtained
from the pH data and eq 11, respectively, reaches a
minimum (footnotes in Table 1).
The concentration of micellized hydroxide ions, [HO ]
-
M
,
at pH 4-5 is orders of magnitude lower than the
-
concentrations of the surfactant counterions (X ) Cl or
-
-
Br and AcO ), and it is estimated in the mixed micelles
-
-
HO
HO
by using KX- and KAcO- (eq 10).
Because of the [HO ] /[AcO ] interdependence men-
m m
-
-
tioned before, it is not possible to obtain at the same time
-
-
HO
M
AcO
s
K and the two micellar rate constants, k
and kM
,
by fitting the experimental data to the total eq 2. Almost
equally good fits of the data are obtained when one or
the other micellar rate term is omitted.
s
The K values (Table 1) obtained from either of these
-1
calculations vary between about 40 and 70 M . The large
uncertainties of their calculation preclude any quantita-
tive discussion of the respective values for E2 and E3.
These values correspond to a weak binding of the
relatively polar ureido esters. As both substrates differ
only by one methyl group, the similarity of these Ks
values is not surprising.
-
-
M a ceta te bu ffer . The concentrations of HO and AcO
in both phases of CTAOAc solutions are calculated by
using eqs 8-10 with â and cmc values obtained from eq
-
-
-
1
0
HO
HO
AcO
6
. A value of 0.49 is used for K
-
.
As regards the rate constants, kM and/or kM , the
AcO
predominant catalysis is determined by comparing the
-
(pH-14)
[
HO ] ) 10
(8)
values, for either pathway, of the k2,m/k
the relative reactivities of E2 and E3 (E2/E3 ratios in
Table 1). On one hand, k2,m/k values are expected to be
w
ratios and of
w
-
-
-
w
[
AcO ] ) â([D ] - cmc) ) [AcO ] - [AcO ]w (9)
M
T
tot
smaller than unity as for most ion-molecule reactions
and, in particular, hydroxide-catalyzed reactions in mi-
celles.4 On the other hand, the hydroxide-catalyzed
reaction should be faster for E2 compared to E3 (E2/E3
-
-
[
AcO ] [HO ]
M w
-
-
OH
[
HO ] ) K
AcO
-
(10)
M
[AcO]w
>
1), while the acetate catalysis is expected to be stronger
for E3 (E2/E3 < 1) in micelles as in water.
7
d
The calculations for CTACl and CTABr need, in
addition, to take into account the exchanges of surfactant
When the data for E2 are calculated as if the only
reaction at the micellar interface was catalysis by hy-
-
counterions for AcO . The concentration of acetate ions

2
128 J . Org. Chem., Vol. 66, No. 6, 2001
Blagoeva et al.
Ta ble 2. Equ ilibr iu m a n d Ra te Con sta n ts for Rin g
Closu r e of E2 a n d E3 a t 25 °C in Micelles of CTAX in 0.2
M Aceta te Bu ffer s 50% Ba sea
AcO-
M
s
3
sub-
strate
k
× 10 ,
Ks, M -
1
-1 f
k2m/kwg E2/E3h
surfactant
E2b CTAOAc
90 ( 16
76 ( 11
1.03 ( 0.18
1.13 ( 0.16
0.44
0.45
0.4
0.9
0.8
b
E2
CTACl
E2c CTAOAc/D2O 96 ( 27 0.716 ( 0.153
E3d CTAOAc
47 ( 5
83 ( 4
2.38 ( 0.13
1.22 ( 0.04
0.936 ( 0.025
0.49
0.25
d
E3
CTACl
E2e CTAOAc/D2O 64 ( 4
HO-
AcO
HO
-
a
Calculated from eq 2 (see text), with K
-
) 0.49, KCl
-
)
-
-
-
AcO
HO
AcO
0
)
9
1
1
M
k
.25, KBr
-
) 0.048, KCl
-
) 0.50, KBr
-
) 0.098 from ref 10, cmc
-
-
4
b
HO
w
4 × 10 M, âCTAOAc ) 0.52, âCTACl ) 0.6, âCTABr) 0.7.
k
)
-
5
-1 -1
AcO
-4
-1 -1
.51 × 10
M
s
; kw
) 3.53 × 10
M
s
; kH2O ) 1.43 ×
-
-
-
5
4
-1
; from ref 7e. c
DO
w
) 1.42 × 10 M-1 s-1; k
6
AcO
0
s
k
) 1.18 ×
w
-
0- M-1
s
-1
; kD O ) 7 × 10
-6 -1
s
; from ref 7e. d
k
HO
w
) 2.17 × 10
5
2
-
-
1
s-1; kw
AcO
) 6.77 × 10 M-1 s-1; kH2O ) 1.68 × 10
-4
-5 -1
s
;
-1
-
AcOH
w
s-1; kw
10-
-4
-1
-1; from ref 7e. e
DO
w
5
) 2.27 × 10
M
-3
s
k
) 1.21 × 10 M
-
AcO
) 3.3 × 10 M-1 s-1; kD O ) 8.5 × 10
-6 -1
AcOH
w
s
; k
) 1.1
from
2
HO-
4
-1 -1
from ref 7e. f From eq 2 with the term k
×
M
s
M
Table 1. With Vm ) 0.14 M , ref 1a. h In water E2/E3 ) 0.52.
g
-1
specific base-catalyzed reaction and 1.79 of the general
-
base-catalyzed HO reaction of E3) were decisive in
assigning the reaction mechanisms for these substrates.
-
-
HO
DO
M
The KSIEs (kM /k
) measured in micellar solutions of
0
.78 ( 0.06 for E2 and of 1.5 ( 0.1 for E3 (data from
Table 1) are very similar to the values in water and
support the predominance of the hydroxide-catalyzed
reaction of the two substrates in 0.02 M acetate buffers.
In conclusion, only the calculations related to the
F igu r e 4. Rate constants for ring closure of E2 and E3 in
.2 M acetate buffers at 25 °C in micelles of (A) CTAOAc and
0
(
B) CTACl. b, E2; 9, E3. The full lines are calculated by
-
AcO
complete eq 2 with the rate constants kM from Table 2. The
dashed lines (- - - - - - for E2 and - - - - for E3) represent
the rate surfactant profiles calculated with the respective rate
-
HO
k
pathway (Table 1) are chemically meaningful be-
M
cause they are consistent with the KSIEs, k2,m/k
E2/E3 ratios, whereas those with the kM assumption
are not.
w
, and
-
-
AcO
HO
constants for kM from Table 1 (see text).
Micella r Ra te Con sta n ts of th e Aceta te-Ca ta lyzed
Rea ction . The pH values of the con cen tr a ted (0.2 M)
a ceta te bu ffer in micellar solutions vary much less than
those of the dilute buffer (Figure 3). In CTACl, the pH is
almost constant and in CTAOAc, the pH increase is not
larger than 0.3 pH units. Analogously, the micellar
accelerations are markedly smaller (Figures 1 and 2). The
contributions of the hydroxide reaction to the overall
rates are estimated using the pH values in the concen-
w
droxide ions, a “normal” k2,m/k ratio of 0.2 is obtained,
whatever the surfactant counterion. When the same data
are analyzed as if only catalysis by acetate ions was
present, unreasonably large values for catalysis by
acetate, k2,m/k
w
∼10, are obtained. The calculations for
E3, the substrate with more pronounced acetate cata-
lyzed reaction in water, give similar results. The k2,m/k
ratios for kM are higher than the those calculated for
w
-
HO
-
HO
E2 but still less than unity, whereas the ratios k2,m/k
w
,
trated buffer and the rate constants kM obtained in
the dilute buffer solutions (Table 1). The calculated rates
for the hydroxide-catalyzed reaction are maximum evalu-
-
AcO
for kM , of ∼3 are larger than unity as in the case of
E2. Therefore, the hydroxide-catalyzed pathway is also
predominant for E3, although some acetate catalysis
cannot be totally excluded.
-
HO
ations since a kM decrease can result from AcOH
incorporation decreasing the interface polarity (vide
infra) and since the minor contribution of acetate cataly-
sis in the dilute buffer was neglected.
The micellar rate constant ratios, E2/E3, are larger
-
-
HO
AcO
than unity with both assumptions (kM and kM
in
Figure 4 (dashed lines) shows that the contributions
Table 1). They are consistent only with a predominant
-
-
from a HO -catalyzed reaction are insufficient to account
HO pathway since they agree with what is expected for
for reaction rates in the more concentrated buffer. The
differences between the calculated and experimental rate
constants are attributed to the acetate catalysis. Table
the hydroxide-catalyzed reaction but not for the acetate
catalysis. This result can be readily understood when the
micellization of the two catalysts in the 0.02 M buffer is
considered. In CTACl, the concentrations of micellized
2
lists the rate constants for acetate catalysis calculated
-
HO
-
from complete eq 2 with the kM values of Table 1.23
acetate ions are too small to overwhelm catalysis by HO .
In CTAOAc, the large changes in the pH values make
-
the variation in the rates of the HO -catalyzed reaction
(23) The data for CTABr in 0.2 M buffers did not give reliable results
for acetate catalysis. This is probably due to the much less favorable
-
predominant, masking the contribution of AcO .
Finally, the kinetic solvent isotope effects (KSIE),
/kw , measured in water7e (0.67 for E2, typical of a
-
exchange of the reactive anions from the solution for Br compared to
Y-
X
-
being 0.048 and 0.48 for HO- and 0.098 and
Cl , the respective K
-
-
-
HO
w
DO
k
0.50 for AcO- (ref 10).

Specific and General Base Catalysis in Micelles
J . Org. Chem., Vol. 66, No. 6, 2001 2129
Ta ble 3. Ra tios of Secon d -Or d er Ra te Con sta n ts of
Aceta te- a n d Hyd r oxid e-Ca ta lyzed Rea ction s for Rin g
Closu r e of E2 a n d E3 in Micella r Med ia a n d in Wa ter
substrate
medium
kAcO-/kHO- × 109
E2
E2
E2
CTAOAc
CTACl
H2O
0.75a
1.16a
b
0.37
a
E3
E3
E3
CTAOAc
CTACl
H2O
3.4
2.6
3.1
a
b
a
Calculated from data in Tables 1 and 2. b Calculated from
data in ref 7e.
F igu r e 6. Effect of added 10 vol % ethanol on the observed
rate constants for ring closure of E2 and E3 at 25 °C in 0.02
M buffer with increasing concentrations of CTACl. O, E2 in
the absence of EtOH; 0, E3 in the absence of EtOH; b, E2
with added EtOH; 9, E3 with added EtOH.
with the buffer concentration resulting primarily from
the increased buffer catalysis for this substrate. The low
sensitivity to the medium is consistent with a general
base-catalyzed hydroxide reaction involving significant
2
charge delocalization in the transition state. By contrast,
the marked rate decrease for E2 with the decrease in
solvent polarity supports specific catalysis. The data of
Table 3 in micellar media agree with these medium
effects. On going from water to the less polar micellar
interface, the specific base-catalyzed reaction of E2 is
decelerated so that the unchanged general base catalysis
F igu r e 5. Effect of added acetonitrile (vol %) to acetate buffers
on the observed rate constants for ring closure of E2 and E3
at 25 °C without addition of surfactant. O, E2 in 0.02 M buffer;
0, E3 in 0.02 M buffer; b, E2 in 0.2 M buffer; 9, E3 in 0.2 M
buffer.
-
-
AcO
HO
M
becomes significant. The increase in kM /k
ratio for
-
HO-
AcO
M
The calculated
k
values provide
k
2,m/k
w
ratios
E2 is, therefore, attributable to a decrease in k
M
-
AcO
smaller than unity, in the range expected for reactions
taking place in the less polar environment of the micellar
surface. The E2/E3 ratios are also smaller than unity,
in agreement with an acetate-catalyzed reaction for E3
and for E2, as found in water. The KSIEs for both
substrates (1.4 for E2 and 2.5 for E3) are consistent with
a slow proton transfer in the rate-determining step.
All of these results are strong evidence for a large
acetate-catalyzed pathway at the micellar interface for
both E2 and E3, resulting from significant changes in
the relative rate constants of the hydroxide and acetate
reactions going from water to micelles. Table 3 shows
that the ratios of the rate constants for the two base-
catalyzed reactions of E2 in micelles is larger than that
measured in water, while for E3 the ratio in water is
maintained in the micellar media. The evidence for a
significant acetate catalysis of the E2 reaction is an
important conclusion since in pure water this general
catalysis is almost negligible7d and, therefore, difficult to
be measured. The effect of the medium polarity on the
rate constants of the reactions of the two substrates
deserves, therefore, to be considered.
Med iu m Effects. To understand the origins of the
micellar effects on these reactions, the sensitivity of the
model reaction to the medium polarity needs to be known.
Figure 5 shows the effect of increasing the concentration
of acetonitrile in water on the rates of the ring closure
reactions in th e a bsen ce of su r fa cta n t. The difference
in the solvent effects on E2 and E3 reactions is additional
evidence for the different mechanisms by which both
substrates react. For E3 the solvent effect is small in both
rather than to an increase in kM
.
The marked micellar rate decrease observed when the
buffer concentration increases (Figures 1 and 2) is
indicative of an additional reduction of the interface
polarity, which can arise from the substantial micellar
incorporation of the acetic acid (vide supra). Since it was
not possible to investigate this acetic acid effect without
changing markedly the relative contributions of the two
catalysts, we considered the kinetic influence of the
ethanol addition to the buffered micellar solutions.
Significant decelerations of the reaction in the dilute
buffer, approaching those observed on going from the
dilute to the concentrated buffer, are found (Figure 6)
only with the addition of very large EtOH concentration
-
1
(1.7 M ), about 17 times larger than those of acetic acid
EtOH
S
(0.1 M in the concentrated buffer), whereas K
(0.6
-
1
21
AcOH
-1
M
)
is only 3 times smaller than KS
(1.7 M ).
Therefore, the incorporation of acetic acid at the micellar
interface cannot be the only factor responsible for the
observed decrease in the interfacial polarity in the
presence of the more concentrated buffer.
Other related factors and, in particular, a change in
the surface potential can be invoked. It is well estab-
lished1 that salt addition to the water phase decreases
the surface potential of ionic micelles and, therefore, the
electrostatic interactions between the micellar interface
and the charged reagents and/or transition states. Con-
sequently, a rate decrease in the overall reaction on going
from dilute to concentrated acetate buffer can also result
from a surface potential decrease. The specific-base-
catalyzed reaction with a poorly delocalized charge at the
transition state would respond to these electrostatic
e,f
0
.02 and 0.2 M acetate buffers, the reactivity increase

2
130 J . Org. Chem., Vol. 66, No. 6, 2001
Blagoeva et al.
interactions more strongly than the general base cataly-
sis with a more delocalized transition state. This effect
Ta ble 4. Micelliza tion of Aceta te Ion s in Solu tion s of
CTACl in 0.02 a n d 0.2 M Aceta te Bu ffer s 50% Ba se
-
-
HO
AcO
-
θAcO-
in 0.02 M
CTACl], M acetate buffer
AcO-
θ in 0.2 M
[AcO ] 0.2 M
leads also to a larger decrease in kM than in kM
.
M
a,b
a,b
-
[
acetate buffer
[AcO ]M 0.02 M
In conclusion, the different sensitivities of the two
substrates to medium supports the differences in the
mechanisms of their catalysis in water and the significant
contribution of the general catalyzed pathway for E 2
when it reacts in the less polar micellar environment.
0
0
0
0
0
0
0
0
0
0
.0005
.001
.002
.004
.005
.006
.008
.01
0.55
0.50
0.44
0.35
0.32
0.30
0.26
0.23
0.12
0.07
0.05
0.04
0.59
0.59
0.58
0.56
0.55
0.54
0.52
0.50
0.41
0.32
0.27
0.23
1.09
1.17
1.32
1.59
1.71
1.81
2.03
2.22
3.33
4.51
5.29
5.85
Con clu sion
.025
.05
The most striking result of this investigation is the
change in the relative contributions of the two catalyzed
pathways for the E2 reaction. Whereas in pure water the
specific catalysis is largely predominant, hydroxy and
acetate catalysis compete at the micellar interface. This
is, to the best of our knowledge, one of the first examples
of micelle-mediated general base catalysis by a basic
surfactant counterion. In the present case, the increased
contribution of the acetate-catalyzed reaction arises not
from an increase but from a greater decrease in the
micellar rate constant of the specific base-catalyzed
reaction than the general base-catalyzed one. This is
0.075
0.1
a
θAcO- ) [CTAOAc]M/[CTACl]M + [CTAOAc]M; calculated from
-
AcO
) 0.50. b θAcO- in CTAOAc ) â )
eq 11 with â ) 0.60 and KCl
0.52, whatever the buffer concentration.
-
cantly on that of the buffer since it is controlled mainly
by the â-parameter of the surfactant. In this case, the
rate decrease on going from the dilute to the concentrated
buffer is to be related to the decrease in interfacial
polarity. In contrast with CTACl, the increase in buffer
-
concentration results in an increase in |AcO ]
M
because
quite obvious in Tables 1 and 2; k2,m/k
w
is 0.2 for the
of the exchange equilibrium 12:
specific reaction of E2 and about 0.45 for the general
hydroxy- and acetate-catalyzed reactions of E2 and E3
-
-
CTACl + AcO w h CTAOAc + Cl w
(12)
(Schemes 2-4).
-
Another finding is that all of the rate constants at the
However, |AcO ]
M
are quite similar in CTAOAc and
micellar interfaces are smaller than those in water,
whatever the catalysis mechanism. This is consistent
with the micellar interface being less polar than water,
as supported by the kinetic results in acetonitrile-water
mixtures in which the two mechanisms respond quite
differently to the medium effect. Whereas the specific
catalysis depends markedly on the medium polarity, the
general catalysis does not. This is evidenced by the
relative reactivity ratios E2/E3 and their sensitivity to
the reaction medium. In water, the rate constant for the
CTACl solutions in the concentrated buffer, as shown by
calculations using eq 11 (Table 4). For example, [AcO ]
-
M
/
([D] - cmc) ) 0.52 and 0.50 in CTAOAc and 0.01 M
T
CTACl, respectively, so that the actual surfactant is
CTAOAc in both cases. In other words, the use of a
concentrated buffer favors the acetate catalysis by in-
creasing the concentration of micellized acetate ions
without altering markedly the hydroxide concentration.
This agrees with a recent finding15 that, in the presence
of buffers, the actual counterion is the buffer base at
small surfactant concentrations because of a significant
shift of eq 12 arising from high buffer and small surfac-
tant concentrations.
-
HO -catalyzed reaction is 4.4 times larger for E2 than
for E3, but in micelles this factor is only 2. In contrast,
the E2/E3 ratios for the general acetate-catalyzed reac-
tions are quite similar in the two media (0.5 in water
and about 0.7 in micelles). The small medium sensitivity
of the general base catalysis is probably related to a
significant charge delocalization in the corresponding
Insofar as micelles are reasonable models of the
microenvironment of enzyme reactions, the significant
increase in the general base catalysis resulting from the
micellar effect found in this work opens new insights in
bioorganic reactivity. More work is in progress to under-
stand the interplay between the medium polarity depen-
dence of the micellar rate constants and the surfactant-
induced pH variations, i.e., the ion-exchange controlled
concentrations of the catalysts, on the efficiency of
micellar catalysis in acid-base-catalyzed reactions.
1
a,24,25
transition states.
Finally, the rate constant decrease raises the question
of the origin of the micellar accelerations. This contradic-
tion is generally solved in terms of increased reagent
concentrations in the small micellar volume. In our study,
the largest accelerations are found (Figure 2) in CTAOAc
micellar solutions with the more dilute buffer for both
substrates. These rate enhancements are unambiguously
attributed to large pH increase (Figure 3), i.e., to an
Ack n ow led gm en t. We are indebted to the BAS and
CNRS for support of I.B. and M.F.R. collaboration. I.B.
gratefully acknowledges the University of Paris 7-Denis
Diderot for a visiting professorship. We thank Professor
O. A. El Seoud for fruitful discussion.
-
increase in [HO ] in CTAOAc. In the more concentrated
buffer, the small pH changes show that the micellized
hydroxide ion concentrations do not change much with
the surfactant concentration. With CTAOAc, the micel-
lized acetate ion concentration does not depend signifi-
Su p p or tin g In for m a tion Ava ila ble: Rate-surfactant pro-
files for ring closure of E2 and E3 in micelles of CTABr in
acetate buffers and in CTACl in acetate buffers with addition
of 0.1 M ethanol. This material is available free of charge via
the Internet at http://pubs.acs.org.
(
24) Buurma, J .; Herranz, A. M.; Engberts, J . B. F. N. J . Chem. Soc.,
Perkin Trans. 2 1999, 113.
25) Bunton, C. A.; Gillitt, N. D.; Mhala, M. M.; Moffatt, J . R.;
Yatsimirsky, A. K. Langmuir 2000, 16, 8595.
(
J O001759W