Spectroscopic kinetic study of the interaction of urethanes with amines

Article abstract of DOI:10.1134/S0023158413050042

The exchange reactions of phenyl-N-phenylurethane with amines varying in structure and nature have been investigated in o-dichlorobenzene. In the absence of a catalyst and proton-donating compound, the unimolecular decomposition of phenyl-N-phenylurethane into isocyanate and alcohol takes place at a noticeable rate starting at 250°C. The exchange reactions at 60-80°C proceed as a direct exchange between the urethane and the proton donor and are second-order up to high conversions, practically until the disappearance of the entire urethane. The activation energies and apparent rate constants of the exchange reactions of phenyl-N-phenylurethane with various amines have been determined. The results have been explained in terms of the dependence of kinetic parameters of the reaction on the amine nature, structure, and nucleophilicity, on the steric accessibility of the amino group, and on the molecular organization of the solution. Pleiades Publishing, Ltd., 2013.

Full text of DOI:10.1134/S0023158413050042

ISSN 0023ꢀ1584, Kinetics and Catalysis, 2013, Vol. 54, No. 6, pp. 656–661. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © A.S. Dzalmukhanova, V.P. Lodygina, V.V. Komratova, E.R. Badamshina, 2013, published in Kinetika i Kataliz, 2013, Vol. 54, No. 6, pp. 696–701.
Spectroscopic Kinetic Study of the Interaction of Urethanes
with Amines
A. S. Dzalmukhanova*, V. P. Lodygina, V. V. Komratova, and E. R. Badamshina
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia
*
eꢀmail: aygulik@mail.ru
Received November 15, 2012
Abstract—The exchange reactions of phenylꢀNꢀphenylurethane with amines varying in structure and nature
have been investigated in
the unimolecular decomposition of phenylꢀ
noticeable rate starting at 250 C. The exchange reactions at 60–80
the urethane and the proton donor and are secondꢀorder up to high conversions, practically until the disapꢀ
pearance of the entire urethane. The activation energies and apparent rate constants of the exchange reacꢀ
tions of phenylꢀ ꢀphenylurethane with various amines have been determined. The results have been
oꢀdichlorobenzene. In the absence of a catalyst and protonꢀdonating compound,
N
ꢀphenylurethane into isocyanate and alcohol takes place at a
C proceed as a direct exchange between
°
°
N
explained in terms of the dependence of kinetic parameters of the reaction on the amine nature, structure,
and nucleophilicity, on the steric accessibility of the amino group, and on the molecular organization of the
solution.
DOI: 10.1134/S0023158413050042
Investigation of polyurethanes is among the most ics and thermodynamics of the reactions of Nꢀphenyꢀ
rapidly developing areas of polymer chemistry. The lurethanes and secondary aliphatic amines were
steadily increasing production of polyurethane mateꢀ investigated at a stoichiometric ratio of the reactants
rials strongly needs efficient methods of utilization of [9]. Experiments conducted in oꢀdichlorobenzene
waste and wornꢀout goods for improving the environꢀ solution at 55–178°С demonstrated that the rate of
mental situation [1, 2]. There are a number of polyureꢀ the reaction obeys a secondꢀorder equation. It was
thane waste processing methods: thermal decomposiꢀ hypothesized that secondary amines used as the coreꢀ
tion (incineration) and physical and chemical proꢀ actant catalyze the urethane deblocking reaction.
cessing. In the latter case, wide use is made of the However, that study [9] suffers from some obvious
ability of urethanes to react with compounds containꢀ inconsistencies. It is not quite clear whether the secꢀ
ing active hydrogen, namely, alcohols, amines, and ond order of the exchange reaction is consistent with
water—glycolysis, aminolysis, and hydrolysis, respecꢀ the elimination–addition mechanism suggested by the
tively. For efficient control over the polyurethane authors, since they themselves claim that the rateꢀlimꢀ
waste processing technology, it is necessary to know iting step of the reaction is urethane decomposition
the underlying kinetic regularities and the mechaꢀ into isocyanate and blocking agent, while the reaction
nisms of the exchange reactions of the urethanes with between the isocyanate and the amine occurs rapidly.
protonꢀdonating compounds.
In addition, the urethane deblocking temperatures are
higher than some experimental temperatures, for
Earlier, we thoroughly investigated the kinetics of
the catalytic exchange reactions of phenylꢀNꢀphenyꢀ
lurethane (PPU) with aliphatic alcohols [3]. Amines
are an equally interesting and promising class of proꢀ
ton donors.
example, in the 55–70°С range, while urethanes do
not dissociate to a significant extent below 170
°С.
Thus, the kinetics and mechanism of the exchange
reactions of urethanes with amines have been insuffiꢀ
ciently studied to date.
An analysis of the literature on the exchange reacꢀ
tions of urethanes with amines suggests that, while
Here, we report the kinetics of the catalytic
there are numerous purely technological studies, there exchange reactions phenylꢀNꢀphenylurethane with
are only a few works dealing with the kinetics and amines varying in their structure and nature, namely,
mechanism of urethane–amine reactions [4–8]. aniline (An), benzylamine (BA), phenylethylamine
There have been kinetic studies on urethane aminolyꢀ (PEA), octylamine (OA), butylamine (BuA), and
sis in a large excess of amine (pseudofirstꢀorder reacꢀ dibutylamine (DBuA), at an equimolar or nearꢀ
tion) and in the absence of a catalyst [6–8]. The kinetꢀ equimolar amine : urethane ratio.
656

SPECTROSCOPIC KINETIC STUDY OF THE INTERACTION OF URETHANES
657
Table 1. IR spectroscopic data for the synthesized phenylureas and phenylꢀ
N
ꢀphenylurethane
, cm–1
3319, 1534 (N–H); 1720 (C=O); 1590, 1492, 693 (aryl);
Product
Empirical formula
C H NO
T
. mp.,°C
124
ν
Phenylꢀ
N
ꢀphenylurethane
13
11
2
1
200 (C–N)
3327, 3290 (sh.), 1555 (N–H); 1648 (C=O); 1592, 1495, 700
phenyl)
3329, 3308 (sh.), 1555 (N–H); 1631 (C=O); 1605, 1499, 700
aryl); 2930, 2917, 2876, 1450, 1440 (CH2)
3346, 3305 (sh.), 1566 (N–H); 1647 (C=O); 1596, 1496, 702
aryl); 2940 (sh.), 2924, 2860, 1450, 1441 (CH2)
3346, 3307 (sh.), 1565(N–H); 1645 (C=O); 1592, 1499, 701
aryl); 2943 (sh.), 2926, 2857, 1450, 1440 (CH2)
Phenylphenylurea
Benzylphenylurea
Phenylethylurea
Octylphenylurea
C H N O
247
175
155
155
13
12
2
(
C H N O
14
14
2
(
C H N O
15
16
2
(
C H N O
15
24
2
(
EXPERIMENTAL
Synthesis of PhenylꢀNꢀPhenylurethane
and Phenylureas
Chemicals
For kinetic experiments, we synthesized urethane
based on phenyl isocyanate and phenol,
Phenyl isocyanate C H NCO (Fluka, >98%, bp
6
5
2
D
0
1
60–164
°
C, d25= 1.093 g/cm3
,
n
°
= 1.536) was puriꢀ
С (10 Torr).
RNCO + R'OH
isocyanate
→
RNHC(O)OR'
urethane
fied by vacuum distillation at 90
and a number of ureas based on phenyl isocyanate and
the amines to be examined,
Phenol С Н ОН (analytical grade for medical purꢀ
poses, USSR Specifications TU 6ꢀ09ꢀ40ꢀ3245ꢀ88,
6
5
4
D
1
RNCO + R'NH2
→
RNHC(O)NHR'.
urea
d41 = 1.05760 g/cm3
temperature of 40.6
20
,
= 1.5478, crystallization
n
isocyanate
°С) was purified by sublimation at
1
°С.
Phenyl isocyanate was placed in a flask with a
groundꢀglass joint, and a proton donor was then
added. (Its amount was adjusted so that the reacting
groups were in equimolar proportions, [NCO] : [proꢀ
ton donor] = 1 : 1.) The reaction mixture was stirred,
and the flask was then placed in an oven preheated to
Aniline С Н NH (pure grade, USSR State Stanꢀ
6
5
2
2
D
0
dard 6006ꢀ51, d25 = 1.01750 g/cm3
84.4 ) was purified by keeping it for several weeks
,
n
= 1.5854, bp
1
°С
over potassium hydroxide and was then distilled, and
the middle fraction was used in the experiments.
60°С. The completeness of the reaction was checked
–1
by IR spectroscopy as an absorption band at 2270 cm ,
Benzylamine С Н CH NH (99%, bp 184– which is due to the antisymmetric stretching vibraꢀ
6
5
2
2
tions of the NCO group. The reaction was performed
until the ~100% conversion of the NCO groups. The
resulting urethane and ureas were identified by IR specꢀ
troscopy and melting point measurements (Table 1).
2
D
0
1
85
°
С, d25 = 0.981 g/cm3
,
n
= 1.5430), phenylethyꢀ
lamine С Н CH CH NH (99%, bp 197–200
°С,
6
5
2
2
2
2
n
D
0
d25 = 0.965 g/cm3
,
= 1.5330), octylamine
СН (CH ) NH (99%, bp 175–177
2
5
°С,
d ,
= 0.782 g/cm3
3
2 7
2
2
D
0
Kinetic Study of PhenylꢀNꢀPhenylurethane Aminolysis
n
= 1.4290), butylamine СН (CH ) NH (99%,
3
2 3
2
2
D
0
bp 78
°
C, d25 = 0.740 g/cm3
,
n
= 1.4010), and dibutyꢀ
The kinetics of the exchange reactions between
PPU and amines was studied in a DCB medium at
lamine СН (CH ) NH(CH ) СН (99%, bp 129.25
°С,
3
2 3
2 3
3
6
0–80
°С and a stoichiometric ratio of the reactants.
2
0
d25 = 0.767 g/cm3
Aldrich, were used as received.
,
n
D
= 1.4170), all purchased from
The concentration of the catalyst—DBTDL—was
–
2
varied between 0 and
5
×
10 mol/L. The reactant
concentrations were limited by the solubility of PPU
and DCB and did not exceed ~0.1 mol/L.
1
,2ꢀDichlorobenzene (DCB) С Н Cl (Fluka, bp
6 4 2
2
D
0
1
79–180° , = 1.552) was puriꢀ
fied by fractional distillation, and the middle fraction
was used in the experiments.
С, d25 = 1.305 g/cm3
n
The kinetics of the exchange reactions was investiꢀ
gated by IR spectroscopic monitoring using a tube
technique [10]. The accuracy of rate constant deterꢀ
mination was 5%.
±
Dibutyltin
dilaurate
(DBTDL)
The aminolysis products—phenol and ureas—
were identified by IR spectroscopy. The IR spectra of
filtered products, recorded as KBr pellets, were comꢀ
25
[
СН (СН ) СО ] Sn(C H ) (Aldrich, 95%,
.066 g/cm3
, = 1.4710) was used as received.
n
D
d
=
3
2 10
2 2
4
9 2
2
0
1
KINETICS AND CATALYSIS Vol. 54
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2013

658
DZALMUKHANOVA et al.
Absorbance, arb. units
NH –
1
1
541 cm
Absorbance, arb. units
.5
–1
1534 cm
225, 1202 cm–1
1
0
.8
.4
0
C=O
1
1
649 cm–
1
2
–1
C=O (1755 cm )
1716 cm–1
1
1
NH
–1
1
.0 3326, 3287 cm
1
1317 cm–1
3
319 cm–
0
2
3
4
2
0
.5
0
1
ν
, cm–1
3
000
2000
1000
, cm–1
Fig. 2. IR spectra of (1) PPU and (2) PPUr.
1775
1750
ν
Fig. 1. IR spectra of solutions of the reaction mixture in
DCB in the region of the stretching vibrations of the carꢀ
bonyl bond of urethane under conditions of the catalytic
reaction between PPU and aniline at urethane conversions
In most cases, the resulting urea precipitated after
the reaction mixture was cooled. The IR spectra of the
filtered crystals were identical to the spectra of the
ureas synthesized for identification (Table 1). By way
of example, we present the IR spectrum of the starting
PPU and phenylphenylurea (PPUr) isolated from the
reaction mixture by filtration (Fig. 2).
of (
ature is 80
1
) 0, (
2
°
) 30, (
3) 60, and (4) 95%. The reaction temperꢀ
C; CCat = 0.0024 mol/L.
pared with the spectra of presynthesized samples of the
corresponding ureas.
IR spectra were obtained on a SpecordꢀM82 specꢀ ysis of the reaction mixture at high PPU conversions,
trophotometer (Carl Zeiss Jena, Germany).
Note that, as was demonstrated by a thorough analꢀ
in no case did the reverse reaction between the liberꢀ
ated phenol and the resulting urea occur.
RESULTS AND DISCUSSION
Earlier, we established that, in the absence of a proꢀ
ton donor and a catalyst, PPU is not deblocked up to
1/СPPU, L/mol
45
40
35
30
25
20
15
10
265
°С
[3]. In addition, we carried out experiments on
2
1
the thermal decomposition of PPU in the presence of
the DBTDL catalyst and on the decomposition of
PPU dissolved in thoroughly dehydrated DCB. In
both cases, there were no indications of urethane
3
5
4
decomposition until 250°С. Therefore, the reaction of
the urethane with protonꢀdonating compounds at
much lower temperatures cannot proceed via a preꢀ
liminary deblocking stage and is apparently a bimolecꢀ
ular reaction. In order to rule out the thermal decomꢀ
position of the urethane into the starting isocyanate
and alcohol, the exchange reactions between PPU and
amines were conducted in the temperature range from
6
0 to 80°C.
As was demonstrated by qualitative and quantitaꢀ
tive IR spectroscopic analyses of the reaction mixture,
the exchange reactions of PPU with all of the amines
examined here proceed with practically 100% PPU
conversion (Fig. 1) and yield the corresponding ureas
0
200
400
600
800
1000
Time, min
1
Fig. 3. Typical anamorphoses of kinetic curves for the
and phenol.
exchange reactions of PPU with amines: (
) octylamine, ( ) phenylethylamine, (
and ( ) aniline. CPPU Camine
1) dibutylamine,
) benzylamine,
(
2
3
4
1
The aminolysis products were identified using ureas synthesized
by the direct reaction between phenyl isocyanate and an amine.
5
=
≈
0.1 mol/L; CCat = 1.7
×
–3
10 mol/L;
T = 70°C.
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SPECTROSCOPIC KINETIC STUDY OF THE INTERACTION OF URETHANES
659
Until high conversions, the kinetic curves for the Table 2. Kinetic parameters of the exchange reactions of PPU
with amines in DCB (CPPU
=
Camine
≈
0.1 mol/L)
exchange reactions of PPU with the amines are linearꢀ
izable in the coordinates of a secondꢀorder rate equaꢀ
tion throughout the temperature and catalyst concenꢀ
tration ranges examined (Fig. 3). Using anamorphoses
of the kinetic curves, we determined the apparent rate
constants kapp for the reactions, and, from the temperaꢀ
ture dependences of these constants, we derived the
effective activation energies Еа (Table 2).
The data presented in Table 2 suggest that the reacꢀ
tivity of the amines in their interaction with PPU
throughout the catalyst concentration and temperaꢀ
ture ranges examined here decreases in the following
102,
kapp
×
10 , L mol s–1
4
–1
E ,
a
kJ/mol
C
×
Cat
Amine
DBuA
mol/L
60°C 70°C 80°C
0
13.3
29.2
39.0
46.8
10.0
15.0
17.0
5.5
–*
–
72
73
0.07
0.21
0
17.7
19.6
4.2
7.2
–*
2.3
3.5
3.7
3.5
3.6
1.2
1.5
1.9
2.5
2.8
0.3
2.1
4.0
3.6
4.0
0
–
79
BuA
–*
80
0
0
0
0
0
0
.10
–
70
.22
–
–**
80
order: DBuA > BuA > OA > PEA > BA > An. These OA
results can be explained under the assumption that,
like the exchange reactions of PPU with aliphatic
alcohols [10], the exchange reactions of PPU with the
amines proceed via a bimolecular nucleophilic substiꢀ
tution mechanism. The kinetics of the exchange reacꢀ
tions depends at least on the structure and nature of
11.6
26.6
32.1
34.0
34.0
10.5
13.3
17.5
27.7
43.7
2.0
.05
.10
.17
10.5
12.9
13.3
16.0
2.5
99
106
112
111
106
106
108
118
135
93
0.26
0
PEA
the amine, which determine its nucleophilicity, and on
the steric accessibility of the reacting functional
groups.
0
.02
.05
4.1
0
5.3
Aromatic amines are generally less nucleophilic
than aliphatic amines, because their benzene ring
reduces the nucleophilicity of the molecule through
the interaction between the lone electron pair of nitroꢀ
0.18
9.1
0
0
0
.38
13.9
0.8
BA
An
.17
6.7
16.7
30.4
30.4
30.4
0
102
99
gen and the delocalized orbitals of the aromatic ring,
π
while the alkyl radicals of the aliphatic amines increase
the electron density on the nitrogen atom. As a conseꢀ
quence, the aliphatic amines are more reactive in the
exchange reactions than the aromatic amines (Table 2).
In the arylamine series, a lengthening of the alkyl moiꢀ
ety linking the amino group with the aromatic ring
enhances the nucleophilicity of the molecule and,
accordingly, the reactivity of the amine in its exchange
reaction with the urethane (PEA > BA > An), since the
insertion of an alkyl moiety between the benzene ring
and the amino group weakens the interaction between
0.52
11.9
11.9
11.9
0
0
2
0
.95
99
.20
99
–***
148
140
145
126
120
120
0.04
0.4
0.8
1.0
1.7
2.7
4.1
1.9
8.3
0.12
0.24
0.41
3.1
14.0
22.0
20.0
29.0
50.0
4.2
6.2
0.80
.62
9.1
the lone pair of nitrogen and the delocalized
of the aromatic ring.
π
orbitals
5
15.0
*
The reaction was not investigated under these conditions.
It was demonstrated earlier that the kinetics of the
exchange reactions of PPU with butyl alcohols
depends on the spatial structure and acidity (basicity)
of the proton donor [3]: the highest activity is shown
by primary butanol, which is sterically least hindered
and least basic. Conversely, the highest activity in the
interaction of PPU with aliphatic amines is displayed
by the secondary, sterically most hindered and most
basic amine. Thus, in the exchange reactions of PPU
with amines, as distinct from the same reactions of
PPU with alcohols, the effect of proton donor basicity
is stronger than the effect of the steric factor. Throughꢀ
out the temperature and catalyst concentration ranges
examined, the ratio of the kapp values for the reactions
of PPU with DBuA, BuA, and OA is 4 : 2 : 1 (Table 2).
The higher basicity of DBuA is confirmed by data
*
* The E value was not calculated.
a
*** The reaction does not occur under these conditions.
BuNH < Bu NH < Bu N [11]. Note that basicity and
2
2
3
nucleophilicity are not identical concepts, but there
are some nucleophilic substitution reactions in which
the reactivity of the attacking reactant increases with
an increase in its basicity [11]. Note that the effective
activation energy of the reactions of PPU with butyꢀ
lamines is practically independent of whether the
amino group is primary (BuA) or secondary (DBuA),
while the activation energy of the reaction between
PPU and OA is substantially higher and is close to the
Е of the reactions of the urethane with arylamines,
а
available from the literature: the basicity of butyꢀ among which the reaction between PPU and aniline is
lamines in chlorobenzene increases in the order characterized by the largest Еа value. It is clear from
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6
60
DZALMUKHANOVA et al.
kapp
×
103, L mol–1 s–1
Absorbance N–H (unassociated)
3389 cm–1
6
3
475 cm–1
1
1
4
2
0
N–H (unassociated)
389 cm–1 N–H (selfꢀassociated
322 cm–1
3
)
3
3
190 cm–1
2
2
3
N–H (unassociated)
3325 cm–1
N–H (selfꢀassociated
)
4
5
6
190 cm–1
3
3
, cm–1
3200
3500
3400
3300
ν
2
4
6
СCat
×
103, mol/L
Fig. 5. Spectra of amine solutions in the region of NH bond
vibrations (DCB solvent): ( ) aniline (0.1246 mol/L),
) butylamine (0.1123 mol/L), and ( ) dibutylamine
0.1077 mol/L).
1
(
(
2
3
Fig. 4. Apparent rate constants of the exchange reactions
of PPU with amines at 70 C versus the catalyst concentraꢀ
tion: ( ) dibutylamine, ( ) butylamine, ( ) octylamine, (
phenylethylamine, ( ) benzylamine, and ( ) aniline.
°
1
2
3
4)
5
6
selfꢀassociation species and heteroassociation species
2
involving the urethane and amino groups.
the data listed in Table 2 that, in almost all cases, an
increase in the catalyst concentration causes a slight
A comparison of the regions of NH group stretchꢀ
–
1
monotonic increase in the activation energy. This ing vibrations (3500–3100 cm ) in the IR spectra of
trend is most likely due to the specific features of the amines—aniline, butylamine, and dibutylamine—in
formation of the catalytic complexes involving one or DCB at the same amine concentration as in the reacꢀ
both reactants. However, additional experiments are tion mixture demonstrates that the selfꢀassociation
necessary to elucidate the mechanism of catalysis in species content of these amines decreases in the order
the exchange reactions.
The dependences of the apparent rate constants of
the reactions of PPU with the amines on the catalyst
DBuA > BuA > An (Fig. 5), which coincides with the
order of their activities in their exchange reactions
with PPU. The spectrum of the aniline solution
concentration are represented by curves tending to (Fig. 5, curve 1) contains practically no absorption
some limit, with plateauing observed at lower catalyst bands characteristic of selfꢀassociation species of NH
concentrations (Fig. 4) than in the case of the groups. As in the case of urethane formation, this is
exchange reactions of PPU with butanols [3]. In addiꢀ due to the absence of noncatalytic interaction between
tion, the apparent rate constants depend only weakly PPU and aniline. In the solutions of butanols in DCB
on the catalyst concentration (Fig. 4).
[10], as in aniline, the selfꢀassociation species of OH
groups at the concentration examined here are almost
absent and, as a consequence, the noncatalytic
exchange reactions of PPU do not take place.
It is remarkable that the exchange reactions of PPU
with the amines (except for aniline) in DCB can occur
in the absence of a catalyst as well (Table 2), and this is
not so for the reactions of PPU with aliphatic alcohols
However, the exchange reaction between PPU and
aniline in an aniline medium, as distinct from the
reactions in DCB, does occur without a catalyst but at
[
3]. This can be explained by considering the effect of
the form of the amino group in the reaction system,
i.e., the molecular organization of the solution on the
exchange kinetics. A similar situation was observed in
urethane formation reactions [12–16], in which the
highest activity in the absence of a catalyst was shown
by hydroxyl group selfꢀassociation species and, conꢀ
versely, the unassociated groups were most active in
the presence of a catalyst [17].
–7
–1 –1
a low rate (kapp = 6
× 10 L mol s , CPPU =
0
.5 mol/L, 60 ). This finding can be explained by
°С
the fact that, according to IR spectroscopic data, the
amino groups of aniline in its own medium exist
mainly as selfꢀassociation species, which are the most
reactive species in the noncatalytic exchange reaction.
The same results were obtained for noncatalytic alcoꢀ
By analogy, it can be supposed that the amino holysis reactions of PPU in respective alcohols [3].
groups in the reaction systems considered here can
exist both in unassociated (monomeric) form and as
2
All reactant molecules were solvated by the solvent.
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SPECTROSCOPIC KINETIC STUDY OF THE INTERACTION OF URETHANES
661
Based on experimental data on the proportions of
different amino group species in DCB solution, one
might expect that aniline will be the most active amine
in the catalytic exchange reactions, since almost all of
its NH2 groups are in monomeric (unassociated)
form, and dibutylamine will be least reactive, because
its solution contains more selfꢀassociation species
6. Shawali, A.S., Harhash, A., Sidky, M.M.,
Hassaneen, H.M., and Elkaabi, Sh.S., J. Org. Chem.,
1986, vol. 51, p. 3498.
7. Menger, F.M. and Glass, L.E., J. Org. Chem., 1974,
vol. 39, p. 2469.
8. Berlin, P.A., Tiger, R.P., Fillipova, I.S., Levina, M.A.,
Dzhaparidze,
Katsarava, R.D., and Entelis, S.G., Zh. Obshch. Khim.
990, vol. 60, no. 9, p. 2140.
. De Aguirre, I. and Collot, J., Bull. Soc. Chim. Belg.
989, vol. 98, no. 1, p. 19.
N.N.,
Kartvelishvili,
T.M.,
,
than the solutions of the other amines (Fig. 5, curve 3).
1
In fact, as was mentioned above, the reactivity of the
amines throughout the catalyst concentration range
examined decreases in the order DBuA > BuA > OA >
PEA > BA > An (Table 2). Therefore, both the associꢀ
ation and amine nucleophilicity effects show themꢀ
selves in the noncatalytic exchange reactions, while
the catalytic reactions are governed by the nucleophiꢀ
licity factor.
9
,
1
1
0. Dzhalmukhanova, A.S., Cand. Sci. (Chem.) Dissertaꢀ
tion, Chernogolovka, Moscow oblast: Inst. of Problems
of Chemical Physics, 2012.
1
1
1
1. A Guidebook to Mechanism in Organic Chemistry,
Sykes, P., Ed., London: Longman, 1971, p. 93.
2. Berlin, P.A., Tiger, R.P., and Entelis, S.G., Kinet.
Katal., 1987, vol. 28, no. 6, p. 1347.
3. Berlin, P.A., Tiger, R.P., Chirkov, Yu.N., and
Entelis, S.G., Kinet. Katal., 1987, vol. 28, no. 6,
p. 1354.
14. Tiger, R.P., Doctoral (Chem.) Dissertation, Moscow:
Inst. of Chemical Physics, 1979.
5. Bondarenko, S.P., Tiger, R.P., and Entelis, S.G., Zh.
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Translated by D. Zvukov
KINETICS AND CATALYSIS Vol. 54
No. 6
2013