Electron donor-acceptor interaction of 3,4-dimethylaniline with 2,3-dicyano-1,4-naphthoquinone

Article abstract of DOI:10.1016/j.saa.2010.11.013

The electron donor-acceptor (EDA) interaction between 2,3-dicyano-1,4- naphthoquinone (DCNQ) and 3,4-dimethylaniline (3,4-DMA) is studied in chloroform, dichloromethane and 1:1 (v/v) mixture of chloroform and dichloromethane. The rate of formation of the product was measured as a function of time using UV-vis spectrophotometer. The formation constant (K) and molar extinction coefficient (ε) values for the formation of EDA complex were evaluated in the temperature range of 20-35 °C. The pseudo-first-order rate constant (k₁) and the second-order rate constant (k₂) for the disappearance of EDA complex and for the formation of product were evaluated. The activation parameters (ΔH^#, ΔS^# and ΔG^#) of the reaction were determined by temperature dependence of rate constants using the Arrhenius plots. The effect of relative permittivity of the medium on the reaction is discussed. The observed results indicate that formation of final product proceeds through initial formation of EDA complex as an intermediate. The product of the reaction was purified by column chromatography method and identified as 3-(N-3,4-dimethyl-phenylamino)-2- cyano-1,4-naphthoquinone by elemental analysis, IR and NMR spectroscopy. On the basis of kinetic, analytical and spectroscopic results, a plausible mechanism for the formation of EDA complex and its transformation into product is proposed.

Full text of DOI:10.1016/j.saa.2010.11.013

Spectrochimica Acta Part A 78 (2011) 480–487
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Electron donor–acceptor interaction of 3,4-dimethylaniline with
2,3-dicyano-1,4-naphthoquinone
Gururaj M. Neelgund∗, Subash R. Magadum1, M.L. Budni
P.G. Department of Studies in Chemistry, Karnatak University, Dharwad 580 003, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 July 2010
Received in revised form 23 October 2010
Accepted 15 November 2010
The electron donor–acceptor (EDA) interaction between 2,3-dicyano-1,4-naphthoquinone (DCNQ) and
3,4-dimethylaniline (3,4-DMA) is studied in chloroform, dichloromethane and 1:1 (v/v) mixture of chlo-
roform and dichloromethane. The rate of formation of the product was measured as a function of time
using UV–vis spectrophotometer. The formation constant (K) and molar extinction coefficient (ε) values
for the formation of EDA complex were evaluated in the temperature range of 20–35 ◦C. The pseudo-first-
order rate constant (k1) and the second-order rate constant (k2) for the disappearance of EDA complex
and for the formation of product were evaluated. The activation parameters (ꢀH#, ꢀS# and ꢀG#) of the
reaction were determined by temperature dependence of rate constants using the Arrhenius plots. The
effect of relative permittivity of the medium on the reaction is discussed. The observed results indicate
that formation of final product proceeds through initial formation of EDA complex as an intermediate.
The product of the reaction was purified by column chromatography method and identified as 3-(N-3,4-
dimethyl-phenylamino)-2-cyano-1,4-naphthoquinone by elemental analysis, IR and NMR spectroscopy.
On the basis of kinetic, analytical and spectroscopic results, a plausible mechanism for the formation of
EDA complex and its transformation into product is proposed.
Keywords:
2,3-Dicyano-1,4-naphthoquinone
3,4-Dimethylaniline
Charge transfer complex
Spectrophotometry
Activation parameters
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
because of their pharmaceutical interests [20–22]. On the other
hand, aromatic donors are well known in forming the EDA com-
The electron donor–acceptor (EDA) complexes are of current
interest owing to their potential utilization in biological sys-
tems [1,2], as organic semiconductors [3] and photocatalyst [4].
EDA complexes are prospective candidates for non-linear opti-
cal materials and electrical conductivities [5,6]. These complexes
are commonly found as intermediates in a variety of reactions
involving electron rich species or donors, such as nucleophiles
and bases, and electron deficient acceptors [7–10]. EDA com-
plexes promote reactivity by bringing the reactants together and
encouraging the correct orbital overlap required for electronic
reorganization [11]. Naphthoquinone and benzoquinone deriva-
tives are eminent ␲-acceptors, their electron accepting ability
can increase by introduction of electron withdrawing groups like
chloro-, nitro-, cyano-, etc., on quinone moiety [12–16]. Naph-
thoquinone derivatives contribute greatly to the commercially
important dyestuffs [17] and drugs [18,19]. Recently, substituted
naphthoquinones have attracted the attention of many researchers
plexes with different electron acceptors [23–25]. Some aromatic
amines are reported to undergo chemical reactions with strong
electron acceptors through formation of EDA complexes [26,27].
However, reports on the detailed kinetic study of reactions pro-
ceeding through the ground state of such complexes are quite a
few in numbers [28,29]. Nagakura and his co-workers have stud-
ied the interaction of aniline with chloranil and the formation
of product was rationalized through EDA complex as an inter-
mediate [29]. Roy et al., performed the spectroscopic and kinetic
studies on EDA interaction between a series of methylated ani-
lines and naphthalene-1,4,5,8-tetracarboxylic dianhydride [30].
The same group has reported another study on decay of EDA
complexes of aniline and 2,4-dimethylaniline with naphthalene-
1,4,5,8-tetracarboxylic dianhydride [31]. In addition, several such
kind of reactions are reported in recent years [9,10,32–38].
The reports on EDA interactions involving 1,4-naphthoquinone
derivatives are rather scanty. So it is our interest to study
the interaction of 2,3-dicyano-1,4-naphthoquinone (DCNQ) with
3,4-dimethylaniline (3,4-DMA). This piece of work reports on
the interaction between DCNQ and 3,4-DMA in chloroform,
dichloromethane and 1:1 (v/v) mixture of chloroform and
dichloromethane using UV–vis spectrophotometeric method. The
kinetic study, including isolation and characterization of final prod-
uct of the reaction is reported. On the basis of analytical, spectral
∗
Corresponding author at: Department of Chemistry, Prairie View A&M Univer-
sity, Prairie View, TX 77446, USA.
E-mail address: gneelgund@yahoo.com (G.M. Neelgund).
Present address: Department of Chemistry, SB Arts and KCP Science College,
1
Bijapur 586 103, Karnataka, India.
1386-1425/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2010.11.013

G.M. Neelgund et al. / Spectrochimica Acta Part A 78 (2011) 480–487
481
and kinetic results, a plausible mechanism for the formation of final
product is proposed.
2. Experimental
3,4-DMA (Fluka) was distilled under reduced pressure prior to
use. The spectral grade chloroform (Ranbaxy) and dichloromethane
(BDH) were used as received. The silica gel (60–120 mesh, Fischer)
was used in packing the column to purify the reaction product by
column chromatography method. The solvents, benzene (Ranbaxy)
and methanol (Ranbaxy) were purified by reported procedures [39]
and were used in column chromatography. The acceptor molecule,
DCNQ was synthesized with the procedure reported earlier [12,40].
The stock solutions of 3,4-DMA and DCNQ were freshly pre-
pared before each series of measurements by dissolving precisely
weighed amount of the component in the appropriate volume of
solvent. All the solutions were protected against light radiations
by keeping them in darkness. In every measurement pure solvent
was used in the reference beam and the molar concentration of
3,4-DMA was maintained 100–800 fold higher than that of DCNQ.
The electronic absorption spectra were recorded by Varian Cary
50 UV–vis spectrophotometer using 1 cm matched quartz cells at
20, 25, 30 and 35 ◦C. The temperature of the cell holder was con-
trolled with a water flow. IR spectrum of the reaction product was
obtained by Nicolet Impact 410, FTIR spectrometer and NMR spec-
trum was recorded on a Brucker 300 MHz NMR spectrometer. The
elemental analysis data of the product was obtained from Thermo
Quest C, H, N and S elemental analyzer.
Fig. 1. Electronic absorption spectra of a mixture of DCNQ (2.36 × 10−4 M) and 3,4-
DMA (0.0346 M) in chloroform at different intervals of time.
In the formulation of EDA complex the arrow serves only as a
symbol for the interaction of the whole molecular orbital of the
planar 3,4-DMA (including the aromatic sextet and the lone pair
of the nitrogen atom) with the molecular orbital of the planar
DCNQ. This is consistent with formulations for other similar EDA
complexes, with the assumption of a ‘sandwich’ structure in which
the component molecules lie in parallel planes [43].
Absorbance of the new low energy, EDA band was measured
with a constant concentration of DCNQ and varying concentration
of 3,4-DMA. The measured values of absorbance (d) were sub-
jected to ln d against time plot and extrapolated to obtain value
of absorbance at zero time (d*) (Fig. 2) [30,31]. The formation con-
stant (K) and molar extinction coefficient (ε) were then determined
using the 1:1 modified Benesi–Hildebrand (B–H) equation for cell
with 1 cm optical path length [44]:
3. Results and discussion
The electronic absorption spectra of DCNQ (2.36 × 10−4 M) in the
presence of excess of 3,4-DMA (0.0346 M) in chloroform at 20 ◦C
were monitored as a function of time and the resulting spectra
are shown in Fig. 1. The absorption spectra are characterized by
maximum absorptions at the wavelengths of 676, 350 and 366 nm.
However, none of the reactants show any absorption in the region
between 500 and 900 nm. The observed gradual decrease in the
intensity of the EDA band at 676 nm could be due to consumption of
EDA complex through an irreversible chemical reaction, while the
continuous increase in the bands at 350 and 366 nm with elapse of
time is indicative of the formation of the final product. An shoulder
appeared at 366 nm in the absorption spectra demonstrate that the
quinone chromophore is not disturbed by the interaction of DCNQ
with 3,4-DMA [41]. Thus the observed results indicate that the for-
mation of product proceeds through spontaneous formation of EDA
complex between electron donor (D) and acceptor (A) (reaction (a)),
followed by two consecutive reactions (b).
CA0CD0l
d∗
CA0 + CD0
1
Kε
=
+
(1)
ε
where CA0 and CD0 are the initial molar concentration of acceptor
(DCNQ) and donor (3,4-DMA), respectively and l is optical path
length. The values of K and ε were determined from the linear plots
of (CA0CD0l/d∗) versus (CA0 + CD0) and a representative plot is shown in
Fig. 3. The linearity of B–H plot shows the formation of 1:1 stoichio-
metric EDA complex between DCNQ and 3,4-DMA. The calculated
values of K and ε are summarized in Table 1. The formation constant
(K) values increases with increasing polarity of the solvent.
D + A ꢀ DA
DA → [D+−A−] → Product
(a)
(b)
The observed increase in the absorption band intensities with
elapse of time supports the fact that the EDA complex formed
between 3,4-DMAand DCNQis ofthedative-typestructure[D+–A−]
which consequently coverts to an ionic intermediate possessing the
spectral characteristics of DCNQ•− radical ion [42].
The pseudo-first-order rate constant (k1) and the second-order
rate constant (k2) for the disappearance of EDA complex were eval-
uated from the plots of ln d versus time using following equations:
k1 = slope
(2)
The formation of EDA complex between DCNQ and 3,4-DMA
could represent in the following way:
O
O
NH2
NH2
CH3
CN
CN
CN
+
CN
CH3
CH3
O
O
CH3

482
G.M. Neelgund et al. / Spectrochimica Acta Part A 78 (2011) 480–487
Table 1
The formation constant (K) and the molar extinction coefficient (ε) values for the EDA interaction between DCNQ and 3,4-DMA.
Solvent
CHCl3
Temperature (◦C)
K (dm3 mol−1 cm−1
)
ε (dm3 mol−1
)
20
25
30
35
20
25
30
35
20
25
30
35
5.91 0.03
4.23 0.05
3.84 0.02
3.12 0.02
7.97 0.06
6.52 0.03
5.89 0.01
4.92 0.03
7.31 0.05
6.14 0.05
5.09 0.02
4.65 0.03
5921 158
6059 182
5827 146
5895 119
3675 175
3921 168
4023 136
3846 164
4240 196
4316 147
4118 155
4221 171
CH2Cl2
1:1 (v/v) mixture of CHCl3 and CH2Cl2
Table 2 indicate that, values of k1 increase with increase in the
concentration of 3,4-DMA, which is in accordance with the results
obtained by Foster and Horman [45]. While the inverse effect of
concentration of donor was observed on the values of k2.
The rate constants, k1 and k2 for the formation of product were
also calculated using the developing bands around 366 and 350 nm
and the values are tabulated in Table 3. The k1 values appeared to be
nearly constant at varying concentrations of 3,4-DMA, which indi-
cates that the formation of product between DCNQ and 3,4-DMA
follow the first order kinetics. The values of k2 for the formation of
product decrease with increase in the concentration of 3,4-DMA.
Both the values of k1 and k2 for EDA complex and for the forma-
tion of product decreases with increasing dielectric constant of the
medium, which is similar to the results reported by Parker [46] and
Roberts [47].
The dependence of k1 on temperature was used to calculate the
activation parameters, Ea, ꢀH#, ꢀS# and ꢀG# for the formation of
product using the Arrhenius plots (Fig. 4) and the acquired values
are given in Table 4. The large negative values of entropy of activa-
tion (ꢀS#) show the existence of strong interaction between DCNQ
and 3,4-DMA. The Ea and ꢀH# values increase with increase in the
relative permittivity of the medium, while the opposite tendency
was observed in the values of ꢀS#. The liner correlation (Fig. 5)
between ꢀH# and ꢀS# values was observed, which indicates that
the interaction between DCNQ and 3,4-DMA follows a common
mechanism in all the solvents. Also it is obvious that the reaction
between DCNQ and 3,4-DMA is spontaneous and the product of the
reaction is stable.
Fig. 2. Plot of ln d against time for EDA complex (676 nm) formed between DCNQ
and 3,4-DMA in chloroform at 25 ◦C, in which CA0 is held constant and CD0 varied (the
numbers in the inset indicate the concentration of the donor).
and
k1
CD0
k2
=
(3)
The calculated values of k1 and k2 for EDA complex formed between
3,4-DMA and DCNQ are summarized in Table 2. The data given in
T-1x103
3.20
3.30
3.40
Chloroform
3.50
-3.10
-3.20
-3.30
-3.40
-3.50
-3.60
-3.70
Dichloromethane
1:1 (v/v) mixture
Fig. 3. Benesi–Hildebrand plot for EDA complex (676 nm) formed between DCNQ
and 3,4-DMA in CHCl3, CH2Cl2 and 1:1 (v/v) mixture of CHCl3 and CH2Cl2 at 25 ◦C.
Fig. 4. Plot of log k1 against T−1 for the reaction between DCNQ and 3,4-DMA.

G.M. Neelgund et al. / Spectrochimica Acta Part A 78 (2011) 480–487
483
Table 2
The first order (k1) and second order (k2) rate constants of EDA complex formed between DCNQ and 3,4-DMA.
Solvent
CHCl3
ꢁmax (nm)
Temperature (◦C)
20
CA0 × 104 (M)
CD0 (M)
k1 × 104 (s−1
)
k2 × 102 (dm3 mol−1 s−1
)
676
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
0.0346
0.0692
0.1038
0.1384
0.173
0.0346
0.0692
0.1038
0.1384
0.173
0.0346
0.0692
0.1038
0.1384
0.173
0.0346
0.0692
0.1038
0.1384
0.173
3.85 0.08
5.75 0.11
6.86 0.09
7.75 0.12
8.94 0.14
4.01 0.06
6.25 0.10
7.59 0.09
7.91 0.09
9.56 0.13
4.54 0.10
6.50 0.07
7.75 0.14
8.16 0.17
9.95 0.15
4.81 0.08
6.73 0.13
7.96 0.15
8.62 0.14
10.01 0.18
1.11 0.03
0.83 0.02
0.66 0.01
0.56 0.01
0.52 0.01
1.16 0.02
0.90 0.02
0.73 0.01
0.57 0.01
0.55 0.01
1.31 0.03
0.94 0.01
0.75 0.01
0.59 0.01
0.57 0.01
1.39 0.02
0.97 0.02
0.77 0.01
0.62 0.01
0.58 0.01
25
30
35
CH2Cl2
666
20
25
30
35
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
0.0372
0.0744
0.1116
0.1488
0.186
0.0372
0.0744
0.1116
0.1488
0.186
0.0372
0.0744
0.1116
0.1488
0.186
0.0372
0.0744
0.1116
0.1488
0.186
0.85 0.01
1.58 0.03
2.18 0.03
2.68 0.05
3.15 0.04
1.01 0.02
2.08 0.03
2.91 0.01
2.84 0.03
3.77 0.04
1.54 0.02
2.33 0.04
3.07 0.04
3.09 0.03
4.16 0.05
1.80 0.03
2.57 0.05
3.26 0.04
3.56 0.05
4.22 0.06
0.23 0.007
0.21 0.006
0.19 0.003
0.18 0.003
0.17 0.002
0.27 0.007
0.28 0.005
0.26 0.006
0.19 0.003
0.20 0.004
0.41 0.007
0.31 0.004
0.27 0.003
0.21 0.002
0.22 0.002
0.48 0.008
0.34 0.007
0.29 0.002
0.24 0.001
0.23 0.002
1:1 (v/v) mixture of CHCl3 and CH2Cl2
671
20
25
30
35
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
0.0368
0.0736
0.1104
0.1472
0.184
0.0368
0.0736
0.1104
0.1472
0.184
0.0368
0.0736
0.1104
0.1472
0.184
0.0368
0.0736
0.1104
0.1472
0.184
1.58 0.05
2.92 0.03
3.55 0.05
4.26 0.09
4.96 0.08
1.74 0.04
3.42 0.04
4.28 0.07
4.42 0.08
5.58 0.09
2.27 0.05
3.67 0.08
4.44 0.08
4.67 0.06
5.97 0.09
2.53 0.04
3.90 0.06
4.64 0.07
5.13 0.06
6.04 0.10
0.43 0.008
0.40 0.007
0.32 0.006
0.29 0.005
0.27 0.005
0.47 0.009
0.46 0.006
0.39 0.004
0.30 0.003
0.30 0.002
0.61 0.010
0.50 0.007
0.40 0.005
0.32 0.004
0.32 0.005
0.69 0.010
0.53 0.010
0.42 0.007
0.35 0.004
0.33 0.003
3.1. Characterization of the reaction product
was selected by preparative thin layer chromatography (TLC)
method. The excess of solvent in the collected fraction was removed
by a rotavapor and the purified product thus obtained was sub-
jected to elemental analysis, IR and 1H NMR spectral studies.
The yield of the product was 69% and the melting point was
161 ◦C. The IR spectrum of the compound in KBr showed a sharp
band of medium intensity appeared at 3250 cm−1, which was
assigned to N–H stretching. Another sharp band again of medium
intensity due to C–N stretching was appeared at 2178 cm−1. There
1 mol of DCNQ and 2 mol of 3,4-DMA were mixed with 50 ml
chloroform and the reaction was allowed to proceed with continu-
ous stirring under inert atmosphere for 50 h at room temperature.
During the course of reaction, initially formed blue color of the
solution went on changing with time. The reaction mixture thus
resulted was subjected to column chromatographic separation
method. The product was separated using suitable eluent, which

484
G.M. Neelgund et al. / Spectrochimica Acta Part A 78 (2011) 480–487
Table 3
The first order (k1) and second order (k2) rate constants for the formation of product between DCNQ and 3,4-DMA.
Solvent
CHCl3
Temperature (◦C)
CA0 × 104 (M)
CD0 (M)
ꢁmax = 366 nm
ꢁmax = 350 nm
k1 × 104 (s−1
)
k2 × 102 (dm3 mol−1 s−1
)
k1 × 104 (s−1
)
k2 × 102 (dm3 mol−1 s−1
)
20
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
0.0346
0.0692
0.1038
0.1384
0.173
0.0346
0.0692
0.1038
0.1384
0.173
0.0346
0.0692
0.1038
0.1384
0.173
0.0346
0.0692
0.1038
0.1384
0.173
5.27 0.10
5.30 0.09
5.03 0.09
4.69 0.08
4.51 0.07
5.43 0.12
5.80 0.11
5.76 0.11
4.85 0.09
5.13 0.08
5.96 0.12
6.05 0.15
5.92 0.09
5.10 0.09
5.52 0.11
6.23 0.18
6.28 0.16
6.12 0.17
5.56 0.11
5.58 0.09
1.52 0.040
0.77 0.020
0.48 0.009
0.34 0.006
0.26 0.004
1.57 0.040
0.84 0.009
0.55 0.008
0.35 0.004
0.30 0.005
1.72 0.050
0.87 0.010
0.57 0.009
0.37 0.005
0.32 0.005
1.80 0.060
0.91 0.030
0.59 0.010
0.40 0.009
0.32 0.007
5.83 0.11
5.67 0.10
5.19 0.09
4.75 0.08
4.50 0.08
5.96 0.12
6.12 0.14
5.92 0.10
4.91 0.09
5.12 0.10
6.52 0.13
6.33 0.13
6.08 0.10
5.16 0.08
5.52 0.09
6.79 0.12
6.60 0.10
6.28 0.11
5.62 0.09
5.57 0.08
1.68 0.050
0.81 0.030
0.50 0.010
0.34 0.010
0.26 0.008
1.73 0.050
0.88 0.020
0.57 0.010
0.35 0.009
0.29 0.005
1.88 0.060
0.92 0.030
0.59 0.020
0.37 0.009
0.32 0.008
1.96 0.060
0.95 0.020
0.60 0.010
0.41 0.008
0.32 0.007
25
30
35
Solvent
CH2Cl2
Temperature (◦C)
20
CA0 × 104 (M)
CD0 (M)
ꢁmax = 365 nm
ꢁmax = 348 nm
k1 × 104 (s−1
)
k2 × 102 (dm3 mol−1 s−1
)
k1 × 104 (s−1
)
k2 × 102 (dm3 mol−1 s−1
)
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
2.37
0.0372
0.0744
0.1116
0.1488
0.186
0.0372
0.0744
0.1116
0.1488
0.186
0.0372
0.0744
0.1116
0.1488
0.186
0.0372
0.0744
0.1116
0.1488
0.186
2.38 0.06
2.88 0.05
2.96 0.07
2.88 0.05
2.78 0.06
2.54 0.05
3.38 0.07
3.69 0.06
3.04 0.06
3.40 0.07
3.07 0.06
3.63 0.07
3.85 0.08
3.29 0.06
3.79 0.08
3.34 0.07
3.87 0.07
4.05 0.08
3.75 0.06
3.85 0.05
0.64 0.020
0.39 0.010
0.26 0.009
0.19 0.006
0.15 0.005
0.73 0.020
0.49 0.010
0.35 0.010
0.22 0.008
0.20 0.007
0.90 0.020
0.52 0.010
0.37 0.009
0.24 0.008
0.22 0.008
1.00 0.030
0.56 0.010
0.39 0.009
0.27 0.006
0.22 0.005
2.83 0.07
3.22 0.08
3.19 0.09
3.03 0.06
2.90 0.05
2.99 0.06
3.72 0.07
3.92 0.06
3.20 0.08
3.52 0.07
3.52 0.05
3.97 0.06
4.08 0.08
3.45 0.07
3.91 0.06
3.79 0.07
4.20 0.08
4.23 0.09
3.91 0.06
3.97 0.06
0.76 0.020
0.43 0.010
0.29 0.008
0.20 0.007
0.15 0.006
0.86 0.020
0.54 0.010
0.38 0.009
0.23 0.009
0.20 0.008
1.02 0.020
0.57 0.010
0.39 0.008
0.25 0.007
0.23 0.007
1.10 0.020
0.61 0.010
0.41 0.009
0.28 0.006
0.23 0.005
25
30
35
Solvent
Temperature (◦C) CA0 × 104 (M) CD0 (M) ꢁmax = 365 nm
ꢁmax = 350 nm
k1 × 104 (s−1
)
k2 × 102 (dm3 mol−1 s−1
)
k1 × 104 (s−1
)
k2 × 102 (dm3 mol−1 s−1
)
1:1 (v/v) mixture of CHCl3 and CH2Cl2 20
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
2.36
0.0368 3.60 0.08
0.0736 3.57 0.06
0.1104 4.21 0.09
0.1472 4.12 0.08
0.98 0.020
0.48 0.010
0.38 0.009
0.28 0.007
0.21 0.005
1.02 0.030
0.55 0.010
0.45 0.010
0.29 0.006
0.25 0.006
1.16 0.030
0.59 0.010
0.46 0.010
0.31 0.008
0.27 0.007
1.24 0.030
0.62 0.010
0.48 0.009
0.34 0.008
0.27 0.006
4.11 0.09
3.90 0.05
4.54 0.07
4.38 0.07
4.17 0.06
4.27 0.07
4.40 0.09
5.27 0.11
4.54 0.09
4.79 0.08
4.80 0.09
4.65 0.09
5.43 0.10
4.79 0.07
5.18 0.11
5.07 0.12
4.88 0.09
5.63 0.08
5.25 0.10
5.24 0.12
1.12 0.030
0.53 0.010
0.41 0.009
0.30 0.009
0.23 0.005
1.16 0.030
0.60 0.010
0.48 0.008
0.31 0.006
0.26 0.004
1.30 0.040
0.63 0.010
0.49 0.009
0.32 0.008
0.28 0.007
1.38 0.040
0.66 0.010
0.51 0.008
0.36 0.006
0.28 0.006
0.184
3.96 0.06
25
30
35
0.0368 3.76 0.07
0.0736 4.07 0.08
0.1104 4.94 0.10
0.1472 4.28 0.09
0.184
4.58 0.10
0.0368 4.29 0.11
0.0736 4.32 0.10
0.1104 5.10 0.13
0.1472 4.53 0.09
0.184
4.97 0.10
0.0368 4.56 0.08
0.0736 4.55 0.09
0.1104 5.30 0.11
0.1472 4.99 0.10
0.184
5.03 0.11

G.M. Neelgund et al. / Spectrochimica Acta Part A 78 (2011) 480–487
485
O
NH2
CN
CN
+
CH3
O
CH3
NH2
O
CN
CN
CH3
O
O
CH3
CH3
CN
H
N
H
CH3
CN
O
O
CH3
CN
H
N
H
CH3
O
O
CN
-HCN
CN
CH3
H
N
CH3
O
3-(N-3,4-dimethyl-phenylamino)-2-cyano-1,4-naphthoquinone
Scheme 1.

486
G.M. Neelgund et al. / Spectrochimica Acta Part A 78 (2011) 480–487
Table 4
Activation parameters of the reaction between DCNQ and 3,4-DMA.
Solvent
ꢁmax (nm)
Ea (kJ mol−1
)
−ꢀS# (J K−1 mol−1
)
ꢀH# (kJ mol−1
)
ꢀG# (kJ mol−1
)
CHCl3
CH2Cl2
350
348
350
8.7 0.2
14.1 0.5
10.5 0.3
282
269
278
8
4
6
6.3 0.1
11.7 0.4
8.1 0.2
89
90
89
1
3
2
1:1 (v/v) mixture of CHCl3 and CH2Cl2
substituted product, 3-(N-3,4-dimethyl-phenylamino)-2-cyano-
1,4-naphthoquinone. On the evidence of above all experimental
results, a plausible mechanism for the formation of product
between DCNQ and 3,4-DMA is illustrated in Scheme 1.
The elimination of HCN during the course of reaction was con-
firmed by performing the classical test [48]. A small quantity of the
reaction mixture was heated in a test tube, while heating a piece
of filter paper which was dipped in yellow ammonium sulphide
solution was held over mouth of the test tube. After spreading a
drop of FeCl3 solution over the filter paper, formation of a blood
red color was observed, which confirms the elimination of HCN in
the process of reaction between DCNQ and 3,4-DMA.
12
(CH Cl )
11
10
9
1:1 (v/v) mixture
8
7
(CHCl )
4. Conclusions
6
268
270
272
274
276
278
280
282
284
The spectro-kinetic study reveals that the interaction between
DCNQ and 3,4-DMA yield the mono-substituted product, 3-(N-3,4-
ΔS (JK mol )
dimethyl-phenylamino)-2-cyano-1,4-naphthoquinone
through
Fig. 5. Relation between enthalpy and entropy of activation for the interaction of
initial formation EDA complex. The reaction parameters are found
to be sensitive with respective to relative permittivity of the
medium. The formation constant (K) values for EDA complex
increases with increase in polarity of the solvent, conversely
there is a decrease in the values of k1 and k2. The large negative
values of entropy of activation (ꢀS#) show the existence of strong
interaction between DCNQ and 3,4-DMA. The results showed that
the interaction between DCNQ and 3,4-DMA is spontaneous and
the formation of product proceeds through the elimination of HCN
as a byproduct.
3,4-DMA with DCNQ.
was a sharp and intense band exhibited at 1690 cm−1, which was
assigned to carbonyl stretching.
The 1H NMR spectrum of the product in CDCl3 showed distinc-
tive resonances. The rather broad signal appeared at the lowest
field with ı value of 8.39, which vanished on deuterium exchange
is assigned to >NH proton. Two signals appeared in the form of sin-
glet at the highest field with ı value of 2.17 and 2.15, are attributed
to two adjacent methyl protons. A doublet with coupling constant,
J = 7.7 Hz, having ı value of 6.9 is from H(1) and another doublet
with J = 7.9 Hz, having ı value of 7.22 is assigned to H(2). A singlet at
ı value 7.06 is assigned to H(3). Two doublets at ı value of 8.22 and
8.18 with coupling constants J = 6.8 and 6.4 Hz, respectively, were
assigned to Ha and Ha1. Other two doublets appeared at ı value of
7.84 and 7.76 with coupling constant, J = 6.2 Hz are assigned to Hb
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1
and Hb of the product molecule. With the combination of IR and
NMR data, structure of the unknown product is assigned as follows:
H(a)
O
H(b)
CN
H(1)
H(2)
(b)H1
N
H
CH3
H1
O
(a)
H(3)
CH3
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Calc: C, 75.27; H, 4.64; and N, 9.27%
Found: C, 75.61; H, 4.37; and N, 9.59%
Elemental analysis data acquired for the product matches well
with the assigned structure, which confirms the structure of the
final product. Thus the product of the reaction between DCNQ
and 3,4-DMA is identified as 3-(N-3,4-dimethyl-phenylamino)-2-
cyano-1,4-naphthoquinone.
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molecules give substituted products by reacting with naph-
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that the reaction between DCNQ and 3,4-DMA provide the
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