Di(2-ethylhexyl)phosphoric acid (D2EHPA, HR) is widely used for solvent extraction of indium from acidic leaching solutions, but indium stripping from the loaded organic phase is difficult because of ...the high affinity of indium for the extractant. Adding proton-donor additives (HA) to the D2EHPA solution is a way to achieve high stripping efficiency for indium. In this work, monocarboxylic acids, aliphatic alcohols, and phenol derivatives were used as additives. Nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy of the organic phases confirm the formation of intermolecular associates (H-complexes) between all additives and D2EHPA. In the case of alcohols and substituted phenols, the interaction of oxygen atoms of alcohols or phenols with the proton of the hydroxyl group of D2EHPA is predominant, while in the case of monocarboxylic acids, an interaction between the hydroxyl proton of the acid and the PO group of D2EHPA mainly occurs. Despite the high In distribution ratio with D2EHPA (100−1000), in all cases investigated the introduction of additives into the organic phase led to an antagonistic extraction effect, however it facilitated efficient In stripping from the loaded organic phase. This effect depends significantly on the type and structure of the additive. Indium extraction in the presence of additives decreases in the series 4-bromophenol >4-t-butylphenol > octanol, 2-ethylhexanol >4-nitrophenol >2-nitrophenol >2,6-di-t-butylphenol, octanoic acid > Versatic 10. Extraction systems containing D2EHPA and 2-ethylhexanol can be used to recover indium from various industrial solutions, in particular, from those derived from lead‑zinc production and from liquid crystal display panel wastes.
•The state of D2EHPA in CCl4 in the presence of proton-donor additives HA was studied.•The interaction between D2EHPA (HR) and HA was shown to occur.•Antagonistic extraction of indium by mixtures of D2EHPA and additives is observed.•D2EHPA and 2-ethylhexanol system is most efficient for In extraction and stripping.
Azide-tetrazole equilibrium in 2-azido-6-phenylpyrimidin-4(3
H
)-one and 2-azido-4-chloro-6-phenylpyrimidine was studied by IR spectroscopy and
1
H and
13
C NMR spectroscopy in a comparison with the ...published data. For 2-azido-6-phenylpyrimidin-4(3
H
)-one isolated from a weakly acidic solution,
1
H NMR (DMSO-d6) spectroscopy revealed a three-component equilibrium between azide
(A)
and tetrazole
(T
and
T
′) forms
T
⇆
A ⇆
T
′ (82: 10: 8) immediately after dissolution and a two-component equilibrium
T
⇆
T
′ (12: 88) in an equilibrium state. For the precipitate recrystallized from ethanol, the
T ⇆
T
′ equilibrium was observed. The structures of both tautomers were confirmed by X-ray diffraction analysis. 2-Azido-4-chloro-6-phenylpyrimidine existed predominantly in the azide form and the
A ⇆ T
(94: 6) equilibrium was found only in the DMSO-d
6
solution.
The nature of products in the diazotization of 1-amino-2-acetylenyl-9,10-anthraquinones strongly depends on the nature of substituents at both the alkyne and at the anthraquinone core. Donor ...substitution (NHAr, OH) at the fourth position stabilizes the diazonium salt at C1, decelerating electrophilic cyclization at the arylethynyl substituent at C2. This effect allows the replacement of the diazonium with azide group and subsequent closure into isoxazole ring with preservation of the alkyne. In contrast, electrophilic 5-exo-dig cyclizations to condensed pyrazoles is observed for the combination of donor substituents at the aryl alkyne moiety and an OAc substituent at C4. The latter process provides a new synthetic route to 3-ethynyl-1,9-cdisoxazol-6-ones that are difficult to access otherwise. DFT calculations suggest that donor substituents have only a minor effect on alkyne and diazonium polarization in the reactant but provide specific transition state stabilization by stabilizing the incipient vinyl cation. This analysis provides the first computational data on electrophilic 5-exo-dig cyclization in its parent form and the nucleophile-promoted version. This cyclization is a relatively fast but endothermic process that is rendered thermodynamically feasible by the enol-keto tautomerization with concomitant aromatization in the five-membered heteroaromatic ring. Computations suggest that the importance of nucleophilic assistance in the transition state for a relatively weak nucleophile such as water is minor because the energy gain due to the Lewis base coordination to the carbocationic center is more than compensated for by the unfavorable entropic term for the bimolecular proces.
Thermodynamic and kinetic parameters of the tautomeric tetrazole-azide rearrangement for a series of 2,6-disubstituted 4-azidopyrimidines are determined by NOESY/EXSY and DNMR: Δ
H
= 15—28 kJ mol
–1
...; Δ
S
= 47—65 J mol
–1
К–1;
Е
a
= 93—117 kJ mol
–1
; lg
A
= 15.1—18.9. They are dependent on electronic properties of the substituents and the polarity of solvent.
Azide-tetrazole equilibrium in azidopyrimidines bearing trifluoromethyl group on the example of 2-azidopyrimidines has been studied. The latter were synthesized
via
nitrosation of ...2-hydrazino-4-trifluoromethylpyrimidine and reaction of NaN
3
with 4-trifluoromethyl-2- chloro-6-(4-chlorophenyl)pyrimidine. The tautomeric equilibrium 5-trifluoro methyl tetrazolo1,5-
a
pyrimidine ⇆ 2-azido-4-trifluoromethylpyrimidine was observed in the absence of solvent and in DMSO-d
6
solution, whereas in CDCl
3
only an azide form exists. For 2-azido- 4-trifluoromethyl-6-(4-chlorophenyl)pyrimidine, only an azide isomer was detected in CDCl
3
solution, and in DMSO-d
6
solution it is in equilibrium with 5-(trifluoromethyl)-7-(4-chlorophenyl) tetrazolo1,5-
a
pyrimidine (the tautomer ratio is 99 : 1). Thermodynamic and kinetic parameters of 5-trifluoromethyltetrazolo1,5-
a
pyrimidine ⇆ 2-azido-4-trifluoromethylpyri midine tautomeric rearrangement in DMSO-d
6
for 5-trifluoromethyltetrazolo1,5-
a
pyrimidine were determined using the exchange spectroscopy (EXSY) technique.
A new approach to the synthesis of natural combretastatin A-4 analogues based on the interaction of α-acetylenic ketones with secondary amines (diethyl amine, pyrrolidine, piperidine, morpholine) was ...proposed. Previously unknown analogues of combretastatin A-4 containing the β-aminovinylcarbonyl bridges were synthesized. Anti-inflammatory activity of the obtained compounds was studied on models of exudative inflammation caused by histamine or concanavalin A.
The cloth specimens of Pazyryk culture from frozen burials of Altai Mountains (500–200 B.C.) were investigated by molecular spectroscopy and high performance liquid chromatography coupled with ...diode-array and mass selective detection. The qualitative and quantitative analyses of ancient red dyes were conducted. Natural dyes of plant origin – alizarin and purpurin and of insect origin – carminic acid and kermesic acid were determined.
1,4-dihydroxythioxanthen-9-one was for the first time subjected to regioselective chlorination into 2-chloro-1,4-dihydroxythioxanthen-9-one effected by SOCl₂ at room temperature. The ...hydrochlorination of thioxanthen-1,4,9-trione led to the formation of 2- and 3-chloro-1,4-dihydroxythioxanthene-9-ones with the 3-isomer prevailing.
New approach to synthesis of analogs of natural Combretastatin A-4 based on interaction of α-acetylenic ketones with secondary amines (diethyl amine, pyrrolidine, piperidine, morpholine) is offered. ...Unknown analogs of Combretastatin A-4 with β-aminovinylcarbonyl bridges are received earlier. Anti-inflammatory activity of the received connections is studied.
Five indices of the straw strength (elastic module, elastic limit, elastic deformation, ultimate strength, ultimate deformation) have been found for the third and the fourth internodes in mutant ...(vitreous culm) and normal rye plants. Considerable differences in mechanical properties of culms and in correlation between indices studied in mutant and normal rye genotypes have been revealed. It was shown that the dynamic indices of the mechanical properties can be used for the evaluation of the cereal genotypes in breeding.
