A comparative study on the hydrolysis of acetic anhydride and N,N-dimethylformamide: Kinetic isotope effect, transition-state structure, polarity, and solvent effect

Article abstract of DOI:10.1002/poc.3701

Recent studies have shown that general-base assisted catalysis is a viable mechanistic pathway for hydrolysis of smaller anhydrides. Therefore, it is the central purpose of the present work to compare and contrast the number of hydrogen atoms in-flight and stationary in the transition state structure of the base-catalyzed mechanisms of 2 hydrolytic reactions as well as determine if any solvent effects occur on the mechanisms. The present research focuses on the hydrolytic mechanisms of N,N-dimethylformamide (DMF) and acetic anhydride in alkali media of varying deuterium oxide mole fractions. Acetic anhydride has been included in this study to enable comparisons with DMF hydrolysis. Comparative studies may give synergistic insight into the detailed structural features of the activated complexes for both systems. Hydrolysis reactions in varying deuterium oxide mole fractions were conducted in concentrations of 2.0M, 2.5M, and 3.0M for DMF and 0.10M for acetic anhydride at 25°C. Studies in varying deuterium mole fractions allow for proton inventory analysis, which sheds light on the number and types of hydrogen atoms involved in the activated complex. For these systems, this type of study can distinguish between direct nucleophilic attack of the hydroxide ion on the carbonyl center and general-base catalysis by the hydroxide ion to facilitate a water molecule attacking the carbonyl center. The numerical data are used to discuss 3 possible mechanisms in the hydrolysis of DMF.

Full text of DOI:10.1002/poc.3701

Received: 2 August 2016
DOI 10.1002/poc.3701
Revised: 23 February 2017
Accepted: 27 February 2017
R E S E A R C H A R T I C L E
A comparative study on the hydrolysis of acetic anhydride and N,
N‐dimethylformamide: Kinetic isotope effect, transition‐state
structure, polarity, and solvent effect
William C. Cooper1
| Abhinay Chilukoorie1 | Suhesh Polam1 | Dane Scott3 | Floyd Wiseman2
1 Department of Physical Sciences, Eastern
New Mexico University, Portales, NM, USA
Abstract
Recent studies have shown that general‐base assisted catalysis is a viable mechanistic
pathway for hydrolysis of smaller anhydrides. Therefore, it is the central purpose of
the present work to compare and contrast the number of hydrogen atoms in‐flight and
stationary in the transition state structure of the base‐catalyzed mechanisms of 2
hydrolytic reactions as well as determine if any solvent effects occur on the mecha-
nisms. The present research focuses on the hydrolytic mechanisms of N,N‐
dimethylformamide (DMF) and acetic anhydride in alkali media of varying
deuterium oxide mole fractions. Acetic anhydride has been included in this study
to enable comparisons with DMF hydrolysis. Comparative studies may give syner-
gistic insight into the detailed structural features of the activated complexes for both
systems. Hydrolysis reactions in varying deuterium oxide mole fractions were con-
ducted in concentrations of 2.0M , 2.5M , and 3.0M for DMF and 0.10M for acetic
anhydride at 25°C. Studies in varying deuterium mole fractions allow for proton
inventory analysis, which sheds light on the number and types of hydrogen atoms
involved in the activated complex. For these systems, this type of study can
distinguish between direct nucleophilic attack of the hydroxide ion on the carbonyl
center and general‐base catalysis by the hydroxide ion to facilitate a water molecule
attacking the carbonyl center. The numerical data are used to discuss 3 possible
mechanisms in the hydrolysis of DMF.
2 Department of Chemistry, Davis and Elkins
College, Elkins, WV, USA
3 Department of Chemistry, East Tennessee
State University, Johnson City, TN, USA
Correspondence
William C. Cooper, Department of Physical
Sciences, Eastern New Mexico University,
1500 S. Ave. K, Portales, NM 88130, USA.
Email: william.cooper@enmu.edu
KEYWORDS
Gross‐Butler plot, hydroxide‐catalyzed acetic anhydride hydrolysis, hydroxide‐catalyzed N,N‐
dimethylformamide hydrolysis, inverse isotope effect, proton inventory studies
1 | INTRODUCTION
for example, proteins. One pathway for the breakdown of
proteins is through base hydrolysis of the amide backbone
Over the years, mechanisms involved in hydrolysis of
anhydrides and esters have been extensively studied using
titration,[1,2] calorimetric,[3–6] conductimetric,[7,8] spectro-
structural units. Simpler molecules, suchas DMF, are expected
to occur by a similar mechanism.[20–22] Furthermore, studies
have been extended to incorporate hydrolysis of sulfanil-
amides. The reason being is that sulfanilamides contain a func-
tional group sulfonic amide moiety that is contained in
compounds of 1 class of antibiotics. The hydrolytic cleavage
of a sulfonic amide group should be comparable to a carbonyl
amide. The sulfonic amide is formed bya sulfur atom replacing
scopic,[9,10] temperature scanning,[11] combination,[12,13]
[15–19]
pH,[14] and chromatographic
techniques. By studying
the mechanism for hydrolysis of N,N‐dimethylformamide
(DMF), one may infer mechanistic characteristics that occur
in other compounds that contain amide structural features,
J Phys Org Chem. 2017;e3701.
wileyonlinelibrary.com/journal/poc
Copyright © 2017 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/poc.3701

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COOPER ET AL.
a carbon atom and an additional =O group has been added to
this sulfinyl group. Therefore, obtaining information
pertaining to hydrolysis of the sulfonic amide functional moi-
ety of sulfanilamides can provide insight to the metabolic fate
of 1 class of antibiotics.[22–26]
mentioned that the rate constants of formation of the tetrahe-
dral intermediate are strongly increased by releasing steric
hindrance in the acyl portion as shown by the
higher reactivity of N‐formyl derivatives in comparison with
N‐acetyl and N‐benzoyl derivatives.
Slebocka‐Tilk and coworkers used nuclear magnetic res-
onance to study the rates of hydroxide‐catalyzed hydrolysis
on formamide in aqueous media.[27] These studies aided in
determining whether the mechanism involved nucleophilic
attack by hydroxide or hydroxide acted as a general base to
deprotonate the attacking water molecule. It was determined
that both mechanisms could be applied to formamide hydro-
lysis. However, proton inventory analysis and an inverse iso-
tope effect (kOH/kOD = 0.77 ꢀ 0.02) showed that the likely
mechanism involves an hydroxide ion solvated by 2 water
molecules with 3 water molecules assisting formation of the
amide hydrate oxy anion. Marlier and co‐workers[28] used
18O‐labeled experiments and concluded that hydroxide acts
as a general base to remove a proton from solvating water
molecules during the formation of the transition state. From
the results of kinetic isotope effect studies of enzyme sys-
tems, Xiong and Zhan[29] and Lynn and Yankwich[30] have
suggested a temperature‐dependent interconversion of 2 or
more types of active sites (directly or indirectly) through
enzyme conformational changes). Mujika et al[31] suggested
that the twist of the amide bond induces an increase on the
reaction rate of acid hydrolysis. Linda[32] and coworkers
On the other hand, simple‐ and acetate‐catalyzed hydroly-
sis of acetic anhydride does not show any kind of inverse iso-
tope effect. Wiseman[14] suggested the transition state
structure in simple acetic anhydride hydrolysis probably has
4 protons, whereas acetate catalyzed hydrolysis has 2, as
shown in Scheme 1. In Scheme 1 (as well as all of the other
schemes), the curved arrows represent movement of electrons.
Proton inventory techniques play a crucial role in eluci-
dating mechanisms by identifying the number and types of
hydrogens involved in the transition‐state structures. Proton
inventory studies, which have been well discussed by Mata‐
Segreda,[33] indicate that esters undergo hydrolysis through
parallel water catalysis and specific hydrogen ion catalysis.
As it became apparent that there is a significant difference
in the deuterium kinetic isotope effect (dkie) between acetic
anhydride and DMF, extensive research has been undertaken
to understand this difference. Using the procedure described
by Laidler and co‐worker,[34] Eyring and Arrhenius graphs
were generated to evaluate the activation parameters for these
reactions. These graphs shed light on the reasons behind dif-
ferent deuterium kinetic isotope effect (dkie) values between
these 2 compounds. For instance, differences in the activation
SCHEME 1 General mechanism: simple‐
and acetate‐catalyzed hydrolysis of acetic
anhydride

COOPER ET AL.
3 of 8
‐
energy would be identified with large differences in the
slopes of the Arrhenius plots. Bunton and coworkers[35]
showed that increasing solvent polarity by increasing the
ionic strength decreased the rate constant of the reaction;
implying that the transition state is less polar than the reac-
tants. The magnitude of the decrease increases with increas-
ing size of cation or anion. The trend is consistent with
work in this paper on sodium chloride effect. They also
showed that anions of weak acids, such as formate and nitrite,
increase the rate by behaving as general‐base catalysts.
This work is aimed at elucidating the number of
hydrogens involved in the transition state and mechanism in
the hydrolysis of acetic anhydride and DMF. Additionally,
this study also shows an inverse kinetic isotope effect
(kOH‐/kOD‐ = 0.51 ꢀ 0.03 at 25°C and an hydroxide concentra-
tion of 2.0M) for the hydroxide reaction with DMF. This value is
consistent with what is observed for other simple amides.[27,28]
15.0 μL (=1.098 e‐6 mol) OD. The NaOD stock concentra-
tion was 40 % by weight in D2O having a density of 1.516 g/
mL.Astockconcentrationof10.0NwasusedforNaOHaswell
thathadadensityof1.11g/mL.Therefore,molefractionofdeu-
terium=0.08247mol+1.098e‐6mol/0.08147mol+1.098e‐
6 mol + 7.426 e‐7 mol + 0.08247 mol. If χd was 0.503, the χh
was 1−0.503 = 0.497. Seven μL of pure acetic anhydride was
added to initiate the assay. The total volume in the cuvette was
3 mL. Similarly, 10 μL of pure DMF was added to initiate the
assay. A typical assay consisted of collecting abs vs time for
1500 seconds for periods of every second on a Perkin Elmer
lambda 35 UV‐visible Spectrophotometer. Absorbance was
converted to concentration by dividing by the absorptivity.
Plots of ‐ln(Conc.) versus time yielded a slope from which rate
constants were obtained. Solvent polarity effects for acetic
anhydride and DMF hydrolyses were studied by conducting
the reactions in aqueous solutions of varying mole fractions of
cyclohexanol and 1‐octanol, and varying sodium chloride
concentration.
2 | MATERIALS AND
INSTRUMENTATION
4 | RESULTS
Deuterium oxide (99.8 %) for the experiments was purchased
from Acros and sodium deuteroxide from Cambridge Isotope
Laboratories Inc. Water was distilled. Other chemicals such
as sodium hydroxide, octanol, cyclohexanol, sodium chlo-
ride, and sodium acetate were used as received from VWR.
All experiments were performed using a Perkin Elmer
Lambda 35 UV/VIS Spectrophotometer.
4.1 | Activation energy (Ea)
Activation parameters such as activation energy, enthalpy,
entropy, and Gibbs free energy were calculated bystudying the
rate of hydrolysis of acetic anhydride and DMF at varying
temperatures. The following analysis is taken from Carroll. [36]
The natural logarithmic form of the Arrhenius equation is
3 | EXPERIMENTAL
Ea
RT
lnk ¼ ‐
þ lnA
(1)
The rate of hydrolysis of acetic anhydride and DMF was deter-
mined by monitoring the loss ofabsorbance at 250 and 230 nm,
respectively. For acetic anhydride and water, temperature stud-
ies were undertaken to calculate activation energy, enthalpy,
and entropy. The rates of hydrolysis of acetic anhydride at
25°C at varying ionic strengths were determined. The kinetic
isotope effect in basic conditions was investigated by varying
the mole fraction of deuterium oxide in water between 0 and
1 at 7 different temperatures using a precision digital con-
trolled‐temperature circulating water bath. For base hydrolysis
of acetic anhydride, the sodium hydroxide concentration was
0.12M. In the case of base hydrolysis of DMF, 2.0M, 2.5M,
and 3.0M sodium hydroxide/sodium deuteroxide concentra-
tions were used. For example, for acetic anhydride, a 0.503
mole fraction of deuterium content, χd = 0.503, was made by
adding 1494 μL (=0.08247 mol) of D2O to 1468 μL
(=0.08147 mol) of H2O. The density of 1.00 and 1.107 g/mL
and a molar mass of 18.01 and 20.02 g/mol were used for
H2O and D2O, respectively. However, NaOD contributed to
the deuterium content as well. In the assay, 0.123M ‐OL was
in which k is the rate constant, Ea is the activation energy, A
is the pre‐exponential factor, R is the gas constant, and T is
temperature.
4.2 | Enthalpy, entropy, and Gibbs free energy
According to transition state theory, the rate constant kr is
defined by Equation 2 given by Wiseman et al in which
the equation is a derivative for the Eyring equation that
corrects for nonlinearity.[37] ln (k/T) vs 1/T were plotted
and fitted according to Equation 2 using Logger Pro. The
slight departure from linearity in the Arrhenius plots may
be attributed to nonlinearity of the heat capacities of activa-
tion at lower temperatures or due to the error in measuring
the rate constants at lower temperatures.
ꢀ
ꢁ
À
Á
‡ −ΔΔS‡ =R
ΔΔH
hkr
kBT
ΔH‡
T
¼ ΔS‡−
–Rln 1 þ e
(2)
T
Rln
‐
obtained by adding 15.0 μL (=7.426 e‐7 mol) of OH and

4 of 8
COOPER ET AL.
TheGross‐Butlerequationwasusetounderstandthemech-
anisms and propose the transition state structures for hydroly-
ses of acetic anhydride and DMF in hydroxide‐catalyzed
medium. The Gross Butler equation is given in Equation 3:
ni
kd ð1−xd þ ϕixdÞ
À
Á
¼
(3)
nj
kh
1−xd þ ϕjxd
where ϕ and n in Equation 3 are the fractionation factor and the
number of protons having a fractionation factor of phi. Table 2
shows results of nonlinear regression analyses of Equation 3
for the basic hydrolysis of acetic anhydride. Upon examining
the values for ϕ = 0.498 and 0.9292 for n1 = 1 and n2 = 3,
respectively, ϕ = 0.498 shows a significant change in the force
field and implies a proton in‐flight. The other 3 protons with ϕ
values near unity show very little change in the force field.
6 | PROTON INVENTORY FOR DMF
HYDROXIDE (BASE‐CATALYZED)
HYDROLYSIS
Unlike acetic anhydride, DMF shows an inverse kinetic iso-
tope effect. The proton inventory data for hydrolysis of DMF
is presented in Figure 3. The Gross‐Butler equation was mod-
ified for the hydrolysis of DMF and as shown in Equation 4.
FIGURE 1 A, Eyring plot of ln k/T versus 1/T for the hydroxide
hydrolysis of acetic anhydride at an ionic strength of 0.123M; B,
Arrhenius plot of ln k versus 1/T for the hydrolysis of N,N‐
dimethylformamide at an ionic strength of 2.0M
ð1−X þ xaÞð1−x þ xbÞð1−x þ xcÞ
Y ¼
(4)
ð1−x þ xdÞð1−x þ xeÞ
The resulting plot is shown in Figure 3, and the inventory
data is in Table 3.
The proton inventory analyses were performed using
Equations 5 and 6, which indicate 6 and 10 protons,
respectively.
where κ is the transmission coefficient; kB is Boltzmans
constant, and h is Plank constant.
Figure 1 below shows a typical Eyring plot.
The calculated values for activation energy, enthalpy,
entropy, and free energy are provided in Table 1.
2
3
5 | PROTON INVENTORY FOR
ACETIC ANHYDRIDE HYDROXIDE
(BASE‐CATALYZED) HYDROLYSIS
Y ¼ ð1−x þ xaÞð1−x þ xbÞ ð1−x þ xcÞ
(5)
(6)
2
3
ð1−x þ xaÞð1−x þ xbÞ ð1−x þ xcÞ
Data forkk vs mole fraction was applied to the proton inventory
d
Y ¼
h
3
ð1−x þ xdÞð1−x þ xeÞ
technique. A plot of kk vs mole fraction for acetic anhydride is
d
h
shown in Figure 2.
The data are summarized in Tables 4 and 5.
TABLE 1 Activation parameters showing the difference in the isotope effects between acetic anhydride and DMF at 25°C
Parameter
Amide
Amide – D2O
Dkie
Anhydride
Anhydride ‐ D2O
Dkie
Ea (kJ/mol)
56.2 (ꢀ0.4)
53.7(ꢀ0.7)
46.9(ꢀ0.4)
44.4 (ꢀ1.4)
‐28.3(ꢀ4.6)
1.20 (ꢀ0.03)
1.21 (ꢀ0.03)
1.82 (ꢀ0.03)
40.8 (ꢀ17.9)
20.1 (ꢀ3.7)
−47.9 (ꢀ11.1)
42.9 (ꢀ0.6)
38.2 (ꢀ3.4)
−0.4 (ꢀ11.1)
**
ΔH‡(kJ/mol)
ΔS‡(J/K*mol)
0.526 (ꢀ0.03)
−51.6
**
**could not be determined.

COOPER ET AL.
5 of 8
TABLE 3 Proton inventory data for hydrolysis of N,N‐
dimethylformamide, which is best fit to Equation 6
n1 = 1
n2 = 2
n3 = 3
n4 = 1
n5 = 3
R2 = 0.9991
a = 1.401
b = 1.33
c = 0.503
d = 0.598
e = 0.601
TABLE 4 Proton inventory data corresponding to Equation 5
n1 = 1
n2 = 2
n3 = 3
R2 = 0.9981
a = 1.756
b = 1.675
c = 0.817
kd
kh
FIGURE 2 A typical plot of vs mole fraction (of h)
TABLE 5 Proton inventory data corresponding to Equation 6
n1 = 1
n2 = 3
n3 = 3
n4 = 1
n5 = 3
R2 = 0.9971
a = 2.651
b = 1.021
c = 1.024
d = 1.038
e = 1.032
TABLE 2 Results of proton inventory analysis for the hydrolysis of
acetic anhydride in 0.1M hydroxide solution at 25°C
Number of protonic sites Regression coefficient Values for ϕ
n1 = 1
n2 = 1
n1 = 1
n2 = 2
n1 = 2
n2 = 2
n1 = 1
n2 = 3
0.9971
0.9980
0.9979
0.9980
0.5075
0.75
7 | KINETIC ISOTOPE EFFECT
0.4873
0.8918
0.6110
1.0249
0.498
The kinetic isotope effects at various temperatures are
presented in Table 6.
These values show decreasing normal dkie values for
acetic anhydride with increasing temperature. An inverse pri-
mary kinetic isotope effect is observed for DMF. A dkie value
decreases with increasing temperature for DMF. Table 7
0.9292
Since the suitable Gross‐Butler equation to study the
hydrolysis of DMF would be the Equation 4 (according to
the R2 coefficient), the proton inventory analysis of DMF
had 10 protons in its transition state corresponding to 5 water
molecules aiding the hydrolysis.
TABLE 6 Temperature dependent dkie values
Temp (°C)
kh/kd (anhydride)
kh/kd(amide)
15
20
25
30
35
40
45
2.652 (ꢀ0.03)
2.812 (ꢀ0.03)
2.795 (ꢀ0.03)
3.037 (ꢀ0.03)
2.714 (ꢀ0.03)
2.645 (ꢀ0.03)
2.425 (ꢀ0.03)
0.314 (ꢀ0.005)
0.430 (ꢀ0.005)
0.391 (ꢀ0.005)
0.358 (ꢀ0.005)
0.475 (ꢀ0.005)
0.551 (ꢀ0.005)
0.512 (ꢀ0.005)
TABLE 7 The rate constants of hydrolysis of acetic anhydride and
DMF in solutions of varying alcohol mole fractions at 25°C and an ionic
strength of 2.0M for DMF and 0.123M for acetic anhydride
Alcohol
k/s‐1 (acetic anhydride)
k/s‐1 (DMF)
No alcohol
0.00250 (ꢀ0.00005)
0.00260 (ꢀ0.00005)
0.00280 (ꢀ0.00005)
0.00110 (ꢀ0.00005)
0.00110 (ꢀ0.00005)
0.00110 (ꢀ0.00005)
Cyclohexanol (0 χ)
1‐octanol (0 χ)
FIGURE
3
Gross‐Butler plot for hydrolysis of N,N‐
dimethylformamide
Abbreviation: DMF, N,N‐dimethylformamide.

6 of 8
COOPER ET AL.
shows results of conducting the reactions in solutions of
varying mole fractions of cyclohexanol and 1‐octanol. There
are no discernible solvent effects for DMF under these condi-
tions within the statistical errors of the rate constants. How-
ever, for acetic anhydride, there is a slight discernable
solvent effect. Making the solvent more nonpolar increases
the rate of hydrolysis for acetic anhydride.
9 | BASE‐CATALYZED ACETIC
ANHYDRIDE HYDROLYSIS
For the mechanism (for base‐catalyzed acetic anhydride
hydrolysis) corresponding to experimental data fitted to the
Gross‐Butler equation, the conclusion was made (in the cur-
rent study) that hydroxide, solvated by a single water mole-
cule, assists in the attack as shown in Scheme 2 and not the
nucleophile. Current data shows that 1 proton has a fraction-
ation factor value of 0.49 that corresponds to the proton in
flight, and the 3 protons have fractionation factor values of
0.929, which do not undergo any significant change in the
force field. If hydroxide was the nucleophile being assisted
by 2 water molecules, then there would possibly be 2 protons
in flight with fractionation factors around 0.5 and 3 protons
with fractionation factors around 0.9. This corresponds to
an incorrect number of protons. In light of ΔH‡, dkie equals
a large inverse isotope effect, 0.526, which implies bonds
are stronger in the transition state than in the reactants state.
In addition, the curvature of the Eyring plot in Figure 1 sug-
gests that the acetic anhydride hydrolysis is a 2‐step process
as illustrated in Scheme 2. Again, curved arrows represent
the flow of electrons. In addition, 1 particular arrow in the
following scheme is showing that the electrons are flowing
from and O─H sigma bond to an H∣∣∣O hydrogen bond. By
doing so, this illustration signifies that an O─H sigma bond
is breaking and a sigma bond is forming at the site of the
H∣∣∣O hydrogen bond.
8 | SOLVENT EFFECTS
The effect of solvent on the rates of hydrolysis was studied
in the presence of sodium chloride for both acetic anhydride
and DMF. Sodium chloride decreased the rate of hydrolysis
of acetic anhydride. Ionic strength had no effect on the rate
of DMF hydrolysis. At 25°C, using the limiting law of the
Debye Huckel equation, the rate of hydrolysis of acetic
anhydride at 5 concentrations of sodium chloride (0M, 1M,
2M, and 3M) were plotted against the square root of the
ionic strength of sodium chloride. This plot is shown in
Figure 4.
The transition state structure involved in the base‐
catalyzed hydrolysis of acetic anhydride has 2 water
molecules corresponding to 4 protons with 1 hydrogen being
in flight (Figure 2). The rate constant obtained for acetic
anhydride hydrolysis at 30°C and 0.123M NaOH was
0.0041 s‐1. Of this rate, ksimple = 0.00312 s‐1. Therefore,
kOH = (k – ksimple) / [‐OH]/[H2O] = 0.539 s‐1. Thus, 76%
of hydrolysis is due to simple hydrolysis (at 0.123M hydrox-
ide concentration). This was determined using the plot from
the salt effect study and fitting to a polynomial (quadratic)
equation. Once, the equation was obtained, the rate for sim-
ple hydrolysis at 25°C at 0.123 M ionic strength was found.
Therefore, kOH in H2O and D2O were determined.
10 | BASE‐CATALYZED DMF
HYDROLYSIS
Based on the kinetic solvent effect data from Scheme 3, it
was assumed that transition state of DMF has to be neutral
charge on the molecule with a negative 1 on the hydroxide
(which is in agreement with Cox[38]). Since the rates of
hydrolysis do not change with added concentrations of salt,
this may mean that there is no major redistribution of charge
between the reactant and transition structures (as shown in
the current study). Since hydroxide is the nucleophile, then
by attacking the carbonyl, carbon creates a negative charge
on the carbonyl oxygen. However, the amide nitrogen gets
protonated and assumes a plus 1 charge (which counters the
negative 1 of oxygen). Overall, the charge is neutral on the
transition state of DMF. The point of difference between
acetic anhydride and DMF may be how the charge redistrib-
utes in the respective transition states. One possibility is a
later transition state for acetic anhydride hydrolysis. The tran-
sition state for DMF would be early. In the transition state, the
mass of the hydrogen or that of the deuterium will affect the
vibration in the same way as that in the reactant. The transi-
tion state structure of DMF has 10 protons in the transition
FIGURE 4 Ionic strength dependence for the hydrolysis of acetic
anhydride in presence of sodium chloride at 25°C and 0M NaOH

COOPER ET AL.
7 of 8
SCHEME 2 Mechanism for the
hydrolysis of acetic anhydride
SCHEME 3 Mechanism involved in
hydrolysis of N,N‐dimethylformamide
state where 7 protons are in flight (consistent with Ślebocka‐
Tilk conclusion that there are 5 water molecules in the transi-
tion state). In light of the activation energy, the dkie is insig-
nificant (=1.20). However, for ΔS‡, there is a dkie (=1.82)
that implies that the bonds are stronger in the reactants state
than in the transition state. There are 2 water molecules
assisting the hydroxide, 1 water molecule is involved in pro-
tonating the amide nitrogen, and 2 water molecules are
involved in protonating the carbonyl oxygen (Scheme 3).
This is consistent with the proton inventory fit and analyses
that includes 3 protons of 1 type are in flight, 3 other protons
of another type are in flight, and 1 proton of a third type is in
flight (the reaction for DMF hydrolysis at pH 7.0 at 25°C was
attempted. However, under these conditions, no reaction took
place. Only under strong hydroxide base catalyzed hydrolysis
does a reaction occur).
higher in nondeuterated media than in deuterated media.
Studies on the rates of hydrolysis of acetic anhydride and
DMF in the solutions of decreasing polarity show that the
transition state of acetic anhydride is less polar than the
reactants. The polarity of the activated complex of DMF is
equal to the reactants due to numerous water molecules in
the transition state. Experiments on kinetic salt effect showed
that the rate of hydrolysis of DMF did not change with the
added concentrations of inorganic or organic salt suggesting
sodium chloride or sodium acetate did not affect the charge
on the reactants. In the case of acetic anhydride, sodium
chloride had a negative effect on the rate of hydrolysis
and the charge of ions involved in the formation of
activated complex is −0.378 e (which has never been shown
before this current study) is tabulated from the following
equation
Log KTS ¼ logKO þ 2AZAZBI1=2
11 | CONCLUSION
where Z is the charge of the cation and anion from the salt
and Ko is the rate without salt present. The reactants have a
charge of −1 for hydroxide, and 0 for the anhydride. This
charge is distributed more in the transition structure of acetic
anhydride hydrolysis but is still −1 due to the stoichiometry.
The assumption was made that an increase in the concen-
tration of sodium chloride causes an increase in the charge on
the formation of activated complex.[39] Thus, since the reac-
tion decreases with increasing solvent polarity, then it is
likely that the transition structure is more nonpolar than the
Table 1 indicates that the free energy barrier for the hydroly-
sis of amide in nondeuterated media is higher than the barrier
in deuterated media. Hence, reactant, DMF, has to cross the
higher barrier to reach the transition state in nondeuterated
media making the reaction slower. In the case of acetic anhy-
dride, the free energy barrier is smaller for hydrolysis in
nondeuterated media. Hence, the reactant has to cross a
higher barrier in deuterated media to reach the transition
state. Hence, the rate of hydrolysis of acetic anhydride is

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COOPER ET AL.
[21] N. Okimoto, T. Tsukui, M. Hata, T. Hoshino, M. Tsuda, J. Am.
Chem. Soc. 1999, 121, 7349.
reactants. This information will become most crucial in
studies such of the role of water in enzymatic protein
hydrolysis.[40] To understand the role of water in the study
of whey protein isolate, at 30% (w/v) whey protein isolate,
the amount of water becomes limited. Therefore, a small
decrease in observed water activity correlates to a large
increase in bound water. This article provides a useful
starting point in understanding the structure of water in the
transition‐state of enzyme‐catalyzed hydrolysis of such
systems.
[22] N. Okimoto, T. Tsukui, J. Am. Chem. Soc. 2000, 122, 5613.
[23] R. A. Khalil, A. H. Jalil, A. Y. J. Abd‐Alrazzak, Iran. Chem. Soc.
2009, 345.
[24] O. Moukha‐Chafiq, R. C. Reynolds, Nucleos. Nucleot. & NA 2014,
33, 709.
[25] E. Kilinc, B. Gumgum, C. Hamamci, F. Aydin, Anal. Chem. 2009,
64, 714.
[26] G. Orsomando, G. G. Bozzo, R. D. de la Garza, G. J. Basset, E. P.
Quinlivan, V. Naponelli, F. Rebeille, S. Ravanel, J. F. Gregory, A.
D. Hanson, J. Plant, Cell & Mole. Biol. 2006, 46, 426.
[27] H. Ślebocka‐Tilk, A. A. Neverov, R. S. J. Brown, Am. Chem. Soc.
2003, 125, 1851.
REFERENCES
[1] K. J. P. Orton, M. J. J. Jones, Am. Chem. Soc. 1912, 101, 1708.
[2] F. A. Cleland, R. H. Wilhelm, AIChE J. 1956, 2, 489.
[3] V. Gold, Trans. Far. Soc. 1948, 44, 506.
[28] J. F. Marlier, N. C. Dopke, K. R. Johnstone, T. J. Wirdzig, J. Am.
Chem. Soc. 1999, 121, 4356.
[29] Y. Xiong, C. J. Zhan, Phys. Chem. A 2006, 110, 12644.
[30] K. R. Lynn, P. E. J. Yankwich, Phys. Chem. 1960, 64, 1719.
[4] T. L. J. Smith, Phys. Chem. 1955, 59, 385.
[31] J. I. Mujika, E. Formoso, J. M. Mercero, X. J. Lopez, Phys. Chem.
B 2006, 30, 15000.
[5] H. J. Janssen, C. H. Haydel, L. H. Greathouse, Ind. Eng. Chem.
1957, 49, 197.
[32] P. Linda, A. Stener, A. Cipiciani, G. J. Savelli, Hetero. Chem. 1983,
20, 247.
[6] D. Glasser, D. F. Williams, Ind. Eng.Chem. Fund. 1971, 10, 516.
[7] A. C. D. Rivett, N. V. J. Sidgwick, Am. Chem. Soc. 1910, 97, 732.
[8] A. K. J. Kralj, Ind. Eng. Chem. 2007, 13, 631.
[33] J. F. Mata‐Segreda, Isotopes in Envirn. and Health St. 2007, 43, 17.
[34] K. J. Laidler, M. C. J. King, Phys. Chem. 1983, 87, 2657.
[9] W. C. Bell, K. S. Booksh, M. L. Myrick, Anal. Chem. 1998, 70,
[35] C. A. Bunton, N. A. Fuller, S. G. Perry, I. H. J. Pitman, Am. Chem.
Soc. 1962, 867, 4478.
332.
[10] S. Haji, C. Erkey, Chem. Eng. Ed. 2005, 39, 56.
[36] F. A. Carroll, In Perspective on Structure and Mechanism in Organic
Chemistry, 2nd ed., John Wiley & Sons, Hoboken, NJ 2010.
[11] S. P. Asprey, B. W. Wojciechowski, N. M. Rice, A. Dorcas, Chem.
Eng. Sci. 1996, 51, 4681.
[37] F. L. Wiseman, W. C. Cooper, B. Robinson, Intrntnl. J. Avd. Res.
Chem. Sci. 2015, 2, 1.
[12] A. Zogg, U. Fischer, K. Hungerbuhler, Chemom. Int. Lab. Sys.
2004, 71, 165.
[38] R. A. Cox, Can. J. Chem. 2005, 83, 1391.
[13] G. Puxty, M. Maeder, R. R. Rhinehardt, S. Alam, S. Moore, P. J. J.
[39] P. W. Atkins, J. de Paula, Physical Chemistry, 9th ed., Oxford Uni-
versity Press, Oxford, UK 2010.
Gemperline, Chem. Commun. 2005, 19, 329.
[14] F. L. J. Wiseman, Phys. Org. Chem. 2012, 25, 1105.
[15] M. C. Cook, A. Bliu, J. P. Kunkel, Vaccine 12, 3702.
[40] C. I. Butre, P. A. Wierenga, H. Gruppen, Process Biochem. 2014,
49, 1903.
[16] J. Lu, H. Yang, J. Hao, C. Wu, L. Liu, N. Xu, R. J. Linhardt, Z.
Zhang, Carb. Poly. 2015, 122, 180.
How to cite this article: Cooper WC, Chilukoorie A,
Polam S, Scott D, Wiseman F. A comparative study on
the hydrolysis of acetic anhydride and N,N‐
dimethylformamide: Kinetic isotope effect, transition‐
state structure, polarity, and solvent effect. J Phys Org
Chem. 2017;e3701. https://doi.org/10.1002/poc.3701
[17] M. A. Rahman, Z. Igbal, M. A. Mirza, A. Hussain, Pharm. Meth.
2012, 3, 62.
[18] H. Li, Q. Qing, R. Kumar, C. J. Wyman, Ind. Microb. & Biotech.
2013, 40, 551.
[19] D. Ellington, T. Pritchard, P. Foy, K. King, B. Mitchell, J. Austad,
D. Winters, D. J. Sullivan, AOAC Int. 2012, 95, 1469.
[20] A. J. Scheidig, C. Burmester, R. S. Goody, Structure 1999, 7, 1311.