Synthesis and reaction with metal ions of a new thionocarbamate

Article abstract of DOI:10.1007/s11164-011-0427-3

The synthesis and research of a novel thionocarbamate N,N′-diethoxy- carbonyl-O,O′-(1,4-butylidene) dithionocarbamate which contains two ester and two thioamide groups are reported. This compound was characterized by elemental analysis, UV spectrum, infrared spectrum, mass spectrum, and ¹H NMR and ¹³C NMR spectroscopy. Additionally, the metal ion-collector interaction in organic solution was put into practice. The results of UV spectroscopic analysis showed that this dithionocarbamate with a new structure exhibited a stronger complex ability with Cu²⁺ than with Ni²⁺ or Fe³⁺. Furthermore, infrared spectroscopic analysis implicated that this dithionocarbamate binds to Cu²⁺ through both the C=O and C=S groups. Bench-scale flotation tests were also carried out, verifying that it has a higher copper flotation recovery and better selectivity to sulfide ores containing Cu compared with universal collectors. Springer Science+Business Media B.V. 2011.

Full text of DOI:10.1007/s11164-011-0427-3

Res Chem Intermed (2012) 38:903–909
DOI 10.1007/s11164-011-0427-3
Synthesis and reaction with metal ions of a new
thionocarbamate
Lu Yuan Hong Zhong
•
Received: 17 July 2011 / Accepted: 21 October 2011 / Published online: 1 November 2011
Ó Springer Science+Business Media B.V. 2011
0
Abstract The synthesis and research of a novel thionocarbamate N,N -diethoxy-
0
carbonyl-O,O -(1,4-butylidene) dithionocarbamate which contains two ester and
two thioamide groups are reported. This compound was characterized by elemental
1
analysis, UV spectrum, infrared spectrum, mass spectrum, and H NMR and
1
3
C NMR spectroscopy. Additionally, the metal ion–collector interaction in organic
solution was put into practice. The results of UV spectroscopic analysis showed that
this dithionocarbamate with a new structure exhibited a stronger complex ability
2
?
2?
3?
with Cu than with Ni or Fe . Furthermore, infrared spectroscopic analysis
2
?
implicated that this dithionocarbamate binds to Cu through both the C=O and
C=S groups. Bench-scale flotation tests were also carried out, verifying that it has a
higher copper flotation recovery and better selectivity to sulfide ores containing Cu
compared with universal collectors.
Keywords Dithionocarbamate ꢀ Synthesis ꢀ Metal ions ꢀ Flotation
Introduction
The thionocarbamates are liquid and their densities are slightly lower than that of
water. Thionocarbamates as intermediates in organic synthesis have been described
[
[
1–4], and they are excellent collectors in the separation of copper and sulphur
5–8]. Due to their characteristic group of –C(=S)–NH–, they exhibit higher
selectivity and less dosage, and have the properties of frothiness. Since industrial
ore deposits at present are barren, fine, and complex, and the grade of minerals
becomes gradually lower and lower, it is necessary to consider the impact of
L. Yuan ꢀ H. Zhong (&)
Key Laboratory of Resources Chemistry of Nonferrous Metals, College of Chemistry and Chemical
Engineering, Central South University, Changsha 410083, China
e-mail: zhonghongcsu@163.com
123

904
L. Yuan, H. Zhong
collectors’ chemical structure on flotation properties such as selectivity, collecting
ability and frothiness.
There are many reports regarding the synthesis of thionocarbamates containing
an ester and a thioamide functional group [9–14]. However, the synthesis of
thionocarbamates with two ester and two thioamide functional groups has seldom
been reported. This kind of compound usually has multiple coordinating atoms and
groups. If these compounds could form complexes with metal ions in flotation, they
would be a new type of high-efficiency collector for the retrieval of minerals, and
their associated noble metal will be intensified. To our best knowledge, there is no
report using this kind of compound to retrieve minerals.
0
0
In this paper, a new thionocarbamate N,N -diethoxycarbonyl-O,O -(1,4-butylidene)
dithionocarbamate was synthesized by a two-step method. This synthesized compound
was characterized by elemental analysis, UV spectrum, infrared spectrum, mass
1
13
spectrum, and H NMR and C NMR spectroscopy. After mixing the compound
3?
solution with Cu and Fe ion solutions, respectively, the changes of absorbance of
three solutions via a UV–VIS spectrophotometer were determined. The precipitate of
2?
2?
dithionocarbamate reacted with Cu ion was analyzed through infrared spectroscopy.
In addition, bench-scale flotation tests were carried out.
Experimental
Regents and instruments
Ethyl chloroformate and 1,4-dihydroxybutane were in chemical grade. N,N-
dimethylaniline, sodium thiocyanate, ethanol and acetone were in analytical grade.
The elemental content was measured by Vario EL III elemental analyzer from
Elementar, Germany. The UV spectra were gained by a UV-2100 UV–VIS
spectrophotometer from UNICO. The infrared spectra were obtained by AVATAR360
infrared spectrophotometer from Nicolet, USA, and solid samples were tested at
-
1
1
wavelengths from 400 to 4,000 cm with the KBr pressed disc method. The H NMR
1
and C NMR spectra were obtained by an ADVANCE III 400 NMR spectrometer
3
from Bruker, Germany, using DMSO-d as solvent. The mass spectrometry was
6
surveyed by a HCT ion trap LC–MS multi-stage mass spectrometer from Bruker
Daltonics, Germany, equipped with an ESI source in positive ion mode for detection.
Synthesis of dithionocarbamate
Synthesis of N-ethoxylcarbonyl isothiocyanate
N-ethoxylcarbonyl isothiocyanate was synthesized by ethyl chloroformate and
sodium thiocyanate. First, 8.11 g (0.1 mol) sodium thiocyanate was dissolved in
2
0 mL water, to which was added 0.51 mL (0.004 mol) N,N-dimethylaniline as
catalyst and the mixture cooled to -1–5 °C. Next, 9.53 mL (0.1 mol) ethyl
chloroformate were dropped into the mixture slowly in 0.5 h which was then held at
3
–8 °C for 4 h with constant stirring. After the reaction completed, the mixture
1
23

Synthesis and reaction with metal ions
905
Scheme 1 Synthetic route of dithionocarbamate
turned into two phases. The product N-ethoxylcarbonyl isothiocyanate was in the
organic phase with a yield of 76.4%.
0
0
Synthesis of N,N -diethoxycarbonyl-O,O -(1,4-butylidene) dithionocarbamate
An amount of 4.43 mL (0.05 mol) 1,4-dihydroxybutane was dissolved in acetone
with the ratio 1:2 and this solution added into 13.1 g (0.1 mol) N-ethoxylcarbonyl
isothiocyanate dropwise at 8–15 °C in 0.5 h. After that, the mixtures were heated to
4
5–55 °C with reflux and stirred for 4 h to obtain the product of yellow cream.
The produced cream was washed with ethanol and distilled water, respectively,
several times and then dried in vacuum. The obtained white needle-like compound
was the target product with a yield of 89.94%. The synthetic route is shown in
Scheme 1.
Results and discussion
0
0
Characterization of N,N -diethoxycarbonyl-O,O -(1,4-butylidene)
dithionocarbamate
The elemental content is as follows: Anal. Calcd for C H O N S (%): C, 40.91;
1
2 20 6 2 2
H, 5.68; N, 7.96; S, 18.18. Found (%): C, 40.94; H, 5.89; N, 7.69; S, 18.01.
UV–VIS (CH OH): kmax = 254 nm.
Infrared spectrum of N,N -diethoxycarbonyl-O,O -(1,4-butylidene) dithionocar-
3
0
0
-
bamate is shown in Fig. 2. Characteristic peaks appeared as follows: 3,187 cm for
1
-
N–H stretch vibration; 2,924 and 2,863 cm for C–H stretch vibration; 1,758 cm
1
-1
-
for C = O stretch vibration; 1,533 cm for –C(= S)–NH– composite vibration;
1
-
,252 cm for C–O and C–N composite vibration; 1,164 cm for O–C(=O)–N–C
1
-1
1
vibration; 1,085 cm
-
1
for C=S stretch vibration. These spectral characteristics
confirm that this dithionocarbamate contains the functional groups of amidocya-
nogen, alkoxycarbonyl and thiocarbonyl.
1
The NMR data are as follow: H NMR (400 MHz, DMSO-d , chemical shift d):
6
1
4
1
.181–1.216 (m, 6H, CH), 1.807 (s, 4H, CH), 4.080–4.133 (m, 4H, CH), 4.452 (s,
1
3
H, CH), 11.504 (s, 2H, NH); C NMR (400 MHz, DMSO-d , chemical shift d):
6
4.56 (s, 2C), 24.81 (s, 2C), 61.84 (s, 2C), 71.23 (s, 2C), 150.60 (s, 2C), 189.57
(
s, 2C).
?
ESI–MS (m/z): 359.4 (M ? Na ).
The characterization above demonstrated that the structure of the prepared
compound is in accordance with our prediction.
123

906
L. Yuan, H. Zhong
Reaction with metal ions
UV spectroscopic analysis
spectroscopy was used to monitor the metal ion–collector interaction in organic
-
5
2?
solution. Solutions (4 9 10 M, in methanol) of Cu , Ni , and Fe were prepared
2?
3?
-5
0
from the corresponding chloride salts. Solutions (4 9 10 M, in methanol) of N,N -
0
diethoxycarbonyl-O,O -(1,4-butylidene) dithionocarbamate were prepared for the
following experiments. Mixing 10 mL of one metal ion solution with 10 mL of the
dithionocarbamate solution, sufficient oscillation and several hours of standing were
required before measuring the absorbance of the supernatant against the metal ion’s
blank. As presented in Fig. 1, after adding those metal ions solutions, the absorbance
of solutions becomes weaker. Moreover, the absorbance at 254 nm was significantly
2
?
2?
reduced in the presence of Cu ions, less weakened for Ni ions, and had little
3?
weakening for Fe ions. These results indicate that this dithionocarbamate possesses
good selectivity towards these metal ions. The decrease in absorbance implies that
dithionocarbamate reacted with metal ions to form complexes to decrease the
concentration of dithionocarbamate in supernatants. Furthermore, it was noteworthy
that the dithionocarbamate exhibited stronger complex ability with Cu(II) than with
Ni(II) or Fe(III). Thus, we believe that this new form of thionocarbamate can be used
in ore flotation fields to collect Cu from copper ore.
Infrared spectroscopic analysis
2
?
After adding the solution of this dithionocarbamate into a Cu solution dropwise
with stirring, a large number of brick-red floc appeared. So, it is necessary to filter
the mixture and wash the precipitate more than once, then let it air-dry. Infrared
spectra of dithionocarbamate and the copper-dithionocarbamate complex are
compared in Fig. 2.
-
1
Figure 2 shows that the C–O and C–N composite vibrations at 1,252 cm are
the same for each compound, while the C–H stretching bands are at around
-
,900 cm . The peak shift caused by reaction with Cu is observed for the N–H
1
2?
2
stretching vibration which shifts 49 cm to low energies at around 3,138 cm
-
1
-1
0.6
0.5
0.4
0.3
0.2
0.1
0
225
245
265
285
305
325
Wavelength(nm)
Fig. 1 UV spectra of solutions before and after the addition of metal ions
1
23

Synthesis and reaction with metal ions
907
(a)
(b)
4000
3500
3000
2500
2000
1500
1000
500
-1
Wavenumbers/cm
0
0
Fig. 2 Infrared spectra of a N,N -diethoxycarbonyl-O,O -(1,4-butylidene) dithionocarbamate, b copper-
dithionocarbamate complex
-
from 3,187 cm ), the C=O stretching vibration which shifts 11 cm to high
1
-1
(
energies at around 1,769 cm (from 1,758 cm ), the –C(=S)–NH– composite
-
1
-1
-
1
-1
vibration which shifts 19 cm
-
to low energies at around 1,514 cm
-1
(from
,533 cm ), the O–C(=O)–N–C vibration which shifts 5 cm to high energies at
1
1
around 1,169 cm (from 1,164 cm ), and the C=S stretch vibration which shifts
-
1
-1
-
1
-1
-1
3
5 cm to low energies at around 1,050 cm (from 1,085 cm ). The C=O and
C=S stretch vibrations in the dithionocarbamate spectrum are significantly sharper
?
after reaction with Cu . This demonstrates that dithionocarbamate binds to the
2
2
?
Cu
through both the C=O and C=S groups. The present infrared study is
supported by the findings of others [15–18]. In addition, the present infrared
evidence suggests that the interaction between the oxygen-to-copper bond is
stronger than the sulfur-to-copper bond in agreement with literature reports [15, 19].
Flotation test
The test material was fractory copper porphyry ore from the Dexing Copper Mine of
Jiangxi Province in China. Among the ore, the copper-bearing minerals were
chalcopyrite, chalcocite, digenite, covellite, tetrahedrite, tennantite, and bornite,
as well as some oxide copper minerals such as malachite and cuprite. The main
iron-bearing minerals were pyrite and marcasite. The molybdenum form was
molybdenite and the gold forms were native gold and electrum. The significant
amounts of non-sulfide gangue minerals were quartz, sericite, chlorite, illite, and
biotite.
The ore (1 kg, crushed to -2 mm during sampling) was ground to 68% passing
7
by weight. The bench-scale flotation tests were performed in a XFD-63 flotation cell
4 lm in a closed steel U200 9 400 mm XMB ball mill at a pulp density of 62.5%
3
self-aeration) whose volume for rougher flotation was 3.0 dm , using 1 kg ore at
(
123

908
L. Yuan, H. Zhong
Fig. 3 Flow sheet of flotation
tests
Feed
Lime
Collector
Frother
5
'
Rough concentrate
Tailing
Table 1 Results of flotation tests
-1
Reagent dosage (g t
)
Product
Yield
%)
Grade (%)
Recovery (%)
Cu
(
Cu
S
S
Butyl xanthate 50
#
Rough concentrate
Tailing
9.86 3.48
23.23
0.58
78.87
21.13
81.42
18.58
2
frothing agent 20
90.14 0.102
Feed
100.00 0.435
6.15 5.58
2.81 100.00 100.00
Z-200 16
#
Rough concentrate
Tailing
20.02
1.66
79.62
20.38
44.13
55.87
2
frothing agent 12
93.85 0.094
100.00 0.431
5.32 6.45
Feed
2.79 100.00 100.00
0
0
N,N -diethoxycarbonyl-O,O -(1,4-
butylidene) dithionocarbamate 16
Rough concentrate
Tailing
17.63
1.99
80.17
19.13
33.26
66.74
94.68 0.090
100.00 0.428
#
2
frothing agent 12
Feed
2.82 100.00 100.00
every turn to obtain a Cu/Fe rougher concentrate. The flotation flow sheet is
described in Fig. 3. After wet grinding, the pH of the pulp slurry was pre-adjusted to
9.0 by the addition of 1,600 g/t lime. The other reagents dosage and the results of
the flotation tesst are presented in Table 1.
The results indicated that the dithionocarbamate reported in this article could
obtain a higher copper flotation recovery compared with butyl xanthate and Z-200,
the two universal collectors. In addition, it has better selectivity to sulfide ores
containing Cu.
Conclusions
0
0
In this paper, N,N -diethoxycarbonyl-O,O -(1,4-butylidene) dithionocarbamate was
synthesized by a two-step method. The intermediate N-ethoxylcarbonyl isothiocya-
nate was synthesized from ethyl chloroformate and sodium thiocyanate by nucleo-
philic substitution reaction and isomerization. Using this intermediate reacted with
0
0
1
,4-dihydroxybutane as raw material, the target product N,N -diethoxycarbonyl-O,O -
1,4-butylidene) dithionocarbamate was obtained by a nucleophilic addition reaction.
(
1
23

Synthesis and reaction with metal ions
909
The metal ion–collector interaction in organic solution was put into practice. The
results of UV spectroscopic analysis showed that this dithionocarbamate with a new
2
structure can react with Cu and Ni separately, and it has the best selectivity to
?
2?
3
the Fe ion. Infrared spectroscopic analysis demonstrated that this dithionocarba-
?
2
?
mate binds to the Cu through both the C=O and C=S groups. Bench-scale flotation
tests were also carried out, the results verifying that it has higher copper flotation
recovery and better selectivity to sulfide ores containing Cu compared with universal
0
0
collectors. Thus, the N,N -diethoxycarbonyl-O,O -(1,4-butylidene) dithionocarba-
mate reported in this paper displayed excellent floating properties to copper, and it is
suggested that it is applied in flotation of sulfur copper as a new collector.
Acknowledgments This study was financially supported by the the National High-Tech Research and
Development Plan of China (Grant No. 2007AA06Z122), the National Basic Research Program of China
(Grant No. 2007CB613602) and the National Natural Science Foundation of China (Grant Nos. 51074183
and 50604016).
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