Activation of reducing agents. Sodium hydride containing complex reducing agents 22. New coupling reaction with “nickel doped” complex reducing agent.

1986 ◽  
Vol 27 (30) ◽  
pp. 3517-3520 ◽  
Author(s):  
Régis Vanderesse ◽  
Yves Fort ◽  
Sandrine Becker ◽  
Paul Caubere
Keyword(s):  
Coupling Reaction ◽  
Sodium Hydride ◽  
Reducing Agents ◽  
Reducing Agent

scholarly journals The Influence of Water Reducing Agents on Early Hydration Property of Ferrite Aluminate Cement Paste

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 731
Author(s):  
Chunlong Huang ◽  
Zirui Cheng ◽  
Jihui Zhao ◽  
Yiren Wang ◽  
Jie Pang
Keyword(s):  
Setting Time ◽  
Critical Role ◽  
Hydration Product ◽  
Reducing Agents ◽  
Reducing Agent ◽  
Hydration Process ◽  
Early Hydration ◽  
Cement Pastes ◽  
Hydration Rate ◽  
Aluminate Cement

The ferrite aluminate cement (FAC) could rapidly lose fluidity or workability due to its excessive hydration rate, and greatly reduce the construction performance. Chemical admixtures are commonly used to provide the workability of cement-based materials. In this study, to ensure required fluidity of FAC, chemically different water reducing agents are incorporated into the FAC pastes. The experiments are performed with aliphatic water reducing agent (AP), polycarboxylic acid water reducing agent (PC) and melamine water reducing agent (MA), respectively. Influence of the water reducing agents on fluidity, setting time, hydration process, hydration product and zeta potential of the fresh cement pastes is investigated. The results show that PC has a better dispersion capacity compared to AP and MA. Besides decreasing water dosage, PC also acts as a retarder, significantly increasing the setting times, delaying the hydration rate and leading to less ettringite in the hydration process of FAC particles. The water reducing agents molecules are adsorbed on the surface of positively charged minerals and hydration products, however, for PC, steric hindrance from the long side chain of PC plays a critical role in dispersing cement particles, whereas AP and MA acting through an electrostatic repulsion force.

scholarly journals Synthesis of Gold Nanoparticles Using p-Aminobenzoic Acid and p-Aminosalicylic Acid as Reducing Agent

2019 ◽  
Vol 19 (1) ◽  
pp. 68
Author(s):  
Abdul Aji ◽  
Eko Sri Kunarti ◽  
Sri Juari Santosa
Keyword(s):  
Gold Nanoparticles ◽  
Optimum Condition ◽  
Reducing Agents ◽  
Reducing Agent ◽  
Hydroxyl Group ◽  
Synthesis Process ◽  
Aminobenzoic Acid ◽  
Aminosalicylic Acid ◽  
Amino Groups ◽  
Transmission Electron

Synthesis of gold nanoparticles (AuNPs) by reduction of HAuCl4 with p-aminobenzoic acid and p-aminosalicylic acid as a reducing agent was investigated. This work was conducted in order to determine the optimum condition of AuNPs synthesis and examine the effect of the hydroxyl group in p-aminosalicylic acid towards the size, shape, and stability of the synthesized gold nanoparticles (AuNPs). The optimum condition of the gold nanoparticles synthesis was determined by UV/Vis spectrophotometer, the shape and size of gold nanoparticles were measured by Transmission Electron Microscope (TEM). The synthesis process was started by reacting HAuCl4 and the reducing agents in an aqueous solution at 86 ºC. The initial gold concentration, reducing agents concentration and pH were varied in order to obtain the optimum condition. In the optimum condition, the results showed that p-aminosalicylic acid containing both hydroxyl and amino groups performed higher reduction ability compared to p-aminobenzoic acid that only containing an amino group. Reducing agents which have a hydroxyl group (p-aminosalicylic acid) could produce AuNPs with a smaller concentration of HAuCl4 than p-aminobenzoic acid. Gold nanoparticles that were synthesized with p-aminosalicylic acid were more stable and had a smaller particle size compared to its counterpart that is synthesized with p-aminobenzoic acid.

scholarly journals Effects of reducing reagents and temperature on conversion of nitrite and nitrate to nitric oxide and detection of NO by chemiluminescence

1997 ◽  
Vol 43 (4) ◽  
pp. 657-662 ◽  
Author(s):  
Fan Yang ◽  
Eric Troncy ◽  
Martin Francœur ◽  
Bernard Vinet ◽  
Patrick Vinay ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Reducing Agents ◽  
Reducing Agent ◽  
Effect Of Temperature ◽  
Fixed Amount ◽  
Increased Temperature

Abstract To measure the concentration of nitrites and nitrates by chemiluminescence, we examined the efficiency of five reducing agents [V(III), Mo(VI) + Fe(II), NaI, Ti(III), and Cr(III)] to reduce nitrite (NO2−) and (or) nitrate (NO3−) to nitric oxide (NO). The effect of each reducing agent on the conversion of different amounts of NO2− and (or) NO3−(100–500 pmol, representing concentrations of 0.4 to 2 μmolar) to NO was determined at 20 °C for NO2− and at 80 °C for NO3−. The effect of temperature from 20 to 90 °C on the conversion of a fixed amount of NO2− or NO3− (400 pmol or 1.6 μmolar) to NO was also determined. These five reducing agents are similarly efficient for the conversion of NO2− to NO at 20 °C. V(III) and Mo(VI) + Fe(II) can completely reduce NO3− to NO at 80 °C. NaI and Cr(III) were unable to convert NO3− to NO. Increased temperature facilitated the conversion of NO3− to NO, rather than that of NO2− to NO. We evaluated the recovery of NO2− and NO3− from plasmas of pig and of dog. Recovery from plasma of both animals was reproducible and near quantitative.

scholarly journals A surprising mechanism lacking the Ni(0) state during the Ni(II)-catalyzed P–C cross-coupling reaction performed in the absence of a reducing agent – An experimental and a theoretical study

2020 ◽  
Vol 92 (3) ◽  
pp. 493-503 ◽  
Author(s):  
Réka Henyecz ◽  
Zoltán Mucsi ◽  
György Keglevich
Keyword(s):  
Theoretical Study ◽  
No Reduction ◽  
Active Catalyst ◽  
Theoretical Calculations ◽  
Coupling Reaction ◽  
Reducing Agent ◽  
Catalyst Precursor ◽  
Ni Catalysts ◽  
Optimum Quantity ◽  
Cross Coupling Reaction

AbstractThe Hirao reaction, i.e. the P–C coupling between a bromoarene and a >P(O)H reagent performed in most cases in the presence of a Pd(0) complex incorporating a P-ligand may also be carried out applying a Ni(II) catalyst precursor with or without Zn or Mg as the reducing agent. The Ni catalysts may include P- or N-ligands. B3LYP/6-31G(d,p)//PCM(MeCN) quantum chemical calculations suggested that the mechanism of the NiX2 catalyzed (X=Cl or Br) P–C couplings performed in the absence of a reducing agent, and in the excess of the >P(O)H reagent serving as the P-ligand (via its tautomeric >POH form) is completely different from that of the Pd(OAc)2 promoted version, as no reduction of the Ni(II) occurs. In the two variations mentioned, the active catalyst is the dehydrobrominated species derived from primary complex [(HO)Y2P]2Ni(II)Br2, and the [(HO)Y2P]2Pd(0) complex itself, respectively. Both species undergo temporary oxidation (to “Ni(IV)” and “Pd(II)”, respectively) in the catalytic cycle. During the catalysis with “P2Ni(II)X2”, one of the P-ligands serves the >P(O)H function of the ArP(O)H <  product. The consequence of this difference is that in the Ni(II)-catalyzed case, somewhat less >P(O)H-species is needed than in the Pd(0)-promoted instance. Applying 10 % of the Pd(OAc)2 or NiX2 precursor, the optimum quantity of the P-reagent is 1.3 equivalent and, in the first approach, 1.1 equivalent, respectively. Preparative experiments justified the new mechanism explored. The ligation of Ni(II) was also investigated by theoretical calculations. It was proved that the bis-complexation is the most favorable energetically as compared to the mono-, tri- and tetra-ligation.

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