Home About us Contact
|
Home About us Contact | ||
|
|
||
Transesterification Reaction (transesterification + reaction)
Selected AbstractsAn Improved Non-Isothermal Kinetic Model for Prediction of Extent of Transesterification Reaction and Degree of Randomness in PET/PEN BlendsMACROMOLECULAR THEORY AND SIMULATIONS, Issue 4-5 2008Mahdi Golriz Abstract An improved non-isothermal kinetic model was developed based on mass balance and Arrhenius laws using a second-order reversible reaction capable of predicting the extent of transesterification reaction (X) and the degree of randomness (RD) in poly(ethylene terephthalate) (PET)/poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) blends prepared by a twin screw micro-compounder over a full composition range under different processing conditions. The experimental values of X and RD were determined by 1H-NMR and a direct relationship between them developed. The model constants were tuned by an optimization method using half of the experimental data, with the other half used for verification. Good agreement was found between the experimental and theoretical data in the verification stage and, therefore, it was concluded that the model is capable of predicting the extent of transesterification reaction with a high level of confidence for a wide range of processing conditions. Similarly to the experimental results, the model showed that, among all parameters affecting the extent of transesterification reaction, the time and temperature play the major role, whereas the blend composition does not have a significant role. [source] Nitrogen-Doped Carbon Materials Prepared by Ammoxidation as Solid Base Catalysts for Knoevenagel Condensation and Transesterification ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Naokatsu Kan-nari Abstract Nitrogen-doped carbon materials were prepared by ammoxidation of commercial carbon sources (carbon black and activated carbon) and applied as base catalysts for Knoevenagel and transesterification reactions. It was shown that these carbon materials were active and the activities were different depending on the ammoxidation conditions (temperature and ammonia concentration in air) and carbon sources used. The bulk, textural, and surface properties of the nitrogen-doped carbon materials were examined by several methods to clarify possible factors determining their final catalytic activities. The activated carbon-derived catalysts were more active than the carbon black-derived ones. The surface area and porosity were not responsible for this difference between the two carbon sources but the difference in the reactivity with oxygen was important. The reactivity of carbon sources with oxygen should influence the doping of nitrogen onto their surfaces by ammoxidation with ammonia and air and the resulting activities as base catalysts. The catalytic activity increases with the amount of nitrogen doped and, therefore, the nitrogen doped should be responsible for the catalytic activities. In addition, the activities are maximal at a ratio of nitrogen to oxygen of around 1, suggesting the importance of cooperative functions of nitrogen and oxygen on the surface of carbons. [source] Biodiesel fuel production via transesterification of oils using lipase biocatalystGCB BIOENERGY, Issue 2 2009MAN XIAO Abstract Biodiesel has gained widespread importance in recent years as an alternative, renewable liquid transportation fuel. It is derived from natural triglycerides in the presence of an alcohol and an alkali catalyst via a transesterification reaction. To date, transesterification based on the use of chemical catalysts has been predominant for biodiesel production at the industrial scale due to its high conversion efficiency at reasonable cost. Recently, biocatalytic transesterification has received considerable attention due to its favorable conversion rate and relatively simple downstream processing demands for the recovery of by-products and purification of biodiesel. Biocatalysis of the transesterification reaction using commercially purified lipase represents a major cost constraint. However, more cost-effective techniques based on the immobilization of both extracellular and intracellular lipases on support materials facilitate the reusability of the catalyst. Other variables, including the presence of alcohol, glycerol and the activity of water can profoundly affect lipase activity and stability during the reaction. This review evaluates the current status for lipase biocatalyst-mediated production of biodiesel, and identifies the key parameters affecting lipase activity and stability. Pioneer studies on reactor-based lipase conversion of triglycerides are presented. [source] Silica-Supported Zirconium Complexes and their Polyoligosilsesquioxane Analogues in the Transesterification of Acrylates: Part 2.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Activity, Recycling, Regeneration Abstract The catalytic activity of both supported and soluble molecular zirconium complexes was studied in the transesterification reaction of ethyl acrylate by butanol. Two series of catalysts were employed: three well defined silica-supported acetylacetonate and n -butoxy zirconium(IV) complexes linked to the surface by one or three siloxane bonds, (SiO)Zr(acac)3 (1) (SiO)3Zr(acac) (2) and (SiO)3Zr(O- n -Bu) (3), and their soluble polyoligosilsesquioxy analogues (c -C5H9)7Si8O12(CH3)2Zr(acac)3 (1,), (c -C5H9)7Si7O12Zr(acac) (2,), and (c -C5H9)7Si7O12Zr(O- n -Bu) (3,). The reactivity of these complexes were compared to relevant molecular catalysts [zirconium tetraacetylacetonate, Zr(acac)4 and zirconium tetra- n -butoxide, Zr(O- n- Bu)4]. Strong activity relationships between the silica-supported complexes and their polyoligosilsesquioxane analogues were established. Acetylacetonate complexes were found to be far superior to alkoxide complexes. The monopodal complexes 1 and 1, were found to be the most active in their respective series. Studies on the recycling of the heterogeneous catalysts showed significant degradation of activity for the acetylacetonate complexes (1 and 2) but not for the less active tripodal alkoxide catalyst, 3. Two factors are thought to contribute to the deactivation of catalyst: the lixivation of zirconium by cleavage of surface siloxide bonds and exchange reactions between acetylacetonate ligands and alcohols in the substrate/product solution. It was shown that the addition of acetylacetone to the low activity catalyst Zr(O- n- Bu)4 produced a system that was as active as Zr(acac)4. The applicability of ligand addition to heterogeneous systems was then studied. The addition of acetylacetone to the low activity solid catalyst 3 produced a highly active catalyst and the addition of a stoichiometric quantity of acetylacetone at each successive batch catalytic run greatly reduced catalyst deactivation for the highly active catalyst 1. [source] Studies in transesterification of ethylene carbonate to dimethyl carbonate over Amberlyst A-21 catalystJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2006Shekhar M Dhuri Abstract Transesterification of ethylene carbonate (EC) with methanol (MeOH) was studied in a slurry reactor using various homogeneous and heterogeneous, acidic as well as basic, catalysts. Among all catalysts studied, the weakly basic anion-exchange resin Amberlyst A-21 gave more than 95% selectivity towards dimethyl carbonate (based on EC converted). Using this Amberlyst A-21 as a catalyst, the kinetics for the transesterification reaction was studied in the range of temperature from 363 to 393 K, varying catalyst loading from 11.24 to 44.97 kg m,3 and the molar ratio MeOH:EC being varied between 4:1 and 16:1. The initial rate data were analysed using a power law model to aid process design. Copyright © 2005 Society of Chemical Industry [source] Selective extraction of organic compounds from transesterification reaction mixtures by using ionic liquidsAICHE JOURNAL, Issue 5 2010F. J. Hernández-Fernández Abstract In this article, we describe assays carried out to determine the suitability of 13 ionic liquids based on 1- n -alkyl-3-methylimidazolium and n -alkylpyridinium cations and a wide range of anions (hexafluorophophate, bis{(trifluoromethyl)sulfonyl}imide, tetrafluoroborate, methylsulfate, 2(2-methoxyethoxy)ethylsulfate, ethylsulfate, n -octylsulfate, dicyanamide, nitrate, tetrafluoroborate and chloride) to carry out the selective separation of the organic compounds involved in a transesterification reaction (butyl butyrate, vinyl butyrate, 1-butanol, and butyric acid) from hexane solutions. The assayed ionic liquids were shown to be suitable solvents for the selective separation of the target compounds, the extraction process being controlled by the hydrophobicity of the compounds. The anion composition of the ionic liquid was seen to strongly influence the average extraction ratio, the highest value being reached with the chloride-based ionic liquid. As regards the cation composition of the ionic liquids, it was seen that the average distribution ratio increased with decreasing length of alkyl chain. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Synthesis and characterization of block copolymers from 2-vinylnaphthalene by anionic polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2002Faquan Zeng Abstract The anionic polymerization of 2-vinylnaphthalene (2VN) has been studied in tetrahydrofuran (THF) at ,78 °C and in toluene at 40 °C. 2VN polymerization in THF, toluene, or toluene/THF (99:1 v/v) initiated by sec -butyllithium (sBuLi) indicates living characteristics, affording polymers with predefined molecular weights and narrow molecular weight distributions. Block copolymers of 2VN with methyl methacrylate (MMA) and tert -butyl acrylate (tBA) have been synthesized successfully by sequential monomer addition in THF at ,78 °C initiated by an adduct of sBuLi,LiCl. The crossover propagation from poly(2-vinylnaphthyllithium) (P2VN) macroanions to MMA and tBA appears to be living, the molecular weight and composition can be predicted, and the molecular weight distribution of the resulting block copolymer is narrow (weight-average molecular/number-average molecular weight < 1.3). Block copolymers with different chain lengths for the P2VN segment can easily be prepared by variations in the monomer ratios. The block copolymerization of 2VN with hexamethylcyclotrisiloxane also results in a block copolymer of P2VN and poly(dimethylsiloxane) (PDMS) contaminated with a significant amount of homo-PDMS. Poly(2VN- b -nBA) (where nBA is n -butyl acrylate) has also been prepared by the transesterification reaction of the poly(2VN- b -tBA) block copolymer. Size exclusion chromatography, Fourier transform infrared, and 1H NMR measurements indicate that the resulting polymers have the required architecture. The corresponding amphiphilic block copolymer of poly(2VN- b -AA) (where AA is acrylic acid) has been synthesized by acidic hydrolysis of the ester group of tert -butyl from the poly(2VN- b -tBA) copolymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4387,4397, 2002 [source] An Improved Non-Isothermal Kinetic Model for Prediction of Extent of Transesterification Reaction and Degree of Randomness in PET/PEN BlendsMACROMOLECULAR THEORY AND SIMULATIONS, Issue 4-5 2008Mahdi Golriz Abstract An improved non-isothermal kinetic model was developed based on mass balance and Arrhenius laws using a second-order reversible reaction capable of predicting the extent of transesterification reaction (X) and the degree of randomness (RD) in poly(ethylene terephthalate) (PET)/poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) blends prepared by a twin screw micro-compounder over a full composition range under different processing conditions. The experimental values of X and RD were determined by 1H-NMR and a direct relationship between them developed. The model constants were tuned by an optimization method using half of the experimental data, with the other half used for verification. Good agreement was found between the experimental and theoretical data in the verification stage and, therefore, it was concluded that the model is capable of predicting the extent of transesterification reaction with a high level of confidence for a wide range of processing conditions. Similarly to the experimental results, the model showed that, among all parameters affecting the extent of transesterification reaction, the time and temperature play the major role, whereas the blend composition does not have a significant role. [source] Influence of the processing conditions on a two-phase reactive blend system: EVA/PP thermoplastic vulcanizatePOLYMER ENGINEERING & SCIENCE, Issue 11 2002Catherine Joubert The elaboration of a TPV based on copolymer of ethylene and vinyl acetate (EVA) and polypropylene (PP) as thermoplastic phase was investigated in a batch mixer. The crosslinking reaction is carried out through a transesterification reaction between ester groups of EVA and alcoxysilane groups of the crosslinker agent tetrapropoxyorthosilicate (TPOS). The main advantage of this crosslinking reaction is that it can be well controlled and suitable for different processing conditions. The aim of the present study is to get a better understanding of the dispersion mechanism and of the phase inversion of the EVA major phase during its dynamic vulcanization into the PP minor phase. It was proved that the initial viscosity ratio, , = ,pp/,EVA, between EVA and PP plays an important part in the morphology development of the reactive blend. The viscosity ratio must be close to the critical ratio expressed by Utracki's model of phase inversion mechanism. Furthermore, the influence of different processing parameters on the variation of the morphology and on the mechanical properties of the ultimate TPV was investigated. The main conclusion of this study is that the characteristic time of crosslinking must be of the same order than the time of mixing. Indeed, better mechanical properties are obtained when a progressive phase inversion occurred and when it is controlled by rheological aspects and transient morphology equilibrium of the two phases and not by the mechanical fragmentation of the crosslinked EVA. For example, in our experimental conditions (concerning the amounts of catalyst and crosslinker reagents), high shear rates can be avoided ( < 80 s,1) as the self-heating of the blend under shear considerably increases (,T , 50°C for = 225 s,1), leading to faster kinetics and consequently to a phase inversion controlled by the fragmentation of the crosslinked EVA phase. [source] Morphology and rheological properties of polypropylene/reactive elastomer blendsPOLYMER ENGINEERING & SCIENCE, Issue 10 2002Frédérique Marguerat The relation of morphology to the linear viscoelastic properties for polymer blends consisting of an inert polypropylene and an elastomeric dispersed phase, made of two miscible copolymers, EVA and EMA, was investigated. The rheological properties of the elastomeric phase were modified by crosslinking in presence of an organometallic catalyst. The activation energy for the transesterification reaction taking place between EVA and EMA has been determined by following the increases of the complex viscosity with time and temperature. The Palierne model has been used to describe the linear viscoelastic behavior of the blends, and to estimate the interfacial tension between the immiscible components. The model was shown to describe relatively well the linear viscoelastic properties of reactive and nonreactive blends containing 30% or less elastomer. In parallel, the morphology of reactive and nonreactive blends (i.e. without catalyst in the elastomeric phase), before and after rheological experiments, has been determined using scanning electron microscopy. The size of the dispersed elastomeric particles for reactive blends prepared using an internal mixer was found to be, in most cases, much smaller than that for nonreactive blends. [source] Properties of poly(ethylene terephthalate),poly(ethylene naphthalene 2,6-dicarboxylate) blends with montmorillonite clayPOLYMER INTERNATIONAL, Issue 12 2005Antonio Sanchez-Solis Abstract The production and properties of blends of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalene 2,6-dicarboxylate) (PEN) with three modified clays are reported. Octadecylammonium chloride and maleic anhydride (MAH) are used to modify the surface of the montmorillonite,Na+ clay particles (clay,Na+) to produce clay,C18 and clay,MAH, respectively, before they are mixed with the PET/PEN system. The transesterification degree, hydrophobicity and the effect of the clays on the mechanical, rheological and thermal properties are analysed. The PET,PEN/clay,C18 system does not show any improvements in the mechanical properties, which is attributed to poor exfoliation. On the other hand, in the PET,PEN/clay,MAH blends, the modified clay restricts crystallization of the matrix, as evidenced in the low value of the crystallization enthalpy. The process-induced PET,PEN transesterification reaction is affected by the clay particles. Clay,C18 induces the largest proportion of naphthalate,ethylene,terephthalate (NET) blocks, as opposed to clay,Na+ which renders the lowest proportion. The clay readily incorporates in the bulk polymer, but receding contact-angle measurements reveal a small influence of the particles on the surface properties of the sample. The clay,Na+ blend shows a predominant solid-like behaviour, as evidenced by the magnitude of the storage modulus in the low-frequency range, which reflects a high entanglement density and a substantial degree of polymer,particle interactions. Copyright © 2005 Society of Chemical Industry [source] Nitrogen-Doped Carbon Materials Prepared by Ammoxidation as Solid Base Catalysts for Knoevenagel Condensation and Transesterification ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Naokatsu Kan-nari Abstract Nitrogen-doped carbon materials were prepared by ammoxidation of commercial carbon sources (carbon black and activated carbon) and applied as base catalysts for Knoevenagel and transesterification reactions. It was shown that these carbon materials were active and the activities were different depending on the ammoxidation conditions (temperature and ammonia concentration in air) and carbon sources used. The bulk, textural, and surface properties of the nitrogen-doped carbon materials were examined by several methods to clarify possible factors determining their final catalytic activities. The activated carbon-derived catalysts were more active than the carbon black-derived ones. The surface area and porosity were not responsible for this difference between the two carbon sources but the difference in the reactivity with oxygen was important. The reactivity of carbon sources with oxygen should influence the doping of nitrogen onto their surfaces by ammoxidation with ammonia and air and the resulting activities as base catalysts. The catalytic activity increases with the amount of nitrogen doped and, therefore, the nitrogen doped should be responsible for the catalytic activities. In addition, the activities are maximal at a ratio of nitrogen to oxygen of around 1, suggesting the importance of cooperative functions of nitrogen and oxygen on the surface of carbons. [source] Preparation and characterization of poly(butylene terephthalate)/poly(ethylene terephthalate) copolymers via solid-state and melt polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2007M. A. G. Jansen Abstract To increase the Tg in combination with a retained crystallization rate, bis(2-hydroxyethyl)terephthalate (BHET) was incorporated into poly(butylene terephthalate) (PBT) via solid-state copolymerization (SSP). The incorporated BHET fraction depends on the miscibility of BHET in the amorphous phase of PBT prior to SSP. DSC measurements showed that BHET is only partially miscible. During SSP, the miscible BHET fraction reacts via transesterification reactions with the mobile amorphous PBT segments. The immiscible BHET fraction reacts by self-condensation, resulting in the formation of poly(ethylene terephthalate) (PET) homopolymer. 1H-NMR sequence distribution analysis showed that self-condensation of BHET proceeded faster than the transesterification with PBT. SAXS measurements showed an increase in the long period with increasing fraction BHET present in the mixtures used for SSP followed by a decrease due to the formation of small PET crystals. DSC confirmed the presence of separate PET crystals. Furthermore, the incorporation of BHET via SSP resulted in PBT-PET copolymers with an increased Tg compared to PBT. However, these copolymers showed a poorer crystallization behavior. The modified copolymer chain segments are apparently fully miscible with the unmodified PBT chains in the molten state. Consequently, the crystal growth process is retarded resulting in a decreased crystallization rate and crystallinity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 882,899, 2007. [source] Synthesis and characterization of multiblock copolymers composed of poly(5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one) outer blocks and poly(L -lactide) inner blocksJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2006Jamie M. Messman Abstract Ethylene glycol (EG) initiated, hydroxyl-telechelic poly(L -lactide) (PLLA) was employed as a macroinitiator in the presence of a stannous octoate catalyst in the ring-opening polymerization of 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MBC) with the goal of creating A,B,A-type block copolymers having polycarbonate outer blocks and a polyester center block. Because of transesterification reactions involving the PLLA block, multiblock copolymers of the A,(B,A)n,B,A type were actually obtained, where A is poly(5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one), B is PLLA, and n is greater than 0. 1H and 13C NMR spectroscopy of the product copolymers yielded evidence of the multiblock structure and provided the lactide sequence length. For a PLLA macroinitiator with a number-average molecular weight of 2500 g/mol, the product block copolymer had an n value of 0.8 and an average lactide sequence length (consecutive C6H8O4 units uninterrupted by either an EG or MBC unit) of 6.1. For a PLLA macroinitiator with a number-average molecular weight of 14,400 g/mol, n was 18, and the average lactide sequence length was 5.0. Additional evidence of the block copolymer architecture was revealed through the retention of PLLA crystallinity as measured by differential scanning calorimetry and wide-angle X-ray diffraction. Multiblock copolymers with PLLA crystallinity could be achieved only with isolated PLLA macroinitiators; sequential addition of MBC to high-conversion L -lactide polymerizations resulted in excessive randomization, presumably because of residual L -lactide monomer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6817,6835, 2006 [source] Organic,Inorganic Interactions in Poly(trimethylene carbonate),Titania HybridsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 21 2009Elisa Cortecchia Abstract Polycarbonate,titania hybrids have been synthesized by a sol,gel reaction, starting from poly(trimethylene carbonate) (PTMC) and titanium isoproproxide in different ratios. PTMC with a given chain length was obtained by ring opening polymerization. FT-IR spectra reveal the presence of TiOC covalent bonds between organic and inorganic phases, and their number increases with increasing inorganic phase content. Solvent extractions show that hybrid soluble fraction contains low PTMC chains with isopropoxide ends, which suggests that TiOC bond formation is mainly promoted by transesterification reactions of isopropyl alcohol onto the polymer chain, catalyzed by Ti compounds. Hybrid thermal properties reflect the combined effect of the decrease of PTMC molecular weight and of bond formation between PTMC and the inorganic network. The nanometric dimension of the TiO2 domains, confirmed by atomic force microscopy, provides optically transparent hybrids. [source] Exothermal Process in Miscible Polylactide/Poly(vinyl phenol) Blends: Mixing Enthalpy or Chemical Reaction?MACROMOLECULAR RAPID COMMUNICATIONS, Issue 23 2006Ester Zuza Abstract Summary: In a previous paper (Macromolecules, 2005, 38, 9221), the enthalpy of mixing in poly(DL -lactide) /poly(vinyl phenol) blends was directly measured by DSC. The first DSC scan for solution/precipitation blends showed phase separation, but miscibility was observed in the second DSC scan. Hence, miscibility was achieved after thermal treatment, an unusual behavior in polymer blend current research. However, the exothermal event observed during the first heating scan could also be the result of a chemical reaction. In this work, a new research study conducted to elucidate the nature of the exothermal heat observed in PDLA/PVPh during the first DSC heating scan. Since the single-phase PDLLA/PVPh blend obtained after thermal treatment can be redissolved and reprecipitated, results obtained in the consecutive DSC scan prove that the process is completely reversible. Furthermore, GPC and 13C NMR results provide evidence that there is no change in the chemical structure of the studied polymers before and after the thermal treatment, which evidences the absence of transesterification reactions. Therefore, it can be concluded that the exothermal heat is the result of a mixing process, and miscibility is a consequence of specific interactions. New structure expected for transesterfication reactions. [source] Organotin catalysts grafted onto cross-linked polystyrene supports through polar spacersAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2010Vanja Pinoie Abstract The present study investigates the suitability of a HypoGel support bearing oligomeric poly(ethylene glycol) (PEG) chains to act as an insoluble carrier for grafted organotin catalysts. Through the introduction of polar spacers, an improved swelling and site accessibility in the polar media typically involved in transesterification reactions are targeted. Advanced structural investigation shows that quantitative conversion into the targeted HypoGel-supported organotin trichloride is hampered by the existence of intra- and/or intermolecular donor-acceptor O,Sn interactions caused by the presence of donor moieties in the PEG-linker. Support is provided to the proposal that the latter interactions are at the origin of the moderate catalytic performance displayed by these HypoGel-supported catalysts, achieving only 41% conversion after 2 hours in the transesterification of ethyl acetate and n -octanol. In contrast with similar organotin catalysts supported by an alkyl spacer, the HypoGel-supported materials appear to be poorly recyclable and display poor leaching resistance. Copyright © 2009 John Wiley & Sons, Ltd. [source] Hydrolysis of C,N -chelated diorganotin(IV) chlorides and catalysis of transesterification reactionsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2009ka Pad, lková Abstract Diorganotin(IV) dichlorides of formula LCNRSnCl2 (where R is nBu or Ph) containing one LCN chelating ligand were hydrolyzed with aqueous sodium hydroxide in benzene. The composition of the products is strongly dependent on the amount of hydroxide. The partially hydrolyzed compounds of composition (LCNRSnCl)2(µ-O) were isolated as crystalline products. A hydrolysis where more than one molar equivalent of NaOH is employed gave only a mixture of unidentifiable products. The structure of (LCNPhSnCl)2(µ-O) was determined by X-ray diffraction techniques in the solid state. In solution there was a mixture of diastereoisomers found, where the tin atoms serve as a stereogenic centers. The catalytic activity of starting dichlorides as well as (LCNPhSnCl)2(µ-O) in various transesterification processes was investigated. The activity is very low in the case of starting dichlorides. When two molar equivalents of NaH are added or (LCNPhSnCl)2(µ-O) is employed in the catalytic experiments, the activity is comparable to the literature data. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||