Reactivity differences of O-aryl O-(4-nitrophenyl) thionocarbonates versus their homolog carbonates: Micellar catalysis in hydrolysis reactions

Article abstract of DOI:10.1002/poc.3845

The alkaline hydrolysis reaction of O-(4-cyanophenyl), O-(4-methylphenyl), and phenyl O-(4-nitrophenyl) thionocarbonates (1, 2, and 3, respectively) and O-(4-cyanophenyl) and phenyl O-(4-nitrophenyl) carbonates (4 and 5, respectively) has been spectrophotometrically studied in aqueous borate buffer media, in the presence of the cationic surfactant CTAB. The pseudophase model successfully explained the results obtained, in the presence of this cationic micelle, and various kinetic parameters were determined. Results show that the catalytic efficiency increases in carbonates and thionocarbonates. In fact, a catalytic efficiency ( kobsmax/k'w) of 485-fold was found in the hydrolysis reaction of thionocarbonate 1, while in the carbonate homolog 4, the effect was of 146-fold. In addition, we found that at the same experimental conditions (Borate buffer pH = 9.0 and 25°C), an increase in the concentration of the buffer led to a decrease of the hydrolysis rate.

Full text of DOI:10.1002/poc.3845

Received: 30 November 2017
DOI: 10.1002/poc.3845
Revised: 23 January 2018
Accepted: 22 February 2018
S P E C I A L I S S U E A R T I C L E
Reactivity differences of O‐aryl O‐(4‐nitrophenyl)
thionocarbonates versus their homolog carbonates: Micellar
catalysis in hydrolysis reactions
José G. Santos
| Margarita E. Aliaga
| Mariana F. Márquez | Mauricio Oyarzún
Facultad de Química, Pontificia
Universidad Católica de Chile, Santiago,
Chile
Abstract
The alkaline hydrolysis reaction of O‐(4‐cyanophenyl), O‐(4‐methylphenyl),
and phenyl O‐(4‐nitrophenyl) thionocarbonates (1, 2, and 3, respectively) and
O‐(4‐cyanophenyl) and phenyl O‐(4‐nitrophenyl) carbonates (4 and 5, respec-
tively) has been spectrophotometrically studied in aqueous borate buffer media,
in the presence of the cationic surfactant CTAB. The pseudophase model suc-
cessfully explained the results obtained, in the presence of this cationic micelle,
and various kinetic parameters were determined. Results show that the cata-
Correspondence
José G. Santos, Facultad de Química,
Pontificia Universidad Católica de Chile,
Casilla 306, Santiago 6094411, Chile.
Email: jgsantos@uc.cl
Funding information
FONDECYT, Grant/Award Number:
1160271
lytic efficiency increases in carbonates and thionocarbonates. In fact, a catalytic
max
obs
efficiency ( k =k′w) of 485‐fold was found in the hydrolysis reaction of
thionocarbonate 1, while in the carbonate homolog 4, the effect was of 146‐fold.
In addition, we found that at the same experimental conditions (Borate buffer
pH = 9.0 and 25°C), an increase in the concentration of the buffer led to a
decrease of the hydrolysis rate.
KEYWORDS
alkaline hydrolysis reaction, catalytic efficiency, micellar catalysis, thionocarbonate and carbonate
reactivity
1 | INTRODUCTION
biological actions, such as analgesics, anesthetics, fungi-
cides, and bactericides.[2] In addition, the hydrolysis of
There is a great variety of organic reactions that are vital for
our ecosystem, both biologically and industrially. That is
why it becomes necessary to study and understand how
these reactions happen, and then optimize them in the best
way at the laboratory level. Among these reactions, one of
the most important involves carbonyl and thiocarbonyl
compounds,[1] and it is relevant to understand their
different reaction mechanisms to be able to establish
working conditions that favor their synthesis or that help
different transformations that lead to new compounds.
For example, the aminolysis reaction of
thionocarbonates, which leads to the subsequent forma-
tion of thionocarbamates, is one of the most important
reactions. Thionocarbamates possess a great number of
thionocarbonates, which is conducive to the formation
of alcohols with their respective acid, is important. In this
context, one of the most important reactions, based on the
dissociation of thionocarbonates, is the Barton‐McCombie
reaction,[3] whose objective is first to derivatize secondary
and tertiary alcohols to thionocarbonates, and then to
reduce them forming alkanes.
Moreover, changes caused by the micelles toward the
medium generate alterations in the kinetics of the reac-
tions,[4] because these can change the local concentration
of the substrates in the reaction medium, or also by the
stabilization of substrates and intermediates affecting the
reaction rate. This stabilization will depend on changes
in charge of the reactants or the micelle. For example,
J Phys Org Chem. 2018;e3845.
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SANTOS ET AL.
the same effect does not occur if it is an acid‐base process,
since the micelle could catalyze or inhibit it, depending on
the type of micelle used.[4b]
On the other hand, another important effect of the
micelle in the medium is the hydrophobic effect, which
causes catalytic effects in micellar systems to be accentu-
ated when the substrate and its substituents possess
greater hydrophobicity.[5]
Several kinetic models[6–8] have been developed to
quantitatively analyze the kinetic effects in the presence
of ionic surfactants.
SCHEME 1 Structures of the studied thionocarbonates and
carbonates compounds
The most frequently used model is the pseudo‐phase‐
ion‐exchange (PIE), throughout the kobs vs surfactant con-
centration profiles.[6a,7] There are 2 important factors in
the accelerations in surfactant solutions: (1) the interfacial
ion exchange catalysis[6–8] and (2) the large reagent con-
centrations in the small interfacial volume in which the
reaction occurs.[9]
The PIE model has been corrected when applied to
nucleophilic substitution in buffered surfactant solutions,
considering the competition of 3 anions in their micellar
binding: the surfactant counterion, the buffer base, and
the nucleophile.[10]
thionocarbonates (1, 2, and 3, respectively; Scheme 1),
and 4‐cyanophenyl and phenyl 4‐nitrophenyl carbonate
(4 and 5, respectively; Scheme 1) in the presence of
increasing concentrations of CTAB was carried out.
2 | EXPERIMENTAL
2.1 | Material
Thionocarbonates 1 to 3 and carbonate 5 were prepared as
described.[13] The carbonate 4 was prepared as in the
Supporting Information.
On the other hand, the existence of catalytic or inhibi-
tion effects by micellar systems on the hydrolysis reaction
of esters derivatives is well recognized. For example,
Iglesias E.[6d] reported that both cationic and nonionic
micelles decrease the rate of the acid‐catalyzed hydrolysis
of the ester function of ethyl cyclohexanone‐2‐carboxyl-
ate. The author also found that keto ester associates
strongly to cationic or nonionic micelles by hydrophobic
interactions, such as the micellar interface.[6c]
In this line, studies conducted by Al‐Lohedan et al
(2017) have demonstrated that the alkaline hydrolysis
of carboxylate (1‐naphthylbutyrate) and carbonate
esters (2‐(methylsulfonyl)‐ethyl‐4‐nitrophenylcarbonate)
is enhanced in the presence of cationic micelles of
cetyltrimethylammonium (CTA) bromide and CTA sulfate
and inhibited by anionic micelles of sodium dodecyl sul-
fate.[11] Recent studies by Hojo et al[12] have reported that
the hydrolysis reactions of p‐nitrophenyl benzoate in the
presence of cationic surfactants, such as CTAB or CTAC,
lead to an increment in the rate constant values of 140‐fold
and 200‐fold for CTAB and CTAC, respectively. Whereas,
the anionic surfactant, sodium dodecyl sulfate, has caused
only a gradual rate deceleration by the same reaction.[12]
Thus, taking into account the catalytic effect that cat-
ionic micelles would have on reactions of hydrolysis of
carbonyl compounds, it is interesting to assess the micel-
lar effect on such reactions in a series of thionocarbonates
and their homolog carbonates. To this end, in the present
work, a kinetic study of the hydrolysis reaction toward 4‐
cyanophenyl, phenyl and 4‐methylphenyl 4‐nitrophenyl
The surfactant hexadecyltrimethylammonium bro-
mide (CTAB, 99%) was supplied by Sigma‐Aldrich.
Solutions were freshly prepared before use and stored
refrigerated for no more than 2 days.
Merck supplied all other reagents, and the solutions
were prepared with doubly distilled water obtained from
a permanganate solution.
Substrates in acetonitrile solutions, buffer, and CTAB
solutions were prepared daily by dilution of the stock
solution. The percentage of organic solvent in the working
solution was less than 2% by volume.
2.2 | Product analysis
In both the absence or presence of surfactant, 4‐nitrophe-
nyl aryl thionocarbonates 1 to 3 and of 4‐nitrophenyl aryl
carbonate 4 to 5 hydrolysis yield 4‐nitrophenolate ion. The
absorption spectra of the studied reactions in basic media
present a band centered at 400 nm that increases with
time because of the formation of 4‐nitrophenolate ion.
2.3 | Kinetic measurements
The kinetics of the hydrolysis reactions of substrates 1 to 5
are analyzed through a diode array spectrophotometer, at
25.0 0.1°C. The reactions were followed in the 250 to
500 nm wavelength range, with the initial concentration
of the substrate being in the range of 2 to 8 × 10−5 M.
This concentration range enables following the reaction
by recording the absorbance of 4‐nitrophenolate ion.

SANTOS ET AL.
3 of 7
Because of the low solubility of substrates, in water and in
lower CTAB concentrations, their concentrations are in a
range near 2 × 10−5 M. pH was maintained constant by
using borate as the external buffer. Under these condi-
tions, pseudo‐first‐order rate coefficients (kobs) were found
throughout, the kinetics being measured for at least 5
half‐lives at 400 nm. The experimental conditions and
the kobs values obtained for the studied reactions are sum-
marized in Tables S1 to S7 in the Supporting Information.
thiocarbonyl, it is more polarizable. This causes a
greater positive charge on the carbon of the C―O
double bond compared to the C―S double bond.[14b]
• On the other hand, the nucleophile, in this case
hydroxide ion, corresponds to a hard nucleophile, so
it has greater affinity with a carbonyl bond than a
thiocarbonyl bond.
Similarly, the comparison between the hydrolysis rate
constant of thionocarbonates and carbonates studied
(see Table 1) shows the effect of the nonleaving group.
In fact, while greater is the electron withdrawing of this
group, more electrophilic is the thiocarbonyl group and
therefore greater hydrolysis rate constants.
3 | RESULTS AND DISCUSSION
3.1 | Hydrolysis reactions of
thionocarbonates and carbonates in the
absence of surfactant
Pseudo‐first‐order rate constant (kobs) in the absence of
CTAB at different NaOH concentrations, by following
the absorbance at 400 nm, were determined (Tables S1
and S2 in the Supporting Information). Plots of kobs
against the hydroxide concentrations obey Equation 1,
where k0 and kw are the rate constants for hydrolysis by
water and hydroxide ion, respectively. The obtained kw
values are summarized in Table 1.
3.2 | Hydrolysis reactions of
thionocarbonates and carbonates in the
presence of surfactant
The pseudo‐first‐order rate constant increases in the pres-
ence of a small amount of surfactant above the critical
micelle concentration (cmc) until it reaches a maximum;
after this point, an increase in surfactant concentration
diminishes the observed rate constant (see Figures 1–3).
This behavior is explained considering the micelle forma-
tion, the amount of substrate in the micelles, the competi-
tion between OH−, borate and the increasing amount of
Br−, and the dilution of the substrate in the micelles.[12]
These studies have suggested strongly that in micellar
media, most reactions take place on the surface of micelle
at or near the highly charged double layer, commonly
called the Stern layer.
kobs ¼ k0 þ kw½OHꢀ
(1)
The comparison between the hydrolysis rate constant
in the reactions of carbonates 4 and 5 shows that kw are
approximately 40 and 180 times faster than those of
thionocarbonates 1 and 2, respectively. There are at least
3 reasons to explain these results:
• The above results have been explained in a destabiliza-
tion of the tetrahedral intermediate because of the
greater ability of O− than S− in the intermediate to
form the double bond with the central carbon and
expel both the leaving group and the nucleophile. This
is because of the stronger pi‐bond energy of the C―O
group (by 40 kcal mol−1) relative to C―S.[14]
• This difference in the hydrolysis rate constant is
because of the different electrophilicity of the carbon
atom present on the carbonyl with respect to the car-
bon atom of the thiocarbonyl, since in the case of the
TABLE 1 Hydrolysis rate constants for the hydrolysis reactions of
substrates (1‐5) in the absence of CTAB
Substrate
kw, s−1 M−1
n
R2
1
2
3
4
5
3.32 0.03
0.18 0.01
0.31 0.01
10
5
0.999
0.977
0.989
0.995
0.997
FIGURE 1 kobs vs CTAB concentration profile in the hydrolysis
reaction of 1, (a) pH = 9.13; (b) pH = 9.05, borate buffer 20 mM;
and (c) pH = 9.0, buffer Borate 40 mM, at 25° C. Points are
5
146
33
5
5
experimental values (Table S3 in the Supporting Information) and the
curves were calculated with Equations 2 to 7 and values of Table 2.
1
4

4 of 7
SANTOS ET AL.
3.2.1 | Hydrolysis reactions of aryl
thionocarbonates
Thionocarbonate 1 hydrolysis reactions were studied
spectrophotometrically in the presence of a variable
amount of CTAB near pH = 9.0 in 2 different borate
buffer concentrations; the experimental conditions and
kobs values found are summarized in Table S3 in the
Supporting Information. Figure 1 shows the kobs vs
[CTAB] profiles of these reactions.
There are two observations from Figure 1:
1. The results show that in curves a and b (also in Table
S3 in the Supporting Information), only 0.08 pH units
in difference lead to changes of 11% in kobs values;
as a consequence of different total OH−.
2. The corresponding curves b and c (in Table S3 in the
Supporting Information) show kinetic differences; in
fact, part of the decrease in kobs is obvious because
of the decrease in pH (0.05 pH units), but most of
the decrease is because of the increased concentration
of the buffer. This is also a consequence of the ion
exchange equilibrium.[10b]
FIGURE 2 kobs vs [CTAB] profiles of the hydrolysis reactions of
(A) O‐phenyl O‐(4‐nitrophenyl) thionocarbonate 2 at pH 9.53 and
(B) of O‐(4‐methylphenyl) O‐(4‐nitrophenyl) thionocarbonate 3 at
pH 9.60 in both in the presence of 20 mM borate buffer, at 25°C.
Points are experimental values (Tables S4 and S5 in the Supporting
Information), and curves were calculated with Equations 2 to 7 and
values of Table 2.
and kobs values found are summarized in Tables S6 and
S7 in the Supporting Information. These results are
shown in Figure 3.
As in aqueous solutions, the kobs for the hydrolysis
reactions of the carbonyl derivatives are greater than
those of thiocarbonyl. The comparison of the correspond-
ing curves in Figures 1–3 clearly shows that the kobs
values for the hydrolysis reactions of the diarylcarbonates
4 and 5 are greater than those of 1 and 2, respectively,
although the carbonates are carried out at minor pH.
It was initially stated that borate anion does not bind
CTA[12]; nevertheless, the micellar effect found is strong
evidence for a binding of borate anion. Probably, even
the borate anion binds micelles weakly, its high concen-
tration (20‐40 mM), relative to the total [OH−]
(~10−5 M), allows its participation in the pseudo phase
and therefore in the kinetic.
The pseudo‐first‐order rate constants obtained of the
hydrolysis reactions of thionocarbonates 2 and 3 at differ-
ent CTAB concentrations are in Tables S4 and S5 in the
Supporting Information. Figure 2 shows the kobs against
[CTAB] profiles for these reactions.
It can be observed that for each concentration of
CTAB, the values of kobs of 2 and 3 hydrolysis reactions
are similar between them, and lower than those of 1,
although 2 and 3 compounds are measured at a higher
pH. The great difference with the hydrolysis of 1 can, in
principle, be attributed to the same reasons discussed
in relation with the same reactions in water solution
(vide supra), although differences in the association of
substrates with micelle cannot be ruled out.
3.2.2 | Hydrolysis reactions of aryl 4‐nitro-
phenyl carbonates
FIGURE 3 kobs vs CTAB concentration profile in the hydrolysis
reaction of (A) 4 at pH = 8.3 and (B) 5 at pH = 9.0; in both
[borate buffer] = 20 mM, at 25°C. Points are experimental values
(Tables S6 and S7 in the Supporting Information), and curves were
calculated with Equations 2 to 7 and values of Table 2.
Carbonates 4 and 5 hydrolysis reactions were studied
spectrophotometrically in the presence of a variable
amount of CTAB at pH = 8.3 and pH = 9.0, respectively,
and 20 mM borate buffer; experimental conditions

SANTOS ET AL.
5 of 7
These can be because of the different hydrophobicity and/
or the different electrophilicity of substrates, and will be
discussed later (see below).
model of Scheme 2, Equation 5; but the mOH− values were
calculated by Equation 6, which consider the ionic
interchange of the 3 counter ions in the micelle.[10a,15a]
In addition, as in the thionocarbonate series, the reac-
tions of carbonates 4 and 5 clearly show the influence of
the nonleaving group in the substrates. This behavior is
because of the differences in solubility in the micelles
and/or differences in the electrophilicity of the electro-
philic group in the substrates.[6]
À
ÁÀ
Á
3
−
−
−
mOH 1−KOH =buffer 1−KOH =Br
Â
À
Á
À
Á
þm2OH A1 1−KOH
þ 1−KOH =Br
−=buffer
−
−
À
ÁÃ
−
½OHꢀTKOH =buffer þ ½bufferꢀT þ mOH½OHꢀT
Â
À
À
ÁÁ
−=Br−
−
KOH
½bufferꢀT−ð1−αÞ½Dnꢀ 1−KOH =buffer
2
þKOH =bufferA1ꢀ−KOH =Br ð1−αÞ½DnꢀKOH =buffer½OH−ꢀT ¼ 0
−
−
−
−
(6)
3.2.3 | Quantitative kinetic study for the
hydrolysis reactions of aryl‐
thionocarbonates and carbonates in CTAB
−
−
−
In this equation, the terms KOH =Br and KOH =buffer
correspond to the ion exchange constant, α corresponds
to the degree of ionization of individual micellar species,
while parameter A1 is defined according to Equation 7.
With the aim to do a quantitative kinetic study for these
reactions, the PIE model[6a,7a] was applied. Scheme 2
shows this model, which consider the partition substrate
between the water (Sw) and the micelle (Sm) with an equi-
librium constant (Kass) and 2 parallel reactions that lead
to the same product; kw′ and km′ are the pseudo‐first‐
order rate constants and Dn = ([surfactant total] − cmc).
In the tested systems, Sw represents the carbonate or
thionocarbonate derivatives, and the micellized surfactant
(Dn) used is CTAB.
−
−
A1 ¼ α½Dnꢀ þ CMC þ KOH =Br ½OHꢀT
−
−
þ ð1−αÞ½DnꢀKOH =Br
(7)
Equation 6 was solved numerically by the Newton‐
Raphson method. Table 2 summarizes the k′m and Kass
obtained from the adjustment of the experimental
results with those obtained in the PIE model. In adjust-
ments of Equation 4, cmc = 0.0005 M (determined in
this study), α = 0.28, and for the interfacial ion
exchange constant (KOH =Br ,) the value 0.048 described
by Sepulveda et al[16] was used as fixed parameters.
For KOH =buffer, the best values was 15.5 in all the reac-
The rate equation deduced for this model is
(Equation 2):
−
−
k′w þ k′mKass½Dnꢀ
kobs
¼
(2)
1 þ Kass½Dnꢀ
−
The pseudo‐first‐order rate constants k′w and k′m are
related to the second‐order rate constants by equations
tions, except for the reactions of
1 in [borate
buffer] = 40 mM, where the best value was 7.75.
Comparison between entries 1 to 3 in Table 2 shows
that, as expected, there are not differences in the k′m
and Kass values, showing that the differences observed in
Figure 1 are only a consequence of the experimental
conditions.
About the change of thiocarbonyl by carbonyl in the
4‐cyanophenyl derivatives 1 and 4, the value of k'm is
about 30 times greater for 4 (entries 1 and 6 in Table 2).
k′w ¼ kw*½OH−ꢀw
(3)
k′m ¼ km*½OH−ꢀm
(4)
Substitution in Equation 2 lead to Equation 5 where
mOH is the concentration ratio of hydroxyl ion in the
micellar pseudo phase, mOH = [OH]m/[Dn]
kw½OH−ꢀT þ ðkmKass−kwÞ½DnꢀmOH
−
kobs
¼
(5)
TABLE 2 Values of Kass and k′m by fitting of the kinetics profiles
of Figures 1–3 with the pseudo‐phase‐ion‐exchange model
1 þ Kass½Dnꢀ
Because we observe an important dependence of kobs
with the buffer concentration in this study, we use the
[Borate],
Entry Substrate pH mM
k′m, s−1
Kass, M−1
1
2
3
4
5
6
7
1
1
1
2
3
4
5
9.05 20
9.13 20
9.00 40
9.53 20
9.60 20
8.30 20
9.00 20
53
51
45
1
1
1
1550 70
1440 70
1500 100
0.19 0.04 3100 200
0.15 0.03 3100 200
1480 50
88
540 40
680 30
SCHEME 2 Equilibrium and hydrolysis reaction step of the
substrates 1‐5 in CTAB micelles
2

6 of 7
SANTOS ET AL.
Likewise, comparison between the phenyl derivatives
It is not possible to directly compare the values of kw
(Table 1) with those of km (Table 2) because they are
defined in different units.[8b] To convert them to the same
units (s−1 M−1), it is common to multiply k′m by the molar
volume of the Stern layer to obtain the term k2m corre-
sponding to the micellar constant in units of second order.
A generally accepted value of molar volume of the Stern
2 and 5 (entries 4 and 7 in Table 2) shows that a k'm is
460 times greater for the carbonyl derivative. On the other
hand, the value of the equilibrium constant of association
Kass is greater for 1 and 2 than 4 and 5, respectively, prob-
ably because of their differences in hydrophobicity.
Related to the nonleaving group's effects, it is con-
cluded that as the hydrophobicity increases, high Kass
values were obtained (3~2 > 1; Table 2). For comparative
purpose of the carbonate series, a Kass value (~200) for
the hydrolysis reaction of bis(4‐nitrophenyl) carbonate,
reported by other authors, has been considered.[5b] In view
of the latter, we observed the same tendency for the car-
bonates series, phenyl > 4‐cyanophenyl > 4‐nitrophenyl.
The comparisons between the results of Table 2
suggest that in the micellar effects, both the association
of substrate to the micelle and the nucleophilic substitu-
tion reaction go in different directions.
The micellar effects can be analyzed from the quotient
between the hydrolysis rate constant in the bulk (kw)
and the maximum value obtained in the presence of
the surfactant ( kmobasx).[10b] Considering that both terms
are dependent on the experimental conditions, to conduct
a more trustworthy comparison, we calculate these values
at the same pH and borate concentration. Table 3 shows
the micelle effects in the studied reactions.
layer is 0.14 l mol−1 [6c,9]
values obtained.
.
Table 3 summarize the k2m
For the hydrolysis reaction of thionocarbonate 1 and
carbonate 4, the k2m/kw ratio is greater than 1, suggesting
that there is a catalytic effect; therefore, the acceleration
observed in the micelle is due to both an increment of
the local concentration of substrate in the micelle and
by a catalytic effect. On the other hand, the values of
k2m/kw are clearly minor than 1 for the thionocarbonates
2 and 3 and carbonate 5, suggesting an inhibiting effect,
and therefore, the observed accelerations are only because
of the increase of the local concentration of substrates in
the micelle. In summary, substrates containing the 4‐
cyanophenyl as nonleaving group (1 and 4) present cata-
lytic effect whereas those with phenyl (2 and 5) or 4‐
methylphenyl (3) as nonleaving groups present inhibition.
4 | CONCLUSIONS
• The pseudophase ion exchange model is highly suc-
cessful in explaining kinetics results obtained for the
hydrolysis of substrates 1 to 5 in CTAB, considering
the ionic interchange of three anions in the micelle
interphase (OH−, Br−, and borate).
The effect on hydrolysis reactions of thionocarbonate
1 is about 3 times greater than that of the carbonate 4.
Undoubtedly, these results may be because of the higher
concentration of thionocarbonate in the micellar
pseudo‐phase derived from its higher constant association
equilibrium; however, a possible catalytic effect in the
hydrolysis step cannot be ruled out. On the contrary,
the effect is 1.5 times greater for the carbonate 5 than
thionocarbonate 2, in spite of the latter presenting a
• The catalytic efficiency increases from carbonate 4 to
max
obs
thionocarbonate 1; a k =k′w ratio of 485 times was
found in the hydrolysis reaction of thionocarbonate
1, while in the carbonate homolog 4, the effect was
146 times.
greater Kass
.
• It is possible to conclude that the micellar effect on the
hydrolysis reaction of thionocarbonate 1 and carbon-
ate 4 is favored for both greater solubility (Kass) and
catalytic effect (k2m/kw).
In both series, it can be observed that the maximal
effect is on the 4‐cyano derivative, which presents the
minor Kass, reinforcing the idea that both factors (associa-
tion in the micelles and catalytic process) are important.
• For the hydrolysis reaction of thionocarbonates 2 and
3 and of carbonate 5, the acceleration observed in
the micellar medium is only because of the concentra-
tion of substrate in the micelle.
TABLE 3 Kinetics parameters obtained for the hydrolysis reac-
tions of substrates 1‐5
Substrate
• Substrates with 4‐cyanophenyl as nonleaving group (1
and 4) present catalytic effect, whereas those with phe-
nyl (2 and 5) or 4‐methylphenyl (3) as nonleaving
groups present inhibition.
• The Kass values between thionocarbonates 1 or 2 and
CTAB micelles are about 3 times higher than those
determined by their homologs 4 and 5 because of the
greater hydrophobicity of the thiocarbonyl group than
carbonyl.
Kinetic Parameters
104 k′w (s−1 a
1
2
3
4
5
)
0.33 0.018
0.031
0.485
16
14.6
3.27
a
104kmobasx ðs−1
Þ
160
485
7.4
0.55
31
2140 160
max
k
=k′w
146
49
obs
k
2m, s−1 M−1
0.0266 0.0212 207
0.141 0.0682 1.42
12.3
0.373
k2m/kw
2.1
aCalculated with the values of Table 2, at pH = 9.0 and [borate] = 20 mM.

SANTOS ET AL.
7 of 7
systems, in Surfactants in Science Series (Eds: M. Gratzel, K.
Kalyanasundaram) Vol. 28, M. Dekker, New York 1991 13; (c)
C. A. Bunton, J. R. Moffatt, J Phys Chem 1988, 92, 2896; (d)
J. D. Morgan, D. H. Napper, G. G. Warr, J Phys Chem 1995,
99, 9458.
ACKNOWLEDGEMENTS
This work was supported by FONDECYT grant 1160271.
ORCID
[9] C. A. Bunton, N. Carrasco, K. Huang, C. Paik, L. S. Romsted,
J Am Chem Soc 1978, 100, 5420.
José G. Santos http://orcid.org/0000-0002-5017-2164
Margarita E. Aliaga http://orcid.org/0000-0002-4143-0301
[10] (a) F. H. Quina, H. Chaimovich, J Phys Chem 1979, 83, 1844; (b)
N. Ouarti, A. Marques, I. Blagoeva, M.‐F. Ruasse, Langmuir
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SUPPORTING INFORMATION
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How to cite this article: Santos JG, Aliaga ME,
Márquez MF, Oyarzún M. Reactivity differences of
O‐aryl O‐(4‐nitrophenyl) thionocarbonates versus
their homolog carbonates: Micellar catalysis in
hydrolysis reactions. J Phys Org Chem. 2018;e3845.
https://doi.org/10.1002/poc.3845
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