4-(8-quinolylazo)resorcinol and 1-(8-quinolylazo)-2-naphthol: Synthesis and sorption properties

Article abstract of DOI:10.1134/S1070363216090383

A methodology of the synthesis of 4-(8-quinolylazo)resorcinol (QAR) and 1-(8-quinolylazo)-2-naphthol (QAN) was developed. The synthesized compounds were used to modify an oxidized charcoal sorbent. The sorbent efficiently adsorbs copper(II) and zinc(II) cations to form surface electroneutral chelate complexes. The conditions of sorption and desorption of zinc(II) and copper(II) were studied.

Full text of DOI:10.1134/S1070363216090383

ISSN 1070-3632, Russian Journal of General Chemistry, 2016, Vol. 86, No. 9, pp. 2232–2235. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © I.A. Vershinina, O.V. Gornukhina, T.V. Lubimova, O.A. Golubchikov, A.S. Semeikin, 2014, published in Rossiiskii Khimicheskii
Zhurnal, 2014, Vol. 58, Nos. 5–6, pp. 85–89.
4-(8-Quinolylazo)resorcinol and 1-(8-Quinolylazo)-2-naphthol:
Synthesis and Sorption Properties
I. A. Vershininaa*, O. V. Gornukhinab, T. V. Lubimovaa,
O. A. Golubchikovb, and A. S. Semeikinb**
a G.A. Krestov Institute of Solution Chemistry, Russian Academy of Sciences, ul. Akademicheskaya 1, Ivanovo, 153045 Russia
e-mail: *vershinina_ia@mail.ru; **semeikin@isuct.ru
b Ivanovo State University of Chemistry and Technology, Sheremetevskii pr. 7, Ivanovo, 153000 Russia
Received September 1, 2014
Absract—A methodology of the synthesis of 4-(8-quinolylazo)resorcinol (QAR) and 1-(8-quinolylazo)-2-
naphthol (QAN) was developed. The synthesized compounds were used to modify an oxidized charcoal
sorbent. The sorbent efficiently adsorbs copper(II) and zinc(II) cations to form surface electroneutral chelate
complexes. The conditions of sorption and desorption of zinc(II) and copper(II) were studied.
DOI: 10.1134/S1070363216090383
The demand for quantification of trace elements in
different materials is constantly growing, especially for
environmental monitoring purposes. Laboratories of
water analysis use atomic emission and atomic absorp-
tion spectroscopy, photometry, fluorimetry, voltammetry,
and potentiometry [1‒3], which makes urgent the
problem of preconcentration of samples before analysis.
The progress of instrumental methods enhances require-
ments to concentration techniques and compatibility of
the latter with the subsequent measurement techniques.
The introduction of new instrumental methods not only
does not restrict the scope of analytical approaches, but
also prompts search for possibilities [4, 5].
aim to assess its feasibility for sample preparation for
atomic absorption or photometric analysis of water.
EXPERIMENTAL
4-(8-Quinolylazo)resorcinol (QAR) and 1-(8-quinolyl-
azo)-2-naphthol (QAN) were synthesized by the Skraup
condensation of 2-nitroaniline (1) with glycerol (2)
followed by the reduction of the resulting 8-nitro-
quinoline (3) to 8-aminoquinoline (4), diazotization of
the latter, and azo coupling of the diazonium salt that
formed with resorcinol or 2-naphthol (see Scheme 1).
8-Nitroquinoline (3). Concentrated sulfuric avid,
385 mL, was slowly added to a suspension of 165.6 g
(1.2 mol) of 2-nitroaniline (1) in 265 mL of water, the
mixture was heated to the boil, and 125 mL (1.71 mol)
of glycerol (2) was slowly added. The resulting mix-
ture was refluxed under stirring for 4 h, cooled, diluted
with equal volume of water, and neutralized with a
25% ammonia solution. The precipitate that formed
was filtered off, washed with water, dried, dissolved in
benzene, and chromatographed on alumina (Brock-
mann activity II) with benzene as eluent. The eluate
was reduced in a minimal volume, 8-nitroquinoline
was precipitated with methanol, filtered off, and dried
at 70°С in air. Yield 75.6 g (72%).
The main methods of microelement concentration
in water analysis include distillation, extraction, and
sorption methods [6, 7]. Ion-exchange concentration
offers certain advantages over other methods, include-
ing simplicity of implementation and possibility of
group and individual elution of elements sorbed on the
ion exchanger, using appropriate solvents. Consider-
able recent attention has been focused on modified
charcoal sorbents, which are most commonly prepared
by surface functionalization of charcoal [3, 8].
In the present work we synthesized 4-(8-quinolyl-
azo)resorcinol and 1-(8-quinolylazo)-2-naphthol and
used them for modification of a charcoal sorbent.
Conditions of sorption and desorption of zinc and
copper on the synthesized sorbent were studied with
8-Aminoquinoline (4). 8-Nitroquinoline, 30.0 g
(0.17 mol) was added to a stirred solution 158.0 g
2232

4-(8-QUINOLYLAZO)RESORCINOL AND 1-(8-QUINOLYLAZO)-2-NAPHTHOL
2233
Scheme 1.
NO2
CH2OH
NH2
(1) NaNO2, H+
(2) ArH
SnCl2
H+
H2SO4
CHOH
N
N
N
CH2OH
N=NAr
NO2
HO
NH2
1
2
3
4
HO
;
XAP: Ar =
XAH:Ar =
OH
(0.7 mol) of SnCl2·2H2O in 200 mL of conc. HCl, the
mixture was stirred for 1 h, and cooled with ice. The
double salt of 8-aminoquinoline and SnCl2, that
precipitated, was filtered off, and decomposed by
treatment of its cold solution with a solution of 50.0 g
(1.25 mol) of NaOH with 200 mL of water. The
mixture was stirred with cooling until the oil that
separated had solidified, the solid was filtered off,
washed with water, dried in air at room temperature,
and recrystallized from petroleum ether. Yield 17.0 g
(69%).
The electronic absorption (EA) spectra were measured
on a Hitachi U-2000 scanning spectrophotometer in
the range 400–800 nm. EA spectrum, λmax, nm
(log ε): QAN: 508 (4.34); QAR: 502 (4.28).
Surface oxidation of charcoal. A BAU-A activated
charcoal (State Standard 6217-74) was refluxed for
30 min in 30% HNO3. The oxidized sorbent was
thoroughly washed with water to remove the acid [8]
and poured with a 0.02% solution of QAN or QAR in
ethanol. The suspension was refluxed with stirring for
6–8 h. The resulting materials were washed with ethanol
and water. The concentration of the immobilized QAR
(QAN) was estimated at 8–10 g per 1 kg of oxidized
coal.
4-(8-Quinolylazo)resorcinol (QAR) and 1-(8-quinol-
ylazo)-2-naphthol (QAN). A solution of 1.0 g
(14.5 mmol) of NaNO2 in 10 mL of water was slowly
added to a stirred and cold (5°С) solution of 2.0 g
(13.9 mmol) of compound 3 in 10 mL of 18% HCl.
The mixture was stirred at 5°С for 30 min, and the
resulting diazonium salt solution was slowly added to
a stirred and cooled (≤15°С) to 1.5 g (13.7 mmol) of
resorcinol (for QAR) or 2.0 g (13.9 mmol) of 2-naphthol
(for QAN) dissolved in a mixture of 5.0 g (0.09 mol)
of KOH and 20.0 mL of water. The mixture was stirred
for 30 min and neutralized with acetic acid. The
precipitates were filtered off, washed with water, and
dried in air at room temperature and then at 90 °С for
2 h. Yield 1.8 g (50%) and 2.2 g (55%) for QAR and
QAN, respectively.
The concentrations of Cu(II) and Zn(II) ions were
measured on a Carl Zeiss Jena AAS-3 flame atomic
absorption spectrometer.
RESULTS AND DISCUSSION
The structures of QAR and QAN were calculated
by the PM3 method using HyperChem 6.01 software.
The calculations predicted a planar structure with the
aromatic fragments trans to the aza bridge for both the
aza compounds. The barrier to rotation of the
quinolone fragment about the Naza-Ar bond is fairly
low (20–25 kJ/mol).
Elemental analysis was performed on a Thermo
The coordination of QAN and QAR with Cu(II)
and Zn(II) ions is likely to stabilize those ligand
conformations, where the donor oxygen and nitrogen
atoms of the quinolone fragment and aza bridge are
spatially proximate to each other. Evidence for this
suggestion is provided by the fact that the EA bands of
ethanolic solutions of the complexes are shifted red
and slightly narrower compared to the respective bands
Scientific FLASH EA 1112 СHNSO analyzer.
QAR: Found,%: C 67.8; Н 4.3; N 15.7; О 12.2.
С15H11N3O2. Calculated,%: C 67.92; Н 4.15; N 15.85;
О 12.08.
QAN: Found,%: C 76.0; Н 4.5; N 13.9; О 5.6.
С19H13N3O. Calculated,%: C 76.24; Н 4.38; N 14.04;
О 5.35.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 9 2016

2234
VERSHININA et al.
Adsorption of Cu(II) and Zn(II) cations was per-
100
80
formed at 298.5 ± 0.1 K from buffer solutions of their
acetates in dynamic conditions, by passing solutions
with concentrations 0.1–5 mg metal/L through sorbent-
packed columns (length 50 cm, diameter 2 cm) at a
rate of 1–15 mL/min. The amounts of the adsorbed
ions were estimated by eluting them with 10% HCl
and analyzing the eluates by atomic adsorption
spectroscopy. The optimal eluent flow rates were 8–
10 mL/s; in this case, 99–100% recoveries of copper
and zinc could be obtained at certain pH values.
Quantitative adsorption of Co(II) and Zn(II) was
observed at рН > 2 and pН > 8, respectively (see
figure). The Co(II) and Zn(II) adsorption capacity of
the synthesized sorbents is 0.18–0.20 mg-equiv/g.
1
2
60
40
20
0
1
2
3
4
5
6
7
8
pH
Dependence of the recoveries of (1) Cu(II) and (2) Zn(II)
ions on pH for the QAR-modified oxidized activated
charcoal. c0[М(АсО)2] = 0.3 mg/L; Т = 298.15 K.
The QAR-modified sorbent provides quantitative
adsorption of metal ions even if the concentrations of
the latter in the solutions are fairly low, as illustrated in
Table 1 on an example of zinc ions.
of the ligands. As shown by the method of isomolar
series, the complexes of QAN and QAR with Cu(II)
and Zn(II) in ethanolic solutions have a 1 : 2
composition. At the same time, QAN and QAR
immobilized on BAU-A activated charcoal were found
not to adsorb Cu(II) and Zn(II) ions from aqueous
solutions. Presumably, 1 : 2 cation–dye complexes do
not form on the coal surface for steric reasons, whereas
1 : 1 complexes are not equilibrated by electrostatic
forces. Aimed at improving the adsorption capacity of
the modified sorbent, before treatment with QAN and
QAR we oxidized the charcoal by the procedure in [5]
to form ionogenic carboxylate groups on its surface.
The possibility of multiple use of the sorbent was
studied in dynamic conditions. In was shown that after
50 runs the Zn(II) adsorption capacity was 95% of the
initial capacity.
The data in Table 2 illustrate the high accuracy of
reproducibility of the determination of metal ions in
model solutions with the use of the QAR-modified
BAU coal sorbent.
Thus, the use of the modified coal in the analysis of
aqueous solutions allows almost complete extraction
of metals from the matrix, which is quite important for
their subsequent atomic adsorption determination.
The charcoal modified in this way efficiently adsorbs
Cu(II) and Zn(II) cations. Obviously, the adsorption
process involves both the surface carboxylate groups
of the oxidized coal and the azo dye molecules. As a
result, electroneutral chelate complexes with the possible
composition coal–СОО–М2+–azo dye on the surface.
The results of the present research were used to
develop the following procedure of the concentration
Table 1. Concentrations of zinc(II) on the surface of the
BAU coal in dynamic conditions(рН = 6.5; Veluate = 5 mL)
Table 2. Determination of Zn(II) and Сu(II) in model solutions
by atomic absorption spectroscopy with preconcentration on
a modified BAU coal
Volume, mL
Spiked, mg
0.100
Founda, mg
0.090 ± 0.005
0.110 ± 0.003
0.100 ± 0.003
0.130 ± 0.005
0.052±0.003
0.023±0.003
0.009±0.003
Metal
Spiked, mg/L
Founda, mg/L
25
50
0.100
0.015
0.010
0.005
0.015
0.010
0.005
0.015 ± 0.002
0.011 ± 0.002
0.005 ± 0.001
0.015 ± 0.003
0.009 ± 0.003
0.004 ± 0.001
100
200
200
200
0.100
Copper
0.050
0.025
0.050
Zinc
200
0.010
a Averaged over 5 runs.
a Averaged over 5 runs.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 9 2016

4-(8-QUINOLYLAZO)RESORCINOL AND 1-(8-QUINOLYLAZO)-2-NAPHTHOL
2235
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of metal ions from water: 200 mL of a water sample
with рН 6–8 [for Cu(II)] or 8–10 [for Zn(II)] is passed
at a rate of 5–10 mL/min through a chromatographic
column packed with the modified activated coal, 5 mL
of 10% HCl is then passed at a rate of 1–1.5 mL/min,
and the concentration of metal ions in the eluate is
measured by atomic absorption spectroscopy.
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ACKNOWLEDGMENTS
The work was funded in the frameworks of the
program for state support of scientific schools under
the President of the Russian Federation (grant no. RF
NSh-6245.2014.3) and the ISUCT’s state contract.
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