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Modified Vegetable Oils for Environmentally Friendly Lubricant Applications
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
Brajendra K. Sharma, Gobinda Karmakar, Sevim Z. Erhan
Sulfurization results in saturation of double bonds and cross-linking (Scheme 24.14). Controlled sulfurization (S content 3–13%) can produce metal passivators, EP additives, and oiliness additives [123]. Sulfur could also be introduced as mercaptans or thio-alcohols to give thio-esters, which could be then converted to disulfides (Scheme 24.14). These compounds have excellent EP and detergency characteristics. Sulfur can also be incorporated into triacylglycerol structure through reaction of epoxidized soybean oil and common organic thiols to form hydroxy thio-ether derivatives of vegetable oils [42,157]. This synthetic process retains the vegetable oil structure, eliminates polyunsaturation in the molecule, and adds polar functional groups on triacylglycerol. The effectiveness of these hydroxy thio-ether derivatives was demonstrated by comparative tests with commercial antiwear additives [52]. These derivatives were found useful as agriculturally based antiwear additives for lubricant applications. Reaction of fatty acid ester with sulfur and thiol.
pe and Natural Systems
Published in James F. Pankow, Aquatic Chemistry Concepts, 2018
A large part of the reason why multiple electron reactions are slow is that they usually entail complex mechanisms involving many steps. The fact that the concentration of the electron in aqueous systems is always very low is also a contributing factor. In the absence of bacteria, many multiple electron redox reactions are so slow that it would be difficult to even think about the application of equilibrium principles on time scales shorter than many thousands to hundreds of millions of years. In exchange for catalyzing a wide variety of redox reactions and moving nature towards equilibrium, bacteria can obtain the chemical potential energy that is stored in a nonequilibrium redox situation. Bacteria use this energy to continue living, to build cell mass, and to reproduce. It is useful to note that in nature, virtually any redox reaction that can be out of equilibrium will have one or more strains of bacteria that can move the system towards equilibrium: if there is a ecological niche that can be occupied, nature will fill it. Many of these bacteria have been given names that reflect what they do. A good example of this is Thiobacillus ferrooxidans. This bacterium can oxidize both H2S and S(s) to SO42−, and can also oxidize Fe(II) to Fe(III). (The prefix thio means sulfur.)
The Prelude of Green Syntheses of Drugs and Natural Products
Published in Ahindra Nag, Greener Synthesis of Organic Compounds, Drugs and Natural Products, 2022
Leonardo Xochicale-Santana, C. C. Vidyasagar, Blanca M. Muñoz-Flores, Víctor M. Jiménez Pérez
Thioesters are a functional group that is found in a great variety of organic compounds, this since the structure is used for the construction of heterocyclic compounds for the development of thio drugs with pharmaceutical importance.47,48 However, there are very few reports for the synthesis of these compounds by ultrasound; one among one of them was reported by Siqueira and co-workers49; they describe a rapid method for the synthesis of thiols from mercaptobenzooxazole and benzoyl chloride, in excellent yields and short reaction times in comparison with conventional thermal methods (Scheme 15.16).
Synthesis, spectral characterization, DFT, and molecular docking studies of metal(II) complexes derived from thiophene-2-carboxaldehyde and 2-amino-6-picoline
Published in Journal of Coordination Chemistry, 2019
Liji John, R. Selwin Joseyphus, I. Hubert Joe
Density functional theory (DFT) has become an increasingly useful tool for theoretical studies on metal complexes to predict the geometry [10]. Metal complexes of Schiff bases derived from aminopyridine derivatives for their wide-range applications in agroindustry, catalysis, and biological activities have been reported widely [11–13]. Similarly, thiophene derivatives are of great interest and the existence of bond formation between imine and thio-group results in generating stable metal complexes [14–16]. In view of the biological importance of parent compounds, it is reported herein that the synthesis and characterization of ligand derived from thiophene-2-carboxaldehyde with 2-amino-6-picoline and its Co(II), Ni(II), Cu(II), and Zn(II) complexes. DFT, molecular docking, in vitro antimicrobial and cytotoxicity activities have also been carried out in order to ascertain their therapeutic values.
Silver Extraction from Hydrochloric Acid Solutions with the Disulfide of Bis(2,4,4-trimethylpentyl)Dithiophosphinic Acid
Published in Solvent Extraction and Ion Exchange, 2018
N.A. Grigorieva, I. Yu. Fleitlikh, O.A. Logutenko
High recovery of silver in one stage (ε = 98.62%) is achieved against the backdrop of an extremely small co-extraction of metal impurities. Obviously, these impurities can easily be washed out from the extract with dilute solutions of hydrochloric acid. Figure 5 shows a silver extraction isotherm with a 0.1 M solution of the disulfide in toluene. It is seen that in two-stage extraction, at the ratio of the flows of aqueous to organic phases of 5:1, silver is recovered almost completely. Silver stripping from the loaded extractant can be carried out with solutions of thiourea (Thio). As seen from Figure 6, almost complete stripping occurs when using thiourea solutions with a concentration of ≥0.25 M.
A brief insight into the use of plant products as green inhibitors for corrosion mitigation of aluminium and aluminium alloys
Published in Canadian Metallurgical Quarterly, 2022
K Namitha, Padmalatha Rao, Suma A. Rao
M. L Zheludkevich et al. [22] used triazole and its derivatives for the corrosion control of aluminium alloy AA2024, and the inhibitor decreased both cathodic and anodic processes [23–25]. 2,6-dimethylpyridine [26] acted as an excellent organic corrosion inhibitor for aluminium in different solutions like NaCl, HCl, and NaOH. Salicylaldoxime, 8-hydroxyquinoline, and quinaldic acid [27] are some organic compounds that gave good inhibition action on AA2024 [28]. Hydrazine derivatives also showed good inhibition efficiency towards aluminium [29]. It was found that organic compounds containing thio group or thiol compounds substituted with N and S show maximum inhibition action on aluminium alloys such as AA2024-T3 and AA7075-T6 [30].