Ultrasound assisted enzyme catalyzed hydrolysis of waste cooking oil under solvent free condition

The present work demonstrates the hydrolysis of waste cooking oil (WCO) under solvent free condition using commercial available immobilized lipase (Novozyme 435) under the influence of ultrasound irradiation. The process parameters were optimized using a sequence of experimental protocol to evaluate the effects of temperature, molar ratios of substrates, enzyme loading, duty cycle and ultrasound intensity. It has been observed that ultrasound-assisted lipase-catalyzed hydrolysis of WCO would be a promising alternative for conventional methods. A maximum conversion of 75.19% was obtained at mild operating parameters: molar ratio of oil to water (buffer pH 7) 3:1, catalyst loading of 1.25% (w/w), lower ultrasound power 100 W (ultrasound intensity – 7356.68 W m⁻²), duty cycle 50% and temperature (50 °C) in a relatively short reaction time (2 h). The activation energy and thermodynamic study shows that the hydrolysis reaction is more feasible when ultrasound is combined with mechanical agitation as compared with the ultrasound alone and simple conventional stirring technique. Application of ultrasound considerably reduced the reaction time as compared to conventional reaction. The successive use of the catalyst for repetitive cycles under the optimum experimental conditions resulted in a loss of enzymatic activity and also minimized the product conversion.     

The effect of the migrating group structure on enantioselectivity in lipase-catalyzed kinetic resolution of 1-phenylethanol

We have studied the effects of the acyl moiety on the enantioselectivity of three lipases: Candida antarctica B, Pseudomonas cepacia and Candida cylindracea, frequently used in kinetic resolutions by acylation or hydrolysis. The size of the acyl group was examined using various enol esters during the transesterification of 1-phenylethanol and the hydrolysis of the corresponding phenylethylesters. C. antarctica-B lipase showed the highest selectivity in the transesterification of 1-phenylethanol with isopropenyl and vinyl acetate, vinyl decanoate, vinyl laurate, (E > 200). The esters 1-phenyl -ethyl-acetate, decanoate and laurate are also hydrolyzed with high selectivities (E > 150) with CAL-B. The results can be correlated to the three-dimensional form of each lipase. The effect of the migrating group on the reactivity and selectivity of the lipases are discussed for both reactions.     

Shape-controlled synthesis of nanocrystalline titania at low temperature

The interesting shape (shuttle-like, sphere with needles, uniform particles) rutile titania were prepared by the hydrolysis of TiCl₄ in high acidic aqueous solution in the absence or presence of PEG-1000. PEG-1000 acted as dispersant, which could control the shape and size of the precipitate of titania. As a result, shuttle-like nanocrystalline appeared and the aggregation was improved with the increase of the amount of acid and the decrease of the concentration of TiCl₄ in the absence of PEG-1000. Uniform nanoparticles were obtained in the presence of PEG-1000 and the diameter of the particles decreased with increasing the amount of PEG-1000. This process simplification will lower production cost and make continuous process possible. The products were analyzed using X-ray diffractometer, transmission electron microscopy.     

2-亚甲基丁二酸酐和甲基丙烯酸甲酯的共聚反应研究

2—亚甲基—丁二酸酐(M_1,ITANH)和甲基丙烯酸甲酯(M_2,MMA)在四氢呋喃(THF)中以过氧化二苯甲酰(BPO)作引发剂进行自由基共聚合。由作图法衣得这两种单体在66℃的共聚竞聚率:表明它们趋于嵌均共聚。用粘度法和GPC测量了共聚物的分子量和分子量分布。共聚物在温和的条件下进行部分水解,得到一带有短的羧基侧链的聚电解质[11]。将[11]与无机盐LiClO_4混合后测得电导率δ-2.8272×10~(-4)S·cm~(-1),表明它具有较好的离子导电性。     

聚苯乙烯—吡啶树脂的合成及催化水解反应

在氢氧化钠作用下，氯甲基化聚苯乙烯与吡啶反应制成聚苯乙烯－吡啶树脂，测定了其化学组成和红外光谱，并考察了在酯水解反应中的催化活性。     

Proton conductivity of phosphoric acid derivative of fullerene

The proton conductive property of methano [60] fullerene diphosphoric acid has been investigated under various humidity conditions at the temperature range between 15 and 45 °C. It shows proton conductivity as high as 10⁻² S cm⁻¹ at 25 °C under relative humidity of 95%. Thermal analyses including TG–DTA and thermal desorption mass spectroscopy (TDS) confirm that the compound is thermally stable up to 200 °C. Proton conduction of the compound depends very much on humidity or water content. The logarithmic conductivity at 25 °C is increased linearly with increasing relative humidity. The activation energy (E_a) estimated from the slope of log(σT) vs. 1/T is decreased from 1.08 to 0.52 eV, as the relative humidity is increased from 40% to 75%. The humidity dependence of conductivity is discussed in the light of the observed hydration isotherm.     

Semiempirical calculations of the hydrolysis of penicillin G

A theoretical study of the gas-phase alkaline hydrolysis of penicillin G on the assumption of a B_AC2 mechanism is reported. Various semiempirical methods were used to determine the influence of different parameterizations on the process. Among the most salient results obtained, the standard AM1 method predicted opening of the thiazolidine ring to yield the corresponding imine and enamine structures.     

Serendipitous and acid catalyzed synthesis of spirolactones

Formation of three diasteroisomeric spirodilactones 14a-c and 11 has been reported from diester 13 and 9, respectively, under the influence of mineral acid.     

Hydrolytic degradation of POSS-PEG-lactide hybrid hydrogels

A polyhedral oligomeric silsesquioxane (POSS), functionalized with eight arms of poly(ethylene glycol) (PEG; MW 400) and then acrylated, was incorporated into a hydrogel network based on triblock copolymers of poly(lactide-b-ethylene glycol-b-lactide) diacrylates using a redox-initiated polymerization. The organic-inorganic hybrid hydrogels so prepared contained the inorganic crosslinker POSS from 1 to 28 wt.%. The degradation properties of the hydrogels in a pH 7.4 phosphate-buffered saline solution at 37 °C were studied using measurements of mass loss, cryogenic SEM, and ATR-FTIR spectroscopy. It was found that copolymerization of acrylated 1kPEG-lactide with increasing amounts of POSS created a more porous network which was more resistant to hydrolysis. The ATR-FTIR technique was used to monitor the progress of degradation with exposure time through the changes in the carbonyl and C-H deformation bands of the lactide and the Si-C stretching band of the POSS. Increasing POSS incorporation resulted in decreased rate of degradation due to its hydrophobic nature and inertness to hydrolysis. Conversely, an increase in lactide content increased the degradation rate due to the increased number of hydrolytically-sensitive ester groups in the network.     

Tryst with a molecular and supramolecular oddity: an anti-Fürst-Plattner epoxide opening product as a designer additive for accessing an elusive polymorph

Additive induced polymorphism of a conformationally locked tetraacetate 3 in presence of its diastereomer 4 is described. The ester 3 was specially crafted on a trans-decalin backbone to relegate the O-H?O H-bond donors to the molecular interior and have the peripheral H-bond acceptors in 1,3-syndiaxial relationship. The supramolecular assembly of 3 was destined to evolve along two mutually exclusive pathways, namely one, which employs intermolecular O-H?O H-bonds (pathway 1) and the other that sacrifices these for intramolecular O-H?O H-bonds and settles for a crystal packing dictated by weak intermolecular interactions alone (pathway 2). Exploiting the similarity between the self-assemblies of 4 and the two recently reported dimorphs of 3, the ester 3 has been stimulated to follow the elusive non-hierarchical pathway 2 through preferential inhibition of pathway 1. Interestingly, the inhibitor 4 was obtained serendipitously en route3 via an apparent breakdown of Fürst-Plattner rule.