نتایج جستجو برای: acidic catalyst

تعداد نتایج: 77393  

2004
C. Y. Hse

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...

2017
Claudio E. Grünenfelder

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...

Journal: :Molecules 2016
Heidi A Dahlmann Amanda J McKinney Maria P Santos Lindsey O Davis

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.

Journal: :Chemical communications 2012
Chun-Hua Cui Hui-Hui Li Huai-Ping Cong Shu-Hong Yu Franklin Feng Tao

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.

Journal: :Organic & biomolecular chemistry 2009
David Linder Martina Austeri Jérôme Lacour

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.

Journal: :Chemical communications 2014
Sang Ho Lee Sung Mook Choi Seungha Yoon Huisu Jeong Gun Young Jung Beong Ki Cho Won Bae Kim

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.

2004
Stephan Schwinghammer Rolf Marr Matthäus Siebenhofer

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...

2013
Adel A. Marzouk Avtandil H. Talybov Shaaban Kamel Mohamed

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...

Journal: :iranian chemical communication 2016
batol zakerinasab mohammad ali nasseri hassan hassani

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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