Kinetics of cyclohexene hydrocarbalkoxylation with cyclohexanol catalyzed by the Pd(PPh3)2Cl2-PPh3-p- toluenesulfonic acid system

Article abstract of DOI:10.1134/S0965544108040063

The reaction kinetics of cyclohexene hydrocarbalkoxylation with cyclohexanol catalyzed by the Pd(PPh₃)₂Cl ₂-PPh₃-p-toluenesulfonic acid system was studied over the temperature range 363-393 K. The reaction rate was found to be a nonlinear function of the Pd(PPh₃)₂Cl₂ concentration or a nonmonotonic function of the PPh₃ and cyclohexanol concentrations or p _CO. The experimental data were interpreted in terms of a mechanism that involves ion pairs containing alkyl and acyl palladium complexes of the cationic type as intermediates. Based on the quasi-steady-state approximation, a rate equation was obtained to adequately describe the experimental data. The rate equation parameters were estimated using the least squares technique. The apparent activation energies of these parameters were determined. The heats of formation of Pd(PPh₃)₂(C₆H₁₁OH) ₂, Pd(PPh₃)₂(CO)₂, and Pd(PPh ₃)₄ complexes from Pd(PPh₃)₂(C ₆H₅CH₃)₂ were estimated. A symbatic change in these values with the donor-acceptor properties of ligands was demonstrated.

Full text of DOI:10.1134/S0965544108040063

ISSN 0965-5441, Petroleum Chemistry, 2008, Vol. 48, No. 4, pp. 287–295. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © V.A. Aver’yanov, N.T. Sevost’yanova, S.A. Batashev, 2008, published in Neftekhimiya, 2008, Vol. 48, No. 4, pp. 286–294.
Kinetics of Cyclohexene Hydrocarbalkoxylation
with Cyclohexanol Catalyzed by the Pd(PPh ) Cl –PPh –p-
3
2
2
3
Toluenesulfonic Acid System
V. A. Aver’yanov, N. T. Sevost’yanova, and S. A. Batashev
Tula State Pedagogical University, pr. Lenina 125, Tula, 300026 Russia
e-mail: piligrim.tula.ru@gmail.com
Received April 19, 2007
Abstract—The reaction kinetics of cyclohexene hydrocarbalkoxylation with cyclohexanol catalyzed by the
Pd(PPh ) Cl –PPh –p-toluenesulfonic acid system was studied over the temperature range 363–393 K. The
3
2
2
3
reaction rate was found to be a nonlinear function of the Pd(PPh ) Cl concentration or a nonmonotonic func-
3
2
2
tion of the PPh and cyclohexanol concentrations or pCO. The experimental data were interpreted in terms of a
3
mechanism that involves ion pairs containing alkyl and acyl palladium complexes of the cationic type as inter-
mediates. Based on the quasi-steady-state approximation, a rate equation was obtained to adequately describe
the experimental data. The rate equation parameters were estimated using the least squares technique. The
apparent activation energies of these parameters were determined. The heats of formation of
Pd(PPh ) (C H OH) , Pd(PPh ) (CO) , and Pd(PPh ) complexes from Pd(PPh ) (C H CH ) were esti-
3
2
6
11
2
3 2
2
3 4
3 2
6
5
3 2
mated. A symbatic change in these values with the donor–acceptor properties of ligands was demonstrated.
DOI: 10.1134/S0965544108040063
Nosova and Astashina [1] demonstrated that, in dures used for preparing and purifying the reagents and
order to determine the activation parameters of the catalytic system components were also described in [6].
apparent constants of the rate equations and to test the
consistency between these parameters and the antici-
RESULTS AND DISCUSSION
pated reaction mechanisms, it is necessary to study the
effect of the temperature on hydrocarbalkoxylation
To study the effect of the temperature on the depen-
reactions. At the same time, these data in combination dence of the rate of cyclohexene hydrocarbalkoxylation
with the results of the direct kinetic experiments on the on the concentration of Pd(PPh ) Cl , we performed
3
2
2
chemical behaviors of hypothetical intermediates [2–4] five series of experiments. The concentration of
provide an opportunity to form a data bank of constants Pd(PPh) Cl in each of the series was varied from 0.0 to
3
2
of elementary reactions responsible for carbonylation 0.015 mol/l. Figure 1a shows the corresponding depen-
processes, as well as the heats and activation energies dence of the reaction rate on the concentration of
of these reactions.
Pd(PPh ) Cl at various temperatures. It can be seen
3 2 2
that this dependence is of a nonlinear character, which
is indicative of a decrease in the activity of a precursor
with an increasing precursor concentration. In this case,
a reaction catalyzed by only an acid occurred in the
absence of a precursor. A statistical analysis of these
data demonstrated that the contribution of the acid-cat-
alyzed reaction is negligibly small in the test range of
Pd(PPh ) Cl concentrations and it can be ignored in
In this context, we studied the effect of the temper-
ature on the kinetic parameters that reflect the contribu-
tions of cyclohexene, reagents (CO and cyclohexanol),
and catalytic system components (the phosphine palla-
dium complex Pd(PPh ) Cl and triphenylphosphine) to
3
2
2
the hydrocarbalkoxylation rate.
3
2
2
EXPERIMENTAL
the treatment of the kinetic data.
Analogous experiments were performed to study the
effect of the temperature on the dependence of the rate
of hydrocarbalkoxylation on the concentration of triph-
enylphosphine. A nonmonotonic extreme character of
the relevant curves with the position of the maximums
The hydrocarbalkoxylation of cyclohexene was
studied in a batch rector, which was described else-
where [5]. Toluene was used as a diluent for the reac-
tion mixture. The procedures of the kinetic experiments
and the analysis of the reaction mixtures were previ-
ously considered in detail [6]. The accuracy in the
determination of the reactant and reaction product con-
centrations was ±3%. The confidence intervals of the
–3
at [PPh ] = 8 × 10 mol/l for the entire test range of tem-
3
peratures can be seen (Fig. 1b).
Figure 2 shows the effect of the temperature on the
kinetic parameters are specified in the text. The proce- dependence of the rate of the reaction on the ëé and
2
87

2
88
AVER’YANOV et al.
cyclohexanol concentration. An extreme character with the -toluenesulfonic acid (TsOH) with the simulation
the positions of the maximums at ëé ≈ 2–2.5 MPa in of the first order after the initial non-steady-state por-
the  – r curves (Fig. 2a) and curves at C H OH] ≈ tion to the point in time at which a constant activity was
ëé
6
11
0
.15 mol/l in the [C H OH] – r (Fig. 2b) can be seen. reached [6].
6 11
Such a character of the dependence of the rate on the
concentrations of the reactants was also demonstrated
in [7–12].
The experimental data can be interpreted using a
mechanism analogous to that proposed previously [6]
for the test system (scheme). Arguments adduced in
Previously, we found the first order with respect to favor of the key role of hydride complexes in the cata-
cyclohexene, an inhibiting effect of chloride anions on lytic cycle of the reaction scheme and the rate-deter-
the reaction, and an S-shaped character of the depen- mining character of step (8) were considered else-
dence of the rate of the reaction on the concentration of where [6].
k0
PdCl (PPh ) + C H OH
Pd(PPh ) + C H O + 2HCl
(1)
(2)
2
3 2
6
11
3 2
6
10
k1
Pd(PPh ) + 2Sol
Pd(PPh ) (Sol)
2
3
2
3 2
k–1
(
X )
(X1)
0
ꢁ
ꢀ
k2
(3)
Pd(PPh ) (Sol) + TsOH
[HPd(Sol)(PPh ) ]TsO + Sol
3
2
2
3 2
k–2
(
X )
(X2)
1
ꢁ
ꢀ
ꢁ
ꢀ
k3
[
HPd(Sol)(PPh ) ]TsO +
[HPd(PPh ) ]TsO + Sol
3
2
3 2
k–3
k4
(
X )
2
(X3)
(5)
k–4
k7
(4)
slow.
O
O
ꢁ
ꢀ
C
(8)
Pd(Sol)(PPh ) TsO
3
2
+
C H OH
6 11
k–5
(6)
(
X )
k5
4
+
CO
ꢁ
ꢀ
ꢁ
ꢀ
k–6
k6
Pd(CO)(PPh ) TsO + Sol
CO Pd(Sol)(PPh ) TsO
3 2
3
2
(7)
(X5)
(
X )
6
Scheme
According to the above scheme, the rate of the reac- and (11) in [6]) was predominant in the region of high
tion can be expressed by the equation
concentrations.
r = k [X ][C H OH].
(9)
7
6
6
11
The determined nonmonotonic dependence of the
rate of the reaction on the concentration of the triphe-
nylphosphine can be interpreted in terms of an equilib-
rium system of ligand exchange reactions with the par-
ticipation of this component (see equilibriums (12)–
Note that, unlike the previously discussed mecha-
nism of this reaction [6], the reaction scheme proposed
shows catalytic cycle intermediates as ion pairs, in
which the tosylate anion occurs as an outer-sphere
counterion rather than cationic palladium complexes.
The insensitivity of the reaction rate to the concentra-
tion of tosylate anions suggests a key role of ion pairs
as catalytic cycle intermediates [6].
The determined nonmonotonic character of the
dependence of the reaction rate on the concentration of
cyclohexanol and the pressure of CO was interpreted
previously [6] in terms of a dual function of these reac-
tants. In the region of low concentrations, an accelerat-
ing function of these reactants was predominant,
whereas a deactivating function associated with the
(14) in [6]).
The fractional order of the reaction with respect to
Pd(PPh ) Cl , which is indicative of a decrease in the
3
2
2
catalytic activity of this compound with the concentra-
tion, was interpreted previously in terms of the inhibit-
ing effect of the chloride anions produced from
Pd(PPh ) Cl . These anions enter into ligand exchange
3 2
2
reactions with the participation of the catalytic cycle to
form low-activity or inactive components. The applica-
removal of a portion of the catalyst from an active spe- tion of the quasi-steady-state principle to the above
cies by ligand exchange reactions (see reactions (10) reaction scheme with consideration for a balance on all
PETROLEUM CHEMISTRY Vol. 48 No. 4 2008

KINETICS OF CYCLOHEXENE HYDROCARBALKOXYLATION
289
r × 10 , mol l min–1
4
–1
r × 10 , mol l min–1
4
–1
5
5
4
3
6
2
4
3
2
1
1
5
4
4
2
3
2
1
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
2
0
1
2
3
4
5
6
[
Pd(PPh ) Cl ] × 10 , mol/l
3 2 2
2
[
PPh ] × 10 , mol/l
(
a)
(b)
3
Fig. 1. Dependence of the rate of hydrocarbalkoxylation on the concentration of (a)Pd(PPh ) Cl or (b) PPh at various tempera-
3
2
2
3
6
–3
tures and êëé = 2.1 × 10 Pa. Concentrations, mol/l: (a, b) [C H ] = 0.1, [C H OH] = 0.4, (b) [Pd(PPh ) Cl ] = 2.0 × 10 ,
6
10
6
11
3 2
2
–
2
–2
–2
(
a) [PPh ] = 4.0 × 10 , and [TsOH] = (a) 3.0 × 10 (‡), or (b) 2.4 × 10 . Temperature, K: (a) (1) 373, (2) 378, (3) 383, (4) 388,
3
and (5) 393; (b) (1) 368, (2) 373, (3) 378, (4) 393, and (5) 388.
r × 10 , mol l min–1
4
–1
r × 10 , mol l min–1
4
–1
6
1
0
8
6
4
2
5
4
3
2
1
1
2
3
4
1
2
3
4
5
5
0
1
2
3
4
5
PCO, MPa
0
0.2
0.4
0.6
0.8
1.0
[
6 11
C H OH], mol/l
(
a)
(b)
Fig. 2. Dependence of the rate of hydrocarbalkoxylation on the (a) êëé and (b) cyclohexanol concentration at various temperatures.
–
3
–3
–2
Concentrations, mol/l: (a, b) [C H ] = 0.1, [Pd(PPh ) Cl ] = 2.0 × 10 , [PPh ] = 8.0 × 10 , [TsOH] = 2.4 × 10 , and (a)
6
10
3 2
2
3
6
[
C H OH] = 0.4; (b) P = 2.1 × 10 Pa. Temperature, K: (a) (1) 363, (2) 368, (3) 373, (4) 378, and (5) 383; (b) (1) 368, (2) 373,
6 11 ëé
(3) 378, (4) 383, and (5) 388.
catalyst species and the first orders in cyclohexene and TsOH led to the following reaction rate equation:
kC [ol][CO][TsOH][C H OH]
M
6
11
r = ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- -- ,
(10)
⎧
⎨
⎩
[CO]
[C H OH]
⎫
⎬
⎭
2
2
6
11
2
–
1
+ d[C H OH] + e[CO] + f ---------------- + g---------------------------- + h[PPh ] + i[Cl ]
6
11
3
[
PPh ]
[PPh ]
3
3
PETROLEUM CHEMISTRY Vol. 48 No. 4 2008

2
90
AVER’YANOV et al.
ë
–3
tion rate on the concentrations of the reactants
Pd(PPh ) Cl and PPh .
Under varying precursor concentration, Eq. (10)
takes the following form:
Ï
×
10 , s
r
3
2
2
3
2
1
1
0
.0
.5
.0
.5
1
2
3
4
5
k C
a1
M
r = ----------------------,
(11)
A + nC
1 M
where
2
e
2
CO
f
P
CO
A = 1 + d[C H OH] + ---------P + --------------------
1
6
11
2
H
PPh
3
H
CO
CO
[C H OH]
6
11
2
+
g---------------------------- + h[PPh ] ,
3
[
PPh ]
3
ka1 = k[ol][CO][TsOH][C H OH]
6
11
0
0.2
0.4
0.6
0.8
1.0
1.2 1.4
2
k
C × 10 , mol/l
Ï
= ---------C [ol][TsOH][C H OH]PCO,
M 6 11
H
CO
Fig. 3. Fitting of Eq. (12) to the experimental data. êCO
=
and çëé is Henry’s constant for CO.
The rearrangement of Eq. (11) leads to the expres-
sion
2
.1 MPa. Concentrations, mol/l: [C H ] = 0.1, [C H OH] =
6 10 6 11
–2
–2
0.4, [PPh ] = 4.0 × 10 , and [TsOH] = 3.0 × 10 . Tempera-
3
ture, K: (1) 373, (2) 378, (3) 383, (4) 388, and (5) 393. Coef-
ficients of correlation: (1) 0.997, (2) 0.998, and (3–5) 0.999.
C
r
A
n
k
f1
M
1
-
---- -- = ----- + -----C .
(12)
M
k
a1
where ëå is the initial precursor concentration; in
accordance with published data [6], the parameters k, a,
d, e, f, g, h, and i are the combinations of the equilibrium
constants of catalytic cycle steps, ligand exchange reac-
tions, and acid–base interactions, and the rate constant
Figure 3 demonstrates a satisfactory agreement
C
M
between the values of ----- -- , calculated from Eq. (12)
r
(
solid lines) and experimental data (points). The table
k7 of a rate-limiting step.
A
n
k
a1
1
summarizes the parameters ----- and ----- estimated
k
The agreement between Eq. (10) and experimental
a1
data can be exemplified by the dependence of the reac- using the least squares technique.
Effective constants of Eqs. (12), (14), (17), and (20) [6]
Temperature, K
363
368
373
378
383
388
393
A
1
–2
-
----- × 10 , s
2.4 ± 0.6
2.0 ± 0.2
1.6 ± 0.1
1.0 ± 0.1
0.6 ± 0.2
k
a1
n
–5
–1
-
----- × 10 , l s mol
1.20 ± 0.06 1.03 ± 0.03 0.97 ± 0.02 0.88 ± 0.02 0.84 ± 0.02
k
a1
A
2
−5
–1
–3
-
----- × 10 , l s mol
3.2 ± 0.1
4.9 ± 0.2
2.9 ± 0.2
8.5 ± 0.2
9.8 ± 0.3
2.6 ± 0.1
2.0 ± 0.3
2.0 ± 0.1
6.5 ± 0.1
7.8 ± 0.5
1.74 ± 0.06 1.74 ± 0.06 1.77 ± 0.05
k
a2
h
–7
3
-
----- × 10 , l s mol
1.9 ± 0.2
1.4 ± 0.1
4.4 ± 0.1
5.9 ± 0.1
0.5 ± 0.2
1.0 ± 0.2
3.1 ± 0.1
5.3 ± 0.2
0.4 ± 0.1
k
a2
A
----- × 10−11, Pa l s mol–1
3
-
3.8 ± 0.2
k
a3
e'
----- × 10 , l s Pa mol–1 11.4 ± 0.2
2
–1
-
k
a3
d
–5
2
–2
-
----- × 10 , l s mol
4.1 ± 0.1
k
a4
PETROLEUM CHEMISTRY Vol. 48 No. 4 2008

KINETICS OF CYCLOHEXENE HYDROCARBALKOXYLATION
291
A1
ka 1
A1
ln
ln
ka 2
5
5
5
5
4
4
4
4
4
.6
12.7
.4
.2
.0
.8
.6
.4
.2
1
1
1
1
1
2.6
2.5
2.4
2.3
2.2
1
1
2.1
2.0
.0
2
2.56 2.58 2.60 2.62 2.64 2.66 2.68 2.70 2.72
.54 2.56 2.58 2.60 2.62 2.64 2.66 2.68 2.70
−1
3
–1
T
× 10 , K
−1
3
–1
T
× 10 , K
(
a)
(b)
A
A
2
1
Fig. 4. Temperature dependence of the parameters (a) ------- and (b) ------- .
k
k
a 2
a 1
A
1
The evaluation of parameters in Eq. (14) by the least
The experimental values of ----- plotted in the
k
a1
f
1
squares method demonstrated that parameter ----- is sta-
Arrhenius coordinates (Fig. 4a) exhibited an inflection
point at 383 K, which is indicative of the different
effects of the temperature on the parameters of the
k
a2
tistically insignificant. The table summarizes parame-
A
h
[PPh ]
2
3
n
ters ----- and ----- . The dependence of ---------------- on [PPh ]
3
polynomial Ä . At the same time, data on ----- are ade-
1
k
k
r
a2
a2
k
a1
shown in Fig. 5 demonstrates a good agreement
between the calculated (solid lines) and experimental
points) data. In this case, the statistical insignificance
quately described by the Arrhenius equation
(
n
2.2
20 ± 3 kJ/mol
l s
⎛
⎞
-
---- = 1 0 exp ---------------------------------- , ------------ .
⎝
⎠
–1
k
RT
a1
mol
Under the conditions of a single-factor experiment
on the effect of triphenylphosphine on the rate of the
reaction, Eq. (10) can be put in the form
[
PPh ]
3
–4
×
10 , s
r
3
3
.5
k
a2
.0
1
r = ----------------------------------------------------------,
(13)
f
1
2
A + ---------------- + h[PPh ]
2
3
2.5
[
PPh ]
3
2
1
.0
.5
2
3
where ka2 = kC [ol][CO][TsOH][C H OH]
M
6
11
k
4
=
---------C [ol][TsOH][C H OH]PCO,
M 6 11
H
1.0
CO
5
0
.5
2
e
2
CO
A = 1 + d[C H OH] + ---------P + nCM,
2
6
11
2
H
CO
0
1
2
3
4
5
6
2
f
[PPh ] × 10 , mol/l
3
f = ---------P + g[C H OH].
1
CO
6
11
H
CO
Fig. 5. Fitting of Eq. (14) to the experimental data for the
hydrocarbalkoxylation of cyclohexene. Pëé = 2.1 × 10 Pa.
6
Equation (13) can be easily rearranged to
PPh ]
Concentrations, mol/l: [C H ] = 0.1, [C H OH] = 0.4,
6
10
6 11
[
f
A
h
3
1
2
3
−3
–2
-
--------------- = ----- + ----- [PPh ] + ----- [PPh ] .
(14)
[Pd(PPh3)2Cl2] = 2.0 × 10 , and [TsOH] = 2.4 × 10 Tem-
perature, K: (1) 368, (2) 373, (3) 378, (4) 393, and (5) 388.
3
3
r
k
k
k
a2
a2
a2
PETROLEUM CHEMISTRY Vol. 48 No. 4 2008

2
92
AVER’YANOV et al.
P
Upon varying the CO pressure at constant concen-
trations of all of the other reactants, Eq. (10) can be put
into the form
CO
r
10–12, Pa l s mol–1
×
4
k P
a3 CO
2
r = -----------------------------------------------,
(15)
1
3
2
1
A + e'P + f P
3
CO
2
CO
[
C H OH]
6 11
2
2
A = 1 + d[C H OH] + g----------------------------
where
3
6
11
[
PPh ]
3
3
2
+
h[PPh ] + nC
3 M
4
5
kC
M
ka3 = -------- -- [ol][TsOH][C H OH],
6
11
H
CO
e
f
0
5
10
15
20
25
30
e' = ---------, f = ---------------------------,
2
2
H
[PPh ]
3
2
–12
2
H
CO
P
× 10 , Pa
CO
CO
and çëé is Henry’s constant for CO.
The rearrangement of Eq. (15) leads to the expres-
sion
Fig. 6. Fitting of (symbols) the experimental data to (lines)
Eq. (17) for the effect of êCO on the kinetics of cyclohexene
hydrocarbalkoxylation. Concentrations, mol/l: [C H ] =
6
10
–
3
P
A
f
2
CO
3
e'
2
CO
0
.1, [C H OH] = 0.4, [Pd(PPh ) Cl ] = 2.0 × 10 ,
6
11
3 2
2
-
------- = ----- + ----- P + ----- P
.
(16)
CO
–3
–2
r
k
k
k
a3
[
PPh ] = 8.0 × 10 , and [TsOH] = 2.4 × 10 . Temperature,
a3
a3
3
K: (1) 363, (2) 368, (3) 373, (4) 378, and (5) 383. Coeffi-
cients of correlation: (1) 0.999, (2) 0.994, (3) 0.999,
(4) 0.997, and (5) 0.992.
The treatment of the experimental data using
Eq. (16) revealed the statistical insignificance of coeffi-
f
2
cient ----- . Then, Eq. (16) takes the more compact form
k
a3
f
1
of parameter ----- is supported by the fact that the lines
P
r
A
e'
k
a3
CO
3
2
CO
k
a2
-------- = ----- + ----- P
.
(17)
k
pass through the origin.
a3
The apparent constants of Eq. (17), which are given
in the table, were determined using a least squares tech-
A
2
The plot of the experimental values of ----- in the
k
a2
A
e'
k
a3
3
nique. It can be seen that the values of ----- and -----
Arrhenius coordinates (Fig. 4b) is nonlinear. This non-
linear dependence reflects the difference in the apparent
activation energies of the parameters that enter into
k
a3
monotonically decreased with the temperature.
polynomial Ä . In the region of high temperatures,
P
r
CO
2
CO
2
Figure 6 shows the dependence of -------- on P ; it
parameters having the highest activation energy, which
is close to the apparent activation energy of constant
can be seen that the calculated (solid lines) and experi-
mental (points) data are in good agreement.
ka. 2, were predominant. Because of this, the values of
A
2
A
3
e'
k
a3
-
---- were constant over the test temperature range.
The experimental values of ----- and ----- are ade-
k
a2
k
a3
Upon moving to lower temperatures, parameters char-
acterized by lower apparent activation energies began
to predominate; this manifested itself in an increase in
quately described by the Arrhenius equations
A
80 ± 2 kJ/mol Pa l s
⎞
3
0.03
⎛
-
---- = 1 0 exp ---------------------------------- , ------------
⎝
⎠
A
k
RT
mol
2
a3
the ratio ----- with a decreasing temperature. On the
k
a2
e'
–12.0
77 ± 4 kJ/mol
l s
Pa mol
⎛
⎞
-
--- -- = 1 0
exp ---------------------------------- , ----------------.
h
⎝
⎠
k
RT
other hand, the values of ----- were adequately described
a3
k
a2
Under the conditions of a single-factor experiment
on the effect of cyclohexanol, Eq. (10) can be put into
the form
by the Arrhenius equation, and this fact manifested
itself in the following relationship:
3
k [C H OH]
h
–14.14
–150 ± 10 kJ/mol
l s
a4
6
11
⎛
⎞
--------------------------------------------------------------------------------------,
2
(18)
-
---- = 1 0
exp ------------------------------------------- , ----------.
r
=
⎝
⎠
3
k
RT
A + d[C H OH] + g'[C H OH]
4 6 11 6 11
a2
mol
PETROLEUM CHEMISTRY Vol. 48 No. 4 2008

KINETICS OF CYCLOHEXENE HYDROCARBALKOXYLATION
293
ka4 = kC [ol][CO][TsOH]
C6H11OH
M
–5
×
10 , s
r
where
k
1
0
8
6
4
2
1
2
3
=
---------C [ol][TsOH]PCO,
M
H
CO
2
CO
g
PPh
2
A4 = 1 + e'P + f2PCO + h[PPh ] + nC , g' = ----------- .
3
M
3
Equation (18) can be easily rearranged to the form
C H OH]
g'
4
5
[
A
4
6
11
-
--------------------------- = ----- + ----- [C H OH]
6 11
r
k
k
a4
a4
(19)
d
2
+
----- [C H OH] .
6 11
k
a4
Through the treatment of the experimental data on
the effect of the cyclohexanol on the rate of the reaction
0
0.2
0.4
0.6
0.8
1.0
2
2 2
[
C H OH] , mol /l
6 11
A
g'
4
using Eq. (19), we found that parameters ----- and -----
k
k
Fig. 7. Fitting of (symbols) the experimental data to (lines)
Eq. (20) for the effect of [C H OH] on the kinetics of
a4
a4
are statistically insignificant; then, Eq. (19) takes the
form
6 11
6
cyclohexene hydrocarbalkoxylation. Pëé = 2.1 × 10 Pa.
Concentrations, mol/l: [C H ] = 0.1, [Pd(PPh ) Cl ] = 2.0 ×
6
10
3 2
–2
2
[
C H OH]
d
k
a4
6
11
2
–3
–3
-
--------------------------- = ----- [C H OH] .
(20)
10 , [PPh ] = 8.0 × 10 , and [TsOH] = 2.4 × 10 . Temper-
6
11
3
r
ature, K: (1) 368, (2) 373, (3) 378, (4) 383, and (5) 388.
Coefficients of correlation: (1) 0.998, (2) 0.996, (3) 0.999,
4) 0.998, and (5) 0.998.
[
C H OH]
6 11
(
Figure 7 shows the dependence of ---------------------------- on
r
2
[
C H OH] in accordance with Eq. (20). A linear char-
6
11
e'
d
Taking into account these assumptions, ----- -- can be
acter suggests that Eq. (20) is valid. The parameters -----
k
a 3
k
a4
represented as
estimated using the least squares technique are given in
the table.
e'
k
a3
e
-
---- = ----------------
2
The treatment of the experimental data using the
Arrhenius equation resulted in the expression
H
k
CO a3
(21)
2
2
K
9
d
54 ± 4 kJ/mol l s
= ---------------------------------------------------------------------------------------------------------------------.
−1.30
⎛
⎞
-
---- = 10 exp ---------------------------------- , ----------.
H
k K K K K K C [ol][TsOH][C H OH]
7 2 3 4 5 6 M 6 11
⎝
⎠
2
CO
k
RT
a4
mol
An analysis of the apparent activation energies
allowed us to estimate the ratios between the heats of
the formation and the activation energies of the elemen-
tary reactions in the catalytic cycle and ligand exchange
reactions that complicated this cycle.
d
Correspondingly, an expression for ----- takes the
k
a4
form
K
d
8
We expected that the equilibrium constant ä would
------ = -------------------------------------------------------------------------------------------
1
k
k K K K K K C [ol][TsOH][CO]
be much greater than unity (K ꢀ 1) because a coordi-
a4
7
2
3
4
5
6
M
1
(
22)
natively unsaturated complex (ï ) acts as a reactant in
0
K H
8 CO
=
------------------------------------------------------------------------------------- -- .
this equilibrium. Then, unity in the denominator of
k K K K K K C [ol][TsOH]P
CO
7
2
3
4
5
6
M
K K
1
K K
K K
1
8
1
9
1 10
expressions for d = ------------- -- , e = ------------- -- , f = ------------- -- , g =
+ K 1 + K 1 + K
1
1
1
From Eqs. (21) and (22), it follows that
K K
K K
2K K K
1 13 14
1
11
1
12
-
------------ -- , h = ------------- -- , n = --------------------------, , and K =
E
a(e'/ka3
)
= ∆H
∆H – ∆H – ∆H – ∆H
6
9
– ∆H
H
– ∆H
7
– ∆H
2
1
+ K 1 + K 1 + K
1
1
1
(23)
–
3
4
5
K K K K K K
6
1
2
3
4
5
-
--------------------------------------, as well as the overall constants k ,
a. 1
E
= ∆H + ∆H – ∆H – ∆H
1
+ K
a(d/ka4
)
8
H
7
2
1
(
24)
k , k , and k (see [6]), can be ignored; this leads to
a. 2 a. 3
a 4
–
∆H – ∆H – ∆H – ∆H .
3 4 5 6
the following relations:
In accordance with Eqs. (23) and (24),
d = K , e = K , f = K , g = K , h = K ,
8
9
10
11
12
Ea(e'/ka3) – Ea(d/ka4) = ∆H – ∆H – 2∆H ,
(25)
n = 2K K , K = K K K K K .
9
8
H
1
3
14
2
3
4
5
6
PETROLEUM CHEMISTRY Vol. 48 No. 4 2008

2
94
AVER’YANOV et al.
Hence, ∆H – ∆H = –77 – (–51) – 2∆H = –26 + 2∆H
9
8
H
H
value of ∆H = –6 kJ/mol, a negative value of E
H
a(e'/ka3)
(kJ/mol).
results from the inequality
According to Zherbaev et al. [7], ∆H = –6 kJ/mol;
H
∆
H – E – ∆H ꢀ –∆H – ∆H
9 7 H 2 3
hence,
(
27)
∆
H – ∆H = – 77 – (–51) + 2∆H
– ∆H – ∆H – ∆H .
4 5 6
9
8
H
(26)
=
–26 + 2(–6) = –38 kJ/mol
Analogously, the following inequality is a prerequi-
This means that the formation of the Pd(PPh ) (CO)
2
site for a negative value of Ea(d/ka4)
3
2
complex from Pd(PPh ) (Sol) through the ligand
3
2
2
exchange is 38 kJ more exothermic than the formation
∆H
8
– E
+ ∆H ꢀ –∆H – ∆H
7 H 2 3
(
28)
of Pd(PPh ) (C H OH) from the same complex (see
3
2
6
11
2
–
∆H – ∆H – ∆H .
4
5
6
reactions (10) and (11) in [6]). This corresponds to the
stronger electron-donor and electron-acceptor proper-
ties of CO, as compared with those of alcohols.
From the values of Ea(e'/k and Ea(d/ka4) , it follows
a3)
that the absolute values of the left-hand sides of Eqs.
An analysis of reactions (2)–(7) shows that all of
these reactions are accompanied by the heat release,
because they result in the formation of stronger chemi-
cal bonds. Therefore, the sum ∆H + ∆H + ∆H + ∆H +
(25) and (24) should satisfy the inequalities
∆H – E ꢀ 83 kJ/mol and
(29)
(30)
9
7
2
3
4
5
∆
H – E ꢀ 45 kJ/mol.
8 7
∆
H in Eqs. (23) and (24) taken with the opposite sign
6
is a positive value. With consideration for the above
Analogously to the above reasoning,
n
2K13K H C
14 CO M
-
---- = -------------------------------------------------------------------------------------------------------------------------------
ꢂ
k
a1
k K K K K K [ol][H Sol] [TsOH][C H OH]P
7
2
3
4
5
6
6
11
CO
double replacement of weakly coordinated solvent
h
and -----
molecules in the palladium complex Pd(PPh ) (Sol) by
3
2
2
k
a2
the strong ligand triphenylphosphine.
K H
CO
1
2
In accordance with Eqs. (24) and (31),
=
--------------------------------------------------------------------------------------------------------------------.
k K K K K K C [ol][TsOH][C H OH]P
7
2
3
4
5
6
M
6
11
CO
E (n/k ) – E (d/k ) = ∆H + ∆H – ∆H ,
a
a1
a
a4
13
14
8
From these expressions, it follows that
E (n/k ) = ∆H + ∆H + ∆H
hence, –20 – (–51) = ∆H + ∆H − ∆H .
13 14 8
a
a1
13
14
H
Because of the mutual compensation of the values
–
E –∆H – ∆H – ∆H – ∆H
5
(31)
7
2
3
4
of ∆H and ∆H , we can consider that
1
3
14
–
∆H = –20 kJ/mol
6
E (n/k ) – E (d/k ) ≈ ∆H or ∆H ≈ –51 – (–20) =
a.
a. 1
a.
a. 4
8
8
and E (h/k ) = ∆H + ∆H
H
–31 kJ/mol.
a
a 2
12
In accordance with (26), taking into account the
–
E – ∆H – ∆H – ∆H – ∆H
5
.
(32)
7
2
3
4
relationship between ∆H and ∆H , we deduce the
9
8
–
∆H = –150 kJ/mol
6
equality ∆H = –38 + ∆H = –38 – 31 = –69 kJ/mol.
9 8
Then,
E (n/k ) – E (h/k ) = ∆H + ∆H
14
In accordance with Eqs. (24) and (32), we obtain
E (h/k ) – E (d/k ) = ∆H – ∆H ,
a
a1
a
a2
13
(33)
a
a1
a
a4
12
8
–
∆H = –20 + 150 = 130 kJ/mol.
12
hence, ∆H – ∆H = –150 – (–51) = –99 kJ/mol.
1
2
8
From a consideration of equilibriums (15) and (16)
in [6], it follows that acid–base reactions of the chloride
ion with Brönsted and Lewis acid sites occur in cases of ∆H , we obtain the heat of the formation of the complex
equilibriums (15) and (16), respectively. The chloride Pd(PPh ) from Pd(PPh ) (Sol) under the action of
With consideration for the previously found value of
8
3
4
3 2
2
ion acts as a product or a reactant in the former and lat- triphenylphosphine:
ter reactions, respectively. For this reason, the signs of
∆
H = –99 + ∆H = –99 – 31 = –130 kJ/mol,
12 8
the enthalpies of the above reactions (∆H and ∆H )
13
14
which is surprisingly consistent with the above estima-
tion based on a comparison between E (n/k ) and
are opposite and the values of these enthalpies are
close. Then, in this case, the value of –130 kJ/mol can
be considered an estimate of ∆H in accordance with
a
a.1
E (n/k ). This fact provides support for the hypothesis
a
a. 2
12
that the values of ∆H and ∆H are close. The resulting
the character of reaction (14) (see [6]), which is the enthalpy values ƍ
Eq. (33): ∆H = –130 kJ/mol. This is consistent with
13
14
12
, ƍ
, and ƍ12 reflect the follow-
8
9
PETROLEUM CHEMISTRY Vol. 48 No. 4 2008

KINETICS OF CYCLOHEXENE HYDROCARBALKOXYLATION
295
ing order of the heats of formation of complexes from
coordinatively unsaturated Pd(PPh ) :
d
tion energy of parameter ------ with a noticeable contri-
3
2
k
a 4
bution from the activation energy of rate-determining
step (8).
Pd(PPh ) < Pd(PPh ) (CO) < Pd(PPh ) (C H OH) <
3
4
3 2
2
3 2
6
11
2
Pd(PPh ) (C H CH ) ,
3
2
6
5
3 2
e'
which is consistent with the donor–acceptor properties
of the corresponding order of ligand-forming agents
PPh > CO > C H OH > C H CH .
Finally, from the expression for parameter ------ , it
k
a 3
follows that
∆H – E + |∆H + ∆H + ∆H + ∆H + ∆H ≈
7 2 3 4 5 6
3
6
11
6
5
3
As demonstrated above, the sum ∆H + ∆H + ∆H +
9
2
3
4
−
83 kJ/mol.
∆
H + ∆H taken with an opposite sign is positive. With
5 6
consideration for ∆H = –6 kJ/mol, the resulting value
H
A comparison of the above equation with the
expression forE (n/k ) suggests a predominant contri-
a a. 1
of E (n/k ) is provided by the equality
a
a. 1
bution from the enthalpy of the formation of complex
∆
H + ∆H – E – ∆H – ∆H – ∆H
13 14 7 2 3 4
.
ï from ï to the apparent activation energy of param-
8
1
–
∆H – ∆H = –14 kJ/mol
5 6
e'
eter ------ with a noticeable contribution from the activa-
k
Because the values of ∆H and ∆H mutually compen-
a 3
13
14
sate each other, we expect that –E + |∆H + ∆H + tion energy of rate-determining step (8).
7
2
3
∆
H + ∆H + ∆H | ≈ –14 kJ/mol.
4 5 6
The above reasoning indicates that the activation
energy of the interaction of an acyl palladium complex
REFERENCES
1
. N. M. Nosova and E. V. Astashina, in Proceedings of
International Conference of Graduate and Post Gradu-
ate Students on Fundamental Sciences “Lomonosov-
2005”, Sect. “Chemistry”, Vol. 2, p. 26.
(
X ) with cyclohexanol makes the greatest contribution
6
n
to the apparent energy of parameter ------ . This is consis-
k
a 1
tent with the character of reaction (8) as a rate-deter-
mining step of the process.
2
. A. Seayad, S. Jayasree, K. Damodaran, et al., J. Orga-
nomet. Chem. 601, 160 (2000).
h
3. G. Cavinato, L. Toniolo, and A. Vavasori, J. Mol. Catal.
An analogous analysis of parameter ------ indicates
k
A: Chem. 219, 233 (2004).
a 2
that the apparent activation energy of this parameter
4. G. Cavinato, A. Vavasori, L. Toniolo, and A. Dolmella,
found with consideration for the above value of ∆HH
Inorg. Chim. Acta. 357, 2737 (2004).
should satisfy the condition ∆H – E + |∆H + ∆H +
12
7
2
3
5. A. R. El’man, V. A. Matveev, E. V. Slivinskii, and
S. M. Loktev, Khim.-Farm. Zh., No. 3, 47 (1990).
∆
H + ∆H + ∆H | ≈ –144 kJ/mol.
4 5 6
This result indicates that the enthalpy of formation
of the complex Pd(PPh ) from Pd(PPh ) (Sol) makes
the greatest contribution to the apparent activation
6. V. A. Aver’yanov, N. T. Sevost’yanova, S. A. Batashev,
and S. V. Nesolenaya, Neftekhimiya 46, 435 (2006) [Pet.
Chem. 46, 405 (2006)].
3
4
3 2
2
7
. H. Yoshida, N. Sugyta, K. Kudo, and Y. Takezaki, Bull.
Chem. Soc. Jpn., No. 8, 2244 (1976).
h
energy of parameter ------ with a noticeable contribution
k
a 2
from the activation energy of rate-determining step (8).
8. A. Vavasori, G. Cavinato, and L. Toniolo, J. Mol. Catal.
A: Chem. 176, 11 (2001).
With the use of the same approach to analyze
9
. A. Vavasori, L. Toniolo, and G. Cavinato, J. Mol. Catal.
d
parameter ------ , we obtain
A: Chem. 191, 9 (2003).
k
a 4
1
1
0. V. A. Aver’yanov, S. A. Batashev, N. T. Sevost’yanova,
and V. M. Zarytovskii, Katal. Prom-sti, No. 2, 25 (2005).
∆
H – E + |∆H + ∆H + ∆H + ∆H + ∆H | ≈
8 7 2 3 4 5 6
−
45 kJ/mol.
This result shows that the heat of the formation of
the complex Pd(PPh ) (C H OH) from Pd(PPh ) (Sol)
1. V. A. Aver’yanov, S. A. Batashev, N. T. Sevost’yanova,
and N. M. Nosova, Kinet. Katal. 47, 381 (2006).
3
2
6
11
2
3 2
2
12. Kh. A. Zherbaev, I. A. Tsukanov, A. R. El’man, and
makes a noticeable contribution to the apparent activa-
K. A. Zhubanov, Zh. Org. Khim. 64, 1189 (1994).
PETROLEUM CHEMISTRY Vol. 48 No. 4 2008