Kinetics of copper(I)-catalyzed dimerization and hydration of acetylene in water

Article abstract of DOI:10.1246/bcsj.77.1395

The kinetics of the dimerization and hydration of acetylene in water with a copper(I) catalyst, a so-called Nieuwland catalyst, were investigated. The stationary state kinetics for both reactions could be described assuming that the rate-controlling step is a second-order reaction of an activated catalyst, [H-Cl-Cu-C₂H], formed in the reaction mixture, with acetylene or water. The activation energies and activation entropies were 12.4 kcal·mol^-1 and -33.3 cal·mol^-1·K ^-1 for the acetylene dimerization, and 17.5 kcal·mol ^-1 and -34.2 cal·mol^-1·K^-1 for the acetylene hydration, respectively. The large negative values of activation entropy for these reactions may be accounted for by the role of water as a kind of cocatalyst.

Full text of DOI:10.1246/bcsj.77.1395

Ó 2004 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 77, 1395–1399 (2004) 1395
Kinetics of Copper(I)-Catalyzed Dimerization and Hydration
of Acetylene in Water
ꢀ
1
1
2
Yuichi Tokita, Akio Okamoto, Kenichiro Nishiwaki, Mineto Kobayashi, and Eiichi Nakamura
Research Center, Denki Kagaku Kogyo K. K., 3-5-1 Asahi-machi, Machida-shi, Tokyo 194-8560
1
Department of Research Division, Ohmi Plant, Denki Kagaku Kogyo K. K.,
2209 Ohmi-machi, Nishi-kubiki-gun, Niigata 949-0393
2
Department of Chemistry, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033
Received January 9, 2004; E-mail: akio-okamoto@denka.co.jp
The kinetics of the dimerization and hydration of acetylene in water with a copper(I) catalyst, a so-called Nieuwland
catalyst, were investigated. The stationary state kinetics for both reactions could be described assuming that the rate-con-
trolling step is a second-order reaction of an activated catalyst, [HꢁꢁꢁCl–Cu–C2H], formed in the reaction mixture, with
ꢂ1
ꢂ1
ꢂ1
K
acetylene or water. The activation energies and activation entropies were 12.4 kcal mol and ꢂ33:3 cal mol
ꢁ
ꢁ ꢁ
ꢂ1
ꢂ1
ꢂ1
for the acetylene dimerization, and 17.5 kcal mol and ꢂ34:2 cal mol
K for the acetylene hydration, respectively.
The large negative values of activation entropy for these reactions may be accounted for by the role of water as a kind of
cocatalyst.
ꢁ
ꢁ ꢁ
ꢂ1
The dimerization of acetylene to vinylacetylene (MVA) in
water catalyzed by cuprous salts, Nieuwland catalyst of
CuCl/(KCl or NH4Cl), is long-standing, but still one of the im-
portant industrial reactions.1 MVA is now produced world
wide (about 30000 metric-ton-per-year) as an intermediate
product for chloroprene rubber based upon a process using ace-
tylene as a starting material. The introduction of acetylene into
the reaction mixture results not only in the formation of MVA,
but also in the formation of side products, such as acetaldehyde
about 5.5 mol L , extremely high as a ‘‘catalyst’’ concentra-
ꢁ
tion. Another noteworthy behavior is the absorption of acety-
lene into the reaction mixture, as shown in Fig. 1. The absorp-
tion of acetylene does not follow Henry’s law, namely the
amount of acetylene absorption does not converge to zero when
the partial pressure of acetylene becomes zero. This abnormal-
ity may be accounted for by the combination of the mere ab-
sorption of acetylene and the production of a copper acetylide,
as shown in Scheme 1. Since the exothermic reaction together
with an abrupt decrease in the pH was observed just after start-
ing the introduction of acetylene into the reaction mixture, cop-
per acetylide seems to be produced immediately by introducing
acetylene.22 Copper acetylide formation must be very fast, and
thus the quantity of acetylene absorption shows a plus value
–4
5
6
–15
(
ACH), by hydration,
divinylacetylene (CH2=CHCꢃ
CCH=CH2: DVA)1 and acetylenedivinyl (HCꢃCCH=
1
CHCH=CH2: ADV), both through trimerization. Although
the catalyst was discovered by Nieuwland in the early 1930s,
the catalytic reaction involves the latest topics in chemistry,
that is, the mechanism of organic reactions in water. Recently,
many new organic reactions, which could not occur in organic
solvents, have been found to take place in water.16 Although
considerable attention has been focused on the mechanism of
dimerization by the Nieuwland catalyst, nothing about the role
of water in the reaction has been reported.1
7–22
This paper pres-
ents the results of kinetic studies of both the dimerization and
hydration of acetylene with the Nieuwland catalyst in water
as well as the reasoning that water molecules may directly con-
tribute to the catalyst mechanism.
Results and Discussion
Although the solubility of CuCl alone is as low as 236 ppm
ꢄ
at 25 C in water, by virtue of the presence of KCl, CuCl is dis-
ꢄ
Fig. 1. A schematic diagram for the pressure dependence of
acetylene absorption.
solved in hot water (70 C) in such a high concentration as
Scheme 1.
Published on the web July 9, 2004; DOI 10.1246/bcsj.77.1395

1
396 Bull. Chem. Soc. Jpn., 77, No. 7 (2004)
Dimerization and Hydration of Acetylene
even when the partial pressure of acetylene is interpolated to
zero. The value of the intercept may be taken as the concentra-
tion of the copper acetylide, expressed as ‘‘activated catalyst’’
in this paper. Furthermore, the pure concentration of acetylene
can be estimated from the amount of acetylene absorption and
the concentration of activated catalyst, as shown in Fig. 1. In
this analysis, we presumed that the concentration of the activat-
ed catalyst is constant. The reasons are as follows: 1) The cop-
per acetylide as an activated catalyst is immediately hydrated
under a low-pH condition, and back to the acetylene molecule
and the polymeric ate-complexes with CuCl–KCl;22 2) the rate
of the AC dimerization is slower than that of hydration of the
tion mixture is calculated to be a hundredth to a fiftieth of the
concentration of CuCl, indicating that the small portion of the
polymeric ate-complexes with CuCl–KCl participates in the re-
action.1
7,18
We also measured the rate-constants of the dimerization and
hydration reactions according to Eqs. 1 and 2. As shown in
Fig. 3, Arrhenius plots of the reactions form a straight line:
2
r ¼ 0:9956 for MVA and 0.9946 for ACH. The thermodynam-
ic parameters obtained from the Arrhenius plots are listed in
ꢂ1
20
Table 2. The activation energies are 12.4 kcal mol
MVA, which is very close to a value already reported, and
for
ꢁ
ꢂ1
17.5 kcal mol for ACH. The activation Gibbs’ free energies
ꢂ1
ꢁ
2
2
ꢂ1
activated catalyst; 3) the relationship between the partial pres-
sure of acetylene and the acetylene absorption is linear in our
experimental condition. The relationships between the partial
pressure of acetylene and the concentration of acetylene in
are 21.5 kcal mol for MVA and 27.2 kcal mol for ACH.
ꢁ
ꢁ
ꢂ1
ꢂ1
The activation entropy for MVA is ꢂ33:3 cal mol
K
,
for ACH
ꢁ
ꢁ
ꢂ1
ꢂ1
which is almost the same as ꢂ34:2 cal mol
K
production. In general, the activation entropies of reactions
ꢁ
ꢁ
ꢄ
ꢂ1
ꢂ1
the reaction mixture at 55 and 70 C are shown in Fig. 2 and
Table 1. The concentration of the activated catalyst in the reac-
with two molecules are about from ꢂ10 cal mol
K to
; for example, the activation entropy of a
ꢁ
ꢁ
ꢂ1
ꢂ1
ꢂ25 cal mol
K
ꢁ
ꢁ
cyclobutane production from two ethylene molecules (2C2H4
ꢂ1
ꢂ1 23
. Thus, the large absolute val-
ues of the activation entropies may be attributed to the partici-
!
Ã) is ꢂ22:6 cal mol
K
ꢁ
ꢁ
þ
pation of water molecules (or oxonium ion (H3O ) because of a
very low value of the pH (<1) in the reaction system) in both
reactions, because the water molecule as a reactant might limit
the movement of water molecules as a solvent through a hydro-
gen-bond network. Furthermore, theoretical calculations on the
mechanism of the Cu(I) catalysed-dimerization and hydration
of acetylene to confirm the contribution of oxonium ion as a co-
catalyst are currently under way. The results of the theoretical
calculations will be published in the near future.
Fig. 2. The relation between the partial pressure of acety-
lene and the concentration of acetylene at 55 ( ) and 70
ꢄ
(
) C.
Table 1. Quantities of the Activation Catalyst and the Pure
Acetylene Absorption
Temperature Activation catalyst Pure acetylene absorption
ꢂ1
ꢄ
ꢂ1
/
C
/mmol L
/mmol L
ꢁ
ꢁ
7
6
6
6
5
5
0
7
4
1
8
5
38.09
41.70
45.30
48.91
50.66
52.42
163.53
174.70
185.87
197.05
209.02
220.99
Fig. 3. Arrhenius plots of the acetylene dimerization and
hydration: (a) MVA and (b) ACH.
Table 2. Thermodynamics Parameters of MVA and ACH Productions
z
z
ꢀG
Ea
log10
/s
A
ꢀS
/cal mol
ꢂ1
ꢂ1
ꢂ1
ꢂ1
ꢂ1
/
kcal mol
ꢁ
K
/kcal mol
ꢁ ꢁ
ꢁ
a)
MVA
ACH
12.4 (15.5 )
17.5
6.17
5.75
ꢂ33:3
ꢂ34:2
21.5
27.2
z
z
Ea, A, ꢀS , and ꢀG are the activation energy, frequency factor, activation en-
tropy, and Gibbs free energy, respectively. a) Ref. 20.

Y. Tokita et al.
Bull. Chem. Soc. Jpn., 77, No. 7 (2004) 1397
respectively, where CA0ðTÞ is the initial concentration of acetylene,
Conclusion
ꢂ1
Cw the water concentration (36.185 mol L ) and SðTÞ the con-
ꢁ
The thermodynamic parameters for the dimerization and hy-
dration of acetylene in water with a copper(I) catalyst were de-
termined by the stationary state kinetics using the concentration
centration of activated catalyst at T Kelvin. Vi is an effusion rate
of gas i, and is defined as
xi
1
1
3
Vi ¼ Z ꢅ
ꢅ ꢅ
;
ð3Þ
of activated catalyst measured experimentally. Although the
ꢂ1
1
00 22:4
activation Gibbs’ free energy for MVA is 21.5 kcal mol
ꢂ1
,
and is smaller than 27.2 kcal mol for ACH, the activation
ꢁ
where xi is the content of gas i (%) and Z is the rate of acetylene
ꢂ1
ꢁ
introduction. Under the experimental condition, Z is 0.208 L s
,
ꢁ
ꢂ1
ꢂ1
entropy for MVA is ꢂ33:3 cal mol
K
, and almost the
for ACH production. The large
ꢁ
ꢁ
which is large enough not to be a feed-controlled reaction (unpub-
lished result). The details of the derivation of rate constants are
described in the appendix.
ꢂ1
ꢂ1
same as ꢂ34:2 cal mol
K
ꢁ
ꢁ
thus-obtained absolute values of the activation entropies
strongly suggest the participation of the oxonium ion in both
reactions as a cocatalyst.
Concentration of Acetylene. In order to obtain the stationary
state concentrations of acetylene and an activated catalyst, we
measured the amount of acetylene absorbed into the reaction
mixture. The apparatus used in the experiment is shown in Fig. 5.
An aqueous catalyst solution of 600 mL contained CuCl (5.50
Experimental
Kinetics. A kinetic model of the reactions is shown in Fig. 4.24
It is assumed that the dimerization and hydration of acetylene are
second-order reactions of an activation catalyst, [HꢁꢁꢁCl–Cu–C2H]
formed in the reaction mixture, with acetylene and water mole-
cules, respectively. We also assume that the formations of DVA
and ADV are bimolecular reactions between the activated catalyst
and MVA. The direct production of DVA and ADV from the com-
plex of the activated catalyst and AC is not included in our model
ꢂ1
ꢂ1
mol L ) and KCl (6.05 mol L ), and was stirred continuously
ꢁ
ꢁ
with an anchor wing at 900 rpm. First, the pressure of an acetylene
tank of 12.25 L was set to P1, followed by opening valve V2 and
introducing acetylene into the reaction vessel; the pressure of the
acetylene tank decreased to P2. The total amount of acetylene sup-
plied into the reaction vessel was estimated from the difference be-
tween P1 and P2. The pressure of the reaction vessel decreased
from P3 to P4 just after closing valve V2. The amount of the ace-
tylene absorbed into the reaction mixture was calculated from the
P4 and the total amount of the acetylene supplied.
1
0
reaction, because since the activated catalyst has a d electronic
structure of Cu(I), multi-ligation of acetylene molecules may be
impossible. This suggestion also agrees with our results of the the-
oretical calculations (unpublished results). Furthermore, since the
intermediate (ClCu–C=C–CꢃCH) may be pushed out by a large
Flow Rate of Effusive Gases. The rate of effusive gas flow was
measured by using the apparatus shown in Fig. 6. The reaction
mixture was stirred by bubbling acetylene at the bottom of the re-
action vessel and inducing a downward flow in the side pipe. The
volume of the reaction mixture was 3 L, and the rate of acetylene
2
2
amount of acetylene, the direct production of DVA and ADV
from the complex of the activated catalyst and AC can be ignored.
Since the reaction system reaches a steady state by 30 min after the
start of acetylene introduction, the kinetics can be described based
upon the stationary state. The rate constants of the dimerization
ꢂ1
supply was 0.208 L s . After confirming the stationary state, the
ꢁ
composition of the effusion gas was determined by GC. The meas-
ꢄ
(
k1) and the hydration of acetylene (k4) are given by
urements were repeated three times at 3 C intervals from 55 to
ꢄ
7
0 C.
VB þ VC þ VD
k1 ¼
ð1Þ
ð2Þ
CA0ðTÞSðTÞ
Appendix
Since acetylene gas is always supplied in excess, the concentra-
tion of acetylene in the reaction mixture (CA) remains unchanged,
and
VE
k4 ¼
;
and is defined as
CwSðTÞ
Fig. 4. A kinetic model of the reactions. AC denotes acetylene, k1, k2, k3, and k4 are the rate constants for MVA, DVA, ADV, and
ACH productions, respectively, and k5, k6, k7, and k8 are the rate constants of the effusion of MVA, DVA, ADV, and ACH, respec-
tively. VB, VC, VD, and VE are the effusion rates of MVA, DVA, ADV, and ACH, respectively.

1
398 Bull. Chem. Soc. Jpn., 77, No. 7 (2004)
Dimerization and Hydration of Acetylene
Fig. 5. A schematic flow diagram for the experiment of the acetylene absorption.
2
dCC
dt
k1k2SðTÞ
¼
ðk2 þ k3ÞSðTÞ þ k5
ꢅ CA0ðTÞð1 ꢂ eꢂðk2SðTÞþk3SðTÞþk5ÞtÞ ꢂ k6CC;
where k6 is the rate constant of DVA effusion. From Eq. 5A the
concentration of DVA leads to
ð5AÞ
CC ¼ ½k1k2SðTÞ CA0ðTÞbfðk2 þ k3ÞSðTÞ þ k5gð1 ꢂ eꢂkotÞ
2
ꢂ k6f1 ꢂ eꢂðk2SðTÞþk3SðTÞþk5Þtgcꢆ
=½k6fðk2 þ k3ÞSðTÞ þ k5gfðk2 þ k3ÞSðTÞ þ k5 ꢂ k6gꢆ: ð6AÞ
In Eq. 6A, CC is constant at infinite time,
2
k1k2CA0ðTÞSðTÞ fðk2 þ k3ÞSðTÞ þ k5 ꢂ k6g
CC ¼
k6fðk2 þ k3ÞSðTÞ þ k5gfðk2 þ k3ÞSðTÞ þ k5 ꢂ k6g
2
k1k2CA0ðTÞSðTÞ
Fig. 6. A schematic diagram for the experiment of the flow
rates of gases.
¼
;
ð7AÞ
k6fðk2 þ k3ÞSðTÞ þ k5g
corresponding to the DVA concentration under the stationary state.
The ADV concentration (CD) at the stationary state is given by
CA ¼ CA0ðTÞ;
ð1AÞ
2
k1k3SðTÞ CA0ðTÞ
CD ¼
;
ð8AÞ
where CA0ðTÞ is the initial concentration of acetylene at T Kelvin.
k7fðk2 þ k3ÞSðTÞ þ k5g
where k7 is the rate constant of ADV effusion. The time differen-
tiation of the concentration of ACH (CE) is given by
The time differentiation of the concentration of MVA (CB) is given
by
dCB
¼
k1CA0ðTÞSðTÞ ꢂ ðk2SðTÞ þ k3SðTÞ þ k5ÞCB; ð2AÞ
dCE
dt
¼ k4CwSðTÞ ꢂ k8CE;
ð9AÞ
dt
where k1, k2, and k3 are the rate constants of MVA, DVA, and ADV
production, respectively, k5 the rate constant of MVA effusion
from the reaction system, and SðTÞ is the concentration of activated
catalyst at T Kelvin. From Eq. 2A the concentration of MVA
leads to
ꢂ1
where Cw is the concentration of water (36.185 mol L ), k4 the
ꢁ
rate constants of ACH production and k8 the rate constant of
ACH effusion. The ACH concentration at the stationary state is
given by
k4
CE ¼
CwSðTÞ:
ð10AÞ
k1
SðTÞCA0ðTÞð1 ꢂ eꢂðk2SðTÞþk3SðTÞþk5ÞtÞ:
k8
CB ¼
ðk2 þ k3ÞSðTÞ þ k5
Assuming that the effusion rates of gases are proportional to each
concentration of ones, the effusion rates are defined as
ð3AÞ
In Eq. 3A, CB is constant at infinite time,
k1
V ¼ k C ;
ð11AÞ
ð12AÞ
ð13AÞ
B
5
B
V ¼ k C ;
C
6
C
CB ¼
SðTÞCA0ðTÞ;
ð4AÞ
ðk2 þ k3ÞSðTÞ þ k5
corresponding to the MVA concentration under the stationary
state. The time differentiation of the concentration of DVA (CC)
is given by
VD ¼ k7CD;
VE ¼ k8CE;
and
ð14AÞ

Y. Tokita et al.
Bull. Chem. Soc. Jpn., 77, No. 7 (2004) 1399
where VB, VC, VD, and VE are the effusion rates of MVA, DVA,
ADV, and ACH, respectively. From Eqs. 4A, 7A, 8A, 11A, 12A,
and 13A, CB, CC, and CD are related to VB, VC, and VD, respective-
ly, in the following forms:
6
N. Yu. Vsesvyatskaya, G. K. Shestakov, and O. N. Temkin,
Kinet. Katal., 29, 965 (1988); Chem. Abstr., 110, 94250 (1988).
N. Yu. Vsesvyatskaya, D. V. Tsyganov, A. M. Bykov, G. K.
7
Shestakov, and O. N. Temkin, Zh. Org. Khim., 21, 2041 (1985);
Chem. Abstr., 104, 167763d (1985).
k1SðTÞ
VB
k5
CB ¼
CC ¼
CA0ðTÞ ¼
;
ð15AÞ
ð16AÞ
8
O. N. Temkin, G. K. Shestakov, and N. Yu. Kozlova, Kinet.
Katal., 31, 850 (1990); Chem. Abstr., 114, 80701 (1990).
G. K. Shestakov, O. N. Temkin, N. Yu. Vsesvyatskaya, and
A. M. Stepanov, Zh. Org. Khim., 15, 248 (1979); Chem. Abstr., 91,
765e (1979).
S. S. Agrawal, G. S. Natarajan, and K. A. Venkatachalam,
Ind. Chem. Eng., 16, 7 (1974).
I. K. Meier and J. A. Marsella, J. Mol. Catal., 78, 31 (1993).
ðk2 þ k3ÞSðTÞ þ k5
2
k1k2SðTÞ
k6fðk2 þ k3ÞSðTÞ þ k5g
VC
k6
9
CA0ðTÞ ¼
;
:
4
and
1
0
2
k1k3SðTÞ
k7fðk2 þ k3ÞSðTÞ þ k5g
VD
k7
CD ¼
CA0ðTÞ ¼
ð17AÞ
ð18AÞ
ð19AÞ
1
1
From Eqs. 15A and 16A, k2 leads to
12 S. Yang, Shiyou Huagong, 17, 353 (1988); Chem. Abstr.,
09, 233112 (1988).
13 D. V. Sokol’skii, B. Yu. Nogerbekov, and Ya. A. Dorfman,
Khim. Atsetilena Tekhnol. Karbida Kal’tsiya, 1972, 371; Chem.
Abstr., 79, 125455 (1972).
1
k5 VC
k2 ¼
:
SðTÞ VB
From Eqs. 15A and 17A, k3 leads to
1
4
O. N. Temkin, G. K. Shestakov, and R. M. Flid, Dokl. Akad.
Nauk SSSR, 184, 362 (1969); Chem. Abstr., 70, 95950s (1969).
I. K. Khristich, Issled. Termogr. Katal., 1966, 53; Chem.
Abstr., 68, 86797d (1966).
P. A. Grieco, ‘‘Organic Synthesis in Water,’’ Blackie
Academic and Professional, London (1998).
B. M. Mykhalichko, M. G. Mys’kiv, P. Yu. Zavalii, M. D.
k5 VD
k3 ¼
:
SðTÞ VB
1
5
When Eqs. 18A and 19A are substituted in Eq. 15A, k1 is obtained
by
1
6
VB þ VC þ VD
k1 ¼
:
ð20AÞ
ð21AÞ
1
7
CA0ðTÞSðTÞ
Finally, from Eqs. 10A and 14A, k4 is given by
Mazus, and S. I. Osechkin, Koord. Khim., 17, 827 (1991); Chem.
Abstr., 116, 31886 (1991).
18 M. G. Mys’kiv and B. M. Mykhalichko, Zh. Strukt. Khim.,
VE
k4 ¼
:
3
5, 120 (1994); Chem. Abstr., 112, 265535 (1994).
L. V. Khazhakyan, Dokl. Akad. Nauk Arm. SSR, 24, 67
1957); Chem. Abstr., 52, 855a (1957).
L. V. Khazhakyan, Izv. Akad. Nauk Arm. SSR, 10, 77
CwSðTÞ
1
9
(
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0
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2
3
4
23 G. M. Barrow, ‘‘Physical Chemistry,’’ 4th ed, McGraw-Hill
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4
5
Nowadays, nearly 90% of the worldwide capacity of
60000 metric tons for the chloroprene rubber production is based
24 Since the total amounts of the others (tetramer, pentamer,
and so on) are less than 2% per acetylene consumed, the material
balance is almost consistent in our experimental condition.
4
upon the process using butadiene as a starting material.