From 4-nitrotoluene and 4,4′-dinitrobibenzyl to: E -4,4′-dinitrostilbene: An electrochemical approach

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B. Gómez, G. Guirado, A. Lariño, M. Moreno, M. Ortigosa and S. Soler, New J. Chem., 2018, DOI:

10.1039/C8NJ00131F.

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ISSN 1144-0546

PAPER

Jason B. Benedict et al.

The role of atropisomers on the photo-reactivity and fatigue of

diarylethene-based metal–organic frameworks

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From

4-nitrotoluene

and

4,4’-dinitrobibenzyl

to

E-4,4’dinitrostilbene: An electrochemical approach

Iluminada Gallardo,^aAna Belén Gómez,^aGonzalo Guirado,^aAdrián Lariño,^aMiquel Moreno,^aManuel

Ortigosa,^aand Sergio Soler ^a

Received 00th January 20xx,

Accepted 00th January 20xx

DOI: 10.1039/x0xx00000x

The dianions formed by electroreduction of Z-O₂NC₆H₄CH=CHC₆H₄NO₂, E-O₂NC₆H₄CH=CHC₆H₄NO₂, O₂NC₆H₄CH₂-CH₂C₆H₄NO₂

or O₂NC₆H₄CMeH-CMeHC₆H₄NO₂, as well as the anion radical arising from 4-nitrotoluene are stable, in the time scale of the

cyclic voltammetry (DMF+0.10 M NBu₄BF₄). However, in the electrolysis time scale (from minutes to hours), only the

www.rsc.org/

2-

dianion O₂NC₆H₄CMeH-CMeHC₆H₄NO₂remains stable, since the reduced species, Z-O₂NC₆H₄CH=CHC₆H₄NO₂

,

2-

-

2-

O₂NC₆H₄CH₂-CH₂C₆H₄NO₂or O₂NC₆H₄Me^, evolve to form the E-O₂NC₆H₄CH=CHC₆H₄NO₂dianion. This intermediate, is

recovered as the neutral species E-O₂NC₆H₄CH=CHC₆H₄NO₂with concomitant water reduction after the work-up with

water, as demonstrated by combined electrolysis, cyclic voltammetry experiments, UV-spectroelectrochochemistry and

theoretical calculations. Bulk electrolysis in optimized conditions (ACN+0.10 M NBu₄BF₄) provides 40% and 67 % isolated

yield

of

E-4,4’-dinitrostilbene

from

4-nitrotoluene

and

4,4’-dinitrobibenzyl,

respectively.

Introduction

Stilbenes have become of particular interest because of wide

range of different applications ,not only in chemistry but also

in life science and material science, in addition to

chemistry.(1–5) Stilbene derivatives are attractive compounds

because they undergo easy cis-trans isomerization that can be

induced both photochemically, as well as by electrochemical

reduction, the latter via an anion radical intermediate.(6–9)

Thereby, although stilbene syntheses have been reported in

the literature for a long time, this still remains as an area of

Moreover, 4,4’-dinitrobibenzyl (O₂NC₆H₄CH₂-CH₂C₆H₄NO₂) is

also obtained by electrodimerization of corresponding

nitrobenzylhalides,(18-20) via C-X heterolytic cleavage of the

anion radical:

interest, judging by the number of reports published in recent Depending on the reaction conditions, both 4,4’-

years.(10–13) In particular, nitroderivatives of stilbene are dinitrobibenzyl and 4,4-’dinitrostilbene can be sequentially

especially appealing because of its use as textile dyes prepared by treating 4-nitrotoluene (O₂NC₆H₄Me) with KMeO

(i.e.4,4’-dinitrostilbene-2,2’-disulphonic

acid).(14,15) in MeOH in the presence of air and with or without other

Furthermore, nitrostilbenes are reduced at less negative stoichiometric oxidizing agent:(21–23)

potentials than other stilbene derivatives,(16) thus facilitating

their electrochemical cis-trans isomerization.

Up to now, it is known that, dinitrobibenzyls and the

corresponding dinitrostilbenes are obtained by a reaction

between nitrobenzylchlorides and alkoxides. For example,

4-nitrobenzylchloride

yields

4,4’-dinitrostilbene Based on kinetic studies, a mechanism for conversion of

(O₂NC₆H₄CH=CHC₆H₄NO₂) when reacts with an excess of nitrotoluene into dinitrobibenzyl was proposed some time ago,

sodium ethoxide in ethanol:(17)

Scheme 1.(24,25) The reaction starts with deprotonation of

nitrotoluene, followed by the formation of a charge transfer

complex between the anion and the neutral molecule. This

complex evolves following two different routes: (a) losing a

proton and two electrons to form dinitrobibenzyl and/or (b)

completing the electron transfer between the donor and the

acceptor moieties to yield the nitrobenzyl radical and the

nitrotoluene anion radical. The nitrobenzyl radical dimerizes to

dinitrobibenzyl. Next, the nitrotoluene anion radical is oxidized

back to nitrotoluene. The presence of radicals and/or anion

^a.Email: iluminada.gallardo@uab.cat

Electronic Supplementary Information (ESI) available: [details of any

supplementary information available should be included here]. See

DOI: 10.1039/x0xx00000x

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radicals of nitrotoluene, dinitrobibenzyl and dinitrostilbene in charged species do not participate in any other chemical

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DOI: 10.1039/C8NJ00131F

these reaction media was evidenced by EPR and UV-visible reaction.

spectroscopy.(24–26) However, the formation dinitrostilbene The CV in polar aprotic solvents of nitrotoluene,

from dinitrobibenzyl is not described in previous work done.

dinitrobibenzyl and dinitrostilbene show reversible waves,

corresponding to a fast one-electron transfer for nitrotoluene

and fast two-electron transfers for the bis-arene

compounds.(27–36) However, the electrochemical conversion

of nitrotoluene and dinitrobibenzyl to dinitrostilbene has not

been investigated up to now. Hence, the aim of this work is

revisited the electrochemical behavior of cis- and trans-4,4’-

dinitrostilbene

(Z-O₂NC₆H₄CH=CHC₆H₄NO₂

and

E-O₂NC₆H₄CH=CHC₆H₄NO₂),

4,4’-dinitrobibenzyl

Scheme 1.

(O₂NC₆H₄CH₂-CH₂C₆H₄NO₂), α,α’-dibromo-4,4’-dinitrobibenzyl

(O₂NC₆H₄CBrH-CBrHC₆H₄NO₂),

α,α’-dimethyl-4,4’-dinitrobibenzyl(O₂NC₆H₄CMeH-CMeHC₆H₄N

O₂), and 4-nitrotoluene (O₂NC₆H₄Me), (Chart 1), and to

Electrochemistry is a powerful tool to investigate the reaction

mechanism involving electron transfer processes and,

particularly, to generate anion radical intermediates in a

controlled way. The electrochemical reduction of

nitroaromatic compounds, A, in the absence of the other

electroactive substituents, has been subject of numerous

studies.(27,28) When the reduction is conducted in a protic

media, depending on the pH of the medium, a wide variety of

products can be obtained (i.e. anilines, hydroxyl amines,

nitroso-compounds). However, in polar aprotic solvents, the

sole reduction product of a mononitroaromatic compounds is

the anion radical, A^(characterized in different ways), which

in many cases is a persistent species in cyclic voltammetry (CV)

time scale. Notice that in polar aprotic solvents and in the CV

time scale, there are not chemical reactions associated to the

anion radical of mononitroaromatics.

demonstrate

that

is

possible

to

obtain

E-

O₂NC₆H₄CH=CHC₆H₄NO₂by the electrochemical reduction of

both O₂NC₆H₄CH₂-CH₂C₆H₄NO₂and O₂NC₆H₄Me.

In the case of dinitroaromatic compounds,

a two-step

reduction, corresponding to the formation of anion radical,

A^, and dianion, A^2-are generally observed, both usually being

reversible processes:(29–36)

Chart 1.

Results and discussion

CV studies were performed in DMF+0.10 M Bu₄NBF₄with a

glassy carbon millimetric cathode in Ar atmosphere. Slow scan

rates were used in CV experiments described in order to

prevent kinetic control by the charge transfer reaction.

Figure 1 shows an overview for all investigated compounds

before and after electrolysis. Before electrolysis (solid line),

The easiest case is when both electron transfer reactions are

fast. The appearance of the voltammogram depends upon the

location of the standard potentials, E₁⁰and E₂⁰and the spacing

0

between them,

 

E⁰=E₂-E₁.(37) When E⁰>100 mV, the

second electron transfer step takes place at more positive

potentials than the first one, and a single two-electron transfer

most of them exhibit

a single reversible two-electron

reduction wave, which becomes a single reversible one-

electron reduction wave in the case of O₂NC₆H₄Me (Table 1).

These waves are concentration and sweep rate independent,

Nernstian wave is observed. However, if 100 mV>

mV, a single wave occurs, with an increasing voltammetric

peak width, E_p, compared with previous case, and a number

of electrons transferred, z<2. The two waves become

resolvable at

E⁰=-125 mV, where each wave takes on the



E⁰>-100



corresponding

(O₂NC₆H₄CH=CHC₆H₄NO₂

O₂NC₆H₄CMeH-CMeHC₆H₄NO₂

to

the

formation

O₂NC₆H₄CH₂-CH₂C₆H₄NO₂

and anion-radical

of

dianions

2-

,

2-



)

(O₂NC₆H₄Me^), all of them being stable in the time range of

the CV. In the case of O₂NC₆H₄CBrH-CBrHC₆H₄NO₂, two

reduction waves were observed. The first corresponds to a

characteristic of a one-electron Nernstian electron transfer.

Note that in polar aprotic media and in CV time scale, except

for the disproportionation equilibrium of the anion radical A^

into A and A^2-, which is governed by E⁰, the two negatively



2 | J. Name., 2012, 00, 1-3

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two-electron irreversible process, while the second is a two- The detailed electrochemical behavior of each_Vieo_wn_Ae_rtico_lef_Ont_lh_ine_e

electron reversible one.

investigated nitroderivatives is described ^Db^Oel^Io^{: 1}w^0..^{1039/C8NJ00131F}

Table 1 include the values of voltammetric peak widths,



E_p=E_p-E_p/2,standard potential, E⁰, number of electrons, z, cis- and trans-4,4’-Dinitrostilbene (Z-O₂NC₆H₄CH=CHC₆H₄NO₂and

disproportionation equilibrium constant, K_dis

,

applied E-O₂NC₆H₄CH=CHC₆H₄NO₂).

potential, E_app, and number of Faraday consumed for the

compounds in DMF+0.10 M Bu₄NBF₄at 20 ºC. Electrolyses

were carried out at controlled potential, at more negative

potentials than the first cathodic peak, on a graphite cathode

in DMF+0.10 M Bu₄NBF₄and under Ar atmosphere. After the

passage of the desired Faradays (F), solutions were

Both compounds show

a

reversible reduction wave,

concentration and sweep rate independent and the height of

the cathodic peaks correspond to two electron transfer

processes. The E⁰values are -0.89 V and -0.91 V, and the peak

width, E_p, are 53 mV and 48 mV, for the cis- and trans-isomer

respectively:

immediately analyzed by CV.

O₂NC₆H₄CH=CHC₆H₄NO₂, as

The Z- and E-

well as

O₂NC₆H₄CMeH-CMeHC₆H₄NO₂show identical CV as before the

electrolysis, while in the case of O₂NC₆H₄CH₂-CH₂C₆H₄NO₂, and

O₂NC₆H₄Me

dianionO₂NC₆H₄CH₂-CH₂C₆H₄NO₂

a new wave appears, revealing that the

The two-electron transfer processes correspond to two

successive one-electron transfer reductions:

2-

and the anion radical

O₂NC₆H₄Me^are not stables in the time scale of the

electrolysis (Figure 1, Table 1). After electrolysis, solutions

were quenched with water and extracted with toluene.

Composition of the toluene solutions were analyzed by GC-MS

and the product distribution was established by GC.

Since

E_pis 53 mV and 48 mV for the cis and trans isomers

0

respectively, the corresponding



E⁰=E₂-E₁⁰are -27 mV and -15

mV.(38)In summary, the second electron transfer step occurs

at slightly more negative potential than the first one, and the

appearance of the wave is indistinguishable from a single two

electron transfer Nernstian wave, except for the value of

that would be 29 mV in the last case.

From

calculated:

E_p



E⁰, disproportionation equilibrium constant can be

being K_disp=0.34 for Z-O₂NC₆H₄CH=CHC₆H₄NO₂and 0.55 for

E-O₂NC₆H₄CH=CHC₆H₄NO₂,

comproportionation of

indicating

O₂NC₆H₄CH=CHC₆H₄NO₂

that

the

and

2-

O₂NC₆H₄CH=CHC₆H₄NO₂prevails over the disproportionation

of O₂NC₆H₄CH=CHC₆H₄NO₂^. This result was confirmed by

UV-visible spectroelectrochemistry experiments.

After

electrolysis at -1.20 during 90 on solution of

V

s

a

E-O₂NC₆H₄CH=CHC₆H₄NO₂, the spectrum shows several

absorption bands at 350, 604, 641 and 660 nm. The band at

350 nm is due to neutral E-O₂NC₆H₄CH=CHC₆H₄NO₂,(24–26)

while

the

others

bands

are

associated

to

2-



E-O₂NC₆H₄CH=CHC₆H₄NO₂

and E-O₂NC₆H₄CH=CHC₆H₄NO₂

Figure 1. CV of nitroaromatic-compounds (10 mM) in DMF+0.10 M Bu₄NBF₄at glassy

carbon electrode. Scan rate, 0.50 V s^-1; temperature, 20 ºC; Ar atmosphere. (──) Before

electrolysis; (····) After electrolysis (1F), (-·-·-·) After exhaustive electrolysis at more

negative potentials than that of first cathodic peak potential

.(39)Therefore, in the time range corresponding to CV, E-

O₂NC₆H₄CH=CHC₆H₄NO₂remains stable, except for the

disproportionation equilibrium.

2-

When pale yellow solutions of Z-O₂NC₆H₄CH=CHC₆H₄NO₂and

E-O₂NC₆H₄CH=CHC₆H₄NO₂were electrolyzed at -1.20 V (1.0 F),

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they turned dark blue. The CVs of these solutions only show UV-visible spectroelectrochemical experiments _Vic_ewor_Ar_rto_icb_leo_Or_na_lit_ne_e

2-

the wave corresponding to E-O₂NC₆H₄CH=CHC₆H₄NO₂, Figure the

1. Furthermore, when the electrolyzed solutions (2.0 F) of O₂NC₆H₄CH=CHC₆H₄NO₂in the electrolyzed solutions of

E-O₂NC₆H₄CH=CHC₆H₄NO₂, containing the O₂NC₆H₄CH₂-CH₂C₆H₄NO₂. After electrolysis of a solution of this

E-O₂NC₆H₄CH=CHC₆H₄NO₂dianion, were quenched with compound at -1.20 V during 45 s, characteristic bands were

water and extracted with toluene, the observed at 604, 641 and 660 nm, corresponding to products

E-O₂NC₆H₄CH=CHC₆H₄NO₂was obtained with concomitant of electrolysis of O₂NC₆H₄CH=CHC₆H₄NO₂(see above).(39) Both

presence

of

O₂NC₆H₄CH=CHC₆H₄NO₂

^{DOI: 10.1039/C8NJ00}a¹³n¹d^F



2-



reduction of water to H₂. Furthermore, treatment in the same O₂NC₆H₄CH=CHC₆H₄NO₂

and

dianion,

2-

way the electrolyzed solutions of Z-O₂NC₆H₄CH=CHC₆H₄NO₂O₂NC₆H₄CH=CHC₆H₄NO₂evolve to the neutral molecule,

yielded the trans- isomer exclusively, because the already O₂NC₆H₄CH=CHC₆H₄NO₂, in the working-up of the electrolyzed

reported

cis-

to

trans-

isomerization

of

the solution as described above.

2-

O₂NC₆H₄CH=CHC₆H₄NO₂^2-and/or the O₂NC₆H₄CH=CHC₆H₄NO₂

The formation of the O₂NC₆H₄CH=CHC₆H₄NO₂

from



2-

species.(6–9)

O₂NC₆H₄CH₂-CH₂C₆H₄NO₂

during the electrolysis of

O₂NC₆H₄CH₂-CH₂C₆H₄NO₂can be explained by loss of a

hydrogen molecule arising from two acidic benzylic hydrogens

from the dianion, as shown Scheme 2.

A similar process of loss of a hydrogen molecule from a

nitrobenzilyc compound was reported for the anion radical of

4-nitrobenzyl cyanide anion radical that evolves to stable

In the reaction mixture, trace amounts of 4,4’-dinitrostilbine cyano-4-nitrobenzyl anion in a bimolecular process.(40)

and bis(4-nitrophenyl)ethanodione, identified by GC-MS

analysis and H¹NMR, were also detected together with

E-O₂NC₆H₄CH=CHC₆H₄NO₂.

4,4’-Dinitrobibenzyl, O₂NC₆H₄CH₂-CH₂C₆H₄NO₂

In the reduction scan, one two-electron reversible wave

independent of scan rate and concentration was again

obtained. The standard potential, E⁰the peak width,

E_p, and

the number of electrons are -1.15 V, 88 mV and 1.6,

respectively.

Scheme 2.

As in the previous case, this reaction is consistent with two

successive one-electron transfer reductions

Further support for the loss of H₂was provided by DFT

calculations. The O₂NC₆H₄CH₂-CH₂C₆H₄NO₂dianion is stable

2-

being the singlet state the lowest in energy. These calculations

2-

show that the reaction from O₂NC₆H₄CH₂-CH₂C₆H₄NO₂to

2-

E-O₂NC₆H₄CH=CHC₆H₄NO₂(both in its lowest energy singlet

state) plus H₂is almost thermoneutral. Through single bond

rotation around the C-C central bonds two conformers of the

reactants are obtained (Scheme 3). The anti-Ar conformer is

the most stable one with the gauche-Ar form lying 9.8 kcal

mol^-1above. By simultaneous enlargement of the two C-H

distances of sp³carbons the approximate transition state can

be located. The calculated energy barriers are quite high 50.4

kcal mol^-1for the anti-Ar and 95.0 kcal mol^-1for the gauche-Ar.

The values of



E_p=88 mV and z=1.6 are in agreement with

0

E⁰=E₂-E₁⁰-63 mV that correspond to K_disp=0.08.(37,38)

2-

Therefore, in the time scale CV, O₂NC₆H₄CH₂-CH₂C₆H₄NO₂

remains stable, except for the disproportionation

equilibrium.After potential controlled electrolysis of

a

O₂NC₆H₄CH₂-CH₂C₆H₄NO₂at -1.20 V (1.2 F), the initial pale-

yellow solution becomes dark blue. The CV of the blue solution

(dotted line in Figure 1) shows a significant decrease in the

peak corresponding to O₂NC₆H₄CH₂-CH₂C₆H₄NO₂and the rise

of the peak corresponding to the electroreduction of

O₂NC₆H₄CH=CHC₆H₄NO₂. After treatment of the solution as

described above, E-O₂NC₆H₄CH=CHC₆H₄NO₂was obtained with

76% of yield and 15% of unreacted O₂NC₆H₄CH₂-CH₂C₆H₄NO₂.

The C-H distances at the transition state are



1.7 Å (anti-) and

1.8 Å in both



1.9 Å (gauche-) where the H-H distances are



cases. Given that the reaction coordinate procedure only

provides a crude estimation to the structure of the transition

state (more so in this case when the two C-H distances are

artificially constrained to enlarge simultaneously) this quite

high value must be considered an upper limit to the actual

energy barrier of the process. The solvent effect, another

4 | J. Name., 2012, 00, 1-3

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factor not considered in the theoretical calculations, is also isomer. Additionally, the two reactions are almost

View Article Online

-1

probably lowering this value. The reaction coordinates allows thermoneutral, and the products are -0.^D4^Oa^I:n¹d^0.1+⁰0³.⁹2^/Ck⁸c^Na^Jl⁰m⁰¹o³l^1F

also the elucidation of the products after H₂elimination. In the for the anti- and gauche-, respectively.

anti-conformer the final product is obtained in the trans-

geometry whereas the gauche- structure leads to the cis-

Table 1. Voltammetric Peak Widths, E_p=E_p–E_p/2; Standard Potential, E⁰; Electron’s number, z; Disproportionation Equilibrium Constant, K_dis, Applied Potential, E_ap

,

Number of Faraday consumed (F=96500 C mol^-1) for the compounds in DMF+0.10 M Bu₄NBF₄at glassy carbon electrode (CV) or graphite electrode (Electrolysis).

20 °C.

Cyclic Voltammetry

Compound

E_p/ mV

E⁰/Vvs. SCE

z

K_disp

Z-O₂NC₆H₄CH=CHC₆H₄NO₂

E-O₂NC₆H₄CH=CHC₆H₄NO₂

53

48

- 0.89

- 0.91

1.8

2.0

0.34

0.55

O₂NC₆H₄CH₂-CH₂C₆H₄NO₂

O₂NC₆H₄CMeH-CMeHC₆H₄NO₂

O₂NC₆H₄CBrH-CBrHC₆H₄NO₂

PhCBrH-CBrHPh^[a]

88

89

- 1.15

1.6

1.5

1.7

1.0

0.08

- 1.15

0.06

77

- 0.80^[b]

- 1.55^[b]

- 1.18

-

146

60

O₂NC₆H₄Me

Electrolysis

Compound

E_ap/Vvs. SCE

-1.20

F

conversion reactant/%^[c]

E-O₂NC₆H₄CH=CHC₆H₄NO₂/%^[c]

Z-O₂NC₆H₄CH=CHC₆H₄NO₂

E- O₂NC₆H₄CH=CHC₆H₄NO₂

O₂NC₆H₄CH₂-CH₂C₆H₄NO₂

O₂NC₆H₄CMeH-CMeHC₆H₄NO₂

O₂NC₆H₄CBrH-CBrHC₆H₄NO₂

PhCBrH-CBrHPh^e

2.0

100

0

89^[d]

70^[d,e]

76^[d]

0

89^[d]

80^[g]

13^[d]

-1.20

1.2

[f]

85

0

-1.40

[f]

- 0.85

100

37

-1.90

O₂NC₆H₄Me

-1.20

1.0

[a] meso-1,2-dibromo-1,2-diphenylethane.

[b] Value of peak potential of first wave at 0.50 V s^-1.

[c] By CV just after electrolysis and GC-MS analysis after treatment of electrolyzed solution.

[d] Others products are not identified.

*e+ Trace amounts of 4.4’-dinitrostilibine and bis(4-nitrophenyl)ethanodione are identified by GC-MS analysis and H¹-NMR.

[f] Exhaustive

[g] Stilbene (80%) and 1-bromo,1-phenylethane (5%) are identified by GC-MS analysis after treatment of electrolyzed solution.

α,α’-Dimethyl-4,4’-dinitrobibenzyl, O₂NC₆H₄CMeH-CMeHC₆H₄NO₂

The presence of two methyl groups in α-position does not

change the shape of the CV wave. Thus, in the reduction scan,

one two-electron reversible wave, independent of scan rate

and concentration, is obtained. The standard potential, E⁰, the

peak width, E_p, and the number of electrons are -1.15 V, 89

mV and 1.6 respectively:

anti- Ar

0.0

gauche-Ar

9.8

Relative energy of reactants /kcal mol^-1

Transition state energy^[a]/kcal mol^-1

Energy of products/kcal mol^-1

50.4

104.8

-0.4 ^[b]

10.0 ^[c]

As in the previous cases of O₂NC₆H₄CH=CHC₆H₄NO₂and

O₂NC₆H₄CH₂-CH₂C₆H₄NO₂, this reaction is consistent with two

successive one-electron transfer reductions:

[a] for: O₂NC₆H₄CH₂-CH₂C₆H₄NO₂^2-O₂NC₆H₄CH=CHC₆H₄NO₂^2-+H₂.

[b] E-O₂NC₆H₄CH=CHC₆H₄NO₂. [c] Z-O₂NC₆H₄CH=CHC₆H₄NO₂.

Scheme 3.

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a reaction coordinate calculation analogous to the one

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previously discussed for the parent^DO4^I:,4¹⁰’-^.1d⁰i³n⁹it^/Cro⁸b^Ni^Jb⁰e⁰n¹³z¹y^Fl

2-

dianion, O₂NC₆H₄CH₂-CH₂C₆H₄NO₂

, and in this case a

continuous increase in energy is found as the two hydrogen

atoms remain unbounded along all the calculated points.

However, we have also calculated the gauche conformers

(anti-Me and anti-Ar). These conformers are just 1.1 and 7.0

kcal mol^-1above the more stable anti-conformation,

respectively, so that the two forms are predicted to be in

thermal equilibrium at normal temperatures. A new reaction

coordinate calculation from anti-Me and anti-Ar confirms that

now the H₂molecule can be formed at the end of the two

simultaneous C-H cleavages but, surprisingly enough, the

energy barriers for the process are quite high, 106.1 and 75.0

kcal mol^-1, respectively. A careful look at the full picture of the

bond breaking reaction coordinate reveals that in the more

overcrowded gauche conformations the different skeletal

motions (involving both the methyl and the bulk nitrophenyl

groups) that facilitate the formation of the H₂molecule are

sterically hindered and so the energy barrier is higher than the

The values of



E_p=89 mV and z=1.6 are in agreement with

0

E⁰=E₂-E₁⁰-64 mV that correspond to K_disp=0.06.(37,38) That

is, the comproportionation of O₂NC₆H₄CMeH-CMeHC₆H₄NO₂

2-

and

O₂NC₆H₄CMeH-CMeHC₆H₄NO₂

overcomes

the



disproportionation of O₂NC₆H₄CMeH-CMeHC₆H₄NO₂

.

A CV after a potential controlled exhaustive electrolysis at

-1.40 V, shows that the dianion is stable. Furthermore, when

the solution is quenched with water the reactant is recovered

and identified by GC-MS analysis. In others words, the

corresponding α,α’-dimethyl-4,4’-dinitrostilbene is not formed

in the electrolysis time scale from the dianion

value calculated for the 4,4’-dinitrobibenzyl dianion,

2-

O₂NC₆H₄CH₂-CH₂C₆H₄NO₂

.

O₂NC₆H₄CMeH-CMeHC₆H₄NO₂^2-, contrary to what happens

with the related dianion O₂NC₆H₄CH₂-CH₂C₆H₄NO₂

suggests that the loss of hydrogen from the dianion

O₂NC₆H₄CMeH-CMeHC₆H₄NO₂

hindrance of the two methyl groups in α-position. Additionally,

a theoretical study is consistent with previous electrochemical

2-

. This

α,α’-Dibromo-4,4’-dinitrobibenzyl, O₂NC₆H₄CBrH-CBrHC₆H₄NO₂

At 0.50 V s^-1, in a reduction scan, two closely spaced two-

electron waves, with the first irreversible and narrow

2-

is prevented by steric

(E_p=- 0.80 V vs. SCE,

E_p=77 mV) and the second reversible

(E⁰=-0.90 V vs. SCE), are observed. Upon raising the scan rate

up to 100 V s^-1, the first wave remains irreversible, and no

change was observed in the second one. Moreover, after the

first irreversible wave, and regardless of the sweep rate used,

the CV shows an anodic irreversible wave at +0.80 V vs. SCE

corresponding to oxidation of bromide anion.(41–43)After an

exhaustive electrolysis at -0.85 V vs. SCE in Ar atmosphere, CV

of the solution only shows the second reversible wave, while

the first one has disappeared. This second wave corresponds

to O₂NC₆H₄CH=CHC₆H₄NO₂, as consistently demonstrated by

GC-MS analysis of the solution after quenching with water and

extraction with toluene. GC analysis of the previous solution

show 100% conversion of the dibromo derivative, with 89%

yield in E-O₂NC₆H₄CH=CHC₆H₄NO₂:

results.

Calculations

indicated

that

the

2-

O₂NC₆H₄CMeH-CMeHC₆H₄NO₂dianion is also stable, with the

singlet state being the lowest in energy. (Scheme 4)

anti-H

0

anti-Me

1.1

anti-Ar

7.0

Relative energy of reactants /kcal mol^-1

Transition state energy^[a]/kcal mol^-1

--^[b]

106.1

75.0

In

the

same

way,

the

meso-1,2-dibromo-1,2-diphenylethane

(PhCBrH-CBrHPh)

(Figure 2 and Table 1) shows a similar electrochemical

behaviour, independently of the scan rate used. As expected, it

is more difficult to reduce (i.e. the Ep of the first wave is ca.

650 mV more negative than in the dinitrophenyl derivative),

because of the lack of the electrowithdrawing NO₂groups. In a

reduction scan at 0.50 V s^-1, three waves are observed. The

first is irreversible and wide, and corresponds to two-electron

[b] The energy continuously rises as the two H-atoms are separated and the H₂product

cannot be formed.

Scheme 4.

The most stable conformation of the two central sp³carbon

atoms has the two hydrogen atoms in anti-position so that

when enlarging the two C-H bonds the formation of the H₂

molecule is unlikely. This point has been verified by performing

transfer (E_p=-1.55 V vs. SCE,

E_p=146 mV); the second is a

reversible one-electron wave (E⁰=-2.20 V vs. SCE) and the

6 | J. Name., 2012, 00, 1-3

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ARTICLE

third, is an irreversible and narrow one-electron wave (E_p=-

2.62 V vs. SCE, E_p=70 mV). The latter two waves correspond

View Article Online

DOI: 10.1039/C8NJ00131F



to stilbene (cis- or trans-) in accordance with literature.(44–47)

Moreover, after the first irreversible wave, and for all sweep

rates used, the CV shows an anodic irreversible wave at +0.80

V vs SCE, corresponding to oxidation of bromide anion.(41–43)

Furthermore, after exhaustive electrolysis at -1.90 V, the CV

only shows the presence of the characteristic waves of the

stilbene. Again, GC-MS analysis of the solution quenched with

water show the presence of stilbene, as the only product

(100% conversion of the reagent and 80% yield)

Scheme 5.

Additionally, theoretical results are in good agreement with

electrochemical results. It was not possible to optimize the

O₂NC₆H₄CBrH-CBrHC₆H₄NO₂

spontaneously breaks

2-

dianion,

to

because

produce neutral

it

down

4,4’-dinitrostilbene, E-O₂NC₆H₄CH=CHC₆H₄NO₂, and two

bromide anions (the alternative breaking down to Br₂is found

to be 76.13 kcal mol^-1higher in energy at the considered level

of calculation).

4-Nitrotoluene, O₂NC₆H₄Me

In a reduction scan, one-electron reversible wave independent

of scan rate and concentration is observed. Values of E⁰, the

peak width, E_p, and the number of electrons are -1.18 V, 60

mV and 1.0 respectively, which are in agreement with

previously reported data in the literature.(29–36) In other

words, the anion radical formed in the reduction scan is stable

along CV time scale.

However, when a constant potential electrolysis at potential

more negative than -1.18 V was carried out, the initial

pale-yellow solution evolves to a blue dark solution. When this

solution was analyzed by CV, a decrease in the wave

corresponding to O₂NC₆H₄Me was observed, concomitant with

Figure 2. CV of PhCBrH-CBrHPh (6.99 mM) before (──) and after exhaustive

electrolysis (····) at more negative potentials that of first cathodic peak potential)

and CV of stilbene (5.97 mM) (─ · ─). In DMF+0.10 M Bu₄NBF₄at glassy carbon

electrode. Scan rate, 0.50 V s^-1; temperature, 20 ºC; Ar atmosphere.

an

increase

in

the

wave

corresponding

to

O₂NC₆H₄CH=CHC₆H₄NO₂. Moreover, only O₂NC₆H₄Me and

O₂NC₆H₄CH=CHC₆H₄NO₂were recovered after the work-up of

the electrolyzed solution. Noticeably O₂NC₆H₄CH₂-CH₂C₆H₄NO₂

was not detected in the reaction mixture. The combined CV

and electrolysis results indicate that the chemical reactions

coupled to an electron transfer process are slow. Thus,

conversions and yields were consistently moderate; at -1.20 V

In summary, both O₂NC₆H₄CBrH-CBrHC₆H₄NO₂and related

PhCBrH-CBrHPh show, after the first cathodic reduction

irreversible wave, an anodic one at +0.80

V vs SCE

corresponding to the oxidation of the bromide anion.

Furthermore, after the first cathodic wave, those

corresponding to the presence of O₂NC₆H₄CH=CHC₆H₄NO₂and

stilbene are observed, respectively. All these results allow us

to conclude that the first reduction waves correspond to the

reductive cleavage of both dibromo compounds,

O₂NC₆H₄CBrH-CBrHC₆H₄NO₂and PhCBrH-CBrHPh, leading to

the corresponding stilbene derivatives and bromide anion.

Furthermore, from the shapes of the first waves, the nitro-

derivative, O₂NC₆H₄CBrH-CBrHC₆H₄NO₂evolves to the stilbene

derivative through a stepwise mechanism, with k > 4 10³s^-

¹,(48) while PhCBrH-CBrHPh exhibit a concerted reductive

cleavage mechanism, Scheme 5.(49,50)

(1F),

a 13% yield of O2NC6H4CH=CHC6H4NO2, at37%

conversion of O₂NC₆H₄Me was achieved, and at -1.70 V (1F)

these increase to 22% and 62% respectively. In both cases, the

remaining material was recovered as O₂NC₆H₄Me:

The previous results were confirmed by UV-visible

spectroelectrochemistry experiments. After electrolysis at -

1.20 V during 90 s of a solution of O₂NC₆H₄Me (10 mM in DMF

+ 0.1 M Bu₄NBF₄), the spectrum shows bands at 604, 641 and

660 nm, corresponding to electrolysis products, namely of

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2-

O₂NC₆H₄CH=CHC₆H₄NO₂,

O₂NC₆H₄CH=CHC₆H₄NO₂

and The CV of O₂NC₆H₄Me and O₂NC₆H₄CH₂-CH₂C₆H₄NO₂,

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O₂NC₆H₄CH=CHC₆H₄NO₂^.(39)

O₂NC₆H₄CMeH-CMeHC₆H₄NO₂and O₂NC₆^DH^O₄^IC^:H¹⁰=^.1C⁰H³⁹C^/₆^CH⁸₄^NN^JO⁰⁰₂¹³¹in^F

Several authors have shown that the reaction of O₂NC₆H₄Me DMF shows a fast two electron transfer reduction for all

with an excess of potassium tert-butoxide renders compounds, except for O₂NC₆H₄Me that shows a one-electron

O₂NC₆H₄CH=CHC₆H₄NO₂, via the nitrobenzyl anion.(21–23) A transfer one. The standard potential, E⁰, the peak width,

E_p,

similar process was repeated here by adding 10 equivalents of the number of electrons, z as well as the shape of waves are

PhLi and iPr2NH in THF to a solution of O₂NC₆H₄Me in DMF. not dependent on scan rates or the concentration used. E⁰

This forms the nitrobenzyl anion that again evolves to values for all compounds, except for O₂NC₆H₄CH=CHC₆H₄NO₂,

O₂NC₆H₄CH=CHC₆H₄NO₂, as shown by CV analysis. This differ ca. 30 mV. In the case of dinitrostilbene, because the

suggests that in the electrochemical reduction of O₂NC₆H₄Me, two negative charges are more easily delocalized between the

the anion radical, O₂NC₆H₄Me^formed evolves to the two conjugated aromatic rings the E⁰is 240 mV more positive

4-nitrotoluene benzyl anion, by a H-atom transfer reaction to a than the rest of above mentioned compounds. When

neutral molecule.

comparing the E_pand z for the bielectronic processes, the

expected correlation was observed to be in good agreement

with the theory. Finally, the K_dis<1 of the anion radicals

indicates the coexistence of the neutral molecule, the anion

radical and the dianion. In summary, the four nitroaromatics

show the expected reduction mechanism and the reduced

species, dianion for the biaryl species or the anion radical

anion for nitrotoluene are stable in the CV time scale.

A

similar process was proposed in the evolution of

4-nitrobenzyl cyanide anion radical to the corresponding

anion.(40)

Although the acidic character of O₂NC₆H₄Me is well

established, theoretical calculations reveal that in the anion

radical O₂NC₆H₄Me^the process of losing a H-atom is highly

endoergic by 68.1 kcal mol^-1. However, when the H-atom is

transferred to a molecule of O₂NC₆H₄Me the endoergicity

dramatically decreases to 36.7 kcal mol^-1. As expected, the

difference in the energy between the unimolecular and

bimolecular reactions arises from the stabilization provided by

the delocalization of the unpaired electron on the

2-

However, the dianions O₂NC₆H₄CBrH-CBrHC₆H₄NO₂and their

analogue without

a

nitro group, PhCBrH-CBrHPh^2-, are

intrinsically unstable. Both evolve through fast C-Br bond

breaking (k>4x10³s^-1) forming O₂NC₆H₄CH=CHC₆H₄NO₂,

PhCH=CHPh and two bromide anions, as shown by the

appearance of the waves corresponding to the reduction of

O₂NC₆H₄CH=CHC₆H₄NO₂and PhCH=CHPh and that of oxidation

of the bromide anion.

O₂NC₆H₄(H)CH₃radical. A value of ca. 36 kcal mol^-1for the



Comparative electrolysis behavior

bimolecular reaction is still high, but the whole process might

be allowed if the effect of the surrounding media that will

probably favor the reaction were taken into account.

Furthermore, the process can be driven by the coupled

reactions involving the products formed. Thus, the radical

The investigated nitroderivatives show two different

electrolytic behaviors. Identical I-E curves before and after

electrolysis were observed for Z-O₂NC₆H₄CH=CHC₆H₄NO₂,

E-O₂NC₆H₄CH=CHC₆H₄NO₂, O₂NC₆H₄CBrH-CBrHC₆H₄NO₂, and



O₂NC₆H₄CMeH-CMeHC₆H₄NO₂.

However,

formed, O₂NC₆H₄(H)CH₃, is oxidized at the working potential

to O₂NC₆H₄Me and H⁺,(51,52) while the 4-nitrobenzylanion

dimerizes to form O₂NC₆H₄CH₂-CH₂C₆H₄NO₂^2-. This, as was

previously demonstrated (see above), evolves by the loss of a

O₂NC₆H₄CH₂-CH₂C₆H₄NO₂and O₂NC₆H₄Me show dramatically

different I-E curves before and after electrolysis. This is

because, after the electron transfer, a slow chemical reaction

takes place (slower in the case of 4-nitrotoluene). In both cases

the chemical reaction finally evolves to E-4,4’-dinitrostilbene.

With the aim to improve the yields of the synthetic processes,

bulk electrolysis experiments were conducted, both at

constant potential or current. Best results were achieved using

acetonitrile as solvent and a nitrogen flow through the

solution that contains ca. 0.1% of oxygen. In these conditions,

pure E-4,4’-dinitrostilbene precipitates from the solution as a

microcrystalline yellow solid, Scheme 7. Isolated yields range

from 30 to 40% from 4-nitrotoluene and from 45 to 67% in the

case of 4,4’-dinitrobibenzil. In both cases experiments at

constant current provides higher yields, and they are similar to

those measured by GC.

2-

hydrogen molecule to O₂NC₆H₄CH=CHC₆H₄NO₂(Scheme 6).

This dianion, O₂NC₆H₄CH=CHC₆H₄NO₂reacts with water

producing H₂and O₂NC₆H₄CH=CHC₆H₄NO₂during the work-up

of the solution.

2-

Scheme 6.

Comparative CV behavior

8 | J. Name., 2012, 00, 1-3

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electrolysis realized at constant potential and current yields a

View Article Online

yellow solid that is separated by filtratio^Dn^Of^Ir^:o¹⁰m^.10b³l⁹u^/e^C8s^No^Jlu⁰⁰ti¹o³n^1F.

The solid was recrystallized in hot ethanol. Rendering pure

E-O₂NC₆H₄CH=CHC₆H₄NO₂(40% and 67%yield from

4-nitrotoluene and 4.4’dinitrobibenzyl, respectively).

DFT Calculations

The well-known B3LYP hybrid functional has been chosen with

the split-valence 6-31+G(d,p) basis set that includes

polarization functions on all atoms and diffuse sp functions on

all atoms other than hydrogens. Geometries have been fully

optimized and the transition states have been approximately

located by means of a distinguished coordinate calculation

that simultaneously enlarges the two C-H bonds that must be

cleaved. All calculations have been carried out using the

GAUSSIAN09 suite of programs.(53)

Scheme 7.

Experimental

Chemicals

All reagents, ACN, DMF and NBu₄BF₄were of the highest purity

were commercial origin and used as received.

CV and Electrolysis Experiments

Conclusions

Voltammetry and electrolysis experiments were carried out in

a jacketed five neck conical cell at 20 C. Three of the necks

o

The anion radicals from the electroreduction of

Z-O₂NC₆H₄CH=CHC₆H₄NO₂,

O₂NC₆H₄CH₂-CH₂C₆H₄NO₂

E-O₂NC₆H₄CH=CHC₆H₄NO₂,

and O₂NC₆H₄CMeH-

were used for the working, counter, and reference electrodes,

while the other two necks were used for the argon inlet and

outlet.

For cyclic voltammetry experiments a glassy carbon disk with a

1 mm diameter was used as working electrode, with the

counter electrode being a 1 mm diameter Pt disk. The

reference electrode is a saturated calomel electrode (SCE),

separated from the working electrode compartment by a salt

bridge with a ceramic frit.

The number of electrons transferred in an electron transfer

step is calculated as the quotient between the function current

[I_pc^-1v^-1/2] of the electroactive substance and the function

current, [I_pc^-1v^-1/2]₀value of fluorenone (number of electrons

transferred=1) in the same experimental conditions (solution

and working electrode), were I_pis the peak current for

reduction wave, c is the concentration of solution, and v the

scan rate.

Electrolysis were performed at controlled potential (ca. 100

mV more negative than peak potential) using a carbon

graphite rod as a working electrode (8.0 cm²of surface), a Pt

rod as a counter electrode, and a saturated calomel electrode

(SCE) as a reference electrode. The counter electrode and the

SCE were isolated from the working electrode compartment by

a salt bridge, with a glass frit for the counter electrode, and a

ceramic frit for the reference electrode.

CMeHC₆H₄NO₂undergo disproportion into the neutral and

dianionic species with equilibrium constants ranging from 0.06

and 0.55. In the time scale of the CV (θ≤0.5 s), the

corresponding dianions do not evolve by any chemical

reaction, except for the disproportionation. Also, the anion

radical 4-nitrotoluene remains stable in these conditions.

However, in time scale of electrolysis (from minutes to hours),

2-

only the dianion O₂NC₆H₄CMeH-CMeHC₆H₄NO₂remains

2-

stable, since the reduced species, Z-O₂NC₆H₄CH=CHC₆H₄NO₂

,

O₂NC₆H₄CH₂-CH₂C₆H₄NO₂^2-or O₂NC₆H₄Me^•-, evolve totally or in

part to the E-O₂NC₆H₄CH=CHC₆H₄NO₂dianion. This dianion,

2-

after the work-up with water, is recovered as the neutral

species E-O₂NC₆H₄CH=CHC₆H₄NO₂, with concomitant water

reduction.

2-

In the case of the Z-O₂NC₆H₄CH=CHC₆H₄NO₂anion, the

negative charge diminishes the bond order of the central C=C

bond, allowing the cis- to trans- isomerization.

2-

On the other hand, the O₂NC₆H₄CH₂-CH₂C₆H₄NO₂dianion

spontaneously

E-O₂NC₆H₄CH=CHC₆H₄NO₂^2-, as demonstrated by combined

electrolysis CV experiments, spectroelectrochemical

releases

H₂

to

produce

experiments and theoretical calculations.

Therefore, in spite of being in electroreductive conditions, the

oxidized species E-O₂NC₆H₄CH=CHC₆H₄NO₂can be obtained

from O₂NC₆H₄CH₂-CH₂C₆H₄NO₂. A similar situation takes place

in the electroreduction of 4-nitrotoluene, but with a previous

step. The corresponding anion radical, O₂NC₆H₄Me^•-is

converted by intermolecular H-transfer reaction into the

After electrolysis in DMF and at constant potential were

complete after the chosen quantity of coulombs was circulated

or electrolysis were exhaustive (i.e. final current was 5% or less

than the initial current), the reaction mixture was extracted,

on air, with water/toluene. The organic layer was dried with

Na₂SO₄and evaporated yielding a residue that was analyzed by

GC, GC-MS and H¹-NMR.

The electrolysis experiments in ACN+0.10 M NBu₄BF₄were

performed at 10 °C in N₂:O₂(99.9:0.1) atmosphere in solutions

of reagents with concentration

-

benzylic anion O₂NC₆H₄CH₂, which dimerizes to O₂NC₆H₄CH₂-

2-

CH₂C₆H₄NO₂that evolves as previously described. Again, in

this case the oxidized E-O₂NC₆H₄CH=CHC₆H₄NO₂can be

obtained from 4-nitrotoluene under electroreductive

conditions.

20mM in the same

electrochemical cell and electrodes described. The exhaustive

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Bulk electrolysis in optimized conditions provides 40% and 67% 9. Abdul-Rahim O, Simonov AN, Boas JF, Rüther T, Collins DJ,

View Article Online

DOI: 10.1039/C8NJ00131F

isolated yield of E-4,4’-dinitrostilbene from 4-nitrotoluene and Perlmutter P, et al. Studies on the Nuances of the Electrochemically

4,4’-dinitrobibenzyl respectively.

In summary, this electrochemical study shown to be a Acetonitrile and Ionic Liquids. J Phys Chem B [Internet]. 2014 Mar

powerful technique to elucidate the mechanism of, at first 20;118(11):3183–91. Available from:

sight, puzzling reactions, and furthermore allows obtaining by http://pubs.acs.org/doi/abs/10.1021/jp500786j

electrolysis E-dinitrostilbene from 4-nitrotoluene or 4,4‘- 10. Wheeler OH, Pabon HNB de. Synthesis of Stilbenes.

Induced Room Temperature Isomerization of cis -Stilbene in

A

dinitrobibenzyl.

Comparative Study. J Org Chem [Internet]. 1965;30(5):1473–7.

Available from: http://dx.doi.org/10.1021/jo01016a031

11. Becker KB. Synthesis of Stilbenes. Synthesis (Stuttg) [Internet].

1983;1983(5):341–68. Available from: http://www.thieme-

connect.de/DOI/DOI?10.1055/s-1983-30334

12. Moncomble A, Floch P Le, Lledos A, Gosmini C. Cobalt-Catalyzed

Vinylation of Aromatic Halides Using β-Halostyrene: Experimental

and DFT Studies. J Org Chem [Internet]. 2012 Jun;77(11):5056–62.

Available from: http://pubs.acs.org/doi/abs/10.1021/jo3005149

13. Shen Z-L, Knochel P. Stereoselective Preparation of

Polyfunctional Alkenylindium(III) Halides and Their Cross-Coupling

with Unsaturated Halides. Chem - A Eur J [Internet]. 2015 May

Acknowledgements

We gratefully acknowledge the financial support of the

Ministerio de Economia y Competitividad of Spain through

projects CTQ2012-30853 and CTQ2015-65439R and CTQ2014-

53144-P.

We gratefully acknowledge the financial support of Universitat

Autònoma de Barcelona through doctoral scholarship of Sergio

Soler.

We gratefully acknowledge the support during the realization

and writing of manuscript to Prof. J.C. Bayón.

4;21(19):7061–5.

Available

from:

http://doi.wiley.com/10.1002/chem.201500943

14. Sutcliffe D, Greenwood S. Manufacture of 4,4’-diaminostilbene-

2,2’-disulphonic acid. United Kingdom; GB 1404853 A 19750903,

1975. p. 2.

15. Saiyed AS, Patel KN, Kamath B V., Bedekar A V. Synthesis of

stilbene analogues by one-pot oxidation-Wittig and oxidation-

Wittig–Heck reaction. Tetrahedron Lett [Internet]. 2012

References

1. Doody JJ. Production of Stilbene Azo Dyes. U.S.A.; US 3557079A

1970119, 1971. p. 3.

2. Oppliger MD. Stilbeneazo compounds, preparation thereof and

use thereof. Germany; DE 3247605A1 19830707, 1983.

3. Song DH, Yoo HY, Kim JP. Synthesis of stilbene-based azo dyes

and application for dichroic materials in poly(vinyl alcohol)

polarizing films. Dye Pigment [Internet]. 2007;75(3):727–31.

Aug;53(35):4692–6.

Available

from:

http://dx.doi.org/10.1016/j.tetlet.2012.06.090

16. Fry AJ. Synthetic Organic Electrochemistry. In New York: Harper

& Row Publishers; 1972. p. 134–5.

17. Hanna SB, Ruehle PH. The p-nitrobenzyl system. IV. Base-

induced transformations in p-nitrobenzyl chloride, bromide, iodide,

Available

from:

http://linkinghub.elsevier.com/retrieve/pii/S014372080600310X

4. Likhtenshtein G. Stilbenes: Applications in Chemistry, Life

Sciences and Materials Scienc [Internet]. Weinheim, Germany:

Wiley-VCH Verlag GmbH & Co. KGaA; 2009. 360 p. Available from:

http://doi.wiley.com/10.1002/9783527628087

5. Chen Y, Peng W, Wang S, Zhang F, Zhang G, Fan X. Supported

nano-sized gold catalysts for selective reduction of 4,4’-

dinitrostilbene-2,2’-disulfonic acid using different reductants. Dye

Pigment [Internet]. 2012 Nov;95(2):215–20. Available from:

http://dx.doi.org/10.1016/j.dyepig.2012.03.009

tosylate, and sulfonium salts.

Dec;40(26):3882–5.

J

Org Chem [Internet]. 1975

Available from:

http://pubs.acs.org/doi/abs/10.1021/jo00914a015

18. Lawless JG, Bartak DE, Hawley MD. Electrochemical reduction of

nitrobenzyl halides in acetonitrile. J Am Chem Soc [Internet]. 1969

Dec;91(25):7121–7.

Available

from:

http://pubs.acs.org/doi/abs/10.1021/ja01053a038

19. Kirkpatrick DL, Johnson KE, Sartorelli AC. Nitrobenzyl derivatives

as bioreductive alkylating agents: evidence for the reductive

formation of a reactive intermediate. J Med Chem [Internet]. 1986

6. Schulte-Frohlinde D, Blume H, Güsten H. PHOTOCHEMICAL cis-

trans-ISOMERIZATION OF SUBSTITUTED STILBENES. J Phys Chem

Oct;29(10):2048–52.

Available

from:

[Internet].

1962

Dec;66(12):2486–91.

Available

from:

http://pubs.acs.org/doi/abs/10.1021/jm00160a043

http://pubs.acs.org/doi/abs/10.1021/j100818a039

20. Andrieux CP, Le Gorande A, Saveant JM. Electron transfer and

bond breaking. Examples of passage from a sequential to a

concerted mechanism in the electrochemical reductive cleavage of

7. Bard AJ, Puglisi VJ, Kenkel J V., Lomax A. Reductive coupling and

isomerization of electrogenerated radical ions of cis- and trans-

isomers. Faraday Discuss Chem Soc [Internet]. 1973;56:353.

Available from: http://www.scopus.com/inward/record.url?eid=2-

s2.0-0009649186&partnerID=tZOtx3y1

8. Yamauchi K, Takashima Y, Hashidzume A, Yamaguchi H, Harada

A. Switching between Supramolecular Dimer and Nonthreaded

Supramolecular Self-Assembly of Stilbene Amide-α-Cyclodextrin by

arylmethyl halides.

Aug;114(17):6892–904.

J

Am Chem Soc [Internet]. 1992

Available from:

http://pubs.acs.org/doi/abs/10.1021/ja00043a039

21. Stansbury H, Proops W. Oxidation of p-Nitrotoluene to 4,4’-

Dinitrobibenzyl and 4,4’-Dinitrostilbene. J Org Chem [Internet].

1961

Oct;26(10):4162–4.

Available

from:

Photoirradiation.

Apr;130(15):5024–5.

http://pubs.acs.org/doi/abs/10.1021/ja7113135

J

Am

Chem

Soc

[Internet].

2008

from:

http://pubs.acs.org/doi/abs/10.1021/jo01068a640

22. Russell GA, Moye AJ, Janzen EG, Mak S, Talaty ER. Reaction of

resonance stabilized anions. XXVII. Oxidation of carbanions. 2.

Available

10 | J. Name., 2012, 00, 1-3

Please do not adjust margins

Page 11 of 13

New Journal of Chemistry

Please do not adjust margins

Journal Name

ARTICLE

Oxidation of p-nitrotoluene and derivatives in basic solution. J Org http://linkinghub.elsevier.com/retrieve/pii/S0022072806005705

View Article Online

DOI: 10.1039/C8NJ00131F

Chem [Internet]. 1967 Jan;32(1):137–46. Available from: 37. Bard AJ, Faulkner LR. Electrochemical Methods: Fundamental

http://pubs.acs.org/doi/abs/10.1021/jo01277a035

23. Lu J-R, Wang Y-L, Feng Y, Gu L. Synthesis of 4, 4’-Dinitrodibenzyl Methods: Fundamental and Applications. 2nd ed. New York: John

and 4, 4’-Dinitrostilbene. Chinese J Appl Chem. 2000;17(6):653–5. Wiley & Son; 2001. p. 505–9.

and Applications. In: Bard AJ, Faulkner LR, editors. Electrochemical

24. Russell GA, Pecoraro JM. Electron transfer processes. 20. 38. Polcyn DS, Shain I. Theory of Stationary Electrode Polarography

Conversion to p,p’-dinitrostilbene and other examples of the SRN1 for a Multistep Charge Transfer with Catalytic (Cyclic) Regeneration

substitution reactions of p-nitrobenzyl derivatives. J Am Chem Soc of the Reactant. Anal Chem [Internet]. 1966 Mar;38(3):376–82.

[Internet].

1979

Jun;101(12):3331–4.

Available

from: Available from: http://pubs.acs.org/doi/abs/10.1021/ac60235a003

39. Álvarez-Griera L, Gallardo I, Guirado G. Estimation of

http://pubs.acs.org/doi/abs/10.1021/ja00506a032

25. Buncel E, Menon BC. Proton-transfer and electron-transfer nitrobenzyl radicals reduction potential using spectro-

processes in reaction of p-nitrotoluene with bases. electrochemical techniques. Electrochim Acta [Internet]. 2009

Am Chem Soc [Internet]. 1980 Sep;54(22):5098–108. Available from:

A

spectrophotometric study.

J

May;102(10):3499–507.

http://pubs.acs.org/doi/abs/10.1021/ja00530a032

Available

from: http://linkinghub.elsevier.com/retrieve/pii/S0013468609002643

40. Bartak DE, Hawley MD. Stabilities of the anion radicals of

26. Miller JM, Pobiner H. A Spectrophotometric Study of the nitrobenzyl derivatives.

Reactions of p -Nitrotoluene in Basic Solution. Anal Chem [Internet]. Jan;94(2):640–2.

J

Am Chem Soc [Internet]. 1972

Available from:

1964

Jan;36(1):238–9.

Available

from: http://pubs.acs.org/doi/abs/10.1021/ja00757a058

41. Rifi MR, Covitz FH. Introduction to Organic Electrochemistry. In:

http://pubs.acs.org/doi/abs/10.1021/ac60207a004

27. Mann CK, Barnes KK. Electrochemical Reactions in Nonaqueous Introduction to Organic Electrochemistry. New York, USA: Marcel

Systems. In: Electrochemical Reactions in Nonaqueous Systems. Dekker, INC; 1974. p. 194–219.

New York, USA: Marcel Dekker, INC; 1970. p. 347–80.

42. Lund T, Lund H. Indirect electrochemical reduction of some

28. Lund H, Hammerich O. Organic Electrochemistry. In: Organic benzyl chlorides. Acta Chem Scand. 1987;41:93–102.

Electrochemistry. 4th ed. New York, USA: Marcel Dekker, INC; 2001. 43. Gallardo I, Guirado G, Marquet J. Nucleophilic Aromatic

p. 379–410.

29. Ammar F, Savéant JM. Thermodynamics of successive electron Cyanation of Nitroarenes. Chem Eur

transfers. J Electroanal Chem Interfacial Electrochem [Internet]. 17;7(8):1759–65. Available

1973 Sep;47(1):115–25. Available from: http://doi.wiley.com/10.1002/1521-

http://linkinghub.elsevier.com/retrieve/pii/S0022072873803511 3765%2820010417%297%3A8%3C1759%3A%3AAID-

30. Mohammad M. single two electron transfer or high CHEM17590%3E3.0.CO%3B2-F

Substitution of Hydrogen: A Novel Electrochemical Approach to the

J

[Internet]. 2001 Apr

from:

A

disproportionation: Electrochemical reduction of dinitrobibenzyl. 44. Gatti N, Pedersen SU, Lund H, Ernster L, Lönnberg H, Berg J-E, et

Electrochim Acta [Internet]. 1977 Apr;22(4):487–8. Available from: al. Electrochemical Methods for Determination of Rate Constants.

http://linkinghub.elsevier.com/retrieve/pii/0013468677851050

31. Kalninsh KK, Kutsenko AD, Archegova AS. Structure, electron- Induced by the Substrate Anion. Acta Chem Scand [Internet].

accepting properties, and reactivity of nitrostilbenes. J Struct Chem 1988;42b(1):11–22. Available from:

III. Homogeneous Electron Transfer Followed by Elimination

[Internet].

1998;39(4):520–31.

Available

from: http://actachemscand.org/doi/10.3891/acta.chem.scand.42b-0011

45. Fawell P, Avraamides J, Hefter G. Reduction of Vicinal Dihalides.

http://link.springer.com/10.1007/BF02701382

32. Halas SM, Okyne K, Fry AJ. Anodic oxidation of stilbenes bearing I. The Electrochemical Reduction of meso and (±)-1,2-Dibromo-1,2-

electron-withdrawing ring substituents. Electrochim Acta [Internet]. diphenylethane. Aust J Chem [Internet]. 1990 Aug 1;43(8):1421.

2003 Jun [cited 2014 Apr 25];48(13):1837–44. Available from: Available from: http://dx.doi.org/10.1071/CH9901421

http://linkinghub.elsevier.com/retrieve/pii/S0013468603002500

33. Kraiya C, Singh P, Todres Z V, Evans DH. Voltammetric studies of Dimerization of α - Substituted Benzyl Radicals. Steric Effects on

the reduction of cis- and trans-α-nitrostilbene. J Electroanal Chem Dimerization. Org Chem [Internet]. 1996 Jan;61(9):3191–4.

46. Fry AJ, Porter JM, Fry PF. Electrochemical Formation and

J

[Internet].

2004

Mar;563(2):171–80.

Available

from: Available from: http://www.ncbi.nlm.nih.gov/pubmed/11667185

47. Bollo S, Soto-Bustamante E, Núñez-Vergara LJ, Squella JA.

http://linkinghub.elsevier.com/retrieve/pii/S0022072803005412

34. Kraiya C, Singh P, Evans DH. Revisiting the heterogeneous Electrochemical study of nitrostilbene derivatives: nitro group as a

electron-transfer kinetics of nitro compounds. J Electroanal Chem probe of the push–pull effect. J Electroanal Chem [Internet]. 2000

[Internet].

2004

Mar;563(2):203–12.

Available

from: Sep;492(1):54–62.

Available

from:

http://linkinghub.elsevier.com/retrieve/pii/S0022072803005448

http://linkinghub.elsevier.com/retrieve/pii/S0022072800002655

35. Macías-Ruvalcaba NA, Evans DH. Study of the Effects of Ion 48. Andrieux CP, Savéant JM. Investigations of Rates and

Pairing and Activity Coefficients on the Separation in Standard Mechanisms of Reactions. In: Bernasconi CF, editor. Investigations

Potentials for Two-Step Reduction of Dinitroaromatics. J Phys Chem of Rates and Mechanisms of Reactions. 4th ed. New York: John

B

[Internet]. 2005 Aug;109(30):14642–7. Available from: Wiley & Sons, Inc; 1986. p. 305–90.

http://pubs.acs.org/doi/abs/10.1021/jp051641p 49. Andrieux CP, Gallardo I, Saveant JM. Outer-sphere electron-

36. Macías-Ruvalcaba NA, Telo JP, Evans DH. Studies of the transfer reduction of alkyl halides. A source of alkyl radicals or of

electrochemical reduction of some dinitroaromatics. J Electroanal carbanions? Reduction of alkyl radicals. J Am Chem Soc [Internet].

Chem [Internet]. 2007 Feb;600(2):294–302. Available from: 1989

Mar;111(5):1620–6.

Available

from:

J. Name., 2013, 00, 1-3 | 11

Please do not adjust margins

New Journal of Chemistry

Page 12 of 13

ARTICLE

Journal Name

http://pubs.acs.org/doi/abs/10.1021/ja00187a014

View Article Online

DOI: 10.1039/C8NJ00131F

50. Andrieux CP, Grzeszczuk M, Saveant JM. Electrochemical

generation and reduction of organic free radicals. alpha-

Hydroxybenzyl radicals from the reduction of benzaldehyde. J Am

Chem Soc [Internet]. 1991 Nov;113(23):8811–7. Available from:

http://pubs.acs.org/doi/abs/10.1021/ja00023a032

51. Andrieux CP, Pinson J. The Standard Redox Potential of the

Phenyl Radical/Anion Couple. J Am Chem Soc [Internet]. 2003

Dec;125(48):14801–6.

http://pubs.acs.org/doi/abs/10.1021/ja0374574

52. Gallardo I, Soler S. Electrochemically promoted arylation of

Available

from:

iodoaromatics.

J

Electroanal

Chem

[Internet].

2017

Aug;799(May):9–16.

Available

from:

http://linkinghub.elsevier.com/retrieve/pii/S1572665717303946

53. Frisch MJ, Trucks GW, Schlegel HB, Scuseria GE, Robb MA,

Cheeseman JR, et al. Gaussian 09, Revision B.01 [Internet]. Gaussian

09, Revision B.01, Gaussian, Inc., Wallingford CT. Wallingford CT;

2009. Available from: citeulike-article-id:9096580

12 | J. Name., 2012, 00, 1-3

Please do not adjust margins

Page 13 of 13

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View Article Online

DOI: 10.1039/C8NJ00131F

Oxidation of nitroarenes under electroreductive conditions: the electrochemical reduction of

4,4’-dinitrobibenzyl and 4-nitrotoluene lead to the dianion of E-4,4’-dinitrostilbene.

Article Doi

From 4-nitrotoluene and 4,4′-dinitrobibenzyl to: E -4,4′-dinitrostilbene: An electrochemical approach

DOI: 10.1039/c8nj00131f

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Authors:

Article abstract of DOI:10.1039/c8nj00131f

Full text of DOI:10.1039/c8nj00131f

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