p today, computational chemistry has evolved into
a powerful tool to be used to study in many areas. In
this review, the computational quantum chemical
methods based on B3LYP functional have been
applied to determine the bond dissociation
enthalpies of a variety of substituted benzenes
derivatives. In searching for suitable methods to be
used in the evaluation of BDEs, the good
performance of the density functional theory using
restricted open-shell formalism ROB3LYP at the
basis set of 6-311++G(2df,2p) in conjunction with
geometries optimized at the B3LYP/6-311G(d,p)
level has been demonstrated by its capacity to
reproduce the BDEs of a series of X‒H bond types
in a range of substituted aromatic compounds
YC6H4XH (X= O, S, Se, NH, PH, CH2 and SiH2; Y
= H, F, Cl, CH3, OCH3, NH2, CF3, CN and NO2).
The calculated BDEs of the studied benzene
derivatives have been reviewed and hence the model
chemistry of ROB3LYP/6-
311++G(2df,2p)//B3LYP/6-311G(d,p) is defined as
a convenient and economic manner, but with reliable
results as compared to available experimental values
with the accuracy of 1.0-2.0 kcal/mol.
Depending on the nature of centered atom X,
which is polar or non-polar, the behavior of
substituents at the para and meta position is quite
different. The success of correlation between
Hammett constants was found for substituted
benzene derivatives with hetero atom X belongs to
class “O” category including phenols, thiophenols,
benzeneselenols, anilines and phenylphosphines. In
contrast, the poor correlations are seen between
BDE values of the C‒H and Si‒H bonds in toluenes
and phenylsilanes, respectively with the Hammett
substituent constants at the para and meta position
of aromatic ring. Small effects of the Y-substituents
have similarly observed for both C‒H and Si‒H
bonds in substituted toluenes and phenylsilanes
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e
of crucial importance. For example, in a chemical
reaction there are disruption and formation of
chemical bonds. The making and breaking of bonds
is the basis of all chemical transformation. A sound
knowledge of the energies required to break bonds
and the energies released upon their formation is
fundamental to understanding chemical processes.
The energy required to homolytic bond cleavage at
298 K and 1 atm corresponds to the enthalpy of
reaction: A B A + B , which is defined as the
bond dissociation enthalpy of the A B bond and
symbolized by BDE(A B) [7]. It should be noted
that by definition of IUPAC, the bond dissociation
energy is sometimes called the bond dissociation
enthalpy (or bond enthalpy), but these terms may not
be strictly equivalent [8]. Conversely, if the radicals
A and B recombine to form the molecule AB, then
thermal energy equivalent to the bond dissociation
enthalpy is released, according to the first law of
thermodynamics [9].
Hence it is essential to establish reliable data of
bond dissociation enthalpies (BDEs) as direct
information about the strength of the relevant
chemical bond in order to understand the inherent
reaction mechanism. Therefore, the BDEs already
provide valuable criteria for the analysis and
selection of antioxidants derived from the natural
compounds extracted from plants.
The bond strength of a given bond can be
VJC, 55(6), 2017 Pham Cam Nam et al.
680
experimentally measured or computationally
calculated. It exists many experiments that allow
measuring the bond dissociation enthalpy [10].
Despite compilations of experimental
thermochemical data for many molecules, there are
numerous species for which there are no available.
In addition, the data in the compilations are
sometimes incorrect [11].
Experimental measurements of thermochemical
processes are often expensive, difficult and need a
careful manipulation, so it is highly desirable to have
computational methods that can make reliable
predictions and inexpensive [9]. With the recent
advances in computation methods and computer
capacity, this becomes more and more reality.
To the best of our knowledge, there has been no
recent review on the B3LYP method for predicting
the accurate BDEs in benzene derivatives and their
analogues as well as the effect of substituents at the
para and meta positions of the benzene ring, a short
review on these topics is urgent and necessary. For
the results, this review includes several sections
organized in three parts. In the first part, the model
chemistry of ROB3LYP/6-
311++G(2df,2p)//B3LYP/6-311G(d,p) was analyzed
and evaluated by comparing the calculated results
with the available experimental values as well as by
benchmarking against the other computational
methods. Conventionally, the model to the right of
the double slash i.e. B3LYP/6-311G(d,p) is the one
at which the molecular geometry was optimized and
the model to the left of the double slash i.e.
ROB3LYP/6-311++G(2df,2p) is the one at which
the energy is computed. In case of radical species,
specification of a restricted open shell wave function
for the Becke3LYP hybrid functional requires
the ROB3LYP keyword, while the unrestricted
version denoted as UB3LYP is applied for
geometrical optimization of the radicals. The second
one, the homolytic bond dissociation enthalpies of
the X‒H bonds (X = O, S, Se, NH, PH, CH2 and
SiH2) of the related benzene derivatives have been
reviewed and evaluated by using ROB3LYP/6-
311++G(2df,2p)//B3LYP/6-311G(d,p). In addition,
the updated BDEs for a series of aniline derivatives
and phenylsilane analogues were also calculated
using the same procedure of computational method.
The third part of this review, the effect of para and
meta substituents on the BDE(X‒H) have been
critically analyzed considering the nature of
substituent and the substituted position. The idea of
a quantitative description of the substituent effect on
rates and equilibria of chemical reaction (log(k) or
log(K), respectively) by use of a linear regression in
which the nature of the substituent (X) is described
numerically by a substituent constant was ingenious
and opened a great field for further investigations
[12]. Therefore in this review the correlations of
Hammett’s substituent constants with the
BDE(X‒H) values have also been explored.
2. METHODOLOGY FOR PREDICTING
BDE(X‒H)s
Because of the important of bond dissociation
enthalpy in many reactions, the accurate
determination of BDE is an urgent task for both
experimental and computational researchers and this
continues to be a steady stream of work in the field
from practitioners in both areas [13].
2.1. Experimental methods
Experimental determinations of BDE are still limited
to simple or small molecules and are insufficient in
many practical cases, in which large and complex
systems have frequently to be treated [14]. In
addition, experimental BDE data have large
uncertainties (2.0-3.0 kcal/mol and more in some
cases), making the development and comparisons of
new computational technique challenges. A very
concise of description of experimental methods can
be found in details from Ref. [15] and references
therein. For a given X‒H bond in polyatomic
molecules, three applicable techniques are usually
proposed: i) The study of radical kinetics; ii)
Photoionization mass spectrometry (PIMS) and iii)
the acidity/electron affinity cycle. The abstraction of
a hydrogen atom and creation of radical is
considered in the study of radical kinetics. In this
method, the concentration of atoms, free radicals,
and molecules at one or several temperatures using
various detecting methods [16].
Spectrometry method is used to predict the BDEs
of the bond of diatomic molecules in gas phase. Mass
spectrometry is a powerful tool for the study of
molecular thermochemistry. There are several mass
spectrometry methods used to investigate in
molecular thermochemistry such as electron impact,
guided ion beam, high pressure, photoionization mass
spectrometry and so on [9, 15, 17]. Photoionization
mass spectrometry uses a tunable light source to
dissociatively ionize a target species and measures ion
intensities versus photon energy and this method is
widely used for the X‒H bond [9].
2.2. Computational methods
In computational approach, the homolytic X‒H bond
dissociation enthalpies at 298.15 K and 1 atm for the
VJC, 55(6), 2017 Review. Bond dissociation enthalpies in benzene
681
AXH molecule can be estimated from the
expression.
BDE(X‒H) = Hf(AX ) + Hf(H ) – Hf(AXH) (1) (1)
Where Hf
’
s
are the enthalpies of the different species
at 298.15 K and 1 atm. The enthalpy of each species
was calculated from the following equation:
Hf = E0 + ZPE + Htrans + Hvib + Hrot + RT (2)
Where ZPE is zero point energy, Htrans, Hvib, Hrot are
the standard temperature correction term calculated
with the equilibrium statistical mechanics with
harmonic oscillator and rigid rotor approximation.
In this review, the computational calculations for
thiophenols, phenylphosphines, toluenes were
performed using the Gaussian 03 software and the
computational calculations for phenols,
benzeneselenols and phenylsilanes were newly
carried out using Gaussian 09 software [18].
2.3. Benchmark the computational methods for
determining BDE
Based on the equations (1) and (2), a larger number of
theoretical studies have been carried out over the last
decade to assess the accuracy of the computational
procedures for predicting the BDE [13, 14, 19-42].
Radom and coworkers [28, 43] investigated the
performance of a variety of theoretical methods for
the calculation of radical stabilization energies of six
substituted methyl and vinyl radicals. The conclusion
confirmed that UHF (unrestricted Hatree Fock) and
PMP (Projected Møller-Plesset) performed poorly for
radicals with significant spin contamination in the
wave function. On the other hand, the calculation
using RMP2/6-311+G(2df,p) single point energies
were computationally inexpensive. The results for
BDE using several composite methods like
CBSRAD, G3(MP2)-RAD and the high level G2
[44], CBS-4 [44], W1
’
showed the reasonable
agreement with the experimental values. Guo and
coworkers applied ONIOM-G3B3 method to predict
the bond dissociation enthalpies (BDEs) of coenzyme
Q, flavonoids, olives, curcumins, indolinonic
hydroxylamines, phenothiazines, edaravones and
antioxidants used as food additives as well as the C‒
H and N‒H BDEs of ribonucleosides and
deoxyribonucleosides [31, 34]. Especially, the DFT
are now capable of providing excellent agreement
with benchmark binding energies of a variety of
dimers systems [45]. It also appears obligatory to use
the DFT methods which can dramatically decrease
the CPU time vs. ab initio methods of similar
accuracy [42]. In 1999, Dilabio and Pratt tested three
DFT based procedures to evaluate the BDE for a
variety of molecules containing C‒H, O‒H, N‒H and
S‒H. The results showed that ROB3LYP/6-
311++G(2d,2p)/AM1; ROB3LYP/6-
311++G(2d,2p)//(U)MP2(fu)/6-31G(d)/HF/6-31G(d)
and ROB3LYP/6-311++G(2d,2p)//(U)B3LYP/6-
31G(d)/B3LYP/6-31G(d) can generate the BDEs of
these bonds with the accuracy of 1.0 to 2.0 kcal/mol
[46].
The recent studied on phenol [47], thiophenol,
[29] benzeneselenol [48], phenylphosphine [49] and
toluene [50] and have showed that calculations with
ROB3LYP/6-311++G(2df,2p)/B3LYP/6-311G(d,p)
procedure using Gaussian suit of program can
predict the BDEs of O‒H, S‒H, Se‒H, P‒H and C‒
H with the accuracy within 1‒2 kcal/mol. To
validate this procedure, a number of small
compounds have been calculated and benchmarked.
In case of S‒H bond, the BDE(S‒H) of two model
systems namely H2S and CH3SH for which exact
experimental results are known were calculated and
compared. The calculated BDE(S‒H) values for H2S
and CH3SH are 91.5 and 86.8 kcal/mol [29],
respectively, which are very close to the
experimental values of 91.2 0.7 kcal/mol for the
former and 87.4 0.5 kcal/mol for the latter molecule
[15]. A set of small compounds in which the central
atoms belong to the group VA including PH3, NH3,
and AsH3 were calculated using different DFT
methods with a variety of basis set then being
compared with the results at CCSD(T) and MP2
with a larger basis set such as aug-cc-pvTZ. The
sequential results for BDE(P‒H), BDE(N‒H) and
BDE(As‒H) based on ROB3LYP/6-311++G(2df,2p)
are 81.3, 107.4 and 76.1 kcal/mol, being very
agreement with the experimental data of 83.9 0.5;
108.0 0.3 and 76.3 0.2 kcal/mol [15], respectively.
Moreover, the calculated results for BDEs using
several density functionals like B3P86, B3PW91 and
O3LYP at the same basis set of 6-311++G(2df,2p)
based on the optimized structures and frequency
calculations at B3LYP/6-311G(d,p) have been
evaluated for a variety of compounds having P‒H,
N‒H, As‒H, C‒H bonds. In fact, the ROB3LYP/6-
311++G(2df,2p)//B3LYP/6-311G(d,p) procedure
could be used as an accurate model for determining
the bond strength of various types of bonds in
organic molecules [48-52].
VJC, 55(6), 2017 Pham Cam Nam et al.
682
3. THE ROB3LYP/6-311G(2DF,2P)/B3LYP/6-
311G(D,P) CALCULATED FOR X‒H BOND IN
BENZENE DERIVATIVES
3.1. The homolytic X‒H bond dissociation
enthalpies of C6H5X‒H (X = O, S, Se, NH, PH,
CH2, SiH2)
Very recently, BDEs were computed for a variety of
bonds in aromatic compounds such as C6H5X‒H
where X = O, S, Se, NH, PH, CH2 and SiH2. In
terms of predicting the reliable values of BDEs, the
computational procedure of B3LYP/6-
311++G(2df,2p)//B3LYP/6-311G(d,p) could be used
as an accurate model. First, in this section, once
again we reviewed the validation of this
computational procedure for calculating the
BDE(X‒H) of phenol, thiophenol, benzeneselenol,
aniline, benzenephenylphosphine, toluene and
phenylsilane. The calculated BDE(X‒H) values (X =
O, S, Se, NH2, PH2, CH3, SiH3) are given in Table 1
along with the available experimental values. It
should be noted that there are a number of
experimental values for the studied aromatic
compounds and these estimated values vary in a
wide range. Therefore, the analysis as well as the
comparison with the available experimental values
are necessary for reconfirming the efficacy of
ROB3LYP/6-311++G(2df,2p)//B3LYP/6-311G(d,p)
procedure. First, the calculated BDE(O‒H) for
phenol using ROB3LYP/6-311++G(2df,2p) based
on the optimized structure at B3LYP/6-311G(d,p) is
87.5 kcal/mol, being very close to the experimental
value of 87.3 1.5 kcal/mol measured using
photoacoustic calorimetry (TR-PAC) [53]. Although
there are several experimental values of the O‒H
BDE, varying within a wide range from 84.4
kcal/mol to 91.0 kcal/mol, [15, 21, 53-64] but the
recommended data for BDE(O‒H) of phenol is 88.0
1.5 kcal/mol [15] which is larger than that in this
study about 1.5 kcal/mol. It should be indicated that
the ROB3LYP usually raises the BDE to be close
the accurate values than the UB3LYP. The predicted
value of BDE(O‒H) for phenol using UB3LYP/6-
311++G(2d,2p)/B3LYP/6-311G(d,p) was 82.2
kcal/mol [65] which is underestimated the
experimental value. In case of thiophenol, the
experimental BDE(S-H) values also vary within in a
wide range of 79.4 to 83.5 kcal/mol [66-70]. The
most recent value (83.4 kcal/mol) was determined
from the time resolved photoacoustic calorimetry
(TR-PAC) experiment by dos Santos et al. [71]. It
should be noted here the margin of error is very
large up to 4 kcal/mol in this measurement. The
calculated BDE(S‒H) in this review is very close to
that estimated by Venimadhavan et al. (79.4
kcal/mol) [68]. Especially for BDE(Se‒H) of
benzeneselenol, there is a larger deviation between
the calculated value using ROB3LYP/6-
311++G(2df,2p) given in Table with the
experimental values. This can be explained on the
basis of the existence of two lower lying electronic
states of C6H5S radical, namely
2A’ and 2A and the
calculated BDE(Se‒H) in table 1 is predicted for the
latter one.
Table 1: The calculated BDE(X‒H) of C6H5XH (X = O, S, Se, NH, PH, CH2, SiH2) using
ROB3LYP/6-311++G(2df,2p)//B3LYP/6-311G(d,p)
X Calculated values (in kcal/mol) Experimental values
a
(in kcal/mol)
O 87.5
89.5 1.0; 88.3 1.5; 88.0 1.5; 87.3 1.5 [10, 53]
S 79.5
83.3 2; 79.4 [68]; 80.0; 80.8; 83.5 1.1
Se 73.5 67.0; 78.0 4.0
N 92.4
b
88.0 2.0; 92.3; 89.1; 89.7
P 76.3
N/A
C 89.4 87.9 1.5; 88.1 2.2; 88.6; 88.5 1.5; 89.6 1.0
Si 89.6
b
88.2 [17]
a
All experimental values can be found in Ref. [15] and references therein. For specific values, references are given right
behind.
b
in this work.
For aniline, our calculated BDE(N‒H) is 92.4
kcal/mol, larger than those experimental values of
89.1 and 89.7 kcal/mol using pulse radiolysis and
photoacoustic calorimetry, respectively [15, 72, 73].
However our predicted value is close to value of
92.3 kcal/mol determined by Bordwell et al using
the measured pKa of aniline (C6H5NH2) in DMSO
and oxidation potential (Eox) of aniline anion
(C6H5NH) [72, 74]. Our estimated value is 1.0
kcal/mol slightly larger than that reported by Guo
VJC, 55(6), 2017 Review. Bond dissociation enthalpies in benzene
683
and coworker using G3 method [31] and Gomes et
al using B3LYP methods [75]. For
phenylphosphine, although no experimental value
for BDE(P‒H) is available, using the same
procedure for calculation, the value should be 76.3
kcal/mol.
The ROB3LYP calculated BDE(C‒H) in CH3
group of toluene is reported to be 89.4 kcal/mol,
which is very close to the recent experimental value
of 88.5 1.5 kcal/mol [15]. The Si‒H BDE of
phenylsilane was calculated using ROB3LYP/6-
311++G(2df,2p) method to be 89.6 kcal/mol. This
value is of 1.4 kcal/mol higher than the experimental
value 88.2 kcal/mol at 298.15 K [17]. However, the
predicted values using unrestricted B3LYP with
small basis set of 6-311G(d,p) and restricted MP2 at
the 6-311++G(d,2p) are underestimated the
experimental values.
Similar underestimation of BDEs was also found
in number of former study not only for silane
centered radicals but also for oxygen-, sulfur-,
carbon-, and phosphine centered radicals. This leads
to a critical conclusion that ROB3LYP appears to be
the best choice for estimating the BDE of
compounds containing X‒H bonds.
3.2. The homolytic BDE(X‒H) of a series of para
and meta substituted Y-C6H5X‒H (X = O, S, Se,
NH, PH, CH2, SiH2 and Y = H, F, Cl, CH3, OCH3,
NH2, CF3, CN and NO2)
In fact, this procedure has been further developed
and applied on various types of bonds. We
subsequently presented the calculated results based
on this model for a series of benzene derivatives
described in figure 1.
Figure 1: Benzene derivatives and their related
substituents
The calculated BDE(X‒H) of 4Y-C6H4X‒H and
3Y-C6H4X‒H (X = O, S, Se, NH, PH, CH2, SiH2)
are also given in tables 2 and 3, respectively. It is
also interesting to observe how the BDE(X‒H) value
changes with the change of substituent at the para
and meta position of the benzene ring.
Table 2: The ROB3LYP/6-311++G(2df,2p)//B3LYP/6-311G(d,p) calculated BDE(X‒H) of 4Y-C6H4X‒H
Substituent
Y
BDE(X‒H) (kcal/mol)
O‒H S‒H Se‒H N‒H P‒H C‒H Si‒H
H 87.5 79.5 73.5 92.4 76.3 89.8 89.6
F 85.4 77.8 73 91.0 76.3 89.8 89.7
Cl 86.1 78 73.3 91.9 76.2 89.6 89.6
CH3 85.1 77.5 72.7 90.8 76 89.4 89.5
OCH3 81.3 75.9 71.4 88.3 75.7 88.9 89.5
NH2 77.9 74.1 70 85.9 75 88.1 89.2
CF3 90.4 81.3 75.4 95 76.7 90.1 89.6
CN 89.4 81.4 75.3 95 76.5 89.4 89.4
NO2 91.7 82.5 76.4 96.5 76.9 89.3 89.3
Table 3: The ROB3LYP/6-311++G(2df,2p)//B3LYP/6-311G(d,p) calculated BDE(X‒H) of 3Y-C6H4X‒H
Substituent
Y
BDE(X‒H) (kcal/mol)
O‒H S‒H Se‒H N‒H P‒H C‒H Si‒H
H 87.5 79.5 73.5 92.4 76.3 89.8 89.6
F 88.4 80.3 74.5 93.5 76.5 90.1 89.7
Cl 88.4 80.3 74.4 93.6 76.5 90.1 89.7
CH3 86.9 79.3 73.5 92.0 76.2 89.7 89.0
OCH3 86.1 79.0 74.2 93.2 76.5 90.2 89.7
NH2 86.9 79.3 73.5 92.1 76.3 89.9 89.6
CF3 89.5 80.6 74.9 94.7 76.7 90.3 89.7
CN 90.3 81.1 74.7 94.9 76.9 90.6 89.8
NO2 90.7 81.4 75.2 95.2 77.1 90.6 89.8
VJC, 55(6), 2017 Pham Cam Nam et al.
684
3.2.1. X belongs to class O category
From the columns containing data for BDE of O‒H,
S‒H, Se‒H, N‒H and P‒H bond of Table 4, it can
be observed that the effect of electron donating
group (EDG) and electron withdrawing group
(EWG) is opposite. Strong electronic donating
substituents like OCH3 and NH2 at the para position
result in sharp decrease for the BDE(X‒H), except
for X = P. For EWG, there is also an increase of the
X‒H BDE in which a larger enhancement is found
for p-NO2. The change of the BDEs also depends on
the nature of X atom and can be placed in the order
O > N > S > Se > P.A similar change of BDE values
in Table 5 is also found when a substituent is at the
meta position. A dramatically BDE(X‒H) decrease
with the presence of electron donating group (EDG)
was found when X is N. In case of O, S and Se the
difference between the parents and the
corresponding meta substituted derivatives is within
0.0-1.5 kcal/mol. For EDG, the change is more
pronounce with the increase of BDE about 1.1‒4.1
kcal/mol. However, when X is P, the substituent
effect is not meaningful with the change is less than
1 kcal/mol for both EDG and EWG.
3.2.2. X belongs to class S category
The change of X‒H BDE of two series of aromatic
compounds, Y-C6H4X‒H with X is C or Si with that
of the parent one C6H5X‒H is presented in the two
last columns of tables 4 and 5. It is clear from the
BDE values in table 4 that the effect of para
substituents on the BDE(C‒H) value of toluene and
BDE(Si‒H) of phenylsilane are not very significant,
except for the strong EDGs, like NH2. For meta
substitution, the effect of substituents on X‒H BDE
is almost trivial (yable 5). It is apparent that the para
substituents on toluenes and phenylsilanes have
different effects than that observed for phenols and
anilines. However, the meta substituent effect on the
BDE(C‒H) or BDE(Si‒H) follows the same pattern
as that is observed for phenols and anilines.
Table 4: The change of BDE(X‒H) of 4Y-C6H4X‒H upon para substitution (in kcal/mol)
Y
para substituents: 4Y-C6H4X‒H
O‒Ha S‒-Hb Se‒Hc N‒Hd P‒He C‒Hf Si‒Hd
H 0.0 0.0 0 0 0.0 0.0 0.0
F -2.1 -1.7 -0.5 -1.4 0.0 0.0 0.1
Cl -1.4 -1.5 -0.3 -0.5 -0.1 -0.2 0.0
CH3 -2.4 -2.0 -0.8 -1.6 -0.3 -0.4 -0.1
OCH3 -6.2 -3.6 -2.1 -4.1 -0.6 -0.9 -0.1
NH2 -9.6 -5.4 -3.5 -6.5 -1.3 -1.7 -0.4
CF3 2.9 1.8 1.9 2.6 0.4 0.3 0.0
CN 1.9 1.9 1.8 2.6 0.2 -0.4 -0.2
NO2 4.2 3.0 2.8 4.1 0.6 -0.5 -0.3
a,b,c,e,f
Data taken from Refs. [47], [29], [48], [49], [50], respectively;
d
In this work
The change of BDE4Y = BDE(X‒H) of 4Y-C6H4XH - BDE(X‒H) of C6H5XH.
Table 5: The change of BDE(X‒H) of 3Y-C6H4X‒H upon meta substitution (in kcal/mol)
Y
meta substituents: 3Y-C6H4X‒H
O‒Ha S‒Hb Se‒Hc N‒Hd P‒He C‒Hf Si‒Hd
H 0.0 0.0 0.0 0.0 0.0 0.0 0.0
F 0.9 0.8 1.0 -1.2 0.2 0.3 0.1
Cl 0.9 0.8 0.9 -0.5 0.2 0.3 0.1
CH3 -0.6 -0.2 0.0 -0.5 -0.1 -0.1 -0.6
OCH3 -1.4 -0.5 0.7 -3.9 0.2 0.4 0.1
NH2 -0.6 -0.2 0.0 -6.0 0.0 0.1 0.0
CF3 2.0 1.1 1.4 1.7 0.4 0.5 0.1
CN 2.8 1.6 1.2 2.4 0.6 0.8 0.2
NO2 3.2 1.9 1.7 4.1 0.8 0.8 0.2
a,b,c,e,f
Data taken from Refs. [47], [29], [48], [49], [50], respectively;
d
In this work
The change of BDE3Y = BDE(X‒H) of 3Y-C6H4XH - BDE(X‒H) of C6H5X.
VJC, 55(6), 2017 Review. Bond dissociation enthalpies in benzene
685
4. SUBSTITUENT EFFECTS AND HAMMETT
EQUATION
Substituent effects are among the most important
structural effects influencing the chemical, physical
and biological properties of a chemical species. The
substituent is a small part of molecule which can be
introduced by a simple chemical operation,
particularly when it replaces a hydrogen atom. The
substituent modified the properties of the molecule
but does not alter its general character. The
substituent effects are always an attractive subject
for chemists [5, 12, 47].
The Hammett equation and its extended forms
have been one of the most widely used means for the
study and interpretation of organic reactions and
their mechanisms [78, 79]. Almost every kind of
organic reaction has been treated via Hammett
equation or its modified forms, Hammett proposed
that there is a relationship between the rate of a
reaction and the equilibrium constant. As a result,
the correlation of Hammett’s substituent constant
with bond dissociation enthalpies has also been
found [12, 76, 78, 80].
Under this regard, the substituent constant at
the reaction site of para and meta is usually
discussed in terms of the stability of the radical
which is generated from the parent molecule.
Figure 2 shows that the BDE(X‒H) when
substituent is placed at the para position of the
aromatic ring depends strongly on the nature of
substituent and the effect is much less in the case of
meta site. Indeed, the correlation of original
Hammett ( ) becomes poorer when the substituents
were conjugated with the reaction center. This
problem was resolved by defining a new constant.
Actually, depending on the hetero atom e.g. O, S,
Se, N, P, C, Si, a suitable modified Hammett
parameter has been chosen for such correlation [4,
6]. For example, in case of phenols and anilines,
when a lone pair of electrons on the O and N atom
could be delocalized on the substituents like p-CN
and p-NO2 a modified Hammett ‒is proposed. On
the other hand, a modified Hammett
+
proposed by
Brown and his colleagues is used when substituents
conjugated with a reaction center which could
effectively delocalized and since it accounts for
through conjugation effects, which will be important
for electron-donor groups at the para position. In the
case of meta substituents, the m
+
and m values are
found to be virtually the same [47].
4.1. Correlation between Hammett constants and
BDE(X‒H), in which X belongs to class O
category
Figure 2 shows a Hammett’s plot for the BDE(X‒H)
values of para 4Y-C6H4X-H (X = O, S, Se, N, P)
and p
+
. The p
+
values were taken from the
compilations of Hammett parameters by Hansch,
Leo and Taft [78].
The obtained equations from such correlations
between the modified Hammett constants (
+
p and
m) and the BDE(X‒H) at the para and meta of Y-
C6H4X‒H (X = O, S, Se, NH, PH) can be express as
follow:
(a) (b)
Figure 2: Plot of BDE(X‒H) of the 4Y-C6H4X‒H and 3Y-C6H4X‒H (X = O, S, Se, NH and PH) with the
Hammett constant p
+
and m, respectively
For 4Y-C6H4X‒H:
Phenol: BDE(O‒H) = 6.2559 p
+
+ 86.290 R
2
= 0.9714 (3)
VJC, 55(6), 2017 Pham Cam Nam et al.
686
Thiophenol: BDE(S‒H) = 3.8817 p
+
+ 78.792 R
2
= 0.9492 (4)
Benzeneselenol BDE(Se‒H) = 2.8876 p
+
+ 73.540 R
2
= 0.9740 (5)
Aniline BDE(N‒H) = 4.8444 p
+
+ 92.023 R
2
= 0.9823 (6)
Phenylphosphine BDE(P‒H) = 0.7976 p
+
+ 76.203 R
2
= 0.9449 (7)
For 3Y-C6H4X‒H:
Phenols: BDE(O‒H) = 4.8707 m + 87.055 R
2
= 0.8194 (8)
Thiophenols: BDE(S‒H) = 2.6924 m + 79.401 R
2
= 0.8797 (9)
Benzeneselenols: BDE(Se‒H) = 2.0705 m + 73.738 R
2
= 0.9252 (10)
Anilines; BDE(N‒H) = 3.9474 m + 95.502 R
2
= 0.9398 (11)
Phenylphosphines: BDE(P‒H) = 0.9284 m + 76.318 R
2
= 0.8742 (12)
The R-squared is a statistical measure of how
close the data are to the fitted regression line. The
higher the R-squared, the better the model fits the
data. Based on the equations (3) to (12), an
impressive linear correlation (R
2
0.97) is observed
between the BDE(X‒H) and p
+
for benzeneselenols
(R
2
= 0.9735), phenols (R
2
= 0.9714) and
thiophenols (R
2
= 0.95). The BDE(X‒H) values of
this group increase with the increasing electron
withdrawing ability of the substituent (i.e. higher
value for p
+
especially with X has a lone pair of
electron like O, S and Se. For example, when X = O,
S and Se, the BDE(X‒H)s increase with the amount
of 4.20, 3.01 and 2.84 kcal/mol, respectively.
The
existence of an electron lone pair at the spin centered
atom make the radical stabilized by EWG but
destabilized by EDG [47, 77, 78]. For instance, the
EDGs like CH3, OCH3, NH2 reduce the BDE(O‒H)s
with the amount of 2.40, 6.20 and 9.60 kcal/mol,
respectively due to the destabilization of the radicals
generated from the parent aromatic derivatives. In
the meantime, the substituents also affect in the
stability the ground state. To further understand the
effect of a substituent on the strength of the X‒H
bond, the ground state effect (GE) and radical effect
(RE) can be calculated from the exchange reactions
between benzeneselenols and related species in
figure 3 [48].
Figure 4 illustrates the change of BDE values
based on the calculated GE and RE for Y-C6H4SeH.
In both radicals and parents, the effect of F and Cl is
insignificant and the total effect (TE = RE-GE) is
very small. EWGs at para position tend to stabilize
the parents but not the radicals. However, the latter
parameter is larger thus leading to the negative TE
value. For EDGs, an opposite trend is observed for
the radical stability and the parent one. The RE
values are found to be larger than the GE
counterpart. Therefore the TE values remain
considerably positive [48].
4.2. Correlation between Hammett constants and
BDE(X‒H), in which X belongs to class S
category
Toluene and phenylsilane are the aromatic
compounds with methyl ( CH3) and silyl ( SiH3)
groups replacing one hydrogen in benzene ring
which are classified as the class S category. This is
due to methyl and silyl groups without any lone pair
and all electrons are used in single bonds with three
hydrogens and one carbon of benzene ring. Because
Figure 3: The exchange reactions for calculating GE and RE
(Reprinted from Ref. [48])
VJC, 55(6), 2017 Review. Bond dissociation enthalpies in benzene
687
Figure 4: Calculated GE and RE for 4Y-C6H4Se-H with Y = H, F, Cl, CH3, OCH3, NH2, CF3, CN, NO2.
(Reprinted from Ref. [48])
of the S pattern, both toluenes and phenylsilanes do
not inhibit of the good correlation between BDE(C‒
H) or BDE(Si‒H) with the Hammett constants. The
correlations between the Hammett p
+
and m
constants and BDE(C‒H)s and BDE(Si‒H)s in
substituted toluenes and phenylsilanes were
displayed in figure 5.
For para substitution, in case of toluene and
phenylsilane, the linear regressions between
BDE(X‒H)s (X = CH2 and SiH2) with p
+
shown in
figure 5 are very poor. However, for meta
substitution, the correlation is slightly better for C‒
H bond but still very poor for Si‒H bond. The
Hammett regression result for the BDE(C‒H)
changes verus m constant is expressed in equation
(13).
BDE(C‒H) = 0.9699x + 89.897 R2 = 0.8184 (13)
This leads to a conclusion that the direction and
magnitude of the effect of Y- substituents on the X‒
H bonds in 4Y- and 3Y-C6H4XH compounds have
some dependence on the polarity of the X‒H bond
undergoing homolytic dissociation [81].
Figure 5: Plot of BDE(X‒H) of the 4Y-C6H4X‒H and 3Y-C6H4X‒H (X = CH2, SiH2) with the Hammett
constant p
+
and m, respectively
VJC, 55(6), 2017 Pham Cam Nam et al.
688
5. CONCLUSION AND OUTLOOK
Up today, computational chemistry has evolved into
a powerful tool to be used to study in many areas. In
this review, the computational quantum chemical
methods based on B3LYP functional have been
applied to determine the bond dissociation
enthalpies of a variety of substituted benzenes
derivatives. In searching for suitable methods to be
used in the evaluation of BDEs, the good
performance of the density functional theory using
restricted open-shell formalism ROB3LYP at the
basis set of 6-311++G(2df,2p) in conjunction with
geometries optimized at the B3LYP/6-311G(d,p)
level has been demonstrated by its capacity to
reproduce the BDEs of a series of X‒H bond types
in a range of substituted aromatic compounds
YC6H4XH (X= O, S, Se, NH, PH, CH2 and SiH2; Y
= H, F, Cl, CH3, OCH3, NH2, CF3, CN and NO2).
The calculated BDEs of the studied benzene
derivatives have been reviewed and hence the model
chemistry of ROB3LYP/6-
311++G(2df,2p)//B3LYP/6-311G(d,p) is defined as
a convenient and economic manner, but with reliable
results as compared to available experimental values
with the accuracy of 1.0-2.0 kcal/mol.
Depending on the nature of centered atom X,
which is polar or non-polar, the behavior of
substituents at the para and meta position is quite
different. The success of correlation between
Hammett constants was found for substituted
benzene derivatives with hetero atom X belongs to
class “O” category including phenols, thiophenols,
benzeneselenols, anilines and phenylphosphines. In
contrast, the poor correlations are seen between
BDE values of the C‒H and Si‒H bonds in toluenes
and phenylsilanes, respectively with the Hammett
substituent constants at the para and meta position
of aromatic ring. Small effects of the Y-substituents
have similarly observed for both C‒H and Si‒H
bonds in substituted toluenes and phenylsilanes.
Acknowledgements. This research is funded by
Vietnam National Foundation for Science and
Technology Development (NAFOSTED) under grant
number “104.06-2016.03" (3/2017/104/HĐTN).
REFERENCES
1. Z. Rappoport. The Chemistry of Phenols, 2 Volume
Set: John Wiley & Sons; 2004.
2. K. Ingold: 60 Years of Research on Free Radical
Physical Organic Chemistry. In: The Foundations of
Physical Organic Chemistry: Fifty Years of the James
Flack Norris Award. ACS Publications, 223-250
(2015).
3. H. Yuzawa, M. Aoki, H. Itoh, H. Yoshida.
Adsorption and photoadsorption states of benzene
derivatives on titanium oxide studied by NMR, The
Journal of Physical Chemistry Letters, 2(15), 1868-
1873 (2011).
4. S. P. Pogorelova, A. B. Kharitonov, I. Willner, C. N.
Sukenik, H. Pizem, T. Bayer. Development of ion-
sensitive field-effect transistor-based sensors for
benzylphosphonic acids and thiophenols using
molecularly imprinted TiO2 films, Analytica chimica
acta, 504(1), 113-122 (2004).
5. R. S. Sengar, V. N. Nemykin, P. Basu. Electronic
properties of para-substituted thiophenols and
disulfides from
13
C NMR spectroscopy and ab initio
calculations: relations to the Hammett parameters
and atomic charges, New Journal of Chemistry,
27(7), 1115-1123 (2003).
6. I. E. H.-G. Franck, J. W. Stadelhofer. Production and
uses of benzene derivatives. In: Industrial Aromatic
Chemistry, Springer, 132-235 (1988).
7. S. W. Benson. Thermochemical kinetics, Wiley,
1976.
8. IUPAC. Compendium of Chemical Terminology, 2nd
ed. In. Blackwell Scientific Publications, Oxford
1997.
9. S. J. Blanksby, G. B. Ellison. Bond dissociation
energies of organic molecules, Accounts of chemical
research, 36(4), 255-263 (2003).
10. J. H. Wang, D. Domin, B. Austin, D. Y. Zubarev, J.
McClean, M. Frenklach, T. A. Cui, W. A. Lester. A
Diffusion Monte Carlo Study of the O-H Bond
Dissociation of Phenol, Journal of Physical
Chemistry A, 114(36), 9832-9835 (2010).
11. L. A. Curtiss, J. A. Pople. Recent Advances in
Computational Thermochemistry and Challenges for
the Future. . In: National Research Council (US)
Chemical Sciences Roundtable. Impact of Advances
in Computing and Communications Technologies on
Chemical Science and Technology: Report of a
Workshop. Washington (DC). National Academies
Press (US), 26-34 (1999).
12. T. M. Krygowski, B. T. Stepień. Sigma-and pi-
electron delocalization: focus on substituent effects,
Chemical reviews, 105(10), 3482-3512 (2005).
13. E. R. Johnson, O. J. Clarkin, G. A. DiLabio. Density
Functional Theory Based Model Calculations for
Accurate Bond Dissociation Enthalpies. 3. A Single
Approach for X−H, X−X, and X−Y (X, Y = C, N, O,
S, Halogen) Bonds, The Journal of Physical
Chemistry A, 107(46), 9953-9963 (2003).
14. X. -Q. Yao, X. -J. Hou, H. Jiao, H. -W. Xiang, Y. -
W. Li. Accurate calculations of bond dissociation
enthalpies with density functional methods, The
VJC, 55(6), 2017 Review. Bond dissociation enthalpies in benzene
689
Journal of Physical Chemistry A, 107(46), 9991-9996
(2003).
15. Y. -R. Luo. Handbook of bond dissociation energies
in organic compounds: CRC press (2002).
16. J. Kerr. Bond dissociation energies by kinetic
methods, Chemical reviews, 66(5), 465-500 (1966).
17. W. M. Haynes. CRC handbook of chemistry and
physics: CRC press (2014).
18. M. Frisch, G. Trucks, H. Schlegel, G. Scuseria, M.
Robb, J. Cheeseman, G. Scalmani, V. Barone, B.
Mennucci, G. Petersson. Gaussian 09, Revision A,
Gaussian, Inc., Wallingford CT (2009).
19. L. A. Curtiss, C. Jones, G. W. Trucks, K.
Raghavachari, J. A. Pople. Gaussian‐1 theory of
molecular energies for second‐row compounds, The
Journal of Chemical Physics, 93(4), 2537-2545
(1990).
20. L. R. Peebles, P. Marshall. High-accuracy coupled-
cluster computations of bond dissociation energies in
SH, H2S, and H2O, The Journal of Chemical Physics,
117(7), 3132-3138 (2002).
21. P. Mulder, H.-G. Korth, D.A. Pratt, G.A. DiLabio, L.
Valgimigli, G. Pedulli, K. Ingold. Critical re-
evaluation of the O−H bond dissociation enthalpy in
phenol, The Journal of Physical Chemistry A,
109(11), 2647-2655 (2005).
22. G. da Silva, C. -C. Chen, J. W. Bozzelli. Bond
dissociation energy of the phenol OH bond from ab
initio calculations, Chemical Physics Letters, 424(1),
42-45 (2006).
23. Y. Zhao, D.G. Truhlar, How well can new-generation
density functionals describe the energetics of bond-
dissociation reactions producing radicals?, The
Journal of Physical Chemistry A, 112(6), 1095-1099
(2008).
24. M. D. Wodrich, C. Corminboeuf, P. R. Schreiner,
A.A. Fokin, P.v.R. Schleyer. How accurate are DFT
treatments of organic energies?, Organic letters,
9(10), 1851-1854 (2007).
25. V. N. Staroverov, G. E. Scuseria, J. Tao, J. P.
Perdew. Comparative assessment of a new
nonempirical density functional: Molecules and
hydrogen-bonded complexes, The Journal of
Chemical Physics, 119(23), 12129-12137 (2003).
26. R. D. Bach, P. Y. Ayala, H. Schlegel. A reassessment
of the bond dissociation energies of peroxides. An ab
initio study, Journal of the American Chemical
Society, 118(50), 12758-12765 (1996).
27. C. Baciu, J. W. Gauld. An assessment of theoretical
methods for the calculation of accurate structures
and SN bond dissociation energies of S-nitrosothiols
(RSNOs), The Journal of Physical Chemistry A,
107(46), 9946-9952 (2003).
28. A. S. Menon, G. P. Wood, D. Moran, L. Radom.
Bond dissociation energies and radical stabilization
energies: An assessment of contemporary theoretical
procedures, The Journal of Physical Chemistry A,
111(51), 13638-13644 (2007).
29. A. K. Chandra, P. -C. Nam, M. T. Nguyen. The S−H
bond dissociation enthalpies and acidities of para
and meta substituted thiophenols: a quantum
chemical study, The Journal of Physical Chemistry A,
107(43), 9182-9188 (2003).
30. Y. Feng, L. Liu, J. -T. Wang, H. Huang, Q.-X. Guo.
Assessment of experimental bond dissociation
energies using composite ab initio methods and
evaluation of the performances of density functional
methods in the calculation of bond dissociation
energies, Journal of chemical information and
computer sciences, 43(6), 2005-2013 (2003).
31. M. -J. Li, L. Liu, Y. Fu, Q. -X. Guo. Development of
an ONIOM-G3B3 Method to Accurately Predict
C−H and N−H Bond Dissociation Enthalpies of
Ribonucleosides and Deoxyribonucleosides, The
Journal of Physical Chemistry B, 109(28), 13818-
13826 (2005).
32. X. -Q. Yao, X. -J. Hou, G. -S. Wu, Y. -Y. Xu, H. -W.
Xiang, H. Jiao, Y. -W. Li. Estimation of C−C bond
dissociation enthalpies of large aromatic
hydrocarbon compounds using DFT methods, The
Journal of Physical Chemistry A, 106(31), 7184-7189
(2002).
33. I. Y. Zhang, J. Wu, Y. Luo, X. Xu. Accurate bond
dissociation enthalpies by using doubly hybrid XYG3
functional, Journal of computational chemistry,
32(9), 1824-1838 (2011).
34. M. -J. Li, L. Liu, Y. Fu, Q. -X. Guo. Accurate bond
dissociation enthalpies of popular antioxidants
predicted by the ONIOM-G3B3 method, Journal of
Molecular Structure: THEOCHEM, 815(1), 1-9
(2007).
35. G. DiLabio, D. Pratt. Density Functional Theory
Based Model Calculations for Accurate Bond
Dissociation Enthalpies. 2. Studies of X−X and X−Y
(X, Y = C, N, O, S, Halogen) Bonds, The Journal of
Physical Chemistry A, 104(9), 1938-1943 (2000).
36. S. L. Khursan. Homodesmotic method of determining
the O-H bond dissociation energies in phenols,
Kinetics and Catalysis, 57(2), 159-169 (2016).
37. N. M. Khlestov, A. N. Shendrik. Quantum-chemical
DFT calculations of the energies of the O-H bond of
phenols, Theoretical and Experimental Chemistry,
46(5), 279-283 (2010).
38. C. Marteau, R. Guitard, C. Penverne, D. Favier, V.
Nardello-Rataj, J. M. Aubry. Boosting effect of ortho-
propenyl substituent on the antioxidant activity of
natural phenols, Food Chemistry, 196, 418-427
(2016).
39. M. S. Miranda, J. da Silva, J. F. Liebman. Gas-phase
thermochemical properties of some tri-substituted
phenols: A density functional theory study, Journal of
Chemical Thermodynamics, 80, 65-72 (2015).
VJC, 55(6), 2017 Pham Cam Nam et al.
690
40. C. A. McFerrin, R. W. Hall, B. Dellinger. Ab initio
study of the formation and degradation reactions of
chlorinated phenols, Journal of Molecular Structure-
Theochem, 902(1-3), 5-14 (2009).
41. J. Shi, S. Liang, Y. S. Feng, H. J. Wang, Q. X. Guo.
Heterocyclic analogs of phenol as novel potential
antioxidants, Journal of Physical Organic Chemistry,
22(11), 1038-1047 (2009).
42. H. -J. Wang, Y. Fu. Designing new free-radical
reducing reagents: Theoretical study on Si–H bond
dissociation energies of organic silanes, Journal of
Molecular Structure: THEOCHEM, 893(1), 67-72
(2009).
43. B. Chan, L. Radom. BDE261: a comprehensive set of
high-level theoretical bond dissociation enthalpies,
The Journal of Physical Chemistry A, 116(20), 4975-
4986 (2012).
44. P. R. Rablen, J. F. Hartwig. Accurate borane
sequential bond dissociation energies by high-level
ab initio computational methods, Journal of the
American Chemical Society, 118(19), 4648-4653
(1996).
45. J. Stewart. Reviews in Computational Chemistry,
Reviews of Computational Chemistry (1990).
46. G. DiLabio, D. Pratt, A. LoFaro, J. Wright.
Theoretical study of X−H bond energetics (X = C, N,
O, S): application to substituent effects, gas phase
acidities, and redox potentials, The Journal of
Physical Chemistry A, 103(11), 1653-1661 (1999).
47. A. K. Chandra, T. Uchimaru. The OH bond
dissociation energies of substituted phenols and
proton affinities of substituted phenoxide ions: A
DFT study, International Journal of Molecular
Sciences, 3(4), 407-422 (2002).
48. P. C. Nam, M. T. Nguyen. The Se–H bond of
benzeneselenols (ArSe-H): Relationship between
bond dissociation enthalpy and spin density of
radicals, Chemical Physics, 415, 18-25 (2013).
49. P. -C. Nam, M. T. Nguyen, A .K. Chandra. Effect of
Substituents on the P−H Bond Dissociation
Enthalpies of Phenylphosphines and Proton Affinities
of Phenylphosphine Anions: A DFT Study, The
Journal of Physical Chemistry A, 108(51), 11362-
11368 (2004).
50. P. -C. Nam, M. T. Nguyen, A. K. Chandra. The C− H
and α (C−X) Bond Dissociation Enthalpies of
Toluene, C6H5-CH2X (X = F, Cl), and Their
Substituted Derivatives: A DFT Study, The Journal of
Physical Chemistry A, 109(45), 10342-10347 (2005).
51. P. C. Nam, M. T. Nguyen, A. K. Chandra.
Theoretical Study of the Substituent Effects on the S−
H Bond Dissociation Energy and Ionization Energy
of 3-Pyridinethiol: Prediction of Novel Antioxidant,
The Journal of Physical Chemistry A, 110(37),
10904-10911 (2006).
52. Pham Thi Quynh Ty, P.C. Nam. (RO)B3LYP/6-
311++G(2df,2p)//B3LYP/6-311G(d,p): Reliable dft
methods for determining bond dissociation
enthalpies, Tạp chí Khoa học và Công nghệ đại học
Đà Nẵng (2011).
53. D. Wayner, E. Lusztyk, K. Ingold, P. Mulder.
Application of Photoacoustic Calorimetry to the
Measurement of the O−H Bond Strength in Vitamin
E (α-and δ-Tocopherol) and Related Phenolic
Antioxidants1, The Journal of organic chemistry,
61(18), 6430-6433 (1996).
54. D. Wayner, E. Lusztyk, D. Pagé, K. Ingold, P.
Mulder, L. Laarhoven, H. Aldrich. Effects of
solvation on the enthalpies of reaction of tert-butoxyl
radicals with phenol and on the calculated OH bond
strength in phenol, Journal of the American Chemical
Society, 117(34), 8737-8744 (1995).
55. V. F. DeTuri, K. M. Ervin. Proton transfer between
Cl
−
and C6H5OH. O H bond energy of phenol,
International Journal of Mass Spectrometry and Ion
Processes, 175(1-2), 123-132 (1998).
56. R. M. Borges dos Santos, J. A. Martinho Simões.
Energetics of the O–H bond in phenol and substituted
phenols: a critical evaluation of literature data,
Journal of Physical and Chemical Reference Data,
27(3), 707-739 (1998).
57. A. Colussi, F. Zabel, S. Benson. The very low‐
pressure pyrolysis of phenyl ethyl ether, phenyl allyl
ether, and benzyl methyl ether and the enthalpy of
formation of the phenoxy radical, International
Journal of Chemical Kinetics, 9(2), 161-178 (1977).
58. D. J. DeFrees, R. T. McIver Jr, W. J. Hehre. Heats of
formation of gaseous free radicals via ion cyclotron
double resonance spectroscopy, Journal of the
American Chemical Society, 102(10), 3334-3338
(1980).
59. F. Bordwell, J. P. Cheng, J. A. Harrelson. Homolytic
bond dissociation energies in solution from
equilibrium acidity and electrochemical data, Journal
of the American Chemical Society, 110(4), 1229-
1231 (1988).
60. J. A. Walker, W. Tsang. Single-pulse shock tube
studies on the thermal decomposition of n-butyl
phenyl ether, n-pentylbenzene, and phenetole and the
heat of formation of phenoxy and benzyl radicals,
Journal of Physical Chemistry, 94(8), 3324-3327
(1990).
61. M. Lucarini, P. Pedrielli, G.F. Pedulli, S. Cabiddu, C.
Fattuoni. Bond dissociation energies of O−H bonds
in substituted phenols from equilibration studies, The
Journal of organic chemistry, 61(26), 9259-9263
(1996).
62. F. G. Bordwell, W. -Z. Liu. Solvent effects on
homolytic bond dissociation energies of hydroxylic
acids, Journal of the American Chemical Society,
118(44), 10819-10823 (1996).
63. H. -T. Kim, R. J. Green, J. Qian, S. L. Anderson.
Proton transfer in the [phenol-NH3]
+
system: An
VJC, 55(6), 2017 Review. Bond dissociation enthalpies in benzene
691
experimental and ab initio study, The Journal of
Chemical Physics, 112(13), 5717-5721 (2000).
64. L. A. Angel, K. M. Ervin. Competitive threshold
collision-induced dissociation: Gas-phase acidity
and O−H bond dissociation enthalpy of phenol, The
Journal of Physical Chemistry A, 108(40), 8346-8352
(2004).
65. C. Marteau, R. Guitard, C. Penverne, D. Favier, V.
Nardello-Rataj, J. -M. Aubry. Boosting effect of
ortho-propenyl substituent on the antioxidant activity
of natural phenols, Food chemistry, 196, 418-427
(2016).
66. D. Armstrong, Q. Sun, R. Schuler. Reduction
Potentials and Kinetics of Electron Transfer
Reactions of Phenylthiyl Radicals: Comparisons with
Phenoxyl Radicals 1, The Journal of Physical
Chemistry, 100(23), 9892-9899 (1996).
67. D. F. McMillen, D. M. Golden. Hydrocarbon bond
dissociation energies, Annual Review of Physical
Chemistry, 33(1), 493-532 (1982).
68. S. Venimadhavan, K. Amarnath, N. G. Harvey, J. P.
Cheng, E. M. Arnett. Heterolysis, homolysis, and
cleavage energies for the cation radicals of some
carbon-sulfur bonds, Journal of the American
Chemical Society, 114(1), 221-229 (1992).
69. E. T. Denisov, T. Denisova: Handbook of
antioxidants: bond dissociation energies, rate
constants, activation energies, and enthalpies of
reactions, vol. 100: CRC press; 1999.
70. C. F. Correia, R. C. Guedes, R. M. B. dos Santos, B.
J. C. Cabral, J. A. M. Simões. O–H Bond dissociation
enthalpies in hydroxyphenols. A time-resolved
photoacoustic calorimetry and quantum chemistry
study, Physical Chemistry Chemical Physics, 6(9),
2109-2118 (2004).
71. R. M. Borges dos Santos, V. S. Muralha, C. F.
Correia, R. C. Guedes, B. J. Costa Cabral, J. A.
Martinho Simões. S−H bond dissociation enthalpies
in thiophenols: a time-resolved photoacoustic
calorimetry and quantum chemistry study, The
Journal of Physical Chemistry A, 106(42), 9883-9889
(2002).
72. Q. Zhu, X. -M. Zhang, A. J. Fry. Bond dissociation
energies of antioxidants, Polymer Degradation and
Stability, 57(1), 43-50 (1997).
73. M. Jonsson, J. Lind, T. E. Eriksen, G. Mereny. Redox
and acidity properties of 4-substituted aniline radical
cations in water, Journal of the American Chemical
Society, 116(4), 1423-1427 (1994).
74. F. Bordwell, X. M. Zhang, J. P. Cheng. Bond
dissociation energies of the nitrogen-hydrogen bonds
in anilines and in the corresponding radical anions.
Equilibrium acidities of aniline radical cations, The
Journal of Organic Chemistry, 58(23), 6410-6416
(1993).
75. J. R. Gomes, M. D. Ribeiro da Silva, M. A. Ribeiro
da Silva. Solvent and Structural Effects in the N−H
Bond Homolytic Dissociation Energy, The Journal of
Physical Chemistry A, 108(11), 2119-2130 (2004).
76. F. G. Bordwell, J. Cheng. Substituent effects on the
stabilities of phenoxyl radicals and the acidities of
phenoxyl radical cations, Journal of the American
Chemical Society, 113(5), 1736-1743 (1991).
77. Z. Li, J. -P. Cheng. A Detailed Investigation of
Subsitituent Effects on N−H Bond Enthalpies in
Aniline Derivatives and on the Stability of
Corresponding N-Centered Radicals, The Journal of
organic chemistry, 68(19), 7350-7360 (2003).
78. C. Hansch, A. Leo, R. Taft. A survey of Hammett
substituent constants and resonance and field
parameters, Chemical reviews, 91(2), 165-195
(1991).
79. O. Exner, S. Böhm. Background of the Hammett
Equation As Observed for Isolated Molecules: Meta-
and Para-Substituted Benzoic Acids, The Journal of
Organic Chemistry, 67(18), 6320-6327 (2002).
80. K.-S. Song, L. Liu, Q. -X. Guo. Remote Substituent
Effects on N−X (X = H, F, Cl, CH3, Li) Bond
Dissociation Energies in P ara-Substituted Anilines,
The Journal of Organic Chemistry, 68(2), 262-266
(2003).
81. Y. -H. Cheng, X. Zhao, K. -S. Song, L. Liu, Q. -X.
Guo. Remote Substituent Effects on Bond
Dissociation Energies of Para-Substituted Aromatic
Silanes, The Journal of Organic Chemistry, 67(19),
6638-6645 (2002).
Corresponding author: Pham Cam Nam
Department of Chemistry, The University of Danang
University of Science and Technology
54, Nguyen Luong Bang, Danang City, Viet Nam
E-mail: pcnam@dut.udn.vn; Telephone: +84 987873154.
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