Effect of cyclodextrins on the reactivity of fenitrothion

Article abstract of DOI:10.1016/j.carres.2010.06.016

The hydrolysis reaction of fenitrothion was studied in water containing 2% dioxane and in the presence of native cyclodextrins (α-, β- and γ-CD) and two commercially available modified derivatives, namely, permethylated β- and α-cyclodextrin (TRIMEB and TRIMEA, respectively). The kinetics of the reaction in the presence of TRIMEA could not be measured because the complex formed is insoluble and precipitated even at low concentration. On the other hand, the reaction is only weakly affected by the presence of α-CD. The hydrolysis reaction is inhibited by all the other cyclodextrins. From the kinetic data the association equilibrium constants for the formation of the 1:1 inclusion complexes were determined as 417, 511 and 99 M^-1 for β-CD, TRIMEB and γ-CD, respectively. Despite the differences in the association constants for β- and γ-CD, the observed inhibition effect is about the same and this is due to the fact that the rate of hydrolysis in the cavity of γ-CD is smaller than that in the cavity of β-CD. The strongest inhibitor is TRIMEB and this result is consistent with the known structure of the complex in the solid state.

Full text of DOI:10.1016/j.carres.2010.06.016

Carbohydrate Research 346 (2011) 322–327
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Effect of cyclodextrins on the reactivity of fenitrothion
Natalia M. Rougier a, Dyanne L. Cruickshank b, Raquel V. Vico a, Susan A. Bourne b, Mino R. Caira b,
a,
Elba I. Buján a, , Rita H. de Rossi
*
*
a Instituto de Investigaciones en Físico Química de Córdoba (INFIQC), Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba,
Ciudad Universitaria, X5000HUA Córdoba, Argentina
b Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 27 April 2010
Received in revised form 17 June 2010
Accepted 28 June 2010
Available online 10 December 2010
The hydrolysis reaction of fenitrothion was studied in water containing 2% dioxane and in the presence of
native cyclodextrins (a-, b- and c-CD) and two commercially available modified derivatives, namely, per-
methylated b- and -cyclodextrin (TRIMEB and TRIMEA, respectively). The kinetics of the reaction in the
a
presence of TRIMEA could not be measured because the complex formed is insoluble and precipitated
even at low concentration. On the other hand, the reaction is only weakly affected by the presence of
a
-CD. The hydrolysis reaction is inhibited by all the other cyclodextrins. From the kinetic data the asso-
ciation equilibrium constants for the formation of the 1:1 inclusion complexes were determined as 417,
511 and 99 Mꢀ1 for b-CD, TRIMEB and
-CD, respectively. Despite the differences in the association con-
stants for b- and -CD, the observed inhibition effect is about the same and this is due to the fact that the
rate of hydrolysis in the cavity of -CD is smaller than that in the cavity of b-CD. The strongest inhibitor is
Keywords:
Cyclodextrins
Fenitrothion
Hydrolysis
Inclusion complexes
Reactivity
c
c
c
TRIMEB and this result is consistent with the known structure of the complex in the solid state.
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
pesticide must be modified and this may be achieved by complex-
ation with cyclodextrins (CDs).
Pesticides are used throughout the world and their application
has become essential in the agricultural industry to keep up with
the high demand and high standard of farming production that is
expected from consumers. It is important to understand the fate
of the pesticides that have been applied during agricultural prac-
tices as well as the environmental impact that some of the degra-
dation products may have on the crop fields.
CDs are macrocyclic molecules that are made up of six, seven or
eight glucopyranose units. The native CDs are known as -CD
(cyclohexaamylose), b-CD (cycloheptaamylose) and -CD (cyclooc-
taamylose), respectively (Fig. 2). Each glucopyranose unit is linked
to the next by an -(1,4) glycosidic bond. These molecules have a
a
c
a
torus shape with a hydrophobic interior cavity and hydrophilic
faces.
Fenitrothion [O,O-dimethyl O-(3-methyl-4-nitrophenyl) phosp-
horothioate], 1 ( Fig. 1) is an organophosphorus insecticide and
acaricide.1 It is effective against a wide range of pests, namely pe-
netrating, chewing and sucking insect pests on cereals, cotton,
orchard fruits, rice, vegetables, and forests. It may also be used as
a fly, mosquito, and cockroach residual contact spray for farms
and public health programs. Its effectiveness as a vector control
agent for malaria is confirmed by the World Health Organization.1
It has been suggested that less than 1% of the total applied pes-
ticide reaches its target, the remaining material entering the water
drainage areas via agricultural runoff and leaching.2 In order to
reduce wastage, render its handling safer, or enhance the stability
of the organophosphorus compound, the physical properties of the
There are two distinct faces known as the primary hydroxyl face
(C-6 hydroxyl group), which is the narrower face and the second-
ary hydroxyl face (C-2 and C-3 hydroxyl groups) which is the wider
one.
Derivatised CDs such as hexakis-(2,3,6-tri-O-methyl)-a-CD (TRI-
MEA), heptakis-(2,3,6-tri-O-methyl)-b-CD (TRIMEB) and heptakis-
(2,6-di-O-methyl)-b-CD (DIMEB) ( Fig. 3) have different physical
properties from those of the native CDs. These derivatives however,
have become of great interest as their solubility in water as well as in
organic solvents is very high and their inclusion behaviours are not
always the same as those of the native CDs. The methylated CDs
CH3
NO2
S
H3CO
O
P
OCH3
* Corresponding authors. Tel.: +54 351 4334173; fax: +54 51 433 4170 (R.H.D.R.).
E-mail addresses: elba@fcq.unc.edu.ar (E.I. Buján), ritah@fcq.unc.edu.ar (R.H. de
Rossi).
Figure 1. The chemical structure of fenitrothion.
0008-6215/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2010.06.016

N. M. Rougier et al. / Carbohydrate Research 346 (2011) 322–327
323
Figure 2. Molecular structures of a-, b- and c-CD and a schematic representation of b-CD.
are either fully methylated (TRIMEB or TRIMEA) or partially methyl-
ated(DIMEB). WerecentlyreportedtheX-raydiffractionstudyofthe
complexes formed between fenitrothion and permethylated
For the reactions in the presence of cyclodextrins, the effective
concentration of NaOH was kept constant at 0.5 M and the concentra-
tion of the particular CD was varied so as to determine whether an in-
creased amount of CD inhibited, catalysed or had no effect on the
a-cyclodextrin (TRIMEA) and permethylated b-cyclodextrin (TRIM-
EB). The former host forms a very interesting complex with host–
guest stoichiometry 2:1 in which the two host molecules are aligned
head-to-head (the two cyclodextrins having their secondary rims
facing one another).3 On the other hand the complex formed with
TRIMEB has stoichiometry 1:1 and the phosphate group is deeply in-
cluded in the cavity.3 We suspected that this would have important
consequences for the reactivity of the complexed substrate and we
report here a study of the hydrolysis reaction as a model for the reac-
tion with nucleophiles.
reaction. We studied this reaction with four different CDs (
b-CD, -CD and TRIMEB). These have different physical properties
such as their size, volume and hydrophobicity of the cavity.5
a-CD,
c
The native CDs have hydroxyl groups that can be deprotonated
by hydroxide ions in basic media. As a consequence it is necessary
to consider the pKa values of the native CDs, which are 12.332,
12.202 and 12.081 for a-, b-, and c
-CD, respectively,6 when calcu-
lating the NaOH concentration required to prepare the solutions.
The concentration of fenitrothion was at least 50 times smaller
than that of the cyclodextrin and several orders of magnitude
smaller than that of the nucleophile; therefore, pseudo-first-order
conditions held throughout the experiments.
The reaction was followed by measuring the increase in absor-
bance of product 2 at 397 nm. Each kobs value was obtained by fit-
ting the non-linear, simple exponential equation to the individual
graphs of absorbance versus time.
2. Results and discussion
2.1. Kinetic studies
The hydrolysis reaction of fenitrothion was studied in the ab-
sence of cyclodextrins at varying concentrations of NaOH in water
containing 2% dioxane as co-solvent.4
The observed rate constants obtained for the reactions in the
The UV–vis spectrum of the product matches that of 3-methyl-
4-nitrophenol at the expected concentration; therefore, the only
reaction taking place is that of P–O bond fission (Eq. 1). The value
of the second order rate constant for this reaction was calculated as
presence of a-CD, b-CD, c-CD and TRIMEB are presented in
Table S1. Figure 4 shows plots of kobs as a function of the concen-
trations of the CDs. The reaction of 1 with NaOH in the presence
of the native cyclodextrins (a-, b- and c-CD) may take place as
(2.50 0.08) ꢁ 10ꢀ3 Mꢀ1 sꢀ1 4
.
shown in Scheme 1,7,8 where ko, k1, and k2 represent the reactions
O-
S
CH3
NO2
H2O
S
P
H3CO
P
O-
+
H3CO
O
ð1Þ
OCH3
NaOH
CH3
OCH3
NO2
1
3
2

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N. M. Rougier et al. / Carbohydrate Research 346 (2011) 322–327
TRIMEA
TRIMEB
DIMEB
OX
number of
glucose units
7
6
7
O
O
CH3
CH3
CH3
X
Y
n
YO
OX
H
CH3
CH3
Figure 3. Structure of methylated cyclodextrins.
of the free substrate, the substrate complexed with the neutral CD
(CDOH) and the reaction with ionized CD (CDOꢀ), respectively; k3
represents the reaction of HOꢀ with fenitrothion included within
the ionized CD (CDOꢀ). The observed rate constant for Scheme 1
is shown in Eq. 2, where f represents the fraction of ionized CD
as defined in Eq. 3 with Kb ¼ Kw=Ka. Under the conditions of our
study, with HOꢀ concentration of 0.5 M, f ꢂ 1 which simplifies
Eq. 2 to Eq. 4.
K1
k1[OH-]
1
1
+
CDOH
P
[1 .CDOH]
K'b
OH-
k2
k3[OH-]
OH-
Kb
K2
+
CDO-
[1 .CDO-]
k0½OHꢀꢃ þ k1K1½OHꢀꢃð1 ꢀ fÞ½CDꢃ þ ðk2 þ k3½OHꢀꢃÞK2f½CDꢃ
k0[OH-]
kobs
f ¼
kobs
¼
ð2Þ
ð3Þ
ð4Þ
1 þ K1ð1 ꢀ fÞ½CDꢃ þ K2f½CDꢃ
½OHꢀꢃ
Scheme 1. Reaction pathways for the hydrolysis of fenitrothion in the presence of
b-cyclodextrin in basic solutions.
½OHꢀꢃ þ Kb
k0½OHꢀꢃ þ ðk2 þ k3½OHꢀꢃÞK2½CDꢃ
1 þ K2½CDꢃ
a = k0[OHꢀ], b and c being adjustable parameters shown in Eqs.
7–10. Parameter a represents the reaction of the free substrate, b is
the product of the rate of reaction that occurs when fenitrothion is
included in the cyclodextrin cavity and the association constant K2,
and parameter c considers only the equilibrium present in the
system.
¼
The hydroxyl groups on C-2, C-3 and C-6 of TRIMEB are methyl-
ated, which simplifies Scheme 1 shown above to Scheme 2 and kobs
for the hydrolysis of 1 in the presence of TRIMEB is given by Eq. 5.
k0½OHꢀꢃ þ k1K1½OHꢀꢃ½CDꢃ
kobs
¼
ð5Þ
a þ b½CDꢃ
1 þ K1½CDꢃ
kobs
¼
ð6Þ
ð7Þ
1 þ c½CDꢃ
For each cyclodextrin the observed rate constant versus
concentration was fitted to an equation of the form of Eq. 6, with
bnativeCD ¼ ðk2 þ k3½OHꢀꢃÞK2
1.3
1.3
1.2
1.1
1.0
0.9
0.8
0.7
α-CD
γ-CD
1.2
1.1
1.0
0.9
0.8
0.7
1.3
1.2
1.2
β-CD
TRIMEB
1.0
0.8
0.6
0.4
0.2
1.1
1.0
0.9
0.8
0.7
0.000 0.005 0.010 0.015 0.020
CD, M
0.000 0.005 0.010 0.015 0.020
CD, M
Figure 4. Plots of kobs versus [CD] for the hydrolysis reaction of fenitrothion at 25 °C at a constant [NaOH] of 0.50 M. Solvent contains 2% 1,4-dioxane/H2O; Ionic strength
I = 1 M (NaCl).

N. M. Rougier et al. / Carbohydrate Research 346 (2011) 322–327
325
Table 1
Parameters for the hydrolysis reaction of fenitrothion in the presence of b-CD,
c-CD and TRIMEB
aa
b
c
b/c
f
CD
b
Cyclodextrin
(k =kobs
)
obs
b-CD
1.26 ꢁ 10ꢀ3
1.26 ꢁ 10ꢀ3
1.26 ꢁ 10ꢀ3
(3.01 0.08) ꢁ 10ꢀ1
(5 3) ꢁ 10ꢀ2
417 18
99 36
511 31
7.2 ꢁ 10ꢀ4
5.0 ꢁ 10ꢀ4
1.6 ꢁ 10ꢀ4
1
1
—
0.68
0.70
0.27
c
-CD
TRIMEB
(8 1) ꢁ 10ꢀ2
a
The experimental value obtained in the absence of CD.
The values were determined at a cyclodextrin concentration of 0.01 M.
b
k1[HO-]
K1
2
1
0
A
P
[1].TRIMEB
[1]
TRIMEB
ko[HO-]
Scheme 2. Reaction pathways for the hydrolysis of fenitrothion in the presence of
TRIMEB in basic solutions.
bTRIMEB ¼ k1K1½HOꢀꢃ
cNativeCD ¼ K2
ð8Þ
ð9Þ
-1
cTRIMEB ¼ K1
ð10Þ
0.4
The data obtained for these parameters for b-CD,
c
-CD and
TRIMEB are shown in Table 1. The parameter b/c is a measure of
B
the rate of reaction taking place within the CD cavity. On the other
CD
obs
0.3
0.2
0.1
0.0
hand k =kobs is the ratio of the observed rate constant in the pres-
ence and absence of each CD at a fixed CD concentration of 0.01 M.
The parameters were not calculated for
a-CD as the association
constant between -CD and fenitrothion is small and so is the ob-
a
served inhibition effect.
The association constant determined for b-CD is in good agree-
ment with the reported literature value of 417 Mꢀ1 9
, as well as
with the results published by Vico et al., namely 415 Mꢀ1 using a
solvent system of 2% acetonitrile/H2O.8 Fenitrothion has a much
weaker association with
c-CD as the cyclodextrin cavity is much
larger; -CD does, however, have a very similar inhibition effect
c
on the hydrolysis reaction of fenitrothion in comparison to b-CD.
The rate of hydrolysis with respect to the free substrate is 73%
slower in the presence of TRIMEB and in the presence of b-CD
250
300
350
λ, nm
400
450
and
c
-CD the rate is 32% and 30% slower, respectively. It should
-CD is slower than that
Figure 5. Induced circular dichroism (A) and UV–vis (B) spectra of 1 in the presence
of -CD (blue) b-CD (pink), -CD (green) and TRIMEB (light blue).
a
c
be noted that the reaction in the cavity of
c
corresponding to b-CD (compare the values of b/c for the two
cyclodextrins in Table 1) and this is the reason for the observation
of similar inhibition effects despite the differences in association
equilibrium constants.
crystals (white precipitate) was clear and the absorbance measure
indicated 100% conversion of the fenitrothion to products. This can
be interpreted as the fenitrothion reacting with the hydroxide ions
and being quantitatively converted to the 3-methyl-4-nitrophenox-
ide and the dimethylphosphorothioate which are soluble in the spe-
cific solution. The reason for the precipitation may be due to the
formation of a complex with stoichiometry 2:1 as was demonstrated
in a previous study.3
Similar hydrolysis experiments have been performed by
Kamiya and Nakamura with fenitrothion and three cyclodextrins
namely b-CD, DIMEB and TRIMEB.9 These authors do not indicate
the use of any co-solvent and they reported that under their
reaction conditions they found some deviation from the strictly
pseudo-first-order behaviour. We were unable to measure rates
either in the presence or in the absence of cyclodextrins without
the use of a small percentage of an organic co-solvent because
we found that fenitrothion in water at 1 M ionic strength was
not sufficiently soluble to ensure reliable kinetic data.
The study of the reaction of fenitrothion in the presence of TRI-
MEA was attempted; however, it was not possible to follow the rate
of the reaction due to the formation of a precipitate as soon as the
substrate was added to the other constituents. This experiment
was performed with a TRIMEA concentration of 0.01 M and an ionic
strength of 1 M. The hydrolysis took place and, 18 h after the addi-
tion of the substrate, the solution that had initially formed white
2.2. Spectroscopic studies
Inclusion complex formation between CDs and different guest
molecules can be detected by a variety of spectroscopic methods.10
UV–vis spectroscopy is one of the most frequently used techniques
to determine the association constants between an organic guest
compound and CDs.11
We intended to determine the binding constant of 1 with all
CDs used in this study by UV–vis spectroscopy. Thus, we recorded
the spectra of 1 in the presence of increasing amounts of the

326
N. M. Rougier et al. / Carbohydrate Research 346 (2011) 322–327
OCH3
Cl
OCH3
OCH3
S
NO2
OCH2CH3
S
S
H3CO
P
P
N
P
H3C
OCH2CH3
Cl
O
O
N
O
N
Cl
5
4
O
CH3
Figure 6. Chemical structures of diazinon (4) and chlorpyrifos methyl (5).
S
P
OCH3
NO2
OCH3
The NMR spectra of TRIMEB in 2% 1,4-dioxane/D2O were re-
corded in the absence and in the presence of 1. All the signals
corresponding to TRIMEB in the presence of 1 appear at lower
fields than those in its absence (Table S2, Fig. S1) particularly in
the region corresponding to H-3 and H-5, which showed a signifi-
cant broadening of the signal. It is also remarkable that the signals
corresponding to the 2, 3 and 6 methoxyl groups are displaced to
lower fields indicating that the inclusion produces changes in the
arrangements of these groups at the rim of TRIMEB. For the
aromatic methyl group of the guest there are two signals which
appear at 2.611 and 2.312 ppm and they correspond to the com-
plexed and free substrate, respectively. The aromatic protons in
the free substrate appeared at 6.901, 6.921 and 7.735 (d) ppm
while in the presence of TRIMEB, there are three additional signals
at 7.266, 7.293 and 8.155 (d) ppm corresponding to the complexed
substrate. The fact that two separate signals are observed indicates
that the exchange is slow on the NMR timescale.19–21
B
A
Scheme 3. Schematic representation of two possible orientations of 1 in the cavity
of CDs.
appropriate CD. Although the spectrum of 1 in the presence of any
of the CDs shows a small hypsochromic shift, the changes in absor-
bance observed are not large enough to enable the determination
of the association constants.
We have also studied the interaction of 1 with CDs by circular
dichroism. The addition of CD to a solution of 1 gives an induced cir-
cular dichroism spectrum (ICD) as shown in Figure 5A. It can be seen
that all the native cyclodextrins show a negative and a positive peak
that coincide with the maxima in the UV–vis spectrum (Fig. 5B). The
negative peaks appear at 280, 325 and 294 nm and the positive ones
at 249, 260 and 252 nm for a-, b-, and c-CD, respectively. As is ob-
Since both, the aromatic protons and those of the OMe of thephos-
phate group showed displacement with respect to the free substrate,
the pesticide in solution must be included in a way that the aromatic
moiety and the phosphate group are influenced by the host. We car-
ried out ROESY experiments in order to get more information about
the mode of inclusion but the signals were not clearly resolved.
Proton-decoupled 31P NMR spectra were recorded for 1 (2 mM)in
aqueous media in the absence and presence of 2 mM TRIMEB. In the
presence of TRIMEB two signals were observed, one at 65.13 ppm
corresponding to 1 and the other at 66.10 ppm (downfield from that
of 1) (Fig. S2) which is attributed to 1 included in TRIMEB. Downfield
changes in the 31P NMR chemical shift for the organophosphorus
pesticide diazinon 4 (Fig. 6) were reported before in the presence
served in other cases where CD is the host,12–15 these peaks are
slightly displaced from the maxima in the UV–vis spectrum. In the
ICD spectrum of fenitrothion in the presence of TRIMEB there is
inversion of the sign of the peaks compared with that of the native
derivatives. The positive and negative peaks appear at 345 and
275–230 nm, respectively. The fact that the ICD signals for the inter-
action with TRIMEB change from negative to positive may indicate
an extrusion of the guest from the cavity or the change in orientation
of the host in the cavity as was suggested before.16,7
There are two possible modes of inclusion of the insecticide 1 in
the cavity of the CDs as shown in Scheme 3, either with the thio-
phosphate moiety (Scheme 3A) or with the aromatic moiety
(Scheme 3B) inside the cavity. For most of the esters having an
aromatic group it is proposed that this residue is included in the
cavity of the CDs. This was suggested for parathion, parathion-
methyl, and paraoxon.9, 15,17
of a-, b-, and c-CD and interpreted as formation of an inclusion com-
plex.22 Also, we observed downfield changes in the 31P NMR spec-
trum of chlorpyrifos methyl 5 (Fig. 6) with b-cyclodextrin.7
Theoretical calculation of the energies of the two types of com-
plexes indicates that in the gas phase there is no significant differ-
ence in their values.18 Therefore it is likely that the permethylation
of the rim of the b-CD (TRIMEB) changes the combination of inter-
actions between the host and the guest which results in a change
of guest orientation in the cavity.
X-ray structural investigation of the complex of 1 with TRIMEA
(Fig. 3) indicates that a dimeric complex (TRIMEA)2ꢄfenitrothion is
formed and shows that both the aromatic and the phosphate ester
moieties of the fenitrothion molecule have the ability to enter the
cavity of the TRIMEA molecule. However, significant strain is in-
duced by inclusion of the aromatic residue, as evidenced by the
accompanying distortion of the host molecule which accommo-
dates it. In the case of the larger macrocyclic host, a monomeric
complex TRIMEBꢄfenitrothion results and again the phosphate es-
ter moiety is fully included in the host cavity.3 Considering all this
information it seems likely that the orientation in the cavity for the
complexes formed in solution is different for the native CD and
TRIMEB.
3. Conclusions
The inclusion of fenitrothion in the cavity of cyclodextrins de-
creases its reactivity, due to the fact that the phosphate group is
protected from nucleophilic attack by external nucleophiles. On
the other hand, the ionized OH groups at the secondary rim of
the native cyclodextrin are probably located in an unfavorable po-
sition for the reaction as nucleophile with the phosphate group. It
is well known that the catalysis observed in many ester hydrolysis
reactions is due to the correct alignment of the carbonyl and OH
groups in the transition state.23,24
The inhibition due to the inclusion is significantly larger in the
case of TRIMEB compared with b-CD; this result is in line with the
finding in the solid state which indicates that the crystals of the
complex TRIMEB-fenitrothion are anhydrous, so the penetration
of the nucleophile into the cavity should be unfavorable.
4. Experimental section
Fenitrothion was isolated from a commercial sample of Sumi-
thion (Sumitomo Chemical) by column chromatography. 1H, 31P
This is an oversimplification of the possible orientation of the guest in the cavity
since there are several others which might be possible; to simplify the discussion we
considered only these two possibilities.
NMR and GC–MS confirmed the isolation of fenitrothion.
a-, b-
and -CD were received from Roquette (Argentina) and TRIMEB
c

N. M. Rougier et al. / Carbohydrate Research 346 (2011) 322–327
327
was purchased from Cyclolab (Hungary). The purities of all the
Supplementary data
cyclodextrins were verified using UV–vis spectroscopy.
Aqueous solutions were prepared using water purified with a
Millipore Milli-Q apparatus. 1,4-Dioxane was purified by the Fieser
method.25 The required amount of 1,4-dioxane was freshly dis-
tilled before use.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.carres.2010.06.016.
References
The UV–vis spectra for each reaction were measured with a
Shimadzu UV-2101 spectrophotometer. Circular dichroism spectra
were recorded on a JASCO Model J-810 spectropolarimeter which
1. http://pmep.cce.cornell.edu/profiles/extoxnet/dienochlor-glyphosate/fenitrothion-
ext.html. Accessed June 14, 2010.
2. Pimental, D. J. Agric. Environ. Ethics 1995, 8, 17–29.
3. Cruickshank, D.; Rougier, N. M.; Vico, R. V.; de Rossi, R. H.; Buján, E. I.; Bourne, S.
A.; Caira, M. R. Carbohydr. Res. 2010, 345, 141–147.
was calibrated with
D
-(+)-ammonium camphorsulfonate. 31P
and 1H NMR spectra were recorded on a Bruker Ultra Shield 400.
GC–MS was performed on a Shimadzu Model CQ5050 instrument.
4. Rougier, N. M.; Vico, R. V.; de Rossi, R. H.; Buján, E. I. J. Org. Chem. 2010, 75,
3427–3436.
5. Dodziuk, H. Molecules with Holes-Cyclodextrins. In Cyclodextrins and Their
Complexes; Dodziuk, H., Ed.; Wiley-VCH: Weinheim, 2006; pp 1–30.
6. Szejtli, J. Chem. Rev. 1998, 98, 1743–1753.
4.1. Kinetic procedures
7. Vico, R. V.; de Rossi, R. H.; Buján, E. I. J. Phys. Org. Chem. 2009, 22, 691–702.
8. Vico, R. V.; Buján, E. I.; de Rossi, R. H. J. Phys. Org. Chem. 2002, 15, 858–862.
9. Kamiya, M.; Nakamura, K. Pest. Sci. 1994, 41, 305–309.
10. Connors, K. A. Binding Constants. The Measurement of Molecular Complex
Stability; John Wiley & Sons: New York, 1987. pp 139–216.
11. Omakor, J. E.; Onyido, I.; vanLoon, G. W.; Buncel, E. J. Chem. Soc., Perkin Trans. 2
2001, 324–330.
12. Kawamura, M.; Higashi, M. J. Inclusion Phenom. Macrocycl. Chem. 2005, 51, 11–
15.
13. Shimizu, H.; Kaito, A.; Hatano, M. Bull. Chem. Soc. Jpn. 1979, 52, 2678–
2684.
14. Shimizu, H.; Kaito, A.; Hatano, M. Bull. Chem. Soc. Jpn. 1981, 54, 513–519.
15. Kamiya, M.; Mitsuhashi, S.; Makino, M.; Yoshioka, H. J. Phys. Chem. 1992, 96,
95–99.
16. Hamai, S.; Ikeda, T.; Nakamura, A.; Ikeda, H.; Ueno, A.; Toda, F. J. Am. Chem. Soc.
1992, 114, 6012–6016.
All the reactions were initiated by adding the substrate (fenitro-
thion) dissolved in 1,4-dioxane to a solution containing all the
other constituents. The kinetic experiments were carried out under
pseudo-first order conditions and the initial concentration of the
substrate was (4.6–5.5) ꢁ 10ꢀ5 M. The reactions were performed
at a constant temperature of 25.0 0.1 °C and they were main-
tained in the dark in order to minimise photolytic effects.
The ionic strength for all reactions was maintained at 1 M and
NaCl was used as the compensating electrolyte. The reactions were
all followed by measuring the increase in absorbance of the reac-
tion mixture at 397 nm, the kmax of the phenoxide formed 2. Cuv-
ettes with an optical path length of 1 cm were used.
17. Kamiya, M.; Nakamura, K.; Sasaki, C. Chemosphere 1995, 30, 653–660.
18. Coscarello, E. N.; Barbiric, D. A.; Castro, E. A.; Vico, R. V.; Buján, E. I.; de Rossi, R.
H. J. Struct. Chem. 2009, 50, 671–679.
Acknowledgments
19. Barthelemy, P.; Tomao, V.; Selb, J.; Chaudier, Y.; Pucci, B. Langmuir 2002, 18,
2557–2563.
20. Coppola, C.; Saggiomo, V.; DiFabio, G.; DeNapoli, L.; Montesarchio, D. J. Org.
Chem. 2007, 72, 9679–9689.
21. Andrade-Dias, C.; Lima, S.; Teixeira-Dias, J. J. J. Colloid Interface Sci. 2007, 316,
31–36.
This material is based upon work supported by the National
Research Foundation under Grant number 67381. M.R.C. and D.C.
express their thanks to the NRF and the University of Cape Town
for financial assistance.
Financial assistance from CONICET, FONCYT, MINCyT-Córdoba
(Argentina) and support from the National University of Córdoba
are greatly acknowledged. This work was carried out as part of a
bilateral cooperation project supported by the NRF (South Africa)
and MINCyT (Argentina). N.M.R. is a grateful recipient of a fellow-
ship from YPF Foundation (Argentina).
22. Churchill, D.; Cheung, J. C. F.; Park, Y. H.; Smith, V. H.; van Loon, G.; Buncel, E.
Can. J. Chem. 2006, 84, 702–708.
23. Fernández, M. A.; de Rossi, R. H. J. Org. Chem. 2003, 68, 6887–6893.
24. Andres, G. O.; de Rossi, R. H. ARKIVOC 2003, 127–138.
25. Fieser, L. F.. Experiments in Organic Chemistry. In 2nd Ed; Heath, D. R.: Boston,
1941. pp 360–361.