557-75-5Relevant academic research and scientific papers
Simple Enols. 2. Kinetics and Mechanism of the Ketonization of Vinyl Alcohol
Capon, Brian,Zucco, Cesar
, p. 7567 - 7572 (1982)
The kinetics of the conversion of vinyl alcohol into acetaldehyde in aqueous solution at 15 deg C were found to depend on pH according to the equation k0 = kH2O + (kH+*10-pH) + (kOH-*kW)/10-pH where KH2O = 1.38*10-2 s-1, KH+ = 20.2 M-1 s-1, and KOH- = 1.50*107 M-1 s-1.Under the same conditions, KH+ for the hydrolysis of ethyl vinyl ether is 1.19 M-1 s-1.The solvent deuterium isotope effrect, KH+/kD+, for the ketonization of vinyl alcohol is 4.75 and for the hydrolysis of ethyl vinyl ether is 2.98; the entropies of activation for the two reactions are -13.3 (esd = 1.7) cal deg-1 mol-1 at 25 deg C.General-base catalysis (β = 0.77) was observed for the ketonization of vinyl alcohol with eight carboxylate ions, and general-acid catalysis (α = 0.45) was observed with five carboxylic acids stronger than and including formic acid.The variation of kH+ with solvent composition in H2O-Me2SO mixtures was much less for the ketonization of vinyl alcohol than for the hydrolysis of ethyl vinyl ether, and as result of this, kH+ for the former reaction is 325 times greater than for the latter in 92.5 mol percent Me2SO; the isotope effect kH+/kD+, for the two reactions in 85.9 mol percent Me2SO are 5.33 and 2.05.It is concluded that these experimental results are best explained by a mechanism for the acid-catalyzed ketonization of vinyl alcohol in which protonation of the double bond by the acid catalyst is concerted with removal of the enolic proton by water acting as a general base and by a mechanism for the base- and water-catalyzed reactions that involves a rate-limiting C-protonation of the enolate anion.The pKenol for acetaldehyde at 25 deg C was estimated to be 6.66 or 6.44 from the value of kH+ for the ketonization of vinyl alcohol determined in this investigation and previously reported values of kH+ for the enolization of acetaldehydeu
The unimolecular decomposition of cyclobutanol: Experimental and theoretical study
Tanaka, Seiji,Tomariguchi, Susumu,Saito, Ko,Takahashi, Osamu,Tabayashi, Kiyohiko
, p. 249 - 255 (1996)
The thermal decomposition of cyclobutanol has been investigated behind incident and reflected shock waves at temperatures between 950 K and 1450 K in the total density region (1.5 × 10-6 - 1.5 × 10-5) mol/cm3. A strong absorption by an intermediate was observed at the wavelength of 193 nm. By comparing the kinetics with that of pyruvic acid, this absorption was identified to be that of vinyl alcohol. The kinetic parameters of vinyl alcohol, both for the production and the decomposition, were determined. The production rate constant was in agreement with that obtained by Back (Can J. Chem. 1982, 60, 2357), who monitored the ethylene production. The total decomposition mechanism of cyclobutanol was discussed on the basis of MO calculations. It was shown that vinyl alcohol was produced through a biradical before it isomerized to acetaldehyde.
(Trans)esterification of mannose catalyzed by lipase B from candida antarctica in an improved reaction medium using co-solvents and molecular sieve
Nott, Katherine,Brognaux, Alison,Richard, Gaetan,Laurent, Pascal,Favrelle, Audrey,Jerome, Christine,Blecker, Christophe,Wathelet, Jean-Paul,Paquot, Michel,Deleu, Magali
, p. 348 - 363 (2012)
Four co-solvents (dimethylformamide [DMF], formamide, dimethyl sulfoxide [DMSO], and pyridine) were tested with tert-butanol (tBut) to optimize the initial rate (v0) and yield of mannosyl myristate synthesis by esterification catalyzed by immobilized lipase B from Candida antarctica. Ten percent by volume of DMSO resulted in the best improvement of v0 and 48-hr yield (respectively 115% and 13% relative gain compared to pure tBut). Use of molecular sieve (5% w/v) enhances the 48-hr yield (55% in tBut/DMSO [9:1, v/v]). Transesterification in tBut/DMSO (9:1, v/v) with vinyl myristate leads to further improvement of v0 and 48-hr yield: a relative gain of 85% and 65%, respectively, without sieve and 25% and 10%, respectively, with sieve, compared to esterification. No difference in v0 and 48-hr yield is observed when transesterification is carried out with or without sieve. Copyright Taylor & Francis Group, LLC.
Immobilized Lipase Based on Hollow Mesoporous Silicon Spheres for Efficient Enzymatic Synthesis of Resveratrol Ester Derivatives
Xu, Liu-Jia,Yang, Tao,Wang, Jing,Huang, Feng-Hong,Zheng, Ming-Ming
, p. 9067 - 9075 (2021/03/01)
Enzymatic esterification of resveratrol is crucial for its potential application in lipophilic foods and drugs. However, the poor activity of the free enzyme hinders the reaction. In this work, the highly efficient enzymatic synthesis of resveratrol ester derivatives was achieved by immobilized lipase on hydrophobic modified hollow mesoporous silicon spheres (HMSS-C8). We preliminarily explored the use of Candida sp. 99-125 lipase (CSL) for the acylation of resveratrol, with a regioselectivity toward 3-OH- over 4'-OH-acylation. HMSS-C8 provided ideal accommodation for CSL with a loading capacity of up to 652 mg/g. The catalytic efficiency of CSL@HMSS-C8 was 15 times higher than that of free CSL, and the conversion of resveratrol reached 98.7% within only 2 h, which is the fastest value recorded in the current literature. After 10 cycles, the conversion remained up to 86.3%. Benefiting from better lipid solubility, the relative oxidation stability index values of oil containing monoester derivatives were 43.1%-68.8% and 23.9%-33.2% higher than that of refined oil and oil containing resveratrol, respectively. This research provides a new pathway for efficient enzymatic synthesis of resveratrol ester derivatives and demonstrates the potential application of resveratrol monoester derivatives as a group of excellent lipid-soluble antioxidants.
Phosphorus and nitrogen-doped palladium nanomaterials support on coral-like carbon materials as the catalyst for semi-hydrogenation of phenylacetylene and mechanism study
Ma, Lei,Jiang, Pengbo,Wang, Kaizhi,Lan, Kai,Huang, Xiaokang,Yang, Ming,Gong, Li,Jia, Qi,Mu, Xiao,Xiong, Yucong,Li, Rong
, (2021/02/26)
In this work, two types of polyporous and coral-like materials (CN) with high specific surface area are prepared using sodium glutamate as a carrier. At the same time, a CN-supported phosphorus-nitrogen-doped palladium nanomaterial CN-P-Pd is synthesized and applied to the preparation of styrene by selective hydrogenation of phenylacetylene under mild conditions. As shown in the TEM images, Pd nanoparticles with a particle size of about 4.4 nm are uniformly dispersed on the surface of the carrier. The results of N2 adsorption–desorption reveal that the surface area of the prepared catalyst (CN-P-Pd) is 1307 m2g?1. In addition, the experimental exploration shows the intervention of P in carbon-nitrogen materials can contribute to improve the selectivity of the reaction, which can be attributed to the fact that P element can change the electron density of Pd. Meanwhile, it is found that the solvent not only affects the activity of catalyst, but also the selectivity of the reaction. Kinetic study shows the activation energy of the reaction is 4.5 kJ/mol. With the increase of the reaction temperature, the dissolution rate of hydrogen in the solvent gradually slows down, which inhibits the progress of the reduction reaction. Mechanistic studies demonstrate that the carbon-nitrogen materials have strong adsorption capacity for substrates, and also provide more adsorption sites for phenylacetylene. Additionally, the optimal catalyst (CN-P-Pd) also has high reaction activity to other alkynes and the conversion can reach at 95%. Moreover, the optimal catalyst can be reused several times without significant reduction in reaction activity.
Enantioselective Radical-Polar Crossover Reactions of Indanonecarboxamides with Alkenes
Cao, Weidi,Feng, Xiaoming,Liu, Xiaohua,Wu, Wangbin,Xu, Xi,Yu, Han,Zhang, Xiying
supporting information, p. 4846 - 4850 (2020/02/11)
Highly efficient asymmetric intermolecular radical-polar crossover reactions were realized by combining a chiral N,N′-dioxide/NiII complex catalyst with Ag2O under mild reaction conditions. Various terminal alkenes and indanonecarboxamides/esters underwent radical addition/cyclization reactions to afford spiro-iminolactones and spirolactones with good to excellent yields (up to 99 %) and enantioselectivities (up to 97 % ee). Furthermore, a range of different radical-mediated oxidation/elimination or epoxide ring-opening products were obtained under mild reaction conditions. The Lewis acid catalysts exhibited excellent performance and precluded the strong background reaction.
Cutinase from Fusarium oxysporum catalyzes the acylation of tyrosol in an aqueous medium: Optimization and thermodynamic study of the reaction
Nikolaivits, Efstratios,Norra, Giannis-Florjan,Voutsas, Epaminondas,Topakas, Evangelos
, p. 29 - 36 (2016/04/20)
Recently, tyrosol has gained attention as a result of its many pharmacological properties and due to the fact that it can be isolated from cheap and abundant resources. Lipophilic tyrosyl esters, which are scarce in nature, have proven in certain cases to acquire improved biological activity compared to tyrosol itself, increasing their potential use in the food and cosmeceutical industries. The enzymatic approach for the synthesis of such esters has prevailed, as it is "green", compared to chemical practices. We hereby report the enzymatic synthesis of tyrosyl esters of various aliphatic fatty acids performed by a recombinant cutinase from Fusarium oxysporum (FoCut5a). The reaction system used consists of an aqueous phase saturated with the corresponding fatty-acid vinyl ester, which played the role of the acyl donor. We also proceeded to the study of several parameters on the yield of the tyrosyl butyrate ester synthesis. The maximum yield achieved was 60.7% after 4 h at 20 °C, in pH 7.0, with initial tyrosol concentration of 12.5 mM and using 5 μg FoCut5a mL-1 reaction as catalyst. The optimum reaction conditions can be considered mild, highlighting the environmentally friendly nature of this reaction, along with the fact that there are not any harmful reagents involved. Additionally, the use of two thermodynamic models, Conductor-like Screening Model for Real Solvents (COSMO-RS) and UNIquac Functional-group Activity Coefficients (UNIFAC), were employed for the prediction of reactants' and products' solubilities and their distribution in the reaction biphasic system, aiming to correlate the reaction yields with these important thermodynamic quantities and understand the ability of this enzymatic reaction in synthesizing tyrosyl esters.
Carbohydrate base co-polymers as an efficient immobilization matrix to enhance lipase activity for potential biocatalytic applications
Badgujar, Kirtikumar Chandulal,Bhanage, Bhalchandra Mahadeo
, p. 709 - 717 (2015/09/02)
In the present study, we have synthesized biocompatible hybrid blend of cellulosic polymers of hydroxypropyl-methyl-cellulose (HPMC) and chitosan (CHY) for the immobilization of Candida rugosa lipase (CRL). The immobilized biocatalyst HPMC:CHY:CRL was subjected for characterization such as SEM, TGA, water content analysis, lipase activity, specific activity and protein content analysis. The kinetic parameter study (Rmax/Km) demonstrated improved biocatalytic activity of lipase after immobilization on carbohydrate co-polymers of HPMC:CHY. This biocatalyst was then employed to study practical biocatalytic applications for kinetic resolution which provided 50% conversion and >94% enantiomeric excess of substrate/product (ees/eep). The protocol demonstrated excellent recyclability upto five cycles. Finally, we studied influence of immobilization on cellulosic polymers for substrate, structure and reactivity for kinetic resolution. Hence, we investigated R0 (initial reaction rate), E-value (enantioselectivity) and Ea (activation energy). This study confirms that, lipase immobilized on carbohydrate polymers had 3-4 folds higher biocatalytic activity as compared to crude CRL.
Novel Zn-MOF compounds, and carbon dioxide sorption and heterogeneous catalysts for transesterification comprising the same
-
Paragraph 0047; 0048, (2017/01/02)
The present invention relates to a zinc-metal organic framework (Zn-MOF) compound with a two-dimensional (2D) structure of [Zn(glu)(andmu;-bpe)andmiddot;2(H_2O)]_n connected by glutaric acid and bipyridine ligands. The zinc-metal organic framework compound of the present invention can be used as a carbon dioxide adsorbent by selectively adsorbing carbon dioxide; and can be used as a heterogeneous catalyst for transesterification capable of being easily reused and being efficient in transesterification.(BB) Desorption isotherm(AA) Adsorption isothermCOPYRIGHT KIPO 2015
Anion effects on crystal structures of CdII complexes containing 2,2'-bipyridine: Photoluminescence and catalytic reactivity
Park, Hyun Min,Hwang, In Hong,Bae, Jeong Mi,Jo, Young Dan,Kim, Cheal,Kim, Ha-Yeong,Kim, Youngmee,Kim, Sung-Jin
experimental part, p. 1517 - 1522 (2012/07/14)
Anion effects on structures of CdII complexes containing 2,2'-bipyridine (2,2'-bpy) ligands have been studied, and compared with ZnII-(2,2'-bpy) complexes. For each anion, different structures have been obtained in both ZnII-(2,2'-bpy) and CdII-(2,2'-bpy). Polymeric structures of CdII-2,2'-bpy complexes can be produced by hydrogen bonding interactions as shown in ZnII-2,2'-bpy complexes. In addition, the bigger size of a CdII ion gives higher coordination numbers forming variety of structures, and it makes that chlorides can act as bridging ligands to form a one-dimensional structure. The compound 5 catalyzed efficiently the transesterification of a variety of esters with methanol, while the rest of the compounds have displayed very slow conversions. In addition, the emission bands of complexes 1, 2, 4, and 6 are blue-shifted compared to the corresponding ligand 2,2'-bpy, whereas 3 and 5 showed the similar emission observed for the ligand. Copyright
