- Design of sulphate modified solid acid catalysts for transesterification of diethyl malonate with benzyl alcohol
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Sulphate ion modified multiwalled carbon nanotubes (S-CNTs), mesoporous carbon (S-MC), zirconia (S-ZrO2), alumina (S-Al2O3) and silica (S-SiO2) were prepared by wet impregnation technique. The physico-chemical properties of the prepared materials were inv
- Minchitha,Hareesh,Venkatesh,Shanty,Nagaraju,Kathyayini
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p. 202 - 214
(2017/12/12)
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- Transesterification of diethyl malonate with benzyl alcohol catalyzed by modified zirconia: Kinetic study
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Zirconia and its modified forms such as 10%Mo(VI)/ZrO2, 10%V(V)/ZrO2, 10%W(VI)/ZrO2 and SO4 2-/ZrO2 were prepared and characterized for their physico-chemical properties such as BET for surface area, NH3-TPD and n-butylamine back titration method for total surface acidity, PXRD technique for crystallinity and ICP-OES technique for elemental analysis. These materials were used as catalysts in liquid phase transesterification reaction of diethyl malonate (DEM) with benzyl alcohol (BA). Optimization of reaction conditions such as reaction time, reaction temperature, weight of the catalyst and molar ratio of reactants were carried out to obtain highest possible transester yield. Dibenzyl malonate (DBM) and benzyl ethyl malonate (BEM) were obtained as major products. Highest total transester yield of (88%) was obtained in the presence of 0.75 g of SZ catalyst at a molar ratio of DEM: BA = 1:3, reaction temperature of 393 K and reaction time 5 h. Kinetic studies were carried out to find out the rate of the reaction and energy of activation values for zirconia catalysts, in order to identify a facile catalyst system for this reaction. A possible reaction mechanism was proposed based on the kinetic data and it was observed that Eley-Rideal mechanism fits well for this reaction. Reactivation and reusability studies of the catalysts were also taken up.
- Thimmaraju,Mohamed Shamshuddin,Pratap,Venkatesh
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- Preparation and characterisation of amorphous mesoporous aluminophosphate and metal aluminophosphate as an efficient heterogeneous catalyst for transesterification reaction
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Preparation, characterisation of pure aluminophosphate and aluminophosphate modified with different transition metals (V, Fe, Co Ni & Cu) and their catalytic activity in mono/dibenzyl substituted malonates synthesis are explained. The materials were prepared by the coprecipitation method in the absence of any structure-directing species and characterized for their composition, crystalline nature, total surface acidity, specific surface area pore diameter and pore volume by different techniques. Catalytic activity of the materials was investigated in transesterification of diethylmalonate with benzyl alcohol in liquid phase. Pure aluminophosphate resulted only in benzyl ethylmalonate whereas the incorporation of transition metals favored the formation of both benzyl ethylmalonate and dibenzylmalonate. Catalytic activity parallels the surface acidity and mesoporosity of the catalysts. The effect of the molar ratio of reactants, amount of catalyst, and reaction time on the conversion of diethyl malonate and transester yield has been studied. The highest activity of iron aluminophosphate is attributed to its mesoporous nature with uniform pore size distribution, higher surface acidity and surface area. Further, the scope and generality of iron aluminophosphate as a catalyst in the transesterification was studied using various aliphatic, alicyclic and aromatic alcohols. The catalysts could be recycled by retaining most of its initial activity.
- Vijayasankar,Nagaraju
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experimental part
p. 1109 - 1116
(2012/03/11)
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- Monoalkylations with alcohols by a cascade reaction on bifunctional solid catalysts: Reaction kinetics and mechanism
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A bifunctional catalytic system formed by Pd on MgO catalyzes the cascade process between benzyl alcohol and phenylacetonitrile, diethylmalonate and nitromethane, to give the respective α-monoalkylated products without external supply of hydrogen. The process involves a series of three cascade reactions occurring on different catalytic sites. The alcohol undergoes oxidation to the corresponding aldehyde with the simultaneous formation of a metal hydride; then, the aldehyde reacts with a nucleophile formed "in situ" to give an alkene, and finally, the hydrogen from the hydride is transferred to the alkene to give a new C-C bond. A kinetic study on the α-monoalkylation reaction of benzylacetonitrile with benzyl alcohol reveals that the rate-controlling step for the one-pot reaction sequence is the hydrogen transfer reaction from the surface hydrides to the olefin, and consequently, the global reaction rate is improved when decreasing the size of the Pd metal particle.
- Corma, Avelino,Rodenas, Tania,Sabater, Maria J.
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experimental part
p. 319 - 327
(2011/05/14)
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- Surface properties and the catalytic activity of amorphous iron aluminophosphates: Effect of fe loading
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Iron aluminophosphates (FeAlP) with different percentage of iron were synthesized and characterized for their surface and bulk properties. The catalytic activity was determined in the transesterification of diethyl malonate with benzyl alcohol. Benzyl ethylmalonate and dibenzyl malonate were obtained as the only products. FeAlP with 0.025 mole % of iron was found to be distinctly different in its textural and catalytic properties. Formation of diester was found to be favored by the acid sites of intermediate strength. The presence of hydrated alumina and the polycondensed phosphates in the materials reduced the catalytic activity of iron aluminophosphates in transesterification reaction.
- Vijayasankar,Aniz,Nagaraju
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body text
p. 131 - 136
(2010/09/09)
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- New trisubstituted cyclopentadienyl ligands: Synthesis, characterisation and catalytic properties of mono and dinuclear cobalt, rhodium, iron and ruthenium complexes
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The synthesis of a set of dialkyl 4-alkoxycarbonylcyclopenta-1,3-diene-1,2-diacetates (1a-e) is described. Their coordinating abilities as anions have been investigated in relation to the formation of new sandwich, half-sandwich and dinuclear complexes and their structural features. We report here the preparation and characterisation of some complexes such as a mononuclear half-sandwich cobalt(1,5-COD) complex which has shown to be a very efficient catalyst for the cyclocotrimerisation reaction of alkynes and nitriles to pyridines. Half-sandwich rhodiumdicarbonyl complexes containing trisubstituted cyclopentadienyl ligands with ester chains of different length have been employed successfully as catalysts for hydroformylation of styrene. Finally ligands 1a-e have been used for the synthesis of ferrocenes and dinuclear carbonyl complexes of iron and ruthenium. The structures of the complexes 1,5-cycloctadiene[1-methoxycarbonyl-3,4-di(methoxycarbonylmethylene) cyclopentadienyl]cobalt [Co(MDMCp)COD] (9), dicarbonyl[1-methoxycarbonyl-3,4-di(methoxycarbonylmethylene)cyclopentadienyl] rhodium [Rh(MDMCp)(CO)2] (2a) and of a new ferrocene complex [Fe(MDMCp)2] (15a) have been determined by X-ray diffraction methods.
- Costa, Mirco,Dalcanale, Enrico,Dias, Francisco Santos,Graiff, Claudia,Tiripicchio, Antonio,Bigliardi, Lorenzo
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p. 179 - 193
(2007/10/03)
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- CHEMIOSELECTIVITY IN THE PRESENCE OF SURFACTANTS. I. C- vs. O-ALKYLATION IN β-DICARBONYL COMPOUNDS
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A number of β-dicarbonyl compounds (2,4-pentanedione, 5,5-dimethyl-1,3-cyclohexanedione, 1,3-cyclopentanedione, ethyl 3-oxobutanoate, and diethyl propanedioate) reacted with benzyl bromide in basic aqueous solutions of hexadecyltrimethylammonium bromide at room temperature.The presence of the cationic surfactant directed the reaction toward the carbon nucleophilic site, with high chemioselectivity.C-Dialkylated species were generally predominant, due to the increased lipophilicity of the monoalkylated species, with respect to the reagent.No hydrolysis of benzyl bromide was observed in the presence of the surfactant.
- Bassetti, Mauro,Cerichelli, Giorgio,Floris, Barbara
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p. 583 - 586
(2007/10/02)
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- A MILD, RAPID AND CONVENIENT ESTERIFICATION OF HALF ESTERS OF MALONIC ACID
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A new method for the esterification of half esters of malonic acid with chloroformates is described.The reaction proceeds via the mixed anhydride followed by spontaneous decarboxylation.
- Gutman, Arie L.,Boltanski, Aviv
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p. 1573 - 1576
(2007/10/02)
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