Influence of components of the PdCl2(PPh3) 2-PPh3-p-toluenesulfonic acid catalytic system on the rate of cyclohexene hydrocarbalkoxylation with m-cresol

Article abstract of DOI:10.1134/S0965544107030048

Kinetic parameters were determined for the cyclohexene hydrocarbalkoxylation reaction catalyzed by the PdCl₂(PPh ₃)₂-PPh₃-p-toluenesulfonic acid (TSA) catalyst system in the presence of m-cresol. It was shown that the reaction is first order in cyclohexene and a fractional order in PdCl₂(PPh ₃)₂ and m-cresol and that the dependences of the reaction rate on P_CO, TSA and PPh₃ concentrations are nonmonotonic in character. The inhibitory effect of tosylate and chloride ions on the reaction was revealed. The results were rationalized in terms of a mechanism that involves hydride complexes of the cation type as intermediates. A rate equation for the reaction was derived in terms of the steady-state hypothesis to fit to experimental data. Nauka/Interperiodica 2007.

Full text of DOI:10.1134/S0965544107030048

ISSN 0965-5441, Petroleum Chemistry, 2007, Vol. 47, No. 3, pp. 167–175. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © V.A. Aver’yanov, N.M. Nosova, E.V. Astashina, N.T. Sevost’yanova, 2007, published in Neftekhimiya, 2007, Vol. 47, No. 3, pp. 186–195.
Influence of Components of the PdCl2(PPh3)2–PPh3–p-
Toluenesulfonic Acid Catalytic System on the Rate
of Cyclohexene Hydrocarbalkoxylation with m-Cresol
V. A. Aver’yanov, N. M. Nosova, E. V. Astashina, and N. T. Sevost’yanova
Tula State University, Tula, Russia
e-mail: piligrim@klax.tula.ru
Received March 20, 2006
Abstract—Kinetic parameters were determined for the cyclohexene hydrocarbalkoxylation reaction catalyzed
by the PdCl2(PPh3)2–PPh3–p-toluenesulfonic acid (TSA) catalyst system in the presence of m-cresol. It was
shown that the reaction is first order in cyclohexene and a fractional order in PdCl2(PPh3)2 and m-cresol and
that the dependences of the reaction rate on PCO, TSA and PPh3 concentrations are nonmonotonic in character.
The inhibitory effect of tosylate and chloride ions on the reaction was revealed. The results were rationalized
in terms of a mechanism that involves hydride complexes of the cation type as intermediates. A rate equation
for the reaction was derived in terms of the steady-state hypothesis to fit to experimental data.
DOI: 10.1134/S0965544107030048
Hydrocarbalkoxylation of alkenes is a promising cyclohexene hydrocarbalkoxylation catalyzed by the
ester synthesis method [1–3]. Of catalytic systems used Pd(PPh3)2Cl2–PPh3–p-toluenesulfonic acid system in
in this reaction, palladium phosphine complexes pro- the presence of m-cresol was attempted.
moted with triphenylphosphine and strong protic acids
are of particular interest [4–8]. Acting in combination,
EXPERIMENTAL
these compounds exert a stabilizing effect on the cata-
lyst. At the same time, protic acids, serving as a hydride
source during the formation of active forms of the cat-
alyst, accelerate the reaction. The acid residues are
weakly coordinated anions and, as such, make the pal-
ladium center of the catalytic complex more accessible,
facilitating its interaction with reactants during cata-
lytic cycles.
The cyclohexene hydrocarbalkoxylation reaction
with m-cresol was studied in a batch reactor described
in [12]. Each experiment was carried out in toluene at a
constant temperature and a constant CO pressure. In the
course of kinetic experiments, the reaction mixture
from the reactor was sampled at a certain intervals and
analyzed by GLC on a Tsvet 162 chromatograph
equipped with a flame-ionization detector. Glass col-
umns of 3 mm in inner diameter packed with Chroma-
ton N-AW-DMCS (0.16–0.20-mm fraction) coated 5%
XE-60; the carrier gas was nitrogen or argon. The inter-
nal standard was o-xylene. The reactant and product
concentrations were determined with an accuracy of
3%. The confidence intervals of the kinetic parameters
of interest are given in the text.
The reactants were cyclohexene, m-cresol, and car-
bon monoxide; the components of the catalyst system
were dichlorobis(triphenylphosphine)palladium, triph-
enylphosphine, and p-toluenesulfonic acid; and the sol-
vent was toluene.
Cyclohexene was prepared by cyclohexanol dehy-
dration in the presence of concentrated phosphoric
acid, according to a procedure described in [13], fol-
lowed by drying over anhydrous calcium chloride and
rectification.
Despite the efficacy of the aforementioned catalyst
systems, the number of works concerning their action is
relatively small. This problem has been studied in some
detail by Toniolo et al. [4, 6–8] and Petrov’s group
[9−11] using the hydrocarbalkoxylation of ethylene,
cyclohexene, 1-heptene, styrene, and phenylacetylene
as examples. The results of these studies show that the
rate, as well as the selectivity, of reactions catalyzed by
the “palladium phosphine complex–free phosphine–
strong protic acid” system is a function of many factors
whose influence is conjugate in character. In addition to
the concentration of reactants and catalyst components,
these factors include the nature of a protic acid, its
anion, a catalyst precursor anion, and an alcohol as a
reactant and a specific component of the reaction
medium. The elucidation of these factors necessitates a
broader variation in the concentrations of components
of the reacting system and setting up special experi-
ments on revealing the effect of the catalyst-precursor
and protic acid anions. In connection with this, a sys-
Pd(PPh3)2Cl2 was prepared from palladium(II) chlo-
tematic study of the kinetics of the model reaction of ride and triphenylphosphine by the procedure described
167

168
AVER’YANOV et al.
3
–1
–1
C
, mol/l
est
r × 10 , mol l min
4
0.08
0.06
0.04
0.02
6
3
2
4
5
3
2
1
1
0
1
2
3
4
5
6
0
20
40
60
t, min
p
, åPa
CO
Fig. 1. Time dependence for ester concentration at different
CO partial pressures in the cyclohexene hydrocarbalkoxyla-
tion reaction with m-cresol. T = 381K; concentrations,
Fig. 2. Influence of p
hydrocarbalkoxylation reaction with m-cresol. T = 381K;
concentrations, mol/l: [C H ] = 0.1, [CH C H OH] = 0.3,
on the initial rate of cyclohexene
ëé
6
10
3 6 4
mol/l: [CH C H OH] = 0.3; [ë H ] = 0.1; [Pd(PPh ) Cl ] =
3
6
4
6
10
3 2
2
–3
–3
–3
–3
–2
[Pd(PPh ) Cl ] = 2 × 10 ; [PPh ] = 8 × 10 ; [p-TSA] =
3 2
2
3
2 × 10 ; [PPh ] = 8 × 10 ; [p-TSA] = 2.4 × 10 ; p , MPa:
3
ëé
–2
2.4 × 10 .
(1) 1.1, (2) 2.1, (3) 3.1, (4) 4.1, (5) 5.1, and (6) 6.1.
The initial reaction rates were determined by differ-
in [14]. According to IR, atomic-absorption, and ele-
mental analysis data, the sample obtained corresponded
to the structure of the Pd(PPh3)2Cl2 complex.
entiating the initial portions of the rate curves next to
the autocatalytic portions. The plot of the initial rate
versus the CO partial pressure given in Fig. 2 exhibits
an extremum at a CO pressure of 3.5 MPa.
The chromatographic standard m-cresyl cyclohex-
anecarboxylate was prepared according to the proce-
dure described above for alkene hydrocarbalkoxyla-
tion, followed by neutralization of the reaction mixture
with NaOH, drying over anhydrous calcium dichloride,
and vacuum distillation.
A similar dependence with a maximum at [PPh3] =
4 × 10–3 mol/l was obtained for the influence of triphe-
nylphosphine. The results agree with the data obtained
by the Toniolo [4, 6], Petrov [9], and El’man [5] groups
for alkene hydrocarbalkoxylation in the presence of
analogous catalytic systems.
The results on the effect of Pd(PPh3)2Cl2 on the
cyclohexene hydrocarbalkoxylation rate are presented
in Fig. 3 as the plot of the initial reaction rate versus the
catalyst concentration. This dependence is nonlinear in
character, indicating a decrease in the catalyst precursor
activity with an increase in its concentration.
The results on the influence of TSA on the reaction
rate are given in Fig. 4. This dependence has a maxi-
mum at [TSA] = 4 × 10–2 mol/l and differs from the data
obtained by Toniolo et al. [4, 6] and the El’man group
[5] for the cyclohexene hydrocarbalkoxylation reaction
catalyzed by the Pd(PPh3)2(TsO)2–PPh3–TSA system.
The cited authors revealed the S-shaped dependence of
the reaction rates on [TSA], which saturated at high
TSA values.
The purification and isolation of desired products or
chromatographic standards involved their distillation
on a fractionating column with Fenske packing and a
height of 20 theoretical plates. The purity criteria for
the substances used were the boiling point and the
refractive index. In chromatographic analysis, all sub-
stances gave one peak each on different phases.
Toluene (analytical grade) was preliminarily dried
over anhydrous calcium dichloride and rectified.
RESULTS AND DISCUSSION
To elucidate the influence of the reactants and the
components of the catalytic system on the reaction rate,
we conducted six series of experiments, varying one of
the factors within each series. Typical experimental
results are represented as m-cresyl cyclohexanecarbox-
The results on the influence of m-cresol on the reac-
ylate buildup curves at different partial pressures of CO tion rate, given in Fig. 5, show a fractional reaction
(Fig. 1). It is seen that these curves are characterized by order in this reagent, a feature that differs in our data
the autocatalytic portion, indicating the formation of from that of Toniolo et al. [6], who found the reaction
active catalyst complexes responsible for the catalytic to be first order in methanol for cyclohexene hydrocar-
cycle.
balkoxylation catalyzed by the Pd(PPh3)2(TsO)2–PPh3–
PETROLEUM CHEMISTRY Vol. 47 No. 3 2007

INFLUENCE OF COMPONENTS
169
3
–1
–1
3
–1
–1
r × 10 , mol l min
2.5
r × 10 , mol l min
3.0
2.5
2.0
1.5
1.0
0.5
2.0
1.5
1.0
0.5
0
2
4
6
8
10
0
2
4
6
8
2
3
[p-TSA] × 10 , mol/l
[Pd(PPh ) Cl ] × 10 , mol/l
3 2
2
Fig. 3. Influence of Pd(PPh ) Cl on the initial rate of cyclo-
Fig. 4. Influence of [p-TSA] on the initial rate of cyclohexene
hydrocarbalkoxylation reaction with m-cresol. T = 381 ä,
3 2
2
hexene hydrocarbalkoxylation reaction with m-cresol.
T = 381 ä, p = 2.1 MPa; concentrations, mol/l: [C H ] =
p
= 2.1 MPa; concentrations, mol/l: [C H ] = 0.1,
CO
6
10
–3
CO
6 10
–2
[CH C H OH] = 0.3, [Pd(PPh ) Cl ] = 1 × 10 ; [PPh ] =
0.1, [CH C H OH] = 0.3, [PPh ] = 4 × 10 ; [p-TSA] = 0.12.
3
6
–3
4
3 2
2
3
3
6
4
3
8 × 10 .
TsOH system over a broad range of CH3OH concentra-
tions (0–7.5 mol/l). Note that the cited authors obtained
their results under the conditions of reaction mixture
dilution with acetone, whereas we used toluene as a
dilutent in all runs.
We found that the reaction was also first order in
cyclohexene over the concentration range examined
(0–0.1 mol/l). These data are consistent with the results
of the Petrov [10] and Toniolo [6] groups for the test
alkenes (styrene and cyclohexene, respectively) in the
catalysis by analogous systems, as well as with the data
of these and other authors on alkene carbonylation in
the presence of palladium phosphine complexes that
did not contain a powerful hydride source [14–18].
INTERPRETATION
OF REACTION MECHANISM
Summarizing the obtained data and current ideas
concerning the mechanism of the hydrocarbalkoxyla-
tion reaction catalyzed by palladium phosphine com-
plexes [2, 4–10, 15–21], we may propose the following
3
–1
–1
r × 10 , mol l min
4
In addition to the above experiments, we examined
the influence of tosylate and chloride ions on the reac-
tion rate. Sodium tosylate and rubidium chloride,
respectively, were the sources of these ions. The exper-
iments were carried out at different concentrations of
these salts, but at a constant temperature and constant
3
2
1
concentrations of other components: í = 381 ä, pëé
=
2.1 MPa; concentrations, mol/l: [C6H10] = 0.1,
[CH3C6H4OH] = 0.3, [Pd(PPh3)2Cl2] = 2 × 10–3;
[PPh3] = 8 × 10–3, [p-TSA] = 2.4 × 10–2. The results are
given below as the dependence of the reaction rate on
the concentration of the corresponding salt.
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
[CH C H OH], mol/l
3
6 4
[TsONa], mol/l
0
0.05 0.1 0.15
0.2
3
–1
–1
r × 10 , mol l min
2.89 2.00 1.55 1.52
1.28
2
Fig. 5. Influence of [CH C H OH] on the initial rate of
3
6 4
[RbCl] × 10 , mol/l
0
0.2 0.4 0.8 1.6 2.8
cyclohexene hydrocarbalkoxylation reaction with m-cresol.
3
–1
–1
r × 10 , mol l min
2.89 2.30 1.46 1.17 0.83 0.15
T = 381 ä; p
= 2.1 MPa; concentrations, mol/l:
ëé
–3
[C H ] = 0.1, [Pd(PPh ) Cl ] = 2 × 10 ; [PPh ] = 8 ×
It is seen that tosylate and chloride anions retard the
reaction.
6
−3
10
3 2
–2
2
3
10 ; [p-TSA] = 2.4 × 10 .
PETROLEUM CHEMISTRY Vol. 47 No. 3 2007

170
AVER’YANOV et al.
k0
PdCl2(PPh3)2 + CO + H2O
Pd(PPh3)2 + CO2 + 2 HCl
(1)
(2)
k1
Pd(PPh3)2 + 2 Sol
(X0)
Pd(PPh3)2(Sol)2
(X1)
k–1
k2
⊕
Pd(PPh3)2(Sol)2 + TsOH
(X1)
HPd(Sol)(PPh3)2 + TsO– + Sol
(3)
k–2
(X2)
2
⊕
k3
⊕
HPd(Sol)(PPh3)2 +
(X2)
HPd(PPh3)2 + Sol
k–3
(X3)
k4
(4)
(5)
k–4
+ CH3C6H4OH
(8)
k
7 slowly
⊕
O
Pd(Sol)(PPh3)2
C
(X4)
O
C6H4CH3
k–5
k5
(6)
+ CO
k–6
k6
⊕
⊕
+ Sol
Pd(CO)(PPh3)2
CO Pd(Sol)(PPh3)2
(X6)
(X5)
(7)
Scheme 1.
reaction route with a key role played by hydride com- concentration of these complexes due to a solvent
plexes (Scheme 1):
excess and an expectedly high value of the equilibrium
constant K7.
The rate-determining character of step (8) is con-
firmed by the reaction sensitivity to the size of alcohol
as a nucleophile [17, 22, 23] and its concentration [6,
18, 23], as well as by the feasibility of isolation of
acylpalladium complexes of the ï6 type in a measur-
able amount from the reaction mixture [21, 24]. In this
context, the fractional reaction order with respect to
m-cresol can be explained in terms of the interplay of
two factors. At low concentrations of m-cresol, this
component prevalently functions as a reactant; at high
concentrations, ligand-exchange reactions of m-cresol
with intermediates of the catalytic cycle begin to play a
progressively more significant role, leading to the with-
drawal of a part of the catalyst from its reaction sphere.
The most likely reaction of this type is reaction (9)
In our opinion, the nonmonotonic character of the
dependence of the reaction rate on pëé is also the result
of the interplay between two factors. At a pressure of up
to 3–3.5 MPa, carbon monoxide predominantly acts as
a reactant that is inserted in one of the intermediates of
the catalytic cycle. However, as the pressure further
grows the CO interaction with palladium-containing
intermediates yielding less active or inactive complexes
becomes progressively more significant. This process
leads to the withdrawal of a part of the catalyst from the
catalytic cycle and, as consequence, to a reduction in
the reaction rate.
This mode of deactivation was experimentally con-
firmed in works by Petrov et al. [16, 21], who not only
kinetically substantiated a possible formation of palla-
dium phosphine intermediates with two or more CO
molecules in the coordination sphere, but also identi-
fied them. They assumed that the deactivating action of
CO on the catalytic system can be interpreted in terms
Pd(PPh3)2(Sol)2
+ CH C H OH
3
6 4
(X )
1
(9)
K7
Pd(PPh3)2(CH C H OH)(Sol) + Sol.
3
6 4
(X )
7
The cause of this behavior is the weak coordination of its interaction with the coordination complex
of solvent molecules in complexes ï1, as well as a high Pd(PPh3)2(Sol)2.
K8
Pd(PPh3)2(CO)2 + 2 Sol.
Pd(PPh3)2(Sol)2 + 2 CO
(10)
(X )
(X )
1
8
PETROLEUM CHEMISTRY Vol. 47 No. 3 2007

INFLUENCE OF COMPONENTS
171
The character of the influence of triphenylphos- with the intermediates of the catalytic cycle and con-
phine on the rate of the test reaction also reflects the verts a part of the catalyst into inactive and less active
dual function of this component. In the concentration forms. The interplay between these factors is ulti-
region to 0.004 mol/l, PPh3 accelerates the reaction. mately responsible for the nonmonotonic character of
This effect seems to be due to fact that PPh3 increases the dependence of the reaction rate on the PPh3 con-
the concentration of the intermediates responsible for centration. The accelerating effect of the PPh3 action
the formation of reaction products. At higher concen- on the reaction rate can be explained in terms of equi-
trations, PPh3 is involved in subsequent interactions libria (11) and (12):
K9
Pd(CO)(PPh3)(Sol)2 + PPh3
Pd(PPh3)2(Sol)2 + CO
(X )
(X )
1
9
(11)
(12)
K10
Pd(PPh3)2(Sol)2 + CH C H OH
Pd(CH C H OH)(PPh3)(Sol)2 + PPh3
3
6 4
3
6 4
(X )
(X )
1
10
which are shifted by the action of triphenylphosphine
toward the complex Pd(PPh3)2(Sol)2 responsible for the
formation of HPd⊕(Sol)(PPh3)2, the key intermediate of
the catalytic cycle. At the same time, the deactivating
action of PPh3, which prevails in the region of its high
concentration, can be interpreted in terms of equilib-
rium (13)
K13
+ Cl–
[Pd(PPh3)2(Sol)Cl]– + Sol.
Pd(PPh3)2(Sol)2
(X )
(X )
1
12
(15)
Complexes ï12 can give rise to the alternative cat-
alytic cycle, which involves neutral hydride com-
plexes as intermediates (Scheme 2), by analogy with
Scheme 1.
These hydride complexes are less reactive than the
cationic complexes, thus causing a decrease in the total
reaction rate.
K11
Pd(PPh3)4 + 2 Sol
Pd(PPh3)2(Sol)2 + 2 PPh3
(13)
(X )
(X )
1
11
Note that, in systems that mediate the reaction pre-
sumably via neutral hydride complexes and involve
PdCl2 or Pd(PPh3)2Cl2 as a catalyst precursor, chloride
whose shift toward the inactive form Pd(PPh3)4 is more
sensitive to PPh3 concentration than equilibria (11) and anions have a promoting effect on the reaction [22, 25].
This makes us confident that the primary cause of the
inhibiting effect of chlorine is formation by the action
of chloride anions of alternative catalytic cycles, which
proceed at a substantially lower rate with neutral chlo-
rine-containing hydride intermediates. The existence of
such cycles was clearly shown by Petrov et al. [2,
16, 21].
Since step (8) is rate determining, all its preceding
steps, as well as reactions (9)–(15), can be considered
equilibrium processes. Then, the reaction rate will be
expressed by the equation
(12).
The retarding effect of tosylate anions seems to be due
to the formation of hydrogen-bonded associates between
these ions and m-cresol molecules, which leads to a
decrease in the acting concentration of m-cresol. It is note-
worthy that the reaction is not responsive to a change in the
tosylate concentration when a low-acidity alcohol, such as
cyclohexanol, is used as an esterifying agent. The addi-
tional argument in favor of the formation of these associ-
ates is a nonmonotonic dependence of the reaction rate on
the TSA concentration: the formation of associates
between TSA and m-cresol molecules must also lead to a
decrease in the concentration of m-cresol and, hence, in
the reaction rate.
r = k7[X6][CH3C6H4OH],
(16)
and the concentrations of all components relevant to
Scheme 1 and reactions (9)–(15) are defined by the
equalities
In our opinion, the inhibiting effect of chloride
anions is caused by a stronger coordinating power of
these anions as compared with solvent molecules. This
coordination leads to the formation of less active inter-
mediates, such as ï12, in accordance with equilibria
[X1]
----------
[X0]
[X2]
-------------------------------
[X1][TsOH]
K1 =
, K2 =
,
[X3]
[X2][ol]
[X4]
[X5]
------------------------
,
--------------------
----------
K3 =
, K4 =
, K5 =
[X7]
[X3]
[X4][CO]
[X6]
⊕
K12
Cl– + HSol
-------------------------------------------------
K6 = ----------, K7 =
,
HCl + Sol
(14)
[X1][CH3C6H4OH]
[X5]
PETROLEUM CHEMISTRY Vol. 47 No. 3 2007

172
AVER’YANOV et al.
The total concentration of monomeric forms of the
catalyst is expressed as
[X8]
[X9][PPh3]
----------------------------
[X1][CO]
--------------------------
K8 =
,
K9 =
,
[X1][CO]2
CM = [X0] + [X1] + [X2] + [X3]
[X10][PPh3]
[X1][CH3C6H4OH]
[X11]
-------------------------------------------------
------------------------------
K10
=
, K11
=
,
[X1][PPh3]2
[X12]
+ [X4] + [X5]+ [X6] + [X7]
(18)
(17)
[Cl–]
---------------
2[CM]
[Cl–]
K12 = -------------- =
[HCl]
+ [X8] + [X9] + [X10] + [X11] + [X12].
------------------------
,
, K13
=
[X1][Cl–]
With allowance for relations between ï0, ï1, …,
ï12, as are determined by the sets of Eqs. (17) and (18),
we obtain:
where [ol] is the olefin concentration.
[X6]
CM = ------------------------------------------------
K[ol][CO][TsOH]
⎧
⎪
⎪
⎨
⎪
⎪
⎩
⎫
⎪
⎪
⎬
⎪
⎪
⎭
1
K1
K
K6
⎛
⎞
1 + ----- + K2[TsOH] + (K2K3 + K2K3K4)[ol][TsOH] + ----- + K [ol][CO][TsOH]
(19)
⎝
⎠
×
,
[CH3C6H4OH]
-------------------------------------
[PPh3]
[CO]
+ K7[CH3C6H4OH] + K8[CO] + K ---------------- + K10
9[PPh3]
2
2
–
+ K11[PPh3] + K13[Cl ]
where K = K2K3K4K5K6.
Solving Eq. (19) in [X6] and substituting this
quantity into rate equation (16) for the rate-deter-
mining step, we obtain the expression for the reac-
tion rate
k7KCM[ol][CO][TsOH][CH3C6H4OH]
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
r =
.
(20)
⎧
⎪
⎪
⎨
⎪
⎪
⎩
⎫
⎪
⎪
⎬
⎪
⎪
⎭
1
K1
K
K6
⎛
⎞
1 + ----- + K2[TsOH] + (K2K3 + K2K3K4)[ol][TsOH] + ----- + K [ol][CO][TsOH]
⎝
⎠
[CH3C6H4OH]
-------------------------------------
[PPh3]
[CO]
+ K7[CH3C6H4OH] + K8[CO] + K ---------------- + K10
9[PPh3]
2
2
–
+ K11[PPh3] + K13[Cl ]
In view of the first reaction order observed with respect ance of palladium complexes is negligible, and Eq. (20)
to cyclohexene, it may be assumed that the contribution will take a more compact form
of terms containing its concentration into the total bal-
k7KCM[ol][CO][TsOH][CH3C6H4OH]
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
r =
.
(21)
[CH C H OH]
⎧
⎪
⎨
⎪
⎩
[CO]
----------------
9[PPh3]
⎫
⎪
⎬
⎪
⎭
1
K1
1 + ----- + K2[TsOH] + K7[CH3C6H4OH] + K8[CO]2 + K
+ K10
3
6
4
-------------------------------------
[PPh3]
+ K11[PPh3]2 + K13[Cl–]
The fitting of Eq. (21) to experimental data can be on pëé and PPh3, m-cresol, and catalyst-precursor
demonstrated using dependences of the reaction rate concentrations. For example, by varying the m-cresol
PETROLEUM CHEMISTRY Vol. 47 No. 3 2007

INFLUENCE OF COMPONENTS
173
[Pd(PPh3)2(Sol)Cl]– + TsOH
HPd(PPh3)2Cl + TsO– + Sol
(X13)
(X12)
HPd(PPh3)2Cl +
(X13)
HPd(PPh3)Cl + PPh3
(X14)
O
Pd(PPh3)2Cl
(X15)
+ CH3C6H4OH
C
O
C6H4CH3
+ CO
+ PPh3
CO Pd(PPh3)2Cl
(X17)
Pd(CO)(PPh3)Cl
(X16)
Scheme 2.
concentration, this equation can be reduced to the where k = k7KCM [ol] [CO] [TsOH] [CH3C6H4OH];
form
E = K9[CO] + K10 [CH3C6H4OH]; and D = 1 +
1
K1
2
–
-----
K2[TsOH] + K7[CH3C6H4OH] + K8[CO] + K13[Cl ].
k[CH3C6H4OH]
----------------------------------------------------
A + B[CH3C6H4OH]
r =
,
(22)
The latter equation is readily transformed into the
relationship
K10
where k = k7KCM[ol][CO][TsOH]; B = K7 + ---------------- ;
[PPh3]
K11
-------
k
[PPh3]
D
k
E
k
3
---
---------------- = --- + [PPh3] +
[PPh3] .
(25)
1
[CO]
----------------
9[PPh3]
r
+ K2[TsOH] + K8[CO]2 + K
+
-----
K1
and A = 1 +
K11[PPh3]2 + K13[Cl–].
[PPh3]
----------------
The dependence of the ratio
concentration is given in Fig. 7.
on the PPh3
r
In turn, Eq. (22) is easy to reduce to the form
A
1
B
k
1
---------------------------------------- ---
-- =
r
+
.
(23)
The evaluation of the parameters of Eq. (25) by the
least squares method and the subsequent verification of
its adequacy demonstrated agreement between the cal-
k [CH3C6H4OH]
1
r
1
--
------------------------------------- culated (curve) and the experimental (symbols) data.
–
The linear character of the
[CH3C6H4OH]
Thus, the proposed mechanism and the correspond-
ing kinetic model describe the experimental data well
on the influence of the PPh3 concentration on the reac-
tion rate.
plots presented in Fig. 6 indicates the validity of the
kinetic derived model and the proposed reaction mech-
anism concerning the influence of m-cresol on the reac-
tion rate.
Under the conditions of a one-factor experiment on
the influence of triphenylphosphine on the reaction
rate, Eq. (21) is reduced to the form
Under the conditions of a one-factor experiment on
the influence of CO pressure on the rate of cyclohexene
hydrocarbalkoxylation reaction, Eq. (21) is reduced to
the form
k
--------------------------------------------------------------
r =
,
(24)
E
kpCO
D + ---------------- + K11[PPh3]2
-----------------------------------------
r =
,
(26)
G + aP2CO + bpCO
[PPh3]
PETROLEUM CHEMISTRY Vol. 47 No. 3 2007

174
AVER’YANOV et al.
[PPh ]/r, min
–2
–1
1/r × 10 , l min mol
3
40
30
20
10
6
5
4
3
2
0
0.01
0.02
0.03
0.04
0.05
0
1
2
3
4
5
6
[PPh ], mol/l
3
[CH C H OH], l/mol
3
6 4
Fig. 6. Fitting Eq. (23) to experimental data. T = 381K;
= 2.1 MPa; concentrations, mol/l: [ë H ] = 0.1,
Fig. 7. Fitting Eq. (25) to experimental data. T = 381K;
p
p
= 2.1 MPa; concentrations, mol/l: [ë H ] = 0.1;
ëé
6 10
ëé
6
10
–3
–3
[Pd(PPh ) Cl ] = 2 × 10 , [PPh ] = 8 × 10 ; [p-TSA] =
–3
3 2
2
3
[CH C H OH] = 0.3; [Pd(PPh ) Cl ] = 2 × 10 , [p-TSA] =
–2
3
6
4
–2
3 2
2
2.4 × 10 .
2.4 × 10 .
k7KCM
----------------
H
K8
H2
Then, in accordance with Eq. (14), the Cl– concentra-
tion is expressed by
------
where k =
[ol] [TsOH] [CH3C6H4OH]; a =
;
K9
---------------------
1
K1
-----
b =
; G = 1 +
+ K2[TsOH] +
–
'
'
[Cl ] = K12[HCl] = 2K12CM,
(29)
H[PPh3]
K7[CH3C6H4OH] + K10
[CH3C6H4OH]
-------------------------------------
[PPh3]
+ K11[PPh3]2 +
'
where K12 = K12[Sol] .
K13[Cl–]; and H is the Henry constant for CO.
Substituting Eq. (29) into Eq. (21), we can obtain
the following expression for the reaction rate:
Transformation of Eq. (26) leads to the expression
kCM
L + dCM
PCO
-------- = --- + pCO + pCO
b
k
a
k
G
k
2
--------------------
r =
,
(30)
--
--
.
(27)
r
The evaluation of the parameters of Eq. (27) by the
least squares method and the subsequent verification of
its adequacy demonstrated the fitting of the calculated
to the experimental data.
where k = k7K[ol][CO][TsOH][CH3C6H4OH], and d =
1
-----
K1
'
2K13 K12 ,
L
=
1
+
+
K2[TsOH]
+
+
[CO]
----------------
9[PPh3]
K7[CH3C6H4OH] + K8[CO]2
[CH3C6H4OH]
+
K
Equation (21) also gives qualitative substantiation
of the fractional reaction order with respect to the cata-
lyst precursor Pd(PPh3)2Cl2. It can be shown that the
concentration of chloride anions in the denominator of
this equation is linearly related to the initial catalyst
concentration CM. Thus, the amount of hydrochloric
acid produced in reaction (1) is equal to double the
amount of the initial catalyst form, [HCl] = 2CM. The
resulting hydrochloric acid is a source of chloride
anions in accordance with acid–base equilibrium (14).
K10
+ K11[PPh3]2.
-------------------------------------
[PPh3]
Reducing Eq. (30) to the linear form
L 1
1
r
d
k
-- ------
k CM
-- = -- +
,
(31)
we represent the data on the influence of the catalyst
Under the conditions of a significant excess of TSA
over the catalyst with allowance for its higher acidity in
comparison with HCl, the concentration of HSol⊕– ions
can be considered to be constant.
1
r
1
CM
-- ------
coordi-
concentration on the reaction rate in
–
nates (Fig. 8). The linear character of this dependence
corroborates the given interpretation of the role of the
catalyst precursor in the reaction under investigation.
⊕
TsOH + Sol
HSol + TsO–.
(28)
KD
PETROLEUM CHEMISTRY Vol. 47 No. 3 2007

INFLUENCE OF COMPONENTS
175
–2
–1
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CONCLUSIONS
Kinetic relationships for the cyclohexene hydrocar-
balkoxylation reaction in the presence of m-cresol cat-
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established. It was shown that the reaction is first order
in cyclohexene and fractional order in both
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are nonmonotonic in character.
The data obtained were interpreted in terms of the
mechanism comprising hydride complexes of the cat-
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rate–TSA concentration dependence and the retarda-
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basis of the steady-state concept, a rate equation ade-
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PETROLEUM CHEMISTRY Vol. 47 No. 3 2007