نتایج جستجو برای: acidic catalyst
تعداد نتایج: 77393 فیلتر نتایج به سال:
Urea formaldehyde resins were formulated with vatiables of three reaction pHs (1.0, 4.8, and 8.0 5.0) and three catalysts (sodium hydroxide, sodium hydroxide/ammonium mix, and triethanolamine) . The resins were prepared by placing all formaldehyde and water in reaction kettle and pH was adjusted with sulfnric acid and sodium hydroxide, respectively. Urea was added in 1.5 equal parts at 1 minute...
This thesis describes the development of peptidic catalysts for stereoselective conjugate addition reactions of aldehydes and ketones to maleimides. In addition, mechanistic aspects of this conjugate addition were investigated and structural aspects of peptidic catalysts of the general H-DPro-Pro-type were studied. From a collection of tripeptides, H-DPro-Pro-Asn-NH2 was found to catalyze the c...
An organocatalyzed intramolecular carbonyl-ene reaction was developed to produce carbocyclic and heterocyclic 5- and 6-membered rings from a citronellal-derived trifluoroketone and a variety of aldehydes. A phosphoramide derivative was found to promote the cyclization of the trifluoroketone, whereas a less acidic phosphoric acid proved to be a superior catalyst for the aldehyde substrates.
The active site-dependent electrochemical formic acid oxidation was evidenced by the increased coverage of Pt in the topmost mixed PtPd alloy layer of ternary PtPdCu upon potential cycling, which demonstrated two catalytic pathways only in one catalyst owing to surface atomic redistribution in an acidic electrolyte environment.
The addition of a Lewis acidic metal triflate salt Mg(OTf)(2) as co-catalyst in the CpRu-catalyzed decarboxylative allylation of in situ-generated ketone enolates allows the reaction to proceed at lower temperature with higher regio- and enantioselectivity. Even so-far-unreactive substrates react.
Nanoscale metal ring and dot catalyst arrays are printed over large substrate areas using vertically aligned carbon-based stamps with the ring- and dot-shaped tips. The fundamental nature of these ring and dot catalysts is successfully compared by applying them in diverse electrocatalytic reactions in acidic and alkaline media.
Esterification of acetic acid with methanol with and without heterogeneous catalyst was carried out in compressed carbon dioxide. In the first part of this project the autocatalytic effect of the compressed CO2 on this equilibrium reaction was investigated. The use of high-pressure carbon dioxide, an environmentally benign solvent, will shift the yield towards the desired product methyl acetate...
A simple highly versatile and efficient synthesis of 2,4,5-trisubstituted imidazoles is achieved by three component cyclocondensation of 1,2-dicarbonyl compounds, aldehydes and ammonium acetate as ammonia source in thermal solvent free condition using Brønsted acidic ionic liquid diethyl ammonium hydrogen phosphate as catalyst. The key advantages of this process are cost effectiveness of cataly...
cellulose bonded n-propyl diethylene tetra sulfamic acid (cbpdetsa) was successfully applied as a green and recyclable acidic catalyst for the synthesis of tetrahydrobenzo [a] xanthene-11-one as an important class of potentially bioactive compounds. the products are obtained by the coupling of 2-naphtol , cyclohexadione and aldehyde derivatives in good to high yields (70- 92%) under solvent-fre...
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