Influence of Operating Parameters on Biomass Conversion under Sub‐ and Supercritical Water Conditions

The influence of reaction pressure, reaction time, reaction temperature, and biomass‐to‐water mass ratio R on the conversion of miscanthus biomass to biofuels under sub‐ and supercritical water (SCW) conditions was investigated. The highest total conversion was obtained under SCW conditions and the heating value increased under subcritical and SCW conditions. The findings herein show that near‐supercritical and supercritical water at 400 °C and high pressure can be an effective reaction medium for converting biomass to oils with relatively low oxygen contents in high yields.     

Release of Hydrogen Cyanide via a Post-secretion Schotten-Baumann Reaction in Defensive Fluids of Polydesmoid Millipedes

Mandelonitrile benzoate, a minor defense component produced by polydesmoid millipedes, is produced in large amounts together with hydrogen cyanide following shake-disturbances administered to individuals of Nedyopus tambanus tambanus, Parafontaria tonominea, Epanerchodus sp., and Epanerchodus fulvus. These species commonly produce mandelonitrile and benzoyl cyanide (the oxidized product after discharge). The newly generated mandelonitrile benzoate was identified as a product of post secretion Schotten-Baumann reaction under basic conditions of bled bodily fluids (pH ca. 9.0), and was not an enzymatic reaction product. The reaction occurred in vitro even under less basic conditions [1M Tris-HCl buffer (pH 8.0)], and could be defined as a new mechanism of hydrogen cyanide release occurring in roughly half of polydesmoid millipedes. Species possessing no benzoyl cyanide, such as Oxidus gracilis and Cryptocorypha sp., could also produce mandelonitrile benzoate under conditions in which benzoyl cyanide was exogenously provided.     

The Partial Oxidation of Isobutene in Sub‐ and Supercritical Water

The task of this work was to investigate which kind of reaction pathway takes place under supercritical water conditions in the oxidation of isobutene with molecular oxygen. The reaction was examined at temperatures of 350–20 °C, pressures of 25–35 MPa, uncatalyzed and under platinum‐catalyses. Isobutyraldehyde was the main product. Tert‐butanol was used as a source for isobutene, which dehydrates to isobutene quantitatively under the conditions used.     

ULTRASOUND-ASSISTED N-ALKYLATION OF PHTHALIMIDE UNDER PHASE-TRANSFER CATALYSIS CONDITIONS AND ITS KINETICS

In this work, N-butylation of potassium phthalimide was carried out under ultrasonic-assisted phase-transfer catalysis condition using n-bromobutane as an alkylating agent. The mechanism of the solid-liquid reaction of alkyl halide and potassium salt of phthalimide in an organic solvent was verified in this work. The kinetics of the reaction depends on the amount of catalyst, agitation speed, type of quaternary ammonium salts, volume of water, type of organic solvent, volume of organic solvents, temperature, and the frequency of the ultrasound. Five different onium salts were examined for the reaction and tetrahexylammonium bromide showed maximum catalytical activity. An improvement of the reaction outcome (yield and reaction time) was achieved through the immersion of the reactor into an ultrasound bath. The rate of the reaction is two times faster under ultrasonic condition (k_app = 10.7 × 10^?3 min^?1) than silent condition (k_app = 5.5 × 10^?3 min^?1) and is five times faster when the reaction is carried out in acetonitrile medium than in cyclohexane medium. The reaction is very fast under anhydrous condition. Based on the experimental data, a rational mechanism for the reaction is proposed.     

Polymer blends with modified coupling agent. I. Preparation and thermal properties of LICA 44 grafted styrene–maleic anhydride copolymer

Neopentyl(diallyl)oxy, tri(N-ethyleneamino)ethyl titanate (LICA 44) was grafted to the styrene/maleic anhydride (SMA) copolymer for the purpose of obtaining a new interfacial coupling agent for flame retardant ABS blends. The graft reaction was proceeded in DMSO under 80°C and reduced pressure. Samples were prepared under various amine/anhydride ratios (AAR) in feed and reaction time. The verification of reaction was based on FTIR spectra and the results of elemental analysis. The reaction percentages were high but decreased with the rising AAR. Both combination types, amide acid and imide, of SMA and LICA 44 were found, and the ratio of amide acid and imide is related to the AAR and reaction time. After the graft reaction, both the initial pyrolysis temperature (T_pi) and the char yield at 800°C of SMA increased significantly. LICA 44 is believed to cause the char promoting effect on SMA-g-L44. And the dealcohol phenomenon of trimethylolpropane diallyl ether (TMPDE) away from SMA-g-L44 was observed during the thermal analysis. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:37–44, 1998     

Solid‐state grafting of succinic anhydride onto poly(vinyl alcohol)

The graft reaction of succinic anhydride onto poly(vinyl alcohol) (PVA) was catalyzed by p‐toluenesulfonic acid monohydrate in solid state. The infrared spectra and ¹H‐NMR spectra confirmed that succinic anhydride was successfully grafted onto PVA backbone. The influences of reaction temperature, reaction time, the amount of succinic anhydride, and the amount of catalyst on the graft reaction were studied. Uncrosslinked PVA graft copolymer with grafting degree up to about 6.5% could be obtained under low reaction temperature, short reaction time, and low amount of catalyst, whereas crosslinked PVA with high gel content could be obtained under high reaction temperature, long reaction time, and high amount of catalyst. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 848–852, 2007     

Ultrasound accelerated sulfonylation of amines by p-acetamidobenzenesulfonyl chloride using Mg–Al hydrotalcite as an efficient green base catalyst

The sulfonylation reaction of various aliphatic, alicyclic, aromatic, and hetero-aromatic amines with p-acetamidobenzenesulfonyl chloride has been investigated using different types of base catalysis under varied reaction conditions. Mg–Al hydrotalcite, characterizable as an inexpensive, reusable, and green solid catalyst, was found to be the most efficient catalyst, when the reaction is carried out in a minimum volume of solvent (acetone). The reaction was found to be accelerated drastically with the support of ultrasound irradiation, affording the sulfonamides in yields better or equivalent to those obtained under the longer lasting conventional stirring conditions.     

Synthesis of p-cymene from limonene, a renewable feedstock

Highly selective limonene conversions to p-cymene in short reaction times were achieved under “solvent free” conditions over mesoporous silica–alumina supports heated by microwave irradiation. An increase in the silica content of these mixed oxides led to increases in the specific surface area, porosity (pore size and volume) and the surface acidity. The conversion and selectivity of limonene to p-cymene under microwave irradiation was also found to rise as the silica content in these mixed oxides was increased. By careful choice of the solid and reaction parameters the activities for the conversion of limonene and selectivity to p-cymene (used as an intermediate in fine chemical syntheses) could be fine tuned. Results are presented under both dry media and reflux conditions.     

Efficient and mild synthesis of ortho-hydroxyaryl ketones catalyzed by zinc chloride under solvent-free condition and microwave irradiation

Preparation of ortho-hydroxyaryl ketones was regioselectively carried out from phenol and naphthol derivatives, in reaction with various organic acids by using a ZnCl₂ as catalyst, under microwave and solvent-free mild conditions. In this reaction, the products were obtained in very high yields and very short reaction times.     

A Viscometric Approach to the Study of the Kinetics of Polyurethane Reactions

Kinetics and rheological studies were carried out on polyurethane reactions involving a new polyol and TDL Conversion of isocyanate by uncatalyzed polymerization under isothermal conditions was monitored by IR spectrometry and titration. Viscosity changes of the reaction mixture were followed by a digital cone-and-plate viscometer under identical conditions. Conversion and viscosity were found to follow a power relationship. A relationship involving the order of the reaction n that connects the viscosity with time was derived. This provides a new viscometric method to find the order of the reaction. The order of the reaction determined by this method was very close to the values obtained by a fractional-life method already reported.     

Moisture curing kinetics of isocyanate ended urethane quasi‐prepolymers monitored by IR spectroscopy and DSC

The study of the kinetics of the curing of isocyanate quasi‐prepolymers with water was performed by infrared spectroscopy and differential scanning calorimetry. The influence of the free isocyanate content, polyol functionality, and of the addition of an amine catalyst (2,2′‐dimorpholinediethylether) in the reaction kinetics and morphology of the final poly(urethane urea) was analyzed. A second‐order autocatalyzed model was successfully applied to reproduce the curing process under isothermal curing conditions, until gelation occurred. A kinetic model‐free approach was used to find the dependence of the effective activation energy (E_a) with the extent of cure, when the reaction was performed under nonisothermal conditions. The dependence of E_a with the reaction progress was different depending on the initial composition of the quasi‐prepolymer, which reveals the complexity of the curing process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Chiral Thiourea‐Phosphine Organocatalysts in the Asymmetric Aza‐Morita–Baylis–Hillman Reaction

A new kind of bifunctional (thio)urea‐phosphine catalyst was synthesized and applied to the aza‐Morita–Baylis–Hillman reaction of N‐sulfonated imines with methyl vinyl ketone, phenyl vinyl ketone, ethyl vinyl ketone or acrolein. Moderate to excellent ee and yields of the products were obtained under mild reaction conditions.     

Kinetic parameters using an immobilized tetrahexylammonium chloride catalyst in glycidyl methacrylate reaction with carbon dioxide

A soluble copolymer-supported catalyst containing pendant tetrahexylammonium chloride was synthesized by the radical copolymerization of p-chloromethylated styrene with styrene followed by the addition reaction of the resulting copolymer with trihexylamine. Initial absorption rate of carbon dioxide into glycidyl methacrylate (GMA) solutions containing the catalyst was measured in a semi-batch stirred tank with a plane gas-liquid interface at 101.3 kPa. The reaction rate constants of the elementary reaction between carbon dioxide and GMA were evaluated from analysis of the mass transfer mechanism accompanied by the elementary reactions based on film theory. Solvents such as toluene, N-methyl-2-pirrolidinone, and dimethyl sulfoxide influenced the reaction rate constants. Furthermore, this catalyst was compared to monomeric tetrahexylammonium chloride under the same reaction conditions.     

A New One‐Pot Synthesis of Polysubstituted Indoles from Pyrroles and β‐Nitroacrylates

The reaction of β‐nitroacrylates with pyrroles, under solvent‐ and catalyst‐free conditions, allows the formation of Friedel–Crafts adducts which, after in situ treatment with Amberlyst 15 in isopropyl alcohol under reflux, provide polysubstituted indoles, via a benzannulation reaction, in a one‐pot process.     

Reaction of 6-bromo-6-deoxycellulose with thiols in lithium bromide-N,N-dimethylacetamide

Nucleophilic substitution reactions of 6-bromo-6-deoxycelluloses of high degrees of substitution with eight thiols having functional groups such as carboxyl and amino groups were studied under homogeneous conditions in LiBr-N, N-dimethylacetamide in the presence of triethylamine. The reactions under the homogeneous conditions proceeded more extensively than those run under heterogeneous conditions in aqueous alkaline solutions. The reactivity of thiols was found to increase with increasing acidity of the mercapto groups of the thiols. Reaction products with 2-mercaptobutanedioic acid and with 2-mercaptobenzoic acid were soluble in alkaline and neutral water but not in 1 N HCl, while the reaction products with 2-aminoethanethiol did not dissolve even in 1 N HCl. The reaction products with cysteine showed amphoteric behavior. © 1996 John Wiley & Sons, Inc.     

Chemically and enzymatically catalyzed synthesis of C6–C10 alkyl benzoates

The esterification of benzoic acid with n‐hexanol, n‐octanol, 2‐ethyl hexanol and n‐decanol was investigated in detail. An analysis of the reaction kinetics of esterification in the presence of different commercially available chemical catalysts was carried out. The effects of catalyst type and loading on the reaction rate were studied. Although the considered reaction is bimolecular, it showed a first‐order behavior, and a linear dependence with respect to the catalyst concentration was observed. Hence, a new approach is presented to describe the reaction kinetics accurately over a wide range. The application of biotechnological synthesis applying different enzymes as catalysts offers an interesting alternative besides chemical synthesis. Especially an esterase from Bacillus subtilis immobilized on Sepabeads EC‐EP showed high stability and was applied for 2 days in the synthesis of hexyl benzoate. Nevertheless, the chemical reaction route remains superior with respect to the catalyst activities under the applied conditions, which were 25 kU/g for the chemical reaction and 0.7 kU/g for the best enzymatic conversion.     

Asymmetric Carbon‐Carbon Bond Forming Reactions Catalysed by Metal(II) Bis(oxazoline) Complexes Immobilized using Supported Ionic Liquids

A series of bis(oxazoline) metal(II) complexes has been supported on silica and carbon supports by non‐covalent immobilisation using an ionic liquid. The catalytic performance of these solids was compared for the enantioselective Diels–Alder reaction between N‐acryloyloxazolidinone and cyclopentadiene and the Mukaiyama‐aldol reaction between methyl pyruvate and 1‐methoxy‐1‐trimethylsilyloxypropene. In both reactions the enantioselectivity was strongly influenced by the choice of support displaying enantioselectivies (ee values) up to 40% higher than those conducted under homogeneous reaction conditions.     

Enzymatic Synthesis of Ether Lipids Rich in Docosahexaenoic Acid with Squalene as Reaction Medium

Using squalene as reaction medium was tried for the enzymatic synthesis of ether lipids rich in docosahexaenoic acid (DHA) via transesterification of alkylglycerols (AKG) obtained from shark liver oil and DHA-enriched ethyl esters (DHA-EE) from Schizochytrium sp. The effects of reaction time, temperature, molar ratio (AKG /DHA-EE), and enzyme dosage were investigated. DHA conversion of 74.47% was achieved for 48 hours of reaction at 60 °C using a molar ratio of 1:2 and an enzyme dosage of 30% based on AKG in the presence of squalene with Lipozyme® 435 (Novozymes, Tianjin, China) as the catalyst. With a high boiling point, squalene could act as a solvent without being vaporized from the reaction system under vacuum and improve the operational stability of immobilized lipase, which may be useful for enzymatic reactions under vacuum for lipid modification with byproducts of low boiling points.     

Gold‐Catalyzed Intermolecular Reactions of (Z)‐Enynols with Indoles for the Construction of Dihydrocyclohepta[b]indole Skeletons through a Cascade Friedel–Crafts/Hydroarylation Sequence

An efficient domino approach for the synthesis of indole‐fused carbocycles and their analogues from the reactions of suitably substituted (Z)‐enynols with indoles or pyrroles under mild reaction conditions was developed. This methodology is realized by a tandem reaction using Au/Ag catalysts, which could catalyze both of the Friedel–Crafts and the hydroarylation reaction in the same vessel.     

Regioselective synthesis of new 5H,10H-dipyrimido[2,1-b:4′,5′-d][1,3]thiazine: a combined experimental and computational study

Several derivatives of the novel tricyclic system ‘dipyrimido[2,1-b:4′,5′-d][1,3]thiazine’ were synthesized via inter- and intramolecular heterocyclization of 2,4-dichloro-5-(chloromethyl)-6-methylpyrimidine and 6-amino-4-aryl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonitrile in short reaction times under mild conditions. An x-ray analysis together with computational calculations was performed to gain an in-depth understanding of regioselectivity of the reaction.