A Density Functional Theory Study on LewisAcid-Catalyzed Transesterification of b-Oxodithioesters

Xiaokang Guo, Lihui Chen, Yanyan Zhu, Anqi Zhang, Donghui Wei,*and Mingsheng Tang*

The detailed mechanisms of the Lewis acid-catalyzed transes-

terification of b-oxodithioesters at a solvent-free condition

were studied using density functional theory. Five possible

reaction pathways, including one noncatalyzed (channel 1)

and four Lewis acid-catalyzed channels (SnCl2-catalyzed

channels 2 and 3 and SnCl2�2H2O-catalyzed channels 4 and

5), were investigated. Our calculated results indicate that the

energy barriers of the catalyzed channels are significantly

lower than that of channel 1. Channel 5, which has an

energy barrier of 33.70 kcal/mol as calculated at the B3LYP/

[6-31G(d, p)1LANL2DZ] level, is the most energy-favorable

channel. Moreover, one water molecule of SnCl2�2H2O par-

ticipated in the transesterification in channel 5. Thus, we

report a novel function of the SnCl2�2H2O catalyst, which is

quite different from the function of the conventional nonhy-

drated Lewis acid SnCl2. To understand the function of these

two Lewis acid catalysts better, the global reactivity indexes

and natural bond orbital charge were analyzed. This work

helps in understanding the function of the Lewis acid in

transesterification, and it can provide valuable insight for the

rational design of new Lewis acid catalysts. VC 2014 Wiley

Periodicals, Inc.

DOI: 10.1002/qua.24669

Introduction

Transesterification is commonly used in modifying the alkoxy

group of an ester into a new target functional group.[1–3]

Moreover, this method is more convenient than direct ester

synthesis from carboxylic acids and alcohols, because specific

carboxylic acids have poor solubility in organic solvents, which

leads to low reactant concentrations and obstructs homogene-

ous esterification.[4]

The transesterification of b-ketoesters has been a pervasive

approach in organic synthesis.[5–7] Methyl and ethyl b-ketoesters

are usually used as starting materials in transesterification because

they are readily or commercially available, whereas their other

counterparts can be a variety of alcohols.[8–10] Generally, transes-

terification does not occur without the presence of strong acids or

bases (corresponding to harsh conditions) and is very wasteful,

which does not meet the requirements of modern synthetic and

green chemistry.[4] Therefore, significant efforts have been dedi-

cated to the design of effective and highly chemoselective and

stereoselective catalysts, such as montmorillonite (MMT)-clay-

exchanged sulphonic acid,[11] iodine,[12] silica-based hybrid materi-

als,[13–16] K5CoW12O40�3H2O,[17] zinc(II) oxide,[3] lanthanum(III),[18]

CeO2,[19] and ionic liquid-regulated sulfamic acid.[20]

Recently, Devi et al. reported a novel and efficient method for

the facile transesterification of b-oxodithioesters promoted by

SnCl2 at a solvent-free condition (Scheme 1).[15] The short reac-

tion time, mild condition, good yields, and inexpensive catalysts

are the attractive features of this method. In their work, the ini-

tial transesterification of different methyl b-oxodithioesters with

various alcohols was performed in the presence of 5 mol%

SnCl2. SnCl2�2H2O was selected as the optimized catalyst in the

reaction thereafter. However, the detailed mechanisms of the

transesterification are still unclear, and several questions remain

unanswered. For example, how can the reaction occur? How do

Lewis acid catalysts complex with b-oxodithioesters? What is the

function of the catalyst? Why does SnCl2�2H2O work better than

SnCl2? All of the above questions prompted us to conduct a

theoretical study on the detailed mechanisms of the reaction.

In this study, we chose the Lewis acid-catalyzed transesterifi-

cation of methyl b-oxodithioester (R1, depicted in Scheme 1)

with 1-butanol (R2, depicted in Scheme 1) to generate n-butyl

b-oxothionoester (P1, depicted in Scheme 1) and methanethiol

(P2, depicted in Scheme 1) as our research subject. The den-

sity functional theory (DFT) approach (which has been widely

used in the study of reaction mechanisms[16],[21–38]) was also

used to investigate the detailed reaction mechanisms. More-

over, to understand the functions of these two Lewis acid cat-

alysts better, global reactivity indexes (GRI) and natural bond

orbital (NBO) charge analyses[39–43] were also performed.

Computational Details

All theoretical calculations were performed using Gaus-

sian09.[44] The geometrical structures of all stationary points

X. Guo, L. Chen, Y. Zhu, A. Zhang, D. Wei, M. Tang

Center of Computational Chemistry, College of Chemistry and Molecular

Engineering, Zhengzhou University, Zhengzhou, Henan 450001, People’s

Republic of China

E-mail: donghuiwei@zzu.edu.cn (D. Wei) or

E-mail: mstang@zzu.edu.cn (M. Tang)

Contract/grant sponsor: The National Natural Science Foundation of China;

contract/grant numbers: 21303167, J1210060.

Contract/grant sponsor: The China Postdoctoral Science Foundation; con-

tract/grant number: 2013M530340.

VC 2014 Wiley Periodicals, Inc.

862 International Journal of Quantum Chemistry 2014, 114, 862–868 WWW.CHEMISTRYVIEWS.ORG

FULL PAPER WWW.Q-CHEM.ORG

were optimized at the B3LYP/[6-31G(d, p)1LANL2DZ] level.[45–47]

The B3LYP method consists of Becke’s three parameter hybrid

exchange function combined with the Lee–Yang–Parr correla-

tion function. The basis set used in this article was [6-31G(d,

p)1LANL2DZ], which included the Los Alamos effective core

potential plus double zeta basis set for Sn and the 6-31G(d, p)

basis set for the other atoms. The corresponding vibrational

frequencies were performed at the optimized geometry of

each reactant, product, transition state, and intermediate at

the same level to take into account the zero-point vibrational

energy. We confirmed that all the reactants and intermediates

have no imaginary frequencies, and each transition state has

only one imaginary frequency. In addition, the structures of

the transition states were reconfirmed using the intrinsic reac-

tion coordinate.[48,49] Additionally, we reoptimized several rep-

resentative stationary points in water, ethanol, DMSO, THF, and

CCl4 solvents at the B3LYP/6–31G(d, p) level via IEFPCM.[50,51]

Results and Discussion

Five possible reaction channels

Five possible reaction channels (depicted in Schemes 2–5)

were studied. As shown in Schemes 2–5, b-oxodithioester and

its three different catalyst-substrate complexes are denoted as

R1 and R3–R5, respectively, whereas 1-butanol is denoted as

R2. Likewise, b-oxothionoester products and its three different

catalyst-substrate complexes are denoted as P1 and P3–P5,

whereas methanethiol is denoted as P2. In each channel, we

set the energies of the two reactants at 0.00 kcal/mol in the

energy profile as reference. The details of the five possible

channels are illustrated below.

First, we explored the noncatalyzed reaction channel (chan-

nel 1). As shown in Scheme 2, we proposed and studied a

concerted reaction channel, in which R1 reacts with R2 to

generate products P1 and P2 via a four-membered ring

(S(1)AH(2)AO(3)AC(4)) transition state TS1. The two single-

bonds S(1)AC(4) and H(2)AO(3) break and two new single-

bonds S(1)AH(2) and O(3)AC(4) are formed in this process.

Figure 1 shows the structures and geometrical parame-

ters of the reactants, transition state, and products in chan-

nel 1. Moreover, Figure 1 shows that the bond lengths of

S(1)AC(4) and H(2)AO(3) are 1.751 (R1) and 0.967 A (R2),

respectively, whereas the distances of S(1)AH(2), H(2)AO(3),

O(3)AC(4), and C(4)AS(1) are 1.662, 1.183, 1.589, and 2.277

A (TS1), respectively. In addition, the bond lengths of

O(3)AC(4) and S(1)AH(2) are 1.329 (P1) and 1.349 A (P2),

respectively.

As shown in Figure 2, the energy barrier of this process in

channel 1 is 43.25 kcal/mol at the B3LYP/[6-31G(d, p)1LANL2DZ]

level, which is excessively high such that channel 1 will not occur

even upon heating.

Second, we tried to explain how this transesterification

occurs at a Lewis acid-catalyzed condition. The transesterifi-

cation was initially performed using 5 mol% SnCl2.[15] Upon

exploring the mechanism, the question “How does SnCl2

complex with b-oxodithioesters?” came up. The unoccupied

orbitals of the Sn metal center can accept electrons from

either electron-rich carbonyl oxygen or thiocarbonyl sulfur,

or from both of them.[52] Accompanied with the electron

transfer process, coordination bonds are formed, and the

coordination number of Sn increases. Herein, we suggested

and investigated the structures of possible complexes R3

and R4, which are depicted in Scheme 3. The coordination

number of Sn differentiates these two modes. The third

mode, in which only one coordination bond connects Sn

and the carbonyl oxygen, is neglected because the metal

center is substantially far from the thiocarbonyl carbon in

the optimized structures.

As shown in Scheme 3 and similar with channel 1, R3 (or

R4) reacts with R2 to form products P3 and P4 via the four-

membered ring (S(1)AH(2)AO(3)AC(4)) transition state TS2 (or

TS3). The two single-bonds S(1)AC(4) and H(2)AO(3) break,

and two new single-bonds S(1)AH(2) and O(3)AC(4) are

formed in those channels. The structures and geometrical

parameters of the reactants, transition states, and products

involved in channels 2 and 3 are shown in Figure 3.

Figure 3 shows that the bond lengths of S(1)AC(4) are 1.718

(R3) and 1.725 A (R4), respectively, whereas the distances of

S(1)AH(2), H(2)AO(3), O(3)AC(4), and C(4)AS(1) are 1.596,

1.269, 1.556, and 2.022 A (TS2), respectively, and 1.582, 1.298,

1.528, and 1.961 A (TS3), respectively. In addition, the bond

lengths of O(3)AC(4) are 1.321 (P3) and 1.309 A (P4).

Scheme 1. Lewis acid-catalyzed transesterification of methyl b-oxodithioester with 1-butanol.

Scheme 2. Noncatalyzed channel (channel 1).

FULL PAPERWWW.Q-CHEM.ORG

International Journal of Quantum Chemistry 2014, 114, 862–868 863

Based on our calculations, the two possible SnCl2-catalyzed

channels (channels 2 and 3) are also concerted reactions via

the four-membered ring transition states. The energy profiles

(Fig. 1) indicate that channel 3 is more favorable than channel

2, and each of the two catalyzed channels has a significantly

lower energy barrier than that of channel 1. Thus, we conclude

that the Lewis acid catalyst SnCl2 should form the coordination

bond with the thiocarbonyl sulfur of R1, which can make the

reaction occur at the experimental conditions.

In the experiment, the transesterification was optimized

using 5 mol% SnCl2�2H2O as replacement for the SnCl2 cata-

lyst.[15] Two coordination modes exist as well. First, the Sn

atom of the hydrated catalyst can form a coordination bond

with the thiocarbonyl sulfur atom exclusively, and second, it

can also form two coordination bonds with thiocarbonyl sulfur

and carbonyl oxygen. However, the latter substrate-catalyst

complex cannot be located. In addition, the two water ligands

increase the coordination number of Sn, thereby making it dif-

ficult to coordinate with the carbonyl oxygen. Hence, only the

possible SnCl2�2H2O-catalyzed channel (channel 4 as depicted

in Scheme 4) is suggested and studied hereafter.

As shown in Scheme 4, channel 4 has the same mechanism

as with channel 3 in all aspects except for catalyst SnCl2�2H2O.

Figure 4 presents the structures and geometrical parameters

of the reactants, transition state, and products in channel 4.

Figure 4 shows that the bond length of S(1)AC(4) is 1.723 A

(R5), whereas the distances of S(1)AH(2), H(2)AO(3), O(3)AC(4),

and C(4)AS(1) are 1.589, 1.294, 1.525, and 1.964 A (TS4), respec-

tively. In addition, the bond length of O(3)AC(4) is 1.318 A (P5).

However, as seen from Figure 5, the calculations show that

the energy barrier of channel 4 is 37.35 kcal/mol, which is 1.4

kcal/mol higher than that of channel 3 (35.95 kcal/mol,

depicted in Fig. 2). Moreover, the results seem to be inconsis-

tent with Devi’s experimental results.[15] Thus, a more energy-

favorable reaction channel should exist at the SnCl2�2H2O-cata-

lyzed condition.

Given the strong strain of the four-membered ring in all the

above four transition states, we suggested and investigated

another possible channel (channel 5), which is illustrated in

Scheme 5 and discussed below.

As seen from Scheme 5, a coordination water of the

SnCl2�2H2O catalyst participated in the reaction. During the

reaction process, O(7) extracts a proton H(2) from R2 and

donates another proton H(8) to the S(1) atom of R1. The two

single-bonds S(1)AC(4) and H(2)AO(3) break, and two new

single-bonds S(1)AH(2) and O(3)AC(4) are formed in this pro-

cess, thereby generating products P2 and P5. Figure 6 shows

the structure and geometrical parameters of the transition

state in channel 5. Figure 6 shows that the distances of

S(1)AH(8), O(7)AH(8), H(2)AO(7), H(2)AO(3), O(3)AC(4), and

C(4)AS(1) are 1.836, 1.096, 1.072, 1.433, 1.481, and 1.952 A

(TS5), respectively.

Figure 5 shows that the energy barrier of channel 5 is 33.70

kcal/mol, which is not a high energy barrier for transesterifica-

tion at the experimental condition (383 K). Moreover, it is 2.25

kcal/mol lower than channel 3 (35.95 kcal/mol, depicted in Fig.

2). Thus, the reaction can occur more easily during Lewis acid

SnCl2�2H2O catalysis, which is in agreement with the experi-

mental results.

Despite the fact that several mechanisms have been pro-

posed for base-catalyzed ester alcoholysis and that the over-

whelming majority of these were described in terms of

tetrahedral intermediates,[53,54] concerted mechanisms are still

reported and adopted in other works.[55–57] For example,

Salem et al. reported a concerted mechanism for the transfer

of the acetyl functional group between phenolate ion nucleo-

philes.[55] Based on ion cyclotron resonance experiments, Kim

and Caserio have shown the concertedness of acyl group

transfer in gas-phase reactions.[56] Zaramello et al. interpreted

the concerted mechanism of the acid-catalyzed ethanolysis of

butyric acid triglyceride in gas phase using DFT, and they con-

cluded that each step of the reaction proceeds through one

concerted transition state without the formation of a tetrahe-

dral intermediate.[57] We tried several times to locate the tetra-

hedral intermediate, but all attempts have failed. Moreover,

our calculated results also indicate that the possible tetrahe-

dral intermediates are also unstable at the experimental condi-

tion. Hence, the mechanism involving a short-lived tetrahedral

intermediate was not discussed in this work.

Figure 1. Structures and geometrical parameters of the stationary points optimized at the B3LYP/6-31G(d, p) level in channel 1 (distance in A). [Color figure

can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

Figure 2. Energy profiles of channels 1, 2, and 3 calculated at the B3LYP/[6-

31G(d, p)1LANL2DZ] level (unit: kcal/mol).

FULL PAPER WWW.Q-CHEM.ORG

864 International Journal of Quantum Chemistry 2014, 114, 862–868 WWW.CHEMISTRYVIEWS.ORG

In addition, the distances between the chloride and hydro-

gen atoms of alcohol in every transition state geometries were

measured; however, none is shorter than 4 A. Therefore, no

hydrogen bond network is in the transition states, which

should help the stability of transition states and lower the

energy barrier.

Scheme 3. Two possible channels catalyzed by SnCl2 (channels 2 and 3).

Figure 3. Structures and geometrical parameters of the stationary points optimized at the B3LYP/[6-31G(d, p)1LANL2DZ] level in channels 2 and 3 (dis-

tance in A). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

Scheme 4. Possible SnCl2�2H2O-catalyzed channel (channel 4).

Figure 4. Structures and geometrical parameters of stationary points optimized at the B3LYP/[6–31G(d, p)1LANL2DZ] level in channel 4 (distance in A).

[Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

FULL PAPERWWW.Q-CHEM.ORG

International Journal of Quantum Chemistry 2014, 114, 862–868 865

Moreover, solvation effects were considered as implemented

with CCl4, THF, ethanol, DMSO, and water solvents. Table 1

shows the energy barriers of the two representative reaction

channels (including channels 1 and 3) in the gas phase and

different solvents. These two channels correspond with differ-

ent circumstances, including noncatalyzed and SnCl2-catalyzed

conditions. The computational results demonstrate that the

energy barriers in the different solvents have insignificant dif-

ferences with those in the gas phase. Considering that no

experimental data are available for the reaction at solvent con-

ditions and that the above results represent the two different

circumstances, further calculations on the solvent effects were

not performed.

GRI analysis

To explain the function of the Lewis acid catalyst, the GRI of

reactants R1 and R3–R5 were calculated. The chemical poten-

tial l is expressed as

l51

2ELUMO 1EHOMOð Þ (1)

and chemical hardness g is defined as

g5ELUMO 2EHOMO : (2)

In addition, the electrophilicity index x can be computed

using the following simple expression in terms of l and g:[58–62]

x5l2

2g5

1

4

ELUMO 1EHOMOð Þ2

ELUMO 2EHOMOð Þ : (3)

The results of frontier molecular orbital (FMO) energies,

chemical potential, chemical hardness, and electrophilicity

index for R1 and R3–R5 are given in Table 2, as well as the

natural charge located on thiocarbonyl carbons (NC1) and total

natural charge on the catalysts (NC2).

Table 2 shows that the electrophilicity indexes of R1 and

R3–R5 are inversely proportional to the energy barriers in

channels 1–4, that is, index x is directly proportional to the

reactivity of the ester-catalyst complex. Likewise, the natural

charge for thiocarbonyl carbon (NC1) fluctuates in the same

manner, which is in agreement with the fact that a lesser

charge on thiocarbonyl carbon makes it more reactive with

R2. In addition, the total natural charge on the catalyst (NC2)

in R3–R5 is negative and is inversely proportional to NC1,

which indicates that the catalyst withdraws electron from the

ester to reduce the electron density in the thiocarbonyl car-

bon. The Sn Lewis acid forms an adduct with the lone-pair-

bearing thiocarbonyl sulfur in the substrate as a portion of the

charge from b-oxodithioester transfers to the Lewis acid. The

charge-transfer process leads to a more electronegative thio-

carbonyl carbon, thereby activating the substrate toward

nucleophilic attack. In conclusion, the catalysts in channels 2–4

affect a traditional Lewis acid, and their classical function in

Scheme 5. The other possible SnCl2�2H2O-catalyzed channel (channel 5).

Figure 5. Energy profiles of channels 4 and 5 calculated at the B3LYP/[6-

31G(d, p)1LANL2DZ] level (unit: kcal/mol).

Figure 6. Structures and geometrical parameters of the stationary points

optimized at the B3LYP/[6-31G(d, p)1LANL2DZ] level in channel 5 (distance

in A). [Color figure can be viewed in the online issue, which is available at

wileyonlinelibrary.com.]

Table 1. Energy barriers of two representative reaction channels at

B3LYP/[6-31G(d,p)1LANL2DZ] level in different solvents (unit: kcal/mol).

DEGas-phase DECCl4 DETHF DEEtOH DEDMSO DEWater

R11R2fiTS1 43.25 43.40 43.12 42.76 42.63 42.60

R41R2fiTS3 35.95 36.52 36.72 36.42 36.37 36.34

FULL PAPER WWW.Q-CHEM.ORG

866 International Journal of Quantum Chemistry 2014, 114, 862–868 WWW.CHEMISTRYVIEWS.ORG

transesterification can be described as follows: the catalyst

withdraws electron from the ester to reduce the electron den-

sity on the thiocarbonyl carbon, which further increases the

electrophilicity of the carbon. As such, the nucleophilic attack

of the alcoholic OH group is facilitated.

Compared with R4, all indexes of R5 in Table 2 indicate a

result contrary to those obtained from catalyst optimization.

For example, the electrophilicity index of R5 is slightly lower

than that of R4, which implies that the water ligands of the

Sn catalyst have a slightly negative impact on the activation of

b-oxodithioester. This result also suggests that the nucleophilic

reactivity of R5 is lower than that of R4 and that SnCl2�2H2O

is a worse catalyst than SnCl2 in transesterification if no special

function of SnCl2�2H2O exists. In transition state TS5, we found

a novel function of Lewis Acid catalyst SnCl2�2H2O, in which

one of its water ligands can assist the proton transfer process

in this catalytic reaction. With this novel function of

SnCl2�2H2O, channel 5 becomes the most energy-favorable

channel even though the nucleophilic reactivity of R5 is lower

than that of R4.

Conclusions

In this work, the detailed mechanisms of the transesterification

of b-oxodithioesters were investigated using DFT. Five possible

reaction channels, including one noncatalyzed reaction chan-

nel and four Lewis acid-catalyzed channels, were suggested

and investigated. The calculated results indicate that channel 5

is the most energy-favorable among all the five channels. Fur-

ther calculations show that solvent effects have little influence

on the transesterification. Moreover, we studied the reactivities

of reactants R1 and R3–R5 by computing the electrophilicity

index and NBO charge distribution. These analyses reveal that

complexes R3–R5 are more reactive than reactant R1, which

indicates that the Lewis acid catalyst increases the electrophi-

licity of the reactants. Given the GRI and the structures of the

transition states in the five channels, the low strain of the six-

membered ring in TS5 should be the main reason for its pref-

erence. All calculated results are in good agreement with

experimental results.

Keywords: density functional theory � global reactivity index-

es � natural bond orbital charge � transesterification � Lewis

acid

How to cite this article: X. Guo, L. Chen, Y. Zhu, A. Zhang, D.

Wei, M. Tang, X. Guo, L. Chen, Y. Zhu, A. Zhang, D. Wei, M.

Tang. Int. J. Quantum Chem. 2014, 114, 862–868. DOI: 10.1002/

qua.24669

[1] R. Singh, R. M. Kissling, M. A. Letellier, S. P. Nolan, J. Org. Chem. 2004,

69, 209.

[2] L. I. Koval, V. I. Dzyuba, O. L. Ilnitska, V. I. Pekhnyo, Tetrahedron Lett.

2008, 49, 1645.

[3] A. Pericas, A. Shafir, A. Vallribera, Tetrahedron 2008, 64, 9258.

[4] J. Otera, Chem. Rev. 1993, 93, 1449.

[5] B. Clapham, S. H. Lee, G. Koch, J. Zimmermann, K. D. Janda, Tetrahe-

dron Lett. 2002, 43, 5407.

[6] M. L. Kantam, V. Neeraja, B. Bharathi, C. V. Reddy, Catal. Lett. 1999, 62,

67.

[7] M. I. de Sairre, E. S. Bronze-Uhle, P. M. Donate, Tetrahedron Lett. 2005,

46, 2705.

[8] S. P. Chavan, K. Shivasankar, R. Sivappa, R. Kale, Tetrahedron Lett. 2002,

43, 8583.

[9] B. P. Bandgar, V. S. Sadavarte, L. S. Uppalla, J. Chem. Res. Synop. 2001,

16.

[10] N. Inahashi, T. Fujiwara, T. Sato, Synlett 2008, 2008, 605.

[11] R. Ratti, S. Kaur, M. Vaultier, V. Singh, Catal. Commun. 2010, 11, 503.

[12] S. P. Chavan, R. R. Kale, K. Shivasankar, S. I. Chandake, S. B. Benjamin,

Synthesis (Stuttg) 2003, 2695.

[13] G. Sathicq, L. Musante, G. Romanelli, G. Pasquale, J. Autino, H. Thomas,

P. Vazquez, Catal. Today 2008, 133, 455.

[14] R. K. Sharma, D. Rawat, J. Inorg. Organomet. Polym. Mater. 2011, 21,

619.

[15] N. S. Devi, S. J. Singh, O. M. Singh, Tetrahedron Lett. 2013, 54, 1432.

[16] D. H. Wei, M. S. Tang, J. Phys. Chem. A 2009, 113, 11035.

[17] D. S. Bose, A. Satyender, A. P. R. Das, H. B. Mereyala, Synthesis (Stuttg)

2006, 14, 2392.

[18] M. Hatano, K. Ishihara, Chem. Commun. 2013, 49, 1983.

[19] M. Tamura, S. M. A. H. Siddiki, K. Shimizu, Chem. Commun. 2013, 15,

1641.

[20] W. Bo, Y. L. Ming, S. J. Shuan, Tetrahedron Lett. 2003, 44, 5037.

[21] H. Shi, X. Huang, G. Liu, K. Yu, C. Xu, W. Li, B. Zeng, Y. Tang, Int. J.

Quantum Chem. 2013, 113, 1339.

[22] C. Zhang, Y. Y. Zhu, D. H. Wei, D. Z. Sun, W. J. Zhang, M. S. Tang,

J. Phys. Chem. A 2010, 114, 2913.

[23] N. Lu, H. Wang, Int. J. Quantum Chem. 2013, 113, 2267.

[24] D. H. Wei, B. L. Lei, M. S. Tang, C. G. Zhan, J. Am. Chem. Soc. 2012, 134,

10436.

[25] O. Brea, M. Loro~no, E. Marquez, J. R. Mora, T. Cordova, G. Chuchani, Int.

J. Quantum Chem. 2012, 112, 2504.

[26] W. J. Zhang, Y. Y. Zhu, D. H. Wei, Y. X. Li, M. S. Tang, J. Org. Chem.

2012, 77, 10729.

[27] Y. Valadbeigi, H. Farrokhpour, Int. J. Quantum Chem. 2013, 113, 2372.

[28] G. Ma, Y. Li, L. Wei, Y. Liu, C. Liu, Int. J. Quantum Chem. 2013, 114, 249.

[29] D. Wei, X. Huang, J. Liu, M. Tang, C.-G. Zhan, Biochemistry 2013, 52,

5145.

[30] J. Zhao, C. Sun, N. Sun, L. Meng, D. Chen, Int. J. Quantum Chem. 2013,

113, 2457.

[31] W. J. Zhang, Y. Y. Zhu, D. H. Wei, M. S. Tang, J. Comput. Chem. 2012,

33, 715.

[32] M. M. Montero-Campillo, M. N. D. S. Cordeiro, Int. J. Quantum Chem.

2013, 113, 2002.

[33] J. Zhang, X. Sheng, Q. Hou, Y. Liu, Int. J. Quantum Chem. 2013, 114,

375.

[34] M. F. Shibl, L. Dang, R. K. Raju, M. B. Hall, E. N. Brothers, Int. J. Quantum

Chem. 2013, 113, 1621.

[35] D. Wei, L. Fang, M. Tang, C. G. Zhan, J. Phys. Chem. B 2013, 117, 13418.

[36] H. Raissi, M. Yoosefian, Int. J. Quantum Chem. 2012, 112, 2378.

[37] H. Chemouri, S. M. Mekelleche, Int. J. Quantum Chem. 2012, 112, 2294.

[38] W. J. Zhang, D. H. Wei, M. S. Tang, J. Org. Chem. 2013, 78, 11849.

[39] H. B. Sun, R. M. Hua, Y. W. Yin, Molecules 2006, 11, 263.

[40] A. Lakshmi, V. Balachandran, A. Janaki, J. Mol. Struct. 2011, 1004, 51.

Table 2. FMO energies, chemical potential, chemical hardness, and elec-

trophilicity index for R1 and R3–R5 (in eV).

ELUMO EHOMO l g x NC1 NC2

R1 21.838 25.985 23.912 4.146 1.845 20.337 –

R3 22.376 26.335 24.356 3.958 2.396 20.310 20.135

R4 22.931 26.726 24.829 3.794 3.073 20.273 20.177

R5 22.679 26.578 24.629 3.899 2.747 20.313 20.070

Natural charge for NC1 in R1 and R3–R5 and the NC2 in R3–R5 (in ele-

mentary charge).

FULL PAPERWWW.Q-CHEM.ORG

International Journal of Quantum Chemistry 2014, 114, 862–868 867

[41] T. Karthick, V. Balachandran, S. Perumal, A. Nataraj, J. Mol. Struct. 2011,

1005, 192.

[42] R. S. Kumar, A. Marwaha, P. V. Bharatam, M. P. Mahajan, J. Mol. Struct.

2003, 640, 1.

[43] S. Boughdiri, K. Hussein, B. Tangour, M. Dahrouch, M. Riviere-Baudet, J.

C. Barthelat, J. Organomet. Chem. 2004, 689, 3279.

[44] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R.

Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H.

Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G.

Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J.

Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T.

Vreven, J. A. Montgomery, Jr, J. E. Peralta, F. Ogliaro, M. Bearpark, J. J.

Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, T. Keith, R. Kobayashi, J.

Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J.

Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross,

V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O.

Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin,

K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J.

Dannenberg, S. Dapprich, A. D. Daniels, O. Farkas, J. B. Foresman, J. V.

Ortiz, J. Cioslowski, D. J. Fox, GAUSSIAN 09; Gaussian Inc.: Wallingford,

CT, 2010.

[45] B. Miehlich, A. Savin, H. Stoll, H. Preuss, Chem. Phys. Lett. 1989, 157, 200.

[46] C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785.

[47] A. D. Becke, J. Chem. Phys. 1993, 98, 5648.

[48] C. Gonzalez, H. B. Schlegel, J. Phys. Chem. 1990, 94, 5523.

[49] C. Gonzalez, H. B. Schlegel, J. Chem. Phys. 1989, 90, 2154.

[50] V. Barone, M. Cossi, J. Phys. Chem. A 1998, 102, 1995.

[51] B. Mennucci, J. Tomasi, J. Chem. Phys. 1997, 106, 5151.

[52] F. A. Carey, R. J. Sundberg, Advanced Organic Chemistry, Part A: Struc-

ture and Mechanisms, 5th ed., Chapter 3; Springer: New York, 2007;

pp. 354–355.

[53] Y. Asakuma, K. Maeda, H. Kuramochi, K. Fukui, Fuel 2009, 88, 786.

[54] N. C. O. Tapanes, D. A. G. Aranda, J. W. D. Carneiro, O. A. C. Antunes,

Fuel 2008, 87, 2286.

[55] B.-S. Salem, K. L. Ajay, W. Andrew, J. Am. Chem. Soc. 1987, 109, 6362.

[56] K. K. Jhong, C. C. Marjorie, J. Am. Chem. Soc. 1981, 103, 2124.

[57] L. Zaramello, C. A. Kuhnen, E. L. Dall’Oglio, P. T. de Sousa, Fuel 2012,

94, 473.

[58] L. R. Domingo, J. A. Saez, R. J. Zaragoza, M. Arno, J. Org. Chem. 2008,

73, 8791.

[59] L. R. Domingo, M. T. Picher, J. A. Saez, J. Org. Chem. 2009, 74, 2726.

[60] L. R. Domingo, J. A. Saez, Org. Biomol. Chem. 2009, 7, 3576.

[61] L. R. Domingo, M. J. Aurell, P. Perez, R. Contreras, Tetrahedron 2002, 58,

4417.

[62] L. R. Domingo, E. Chamorro, P. Perez, Eur. J. Org. Chem. 2009, 2009,

3036.

Received: 24 October 2013Revised: 17 February 2014Accepted: 26 February 2014Published online 17 March 2014

FULL PAPER WWW.Q-CHEM.ORG

868 International Journal of Quantum Chemistry 2014, 114, 862–868 WWW.CHEMISTRYVIEWS.ORG