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Search for "viscosity" in Full Text gives 115 result(s) in Beilstein Journal of Organic Chemistry.

Extrusion – back to the future: Using an established technique to reform automated chemical synthesis

  • Deborah E. Crawford

Beilstein J. Org. Chem. 2017, 13, 65–75, doi:10.3762/bjoc.13.9

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  • turn alters the properties of the materials [6]. Initially, the polymer industry employed only batch mixers to synthesise polymers and carry out post synthetic modification (PSM), however, this proved difficult and inefficient. This was due to a dramatic increase or change in the viscosity and rheology
  • of the material, a common feature of REX, and therefore as reactions proceed, they can become very difficult to mix efficiently, leading to low conversions. A second problem associated with the change in viscosity is the resultant poor heat transfer, meaning that longer heating times are required
  • viscosity, rheology and the kinetics of formation also. The authors report that a reaction between 4,4’-diphenylmethane diisocyanate, polycaprolactonediol and 1,4-butanediol takes place in a twin screw extruder, employing a screw speed of 15 rpm and a temperature of 60 °C [25]. This transformation was
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Published 11 Jan 2017

Poly(ethylene glycol)s as grinding additives in the mechanochemical preparation of highly functionalized 3,5-disubstituted hydantoins

  • Andrea Mascitti,
  • Massimiliano Lupacchini,
  • Ruben Guerra,
  • Ilya Taydakov,
  • Lucia Tonucci,
  • Nicola d’Alessandro,
  • Frederic Lamaty,
  • Jean Martinez and
  • Evelina Colacino

Beilstein J. Org. Chem. 2017, 13, 19–25, doi:10.3762/bjoc.13.3

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  • reaction time (3 h instead of 2 h), when ‘pre-treated’ PEGs were used instead of ‘unfiltered’ PEGs (Table 1, entries 3 and 8). This observation suggested that changes in the ‘physical state of the system could be induced by specific interactions with PEG polymers and influenced both by the viscosity and
  • reactants. Decreased and comparable yields were also observed by reducing the PEG chain length (Table 1, entry 13) and by using glycerol. It is also worth noting here that not only viscosity, but any modification of the physical state of the system impacted the outcome of the reaction. Indeed, HO-PEG-600-OH
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Published 04 Jan 2017

Towards the development of continuous, organocatalytic, and stereoselective reactions in deep eutectic solvents

  • Davide Brenna,
  • Elisabetta Massolo,
  • Alessandra Puglisi,
  • Sergio Rossi,
  • Giuseppe Celentano,
  • Maurizio Benaglia and
  • Vito Capriati

Beilstein J. Org. Chem. 2016, 12, 2620–2626, doi:10.3762/bjoc.12.258

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  • back through DES due to the difference in the viscosity of the two phases, thereby generating a upper organic phase (blue in the picture) which finally ended into the organic phase of the larger tube, that was continuously pumped into the DES phase to realize a closed cycle. In set-up II, the mixture
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Published 05 Dec 2016

Protonated paramagnetic redox forms of di-o-quinone bridged with p-phenylene-extended TTF: A EPR spectroscopy study

  • Nikolay O. Chalkov,
  • Vladimir K. Cherkasov,
  • Gleb A. Abakumov,
  • Andrey G. Starikov and
  • Viacheslav A. Kuropatov

Beilstein J. Org. Chem. 2016, 12, 2450–2456, doi:10.3762/bjoc.12.238

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  • increase in the viscosity of the solvent. According to these data, (1·−)H2 belongs to class III of Robin–Day classification [15] of mixed valence systems. Thus, the molecule does not have distinct catechol or semiquinone oxidation states for the dioxolene moieties on the termini, i.e., an additional
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Published 17 Nov 2016

A flow reactor setup for photochemistry of biphasic gas/liquid reactions

  • Josef Schachtner,
  • Patrick Bayer and
  • Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2016, 12, 1798–1811, doi:10.3762/bjoc.12.170

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  • effects on reaction rates and selectivities. Furthermore, specific properties of the reagents and solvents (viscosity, surface tension, gas solubility) will be critical to the dispersion and slug flow formation. Light source The benefit of microreaction technologies applied to photochemical processes is
  • transfer coefficients compared to traditional stirred tanks [39]. Depending on the flow rates of gas and liquid phases, their ratio, the solvent viscosity and the reactor dimensions, different flow pattern can be obtained. The so-called slug flow leads to very efficient irradiation but also other spatial
  • capillary tubing is dependent on the length and gauge of the capillary and the flow rate of the solution. If the dynamic viscosity of the solution is known, the pressure gradient can be calculated from the Hagen–Poiseuille equation (Scheme 4). Temperature control The microreactor system is equipped with a
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Published 11 Aug 2016

Rearrangements of organic peroxides and related processes

  • Ivan A. Yaremenko,
  • Vera A. Vil’,
  • Dmitry V. Demchuk and
  • Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

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Published 03 Aug 2016

Stimuli-responsive HBPS-g-PDMAEMA and its application as nanocarrier in loading hydrophobic molecules

  • Yongsheng Chen,
  • Li Wang,
  • Haojie Yu,
  • Zain-Ul-Abdin,
  • Ruoli Sun,
  • Guanghui Jing,
  • Rongbai Tong and
  • Zheng Deng

Beilstein J. Org. Chem. 2016, 12, 939–949, doi:10.3762/bjoc.12.92

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  • 400M spectrometer. The molecular weight of polymer was determined by gel permeation chromatography (GPC) (Waters-Wyatt) equipped with RI, UV, viscosity and LS detectors using tetrahydrofuran (THF) as eluent. The UV–vis spectra were recorded on a UV3802 (UNICO) ultraviolet spectrophotometer. The size
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Published 10 May 2016

My maize and blue brick road to physical organic chemistry in materials

  • Anne J. McNeil

Beilstein J. Org. Chem. 2016, 12, 229–238, doi:10.3762/bjoc.12.24

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  • rate in a single round-bottom flask I realized that the stir-rate effect was real. I eliminated obvious culprits, including heterogeneity and high viscosity. Puzzled, I talked about this oddity to whomever would listen and tried every experiment suggested. One day I let a reaction sit unstirred for an
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Published 08 Feb 2016

Supramolecular structures based on regioisomers of cinnamyl-α-cyclodextrins – new media for capillary separation techniques

  • Gabor Benkovics,
  • Ondrej Hodek,
  • Martina Havlikova,
  • Zuzana Bosakova,
  • Pavel Coufal,
  • Milo Malanga,
  • Eva Fenyvesi,
  • Andras Darcsi,
  • Szabolcs Beni and
  • Jindrich Jindrich

Beilstein J. Org. Chem. 2016, 12, 97–109, doi:10.3762/bjoc.12.11

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  • reached higher values due to lower viscosity of the BGE. Subsequently differences between electrophoretic mobilities with and without Cin-α-CDs in BGE decreased because of smaller size of Cin-α-CDs aggregates. The studied α-cyclodextrin derivatives offer a potential for employing them in capillary
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Published 19 Jan 2016

Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host–guest complexation

  • Jie Wang,
  • Zhiqiang Qiu,
  • Yiming Wang,
  • Li Li,
  • Xuhong Guo,
  • Duc-Truc Pham,
  • Stephen F. Lincoln and
  • Robert K. Prud’homme

Beilstein J. Org. Chem. 2016, 12, 50–72, doi:10.3762/bjoc.12.7

Graphical Abstract
  • substituents rendering a solution viscous by forming host–guest complexes with individual hydrophobic substituents and thereby lower solution viscosity [41][42][43][44]. This process may be reversed by adding competing hydrophobes which complex cyclodextrins more strongly than the hydrophobic substituents to
  • restore solution viscosity [45][46]. 1.2 Host–guest complexation of hydrophobic substituents in polymers Hydrophobic associations in aqueous solution between either terminal or multiple hydrophobic substituents along the backbone of a polymer, which generate the high viscosity of associative thickeners
  • , may be disrupted by cyclodextrin host–guest complexation of these substituents (Figure 2) [41][42][43][44][45][46][47][48][49]. Thus, in 1998, Zhang et al. reported that the viscosity of an aqueous solution of perfluorocarbon-substituted poly(ethylene glycol) was decreased through the addition of β-CD
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Published 12 Jan 2016

Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations

  • Giuseppina Raffaini,
  • Antonino Mazzaglia and
  • Fabio Ganazzoli

Beilstein J. Org. Chem. 2015, 11, 2459–2473, doi:10.3762/bjoc.11.267

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  • formation of larger aggregates comprising all the molecules included in the simulations. While specific solvation effects cannot be ruled out, we point out that in vacuo all kinetic processes are much faster than in explicit water because of the lack of the solvent viscosity (the random collisions with the
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Published 07 Dec 2015

Synthesis, structure, and mechanical properties of silica nanocomposite polyrotaxane gels

  • Kazuaki Kato,
  • Daisuke Matsui,
  • Koichi Mayumi and
  • Kohzo Ito

Beilstein J. Org. Chem. 2015, 11, 2194–2201, doi:10.3762/bjoc.11.238

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  • transparent, indicating no significant aggregation. Five gels were synthesized in the same way with different initial concentrations of silica nanoparticles. Notably, in the absence of silica nanoparticles, gelation did not occur; only a slight increase of viscosity was observed. This result clearly shows
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Published 16 Nov 2015

Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study

  • Yulia I. Denisova,
  • Maria L. Gringolts,
  • Alexander S. Peregudov,
  • Liya B. Krentsel,
  • Ekaterina A. Litmanovich,
  • Arkadiy D. Litmanovich,
  • Eugene Sh. Finkelshtein and
  • Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2015, 11, 1796–1808, doi:10.3762/bjoc.11.195

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  • accepted mechanism of olefin metathesis mediated by Gr-1 [30], this signal can be attributed to a new, secondary carbene ([Ru]=PCOE) formed via break up of a PCOE chain attacked by a primary carbene, as shown in Scheme 1. The mixture viscosity was considerably reduced at the early stage of the reaction (10
  • dynamical behavior of PNB solutions in the DLS experiments reported above. We supposed that it could be correlated with a high viscosity of the PNB solution at early stages of the reaction, which was decreased rather slowly due to lower activity of the primary carbene, as compared with the PCOE case
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Published 01 Oct 2015
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  • (Equation 1) is the solvent viscosity. Table 3 summarizes the results of the theoretically calculated hydrodynamic properties of the lipo-oligonucleotides 10–15. The mean diffusion coefficient was found to be 1.2·10−6 ± 0.08 cm2 s−1. We do not exclude the formation of LON aggregates, but under our
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Published 01 Jun 2015

IR and electrochemical synthesis and characterization of thin films of PEDOT grown on platinum single crystal electrodes in [EMMIM]Tf2N ionic liquid

  • Andrea P. Sandoval,
  • Marco F. Suárez-Herrera and
  • Juan M. Feliu

Beilstein J. Org. Chem. 2015, 11, 348–357, doi:10.3762/bjoc.11.40

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  • the fact that the viscosity of the ionic liquid is quite high [16]. It is important to state that the activation energy of the nucleation kinetics related to the ion exchange depends on the overpotential used. Even so, the results shown in Table 1, Figure 3a and Figure 4 show that the kinetics of the
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Published 13 Mar 2015

Formulation development, stability and anticancer efficacy of core-shell cyclodextrin nanocapsules for oral chemotherapy with camptothecin

  • Hale Ünal,
  • Naile Öztürk and
  • Erem Bilensoy

Beilstein J. Org. Chem. 2015, 11, 204–212, doi:10.3762/bjoc.11.22

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  • increases linearly with polymer concentration which is attributed to higher organic solution viscosity with increase in polymer concentration [30]. Although the smallest particle size was obtained with 0.05% w/v concentration of polymer, there is no significant difference between the concentrations of 0.05
  • Table 2, an increase in the concentration of oil resulted in an increase of nanoparticle size. This effect was attributed to the increase of the viscosity of the organic phase, since the higher the oil concentration is, the more viscous the organic phase becomes. However there is no significant
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Published 04 Feb 2015

Articulated rods – a novel class of molecular rods based on oligospiroketals (OSK)

  • Pablo Wessig,
  • Roswitha Merkel and
  • Peter Müller

Beilstein J. Org. Chem. 2015, 11, 74–84, doi:10.3762/bjoc.11.11

Graphical Abstract
  • the influence of temperature and solvent viscosity on the STR–FOL equilibrium. At room temperature a ratio between the monomer and excimer emission IM/IEX of about 100:60 is observed (Figure 4, red curve). The ratio does not change on dilution (1.5·10−5 mol/L → 1.1·10−6 mol/L) indicating that excimer
  • the global minimum. Based on these results we next investigated the IM/IEX ratio in a variety of solvents with different viscosity [26]. In Figure 5 the IM/IEX ratio is represented in dependence on the viscosity η. Two nearly linear correlations are discernable. The first group (circles) with a steep
  • be a versatile tool to investigate the STR/FOL equilibrium. We systematically investigated this phenomenon as a function of solvent viscosity, cyclodextrine addition and in the presence of lipids forming micelles and vesicles. In contrast to these noncovalent STR–FOL transitions we also reported on
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Published 16 Jan 2015

Synthesis and characterization of a hyper-branched water-soluble β-cyclodextrin polymer

  • Francesco Trotta,
  • Fabrizio Caldera,
  • Roberta Cavalli,
  • Andrea Mele,
  • Carlo Punta,
  • Lucio Melone,
  • Franca Castiglione,
  • Barbara Rossi,
  • Monica Ferro,
  • Vincenza Crupi,
  • Domenico Majolino,
  • Valentina Venuti and
  • Dominique Scalarone

Beilstein J. Org. Chem. 2014, 10, 2586–2593, doi:10.3762/bjoc.10.271

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  • used routes to get soluble CD polymers [14]. However, during polymerization the viscosity of the solution increases rapidly, thus leading to broad molecular weight distributions and poor reproducibility. A reduction in the concentration of the reactants leads to low reaction rates, but invariably
  • (e.g., 12:1 molar ratio), the viscosity of the resulting CD-based polymer does not change for many hours, thus proving the stability of the formed branched polymer. The reaction is carried out at room temperature and followed by relative viscosity measurements. TLC analyses confirm the consumption of
  • temperature was observed after the introduction of pyromellitic dianhydride. The viscosity of the solution gradually increases, but after few hours it remains constant. At this point, the solution was precipitated into an excess of diethyl ether, filtered under vacuum, solubilized in deionized water
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Published 06 Nov 2014

End group functionalization of poly(ethylene glycol) with phenolphthalein: towards star-shaped polymers based on supramolecular interactions

  • Carolin Fleischmann,
  • Hendrik Wöhlk and
  • Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 2263–2269, doi:10.3762/bjoc.10.235

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  • be subdivided into regular star polymers and miktoarm star polymers. In analogy to hyperbranched polymers, star shaped polymers have lower viscosities than analogous linear materials of the same molecular weight because the viscosity is rather determined by the mass of one arm than the mass of the
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Published 25 Sep 2014

Photo, thermal and chemical degradation of riboflavin

  • Muhammad Ali Sheraz,
  • Sadia Hafeez Kazi,
  • Sofia Ahmed,
  • Zubair Anwar and
  • Iqbal Ahmad

Beilstein J. Org. Chem. 2014, 10, 1999–2012, doi:10.3762/bjoc.10.208

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  • been identified that affect the stability of RF. These factors include radiation source, its intensity and wavelength, pH, presence of oxygen, buffer concentration and ionic strength, solvent polarity and viscosity, and use of stabilizers and complexing agents. A detailed review of the literature in
  • viscosity The rate of RF photolysis is affected by solvent polarity, which causes changes in the conformation of the ribityl side chain to undergo degradation [83]. RF shows higher photostability in less polar solvents [96]. When RF was irradiated anaerobically in alcohols and alcohol/water mixtures, a
  • , dioxane and its mixtures with water, ethanol and pyridine [96][97][98]. The photodegradation of RF has been found to be more rapid in organic solvents as compared to aqueous solutions [97][99]. This could be linked to the physical properties of the solvents such as polarity, dielectric constant, viscosity
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Published 26 Aug 2014

Efficient CO2 capture by tertiary amine-functionalized ionic liquids through Li+-stabilized zwitterionic adduct formation

  • Zhen-Zhen Yang and
  • Liang-Nian He

Beilstein J. Org. Chem. 2014, 10, 1959–1966, doi:10.3762/bjoc.10.204

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  • absorbed per mol of base) had a CO2 capacity below 1:1 stoichiometry expected from the proposed mechanism (Scheme 1c), owing to highly increased viscosity after CO2 absorption (Table 1, entries 12 and 13). Compared on a weight basis, a CO2 capacity of 5.0 wt % to 8.0 wt % was obtained with ILs from neutral
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Published 21 Aug 2014

Supercritical carbon dioxide: a solvent like no other

  • Jocelyn Peach and
  • Julian Eastoe

Beilstein J. Org. Chem. 2014, 10, 1878–1895, doi:10.3762/bjoc.10.196

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  • of polar and ionic species and attempts to enhance scCO2 viscosity. Keywords: CO2 chemistry; microemulsion; self-assembly; supercritical CO2; surfactant; viscosity; Introduction In this day and age, sustainability and renewability are watchwords. This includes focus within the scientific community
  • properties ordinarily required for an effective solvent, with a lower viscosity, dielectric constant [26][27] and surface tension in comparison to other common reference solvents. Also, as CO2 is a linear molecule with no net dipole moment there is significant difficulty dissolving polar and ionic species
  • managed and controlled; both of these techniques would be both economically and technically more viable if the viscosity of CO2 used could be increased (leading to a reduction of viscous fingering during EOR and giving generally more overall control in CCS). The physicochemical properties of CO2 have thus
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Published 14 Aug 2014

A promising cellulose-based polyzwitterion with pH-sensitive charges

  • Thomas Elschner and
  • Thomas Heinze

Beilstein J. Org. Chem. 2014, 10, 1549–1556, doi:10.3762/bjoc.10.159

Graphical Abstract
  • aqueous solution or the cleavage of carbamate moieties from the polymer backbone during acidic and basic treatment. However, the ratio between amino and carboxylic groups is balanced. In addition, the IP was proofed by rheology. The IP is indicated by a minimum of the relative viscosity of a
  • dynamic light scattering (DLS) and obtained by the cumulants method assuming spherical shape. Each measurement was repeated at least two times. Manual potentiometric titrations were performed with a SevenMulti™ pH meter (Mettler Toledo, Gießen, Germany). The viscosity of the polymer solutions was measured
  • with a Haake Mars II cone-plate rheometer (Thermo Scientific, Schwerte, Germany) in controlled rate mode at 20 °C. Shear rates were varied from 0.1 to 1000 s−1 in a cycle of increasing and decreasing shear rate over 5 min. The linear range was extrapolated to zero shear viscosity. Syntheses Synthesis
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Published 08 Jul 2014

Synthesis and solvodynamic diameter measurements of closely related mannodendrimers for the study of multivalent carbohydrate–protein interactions

  • Yoann M. Chabre,
  • Alex Papadopoulos,
  • Alexandre A. Arnold and
  • René Roy

Beilstein J. Org. Chem. 2014, 10, 1524–1535, doi:10.3762/bjoc.10.157

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  • × rs) can be calculated using the Stokes–Einstein equation and the viscosity of pure D2O (Table 1). As expected, nonavalent conjugates 12, 17, and 21 presented solvodynamic diameters in the range of roughly 3 nm when considering the decay of distinctive and common H-5 signals. These values remained
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Published 04 Jul 2014

An economical and safe procedure to synthesize 2-hydroxy-4-pentynoic acid: A precursor towards ‘clickable’ biodegradable polylactide

  • Quanxuan Zhang,
  • Hong Ren and
  • Gregory L. Baker

Beilstein J. Org. Chem. 2014, 10, 1365–1371, doi:10.3762/bjoc.10.139

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  • 5. The alkylation step was optimized and it can be conducted with an enolate concentration of 4 up to 0.25 M in dioxane (Table 1). The attempt with higher enolate concentration was not smooth due to the increased viscosity of the reaction mixture and thus low efficiency of stirring, even with a
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Published 17 Jun 2014
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