Acetic anhydride hydrolysis at high acetic anhydride to water ratios

Article abstract of DOI:10.1002/kin.20838

The hydrolysis of acetic anhydride in the presence of water is an exothermic reaction that produces acetic acid. Most of the research has focused on low ratios of acetic anhydride to water. The major concern in the industry is the accidental addition of a small amount of water to large quantities of acetic anhydride stored in tanks, or as handled in a manufacturing process. This paper focuses on isothermal and adiabatic experiments that were conducted to understand the effect and rate of hydrolysis at high ratios of acetic anhydride to water. The acetic acid produced in the reaction also affects the rate of reaction. Detailed calorimetric data and specific rate expressions that have been developed are presented in this paper.

Full text of DOI:10.1002/kin.20838

Acetic Anhydride Hydrolysis
at High Acetic Anhydride
to Water Ratios
B. C. FRITZLER, S. DHARMAVARAM, R. T. HARTRIM, G. F. DIFFENDALL
DuPont Engineering Research & Technology, E.I. du Pont de Nemours & Company, 1007 Market Street, Wilmington,
DE 19898
Received 12 April 2013; revised 26 July 2013; 8 October 2013; accepted 17 November 2013
DOI 10.1002/kin.20838
Published online 7 January 2014 in Wiley Online Library (wileyonlinelibrary.com).
ABSTRACT: The hydrolysis of acetic anhydride in the presence of water is an exothermic reaction
that produces acetic acid. Most of the research has focused on low ratios of acetic anhydride
to water. The major concern in the industry is the accidental addition of a small amount of
water to large quantities of acetic anhydride stored in tanks, or as handled in a manufacturing
process. This paper focuses on isothermal and adiabatic experiments that were conducted to
understand the effect and rate of hydrolysis at high ratios of acetic anhydride to water. The
acetic acid produced in the reaction also affects the rate of reaction. Detailed calorimetrꢀiCc data
and specific rate expressions that have been developed are presented in this paper.
Wiley Periodicals, Inc. Int J Chem Kinet 46: 151–160, 2014
2014
ond order; first order in acetic anhydride and first order
in water [8,13,14]. Very few data have been reported
for systems at high acetic anhydride to water ratios, but
it suggests that the reaction rate in concentrated acetic
anhydride is slower than in dilute systems [8].
INTRODUCTION
In industrial facilities handling acetic anhydride
(Ac2O), the inadvertent addition of water (H2O) to a
tank containing acetic anhydride is a significant safety
risk. The reaction of acetic anhydride and water pro-
duces acetic acid (AcOH) and releases heat. Pressure
generated by the vapor pressure of the hot material can
lead to vessel rupture and release of the vapors that are
flammable and toxic.
The reaction of acetic anhydride with water to give
acetic acid has been studied by a number of authors. Be-
cause most of the work on this reaction has been done
in a large excess of water, most of the authors describe
the reaction rate as pseudo-first order in acetic anhy-
dride [1–12] although a few describe it as overall sec-
The response in the presence of acetic acid either
present in the acetic anhydride or formed by the reac-
tion must also be considered. Different authors have
reported different effects of acetic acid [5]. In some
cases, acetic acid slowed the reaction, whereas in oth-
ers, it increased the observed reaction rate. Golding and
Dussault’s [5] results showed that in dilute acetic anhy-
dride solutions (Ac2O–water weight ratio < 0.2), acetic
acid slowed the reaction slightly. Orton and Jones [8]
showed that increasing the acetic acid concentration
from 50 wt% to 97 wt% results in a reduction in the re-
action rate constant (Ac2O–water weight ratio varying
from 0.25 to 0.015).
Correspondence to: S. Dharmavaram; e-mail: Seshu
.Dharmavaram@dupont.com.
Various techniques have been used to measure the
rate of the acetic anhydride hydrolysis reaction. Glasser
and Williams [4] used an isothermal calorimetric
R. T. Hartrim and G. F. Diffendall are retirees from E. I. du Pont
de Nemours & Company.
C
ꢀ
2014 Wiley Periodicals, Inc.

152
FRITZLER ET AL
technique to determine the extent of reaction ver-
sus time. Shatynski and Hanesian [9] used adiabatic
calorimetry to collect rate data on the reaction. The
isothermal methods give data for only one temperature
per experiment. However, they allow for the examina-
tion of any other changes with extent of the reaction
such as acetic-acid formation. The adiabatic experi-
ments give data on rate versus a number of tempera-
tures in each experiment. However, any impact of other
effects is lumped together with the impact of temper-
ature. In this work, both isothermal experiments and
adiabatic experiments were conducted.
Adiabatic experiments were conducted in the
Fauske Vent Sizing Package (VSP2) reactor [15]
(Fauske and Associates LLC, Burr Ridge, IL, USA).
The VSP2 consists of a thin-walled reaction vessel (test
cell) of a nominal 0.12-L volume. The test cells used
for this work were 304 SS weighing about 38 g each.
The test cell is located inside a heavy-wall containment
vessel. High-pressure N2 is introduced into the contain-
ment vessel so that the pressure difference between the
test cell and the containment vessel is minimized to
avoid damage to the test cell from overpressurization.
This prevents the thin-walled test cell from bursting if
high pressure is developed during a reaction. A heater
outside the lower portion of the test cell is used to raise
the sample temperature during the test. A second guard
heater surrounds the test cell and keeps the surround-
ings at the same temperature as the test cell so that
adiabatic conditions are maintained during the test. A
magnetic stirrer is used to provide agitation during the
reaction.
In the adiabatic experiments, the acetic anhydride
and acetic acid were charged to the test cell. The test
cell was placed into the containment vessel and the
containment vessel was sealed. The test cell was then
brought to the desired starting temperature. Tubing
that passed through the containment vessel wall al-
lowed for the introduction of water to the test cell.
At the start of the experiment, the water was quickly
injected into the test cell and the valve in the tub-
ing was closed. An effort was made to heat the water
before injection but its temperature was lower than
the test cell temperature for the higher-temperature
experiments.
EXPERIMENTAL
Isothermal experiments were conducted in a Met-
tler RC-1 Reaction Calorimeter (Mettler-Toledo AG,
Schwerzenbach, Switzerland). The glass MP10 Met-
tler reactor with a nominal 1-L volume was used in
the experiments. The RC-1 comprises a controlled
jacketed reactor, an electrical immersion calibration
heater, an agitator, thermocouples, and a temperature-
controlled, positive displacement ISCO pump (Tele-
dyne Isco, Lincoln, NE, USA) used for the injection of
reactants. The stirrer was used and operated at 200 rpm.
A temperature-controlled heat-transfer oil is circulated
through the jacket of the reactor. The oil temperature
is controlled to maintain the desired temperature of the
sample in the reactor. The RC-1 constantly measures
the difference between the reactor sample temperature,
Tr, and the jacket temperature, Tj. The heat-transfer co-
efficient between the reactor contents and the jacket,
U, is determined by calibrations using an electrical im-
mersion heater. The heat capacity, Cp, of the reactor
contents is determined from a temperature ramp. The
calibrations and Cp determinations are done at the be-
ginning and end of each experiment. The heat transfer
surface, S, is determined from the reactor geometry
and the liquid level in the reactor. The heat-generation
rate at any time can then be calculated from
The acetic anhydride and glacial acetic acid used in
the tests was obtained from Sigma–Aldrich (St. Louis,
MO, USA). The acetic anhydride purity was stated to
be 99.5%. Water used in the tests was deionized.
RESULTS AND DISCUSSION
Isothermal Experiments
The RC-1 calorimeter was used for the isothermal ex-
periments. The RC-1 calculates the rate of heat release
from the reaction from Eq. (1). The reaction rate at
time t can then be calculated from
Qt = U × S × (Tr − Tj)
(1)
In the tests, the acetic anhydride and acetic acid
were charged to the reactor and brought to the de-
sired temperature after the standard calibrations were
done. Deionized water was placed in a temperature-
controlled ISCO pump. At the start of the reaction, the
total amount of water was quickly injected into the re-
actor by the ISCO pump. The reaction was then allowed
to proceed to completion while the data were collected.
After the reaction was complete, the final calibrations
to determine U and the final Cp were done.
Ratet = Qt/ꢀHrxn
(2)
The extent of the reaction at any time can be deter-
mined by comparing the heat released up to that time
to the total heat release for the reaction:
Xt = Ht/ꢀHrxn
(3)
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ACETIC ANHYDRIDE HYDROLYSIS AT HIGH ACETIC ANHYDRIDE TO WATER RATIOS
153
63
62
61
60
59
58
57
56
55
54
°
0
20
40
60
80
100
Time (s)
120
140
160
180
200
Figure 1 Change in temperature due to significant endothermic heat of mixing seen when adding 1.96 wt% water to acetic
anhydride at 60 ◦C. Heat of hydrolysis and the calorimeter controls quickly return the temperature to 60 ◦C.
Upon addition of water to the acetic anhydride, a
significant endothermic heat of mixing was observed.
In the isothermal experiments, the water was at the
same temperature as the acetic anhydride when it was
introduced. Figure 1 shows the temperature of the reac-
tion mass immediately after the addition of 1.96 wt%
water to acetic anhydride with no acetic acid added.
The heat of mixing was not estimated separately from
the total enthalpy change for the experiments. The mea-
sured enthalpy change at 30 ◦C was −55.9 kJ/mol; at
60 ◦C, it was −55.1 kJ/mol. Zogg et al. [11] reported
Toward the end of the reaction, the temperature
difference between the jacket and the reaction mass
becomes very small as the reaction slows. At some
point, the difference is too small to be accurately mea-
sured and the data are not usable. Because of these is-
sues at the beginning and the end of each experiment,
only the data from about 5% conversion to about 80%
conversion were used in determining kinetics for the
reaction.
The reaction was taken to be overall second or-
der; first order in acetic anhydride and first order in
water:
◦
a total enthalpy change of −60 kJ/mol at 25 C and
◦
−57 kJ/mol at 55 C. Visentin et al. [10] reported a
◦
total enthalpy change of −61 kJ/mol at 25 C and
Rate = k × [H2O] × [Ac2O]
(4)
−58 kJ/mol at 55 ◦C.
The solubility of water in acetic anhydride has been
found to be 2 wt% at 20 ◦C [16]. The RC-1 experiments
were carried out using a water concentration just below
2 wt% so as to ensure a single liquid phase in the
reaction mass.
The heat generation rate, Q, was determined by the
RC-1 calorimeter for each data point. Equation (2) was
then used to determine the rate at each data point. The
concentration of water and acetic anhydride at each
point was calculated from the starting concentrations
and the extent of reaction from Eq. (3) as follows:
The RC-1 temperature control via the reactor jacket
and the heat generated from the reaction quickly
raised the temperature back to the desired level af-
ter the injection of the water. However, the temper-
ature upset caused by the heat of mixing and the
RC-1 control system’s effort to return the tempera-
ture to the set point mean that the data during the
very early portion cannot be used to determine reaction
kinetics.
[H2O] = [H2O]0 × (1 − Xt)
(5)
(6)
[Ac2O] = [Ac2O]0 − [H2O]0 × Xt
The reaction rate constant, k, could then be calcu-
lated for each data point from Eq. (4).
International Journal of Chemical Kinetics DOI 10.1002/kin.20838

154
FRITZLER ET AL
1.0E-04
9.0E-05
8.0E-05
7.0E-05
6.0E-05
5.0E-05
4.0E-05
3.0E-05
2.0E-05
1.0E-05
0.0E+00
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Conversion
Figure 2 Change in reaction rate constant seen with increasing conversion for an Ac2O–water ratio of 50:1 at 60 ◦C.
One experiment was conducted at 30 ◦C in an excess
higher Ac2O–water ratio experiment reported by Orton
and Jones [8].
of water (0.1:1 Ac2O–water weight ratio). Then three
experiments at different temperatures were conducted
at a 50:1 Ac2O–water weight ratio. Figure 2 shows
the reaction rate constant versus the conversion for the
experiment at 60 ◦C and an Ac2O–water weight ratio
of 50:1.
Figure 2 shows the reaction rate constant changing
as the reaction proceeds. In contrast to this result at the
high Ac2O–water ratio, Fig. 3 shows the rate constant
versus conversion for the 0.1:1 Ac2O–water experi-
ment. While the reaction-rate constant changes with
conversion at high Ac2O–water ratio, it is constant at
low Ac2O–water ratio. The increase in the rate constant
with conversion was also seen in the experiments with
50:1 Ac2O–water at 30 ◦C and at 90 ◦C.
The comparison shows that the present work at low
Ac2O–water ratio agrees well with the other results at
low ratios. The reaction-rate constants at high Ac2O–
water ratios are clearly smaller than those at low ratios.
Plotting ln(k) versus 1/T for the 50:1 Ac2O–water
ratios using the initial values at zero acetic acid con-
centration, and fitting the points by least squares
gives an Arrhenius expression for the reaction rate
constant:
k = 827.079 m3/kg − mol/sec
× exp (−52,886 J/mol/R/T)
(7)
To determine the reaction-rate constant at the be-
ginning of the experiment for the high Ac2O–water
cases (when acetic acid was zero), the rate constant
versus the conversion curve was extrapolated back to
zero conversion. The results are shown in Table I.
Figure 4 shows the results from the RC-1 experi-
ments and compares them to some values found in the
literature. The results of Asprey et al. [13] are shown
as are the results of Glasser and Williams [4] and of
Cleland and Wilhelm [3]. The results of Glasser and
Williams [4] and of Cleland and Wilhelm [3] were pub-
lished as first-order rate constants but were converted
to second order by dividing by the water concentrations
used in their experiments. Also shown is the result for a
The activation energy determined from these tests,
52,886 J/mol, is larger than the values reported by
Glasser and Williams [4] (45,187 J/mol), Cleland and
Wilhelms [3] (44,392 J/mol), and Asprey et al. [13]
(45,606 J/mol). However, Haji and Erkey [17] reported
an activation energy of 53,408 J/mol, and Ramaswamy
et al. [18] reported the activation energy to fall in
the range of 53,100 to 54,000 J/mol. Golding and
Dussault [5] suggested that the activation energy in-
creases with increasing the acetic anhydride concen-
tration, although no reason was given for this. The data
shown in Table II seem to support their assertion.
It was proposed that the acetic acid formed in the
reaction was catalyzing the reaction leading to the
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ACETIC ANHYDRIDE HYDROLYSIS AT HIGH ACETIC ANHYDRIDE TO WATER RATIOS
155
1.0E-04
9.0E-05
8.0E-05
7.0E-05
6.0E-05
5.0E-05
4.0E-05
3.0E-05
2.0E-05
1.0E-05
0.0E+00
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Conversion
Figure 3 Change in reaction rate constant seen with increasing conversion for an Ac2O–water weight ratio of 0.1:1 at 30 ◦C
Table I Initial Reaction Rate Constants for the Ac2O +
increase in the reaction-rate constant versus the con-
version shown in Fig. 2. To test this, additional exper-
Water Reaction
iments were conducted in the RC-1 with acetic acid
added to the acetic anhydride before the water was
added. The results of these experiments extrapolated
back to the initial acetic acid concentrations are shown
in Table III. These results confirm that the reaction is
catalyzed by acetic acid at large Ac2O–water ratios.
The work by Orton and Jones [8] and by Golding and
Ac2O–Water
Weight Ratio
Temperature
(◦C)
k (m3/kg-mol/s)
0.1:1
50:1
50:1
50:1
30
30
60
90
4.68E-05
6.50E-07
4.05E-06
2.09E-05
1.0E-02
1.0E-03
1.0E-04
1.0E-05
1.0E-06
1.0E-07
1.0E-08
1.0E-09
0.008:1 Ac2O:water - Cleland & Wilhelm [3]
0.03:1 Ac2O:water - Glasser & Williams [4]
0.1:1 Ac2O:water - Asprey et al. [13]
0.1:1 Ac2O:water - Present Work
1:1 Ac2O:water - Orton & Jones [8]
50:1 Ac2O:water + 9% AcOH - Present Work
50:1 Ac2O:water + 3.8% AcOH - Present Work
50:1 Ac2O:water + 1% AcOH - Present Work
50:1 Ac2O:water - Present Work
0
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Figure 4 Comparison of literature results for initial reaction rate constants to the values determined in current work.
International Journal of Chemical Kinetics DOI 10.1002/kin.20838

156
FRITZLER ET AL
Table II Activation Energy and Acetic Anhydride Concentration
Ac2O Concentration (mol/L)
Ac2O–Water Weight Ratio
Activation Energy (kJ/mol)
Reference
0.02
0.075
0.25
0.66
1.0
0.002
0.008
0.03
0.07
0.1
42.95
46.09
49.44
53.408
45.606
53.6
8
3
4
6
13
18
8.3
5.1
10.1
50
52.886
Current Work
Table III Initial Reaction Rate Constants When Water
Is Added to Ac2O in the Presence of Acetic Acid
where
kꢁꢁ = (k + kꢁ × [AcOH]n)
(13)
Ac2O–Water Acetic Acid Temperature
k
Weight Ratio
(wt%)
(◦C)
(m3/kg-mol/s)
The acetic-acid concentration can be calculated
throughout the course of the reaction based on the con-
version. The reaction-rate constants calculated for the
data can then be plotted as a function of the acetic-acid
concentration (Fig. 5). The plot shows good agreement
between the various runs at 60 ◦C.
50:1
50:1
50:1
50:1
0
1
3.8
9.0
60
60
60
60
4.05E-06
8.80E-06
1.75E-05
2.95E-05
Data from the RC-1 experiments at 30 ◦C and 90 ◦C
◦
Dussault [5] show the rate slowing with acetic acid but
their experiments were done in a large excess of water.
An autocatalytic reaction can be expressed as two
reactions: catalyzed and not catalyzed. In the current
case, these reactions can be written shown in Eqs. (8)
and (9) as
combined with the data from the 60 C experiments
allow for determining the value of kꢁ and n in Eq. (11).
A value of 0.85 was found to be the best average value
for n and kꢁ is given by
kꢁ = 7465 (m3/kg − mol)0.85/sec
× exp(−55,342 J/mol/R/T)
(14)
Ac2O + H2O → 2AcOH
(8)
(9)
where kꢁ has units of (m3/kg-mol)0.85/s. Thus, the value
of kꢁꢁ for a 50:1 Ac2O–water weight ratio is
Ac2O + H2O + AcOH → 3AcOH
The rate expression for the reaction of Eq. (8)
was shown above in Eq. (4). The rate expression for
Eq. (9) is
kꢁꢁ = (827.079 m3/kg − mol/sec
× exp(−52,886 J/mol/R/T)
+ 7465 (m3/kg − mol)0.85/sec
× exp(−55,342 J/mol/R/T)
Ratecatalyzed = kꢁ × [H2O] × [Ac2O] × [AcOH]n
(10)
× [AcOH kgmol/m3]0.85
)
(15)
where [AcOH] is the acetic-acid concentration at the
given time (not the initial value).
Figure 6 shows a comparison of the value of kꢁꢁ
calculated from the RC-1 experiments and the fit from
Eq. (15).
The net reaction rate is then given as
Rate = k × [H2O]
× [Ac2O] + kꢁ × [H2O]
Adiabatic Experiments
× [Ac2O] × [AcOH]n
(11)
(12)
Adiabatic VSP2 experiments were conducted at 3:1
and 19:1 Ac2O–water ratios. The adiabatic experi-
ments were conducted at higher water ratios which
would lead to two liquid phases in the reaction mass.
These experiments combine the effects of changing
which can be rewritten as
Rate = kꢁꢁ × [H2O] × [Ac2O]
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ACETIC ANHYDRIDE HYDROLYSIS AT HIGH ACETIC ANHYDRIDE TO WATER RATIOS
157
Figure 5 Reaction rate constant vs. acetic acid concentration for four experiments at 60 ◦C. The rate constant calculated from
Eq. (15) is also shown.
Figure 6 Predicted values of kꢁꢁ using Eq. (15) vs. measured data from the RC-1 experiments.
solubilities, composition, and temperature as one might
expect to see in a large-scale reaction (for example an
Ac2O storage tank accidentally charged with water).
In all of the adiabatic experiments, the acetic anhy-
dride contained 1 wt% acetic acid at the start of the
experiment.
The conversion at any temperature can be calculated
from
XT = (T − T0)/ꢀTa
(17)
The rate of the reaction can be related to the
temperature-rise rate measured by the VSP instrument:
The water and acetic anhydride concentrations can
then be calculated from Eqs. (5) and (6). The reaction
rate constant at each data point can then be calculated
dX/dt = dT /dt/ꢀTa
(16)
International Journal of Chemical Kinetics DOI 10.1002/kin.20838

158
FRITZLER ET AL
1.00E-04
1.00E-05
1.00E-06
1.00E-07
0.1:1 Ac2O:water
VSP2 3:1 Ac2O:water + 1% AcOH
VSP2 19:1 Ac2O:water + 1% AcOH
50:1 Ac2O:water + 1% AcOH
50:1 Ac2O:water
0
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Figure 7 Initial reaction rate constants for the adiabatic experiments at a 19:1 and a 3:1 Ac2O–water ratio and for isothermal
experiments at 50:1 and 0.1:1 Ac2O–water ratios.
1.00E-01
1.00E-02
1.00E-03
1.00E-04
1.00E-05
1.00E-06
VSP2 3:1 Ac2O:water; T0=22.7°C
1.00E-07
1.00E-08
1.00E-09
°
VSP2 19:1 Ac2O:water; T0=25.6 C
VSP2 19:1 Ac2O:water; T0=61.3°C
50:1 Ac2O:water initial rate data
Fit 50:1 Ac2O:water
0
20
40
60
80
100
120
140
160
180
200
Temperature (°C)
Figure 8 Reaction rate constants for the adiabatic experiments at a 19:1 and a 3:1 Ac2O–water ratio as compared to the initial
reaction rate constants (zero AcOH) for a 50:1 Ac2O–water ratio.
from
dX/dt = k × 1/[H2O]0 × [H2O] × [Ac2O]
(and, therefore, initial acetic acid concentrations) were
calculated from the data and are shown in Fig. 7. An
adiabatic run was also made at a 3:1 Ac2O–water ratio.
The initial reaction-rate constant for this run is also
shown in Fig. 7. From these data, it is apparent that
lower Ac2O–water ratios give higher initial reaction-
rate constants.
(18)
Two adiabatic runs were made with an Ac2O–water
ratio of 19:1. One run started at 26 ◦C and the other at
61 ◦C. The rate constants at these initial temperatures
Figure 8 shows the reaction-rate constant versus the
temperature from the adiabatic VSP2 runs compared
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ACETIC ANHYDRIDE HYDROLYSIS AT HIGH ACETIC ANHYDRIDE TO WATER RATIOS
159
Figure 9 Reaction-rate constant calculated from Eq. (15) is compared with the values calculated for the adiabatic experiments
at a 19:1 Ac2O–water ratio with two different starting temperatures.
Figure 10 Reaction-rate constant calculated from Eq. (15) is compared with the values calculated for the adiabatic experiment
at a 3:1 Ac2O–water ratio.
to the data from the isothermal experiments. The in-
crease in the rate constant with temperature seen for the
adiabatic runs is higher than the change due to temper-
ature from the isothermal runs. This may be due to the
formation of acetic acid during the course of the reac-
tion such that the acetic-acid concentration is increas-
ing as the temperature increases. Because the reaction
mass contains more water, it likely formed two phases
during a portion of the experiment. It is possible that
some of the increase in the apparent reaction-rate con-
stant could also be attributed to the change in solubility
of the two phases with temperature.
Reaction rate constants were calculated from
Eq. (15) and are compared to the values from the VSP2
runs in Figs. 9 and 10. While Eq. (15) does not consider
the lower initial Ac2O–water ratio of the VSP2 runs or
the impact of limited solubility, it gives a relatively
good agreement for the VSP2 runs at a 19:1 Ac2O–
water ratio; the agreement for the 3:1 Ac2O ratio run
is not as good.
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Versatile VSP2: A Tool for Adiabatic Thermal Analysis
and Vent Sizing Applications, North American Thermal
Analysis Society, 28th Annual Conference, Orlando, FL,
Oct 4–6, 2000.
The rate of hydrolysis of acetic anhydride in the pres-
ence of water is strongly dependent on the ratios of
acetic anhydride to water. Most of the previous research
work has focused on the low acetic anhydride to water
ratios. Detailed isothermal and adiabatic calorimetric
experiments were conducted at high Ac2O–water ra-
tios and compared with results for the low Ac2O–water
ratios.
Specific rates for the reaction at 3:1, 19:1, and 50:1
ratios were determined. The effect of acetic acid on
the reaction also depends on the Ac2O–water ratio. At
high ratios, acetic acid increases the reaction rate. At
low ratios, it has little effect.
A rate expression describing the impact of the acetic
acid on the rate constant at high Ac2O–water ratios has
been developed.
The authors wish to thank two anonymous reviewers whose
comments helped to significantly improve this paper.
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International Journal of Chemical Kinetics DOI 10.1002/kin.20838