The effect of acid hydrolysis on the technological functional properties of pinhão (Araucaria brasiliensis) starch

Technological functional properties of native and acid-thinned pinhão (seeds of Araucária angustifolia, Brazilian pine) starches were evaluated and compared to those of native and acid-thinned corn starches. The starches were hydrolyzed (3.2 mol.L-1 HCl, 44 ºC, 6 hours) and evaluated before and after the hydrolysis reaction in terms of formation, melting point and thermo-reversibility of gel starches, retrogradation (in a 30-day period and measurements every three days), paste freezing and thawing stability (after six freezing and thawing cycles), swelling power, and solubility. The results of light transmittance (%) of pastes of native and acid-thinned pinhão starches was higher (lower tendency to retrogradation) than that obtained for corn starches after similar storage period. Native pinhão starch (NPS) presented lower syneresis than native corn starch (NCS) when submitted to freeze-thaw cycles. The acid hydrolysis increased the syneresis of the two native varieties under storage at 5 ºC and after freezing and thawing cycles. The solubility of NPS was lower than that of native corn starch at 25, 50, and 70 ºC. However, for the acid-thinned pinhão starch (APS), this property was significantly higher (p < 0.05) when compared to that of acid-thinned corn starch (ACS). From the results obtained, it can be said that the acid treatment was efficient in producing a potential fat substitute from pinhão starch variety, but this ability must be further investigated.

A reaction engineering approach to homogeneously catalyzed glycerol hydrochlorination

The production of biodiesel through transesterification has created a surplus of glycerol on the international market. In few years, glycerol has become an inexpensive and abundant raw material, subject to numerous plausible valorisation strategies. Glycerol hydrochlorination stands out as an economically attractive alternative to the production of biobased epichlorohydrin, an important raw material for the manufacturing of epoxy resins and plasticizers. Glycerol hydrochlorination using gaseous hydrogen chloride (HCl) was studied from a reaction engineering viewpoint. Firstly, a more general and rigorous kinetic model was derived based on a consistent reaction mechanism proposed in the literature. The model was validated with experimental data reported in the literature as well as with new data of our own. Semi-batch experiments were conducted in which the influence of the stirring speed, HCl partial pressure, catalyst concentration and temperature were thoroughly analysed and discussed. Acetic acid was used as a homogeneous catalyst for the experiments. For the first time, it was demonstrated that the liquid-phase volume undergoes a significant increase due to the accumulation of HCl in the liquid phase. Novel and relevant features concerning hydrochlorination kinetics, HCl solubility and mass transfer were investigated. An extended reaction mechanism was proposed and a new kinetic model was derived. The model was tested with the experimental data by means of regression analysis, in which kinetic and mass transfer parameters were successfully estimated. A dimensionless number, called Catalyst Modulus, was proposed as a tool for corroborating the kinetic model. Reactive flash distillation experiments were conducted to check the commonly accepted hypothesis that removal of water should enhance the glycerol hydrochlorination kinetics. The performance of the reactive flash distillation experiments were compared to the semi-batch data previously obtained. An unforeseen effect was observed once the water was let to be stripped out from the liquid phase, exposing a strong correlation between the HCl liquid uptake and the presence of water in the system. Water has revealed to play an important role also in the HCl dissociation: as water was removed, the dissociation of HCl was diminished, which had a retarding effect on the reaction kinetics. In order to obtain a further insight on the influence of water on the hydrochlorination reaction, extra semi-batch experiments were conducted in which initial amounts of water and the desired product were added. This study revealed the possibility to use the desired product as an ideal “solvent” for the glycerol hydrochlorination process. A co-current bubble column was used to investigate the glycerol hydrochlorination process under continuous operation. The influence of liquid flow rate, gas flow rate, temperature and catalyst concentration on the glycerol conversion and product distribution was studied. The fluid dynamics of the system showed a remarkable behaviour, which was carefully investigated and described. Highspeed camera images and residence time distribution experiments were conducted to collect relevant information about the flow conditions inside the tube. A model based on the axial dispersion concept was proposed and confronted with the experimental data. The kinetic and solubility parameters estimated from the semi-batch experiments were successfully used in the description of mass transfer and fluid dynamics of the bubble column reactor. In light of the results brought by the present work, the glycerol hydrochlorination reaction mechanism has been finally clarified. It has been demonstrated that the reactive distillation technology may cause drawbacks to the glycerol hydrochlorination reaction rate under certain conditions. Furthermore, continuous reactor technology showed a high selectivity towards monochlorohydrins, whilst semibatch technology was demonstrated to be more efficient towards the production of dichlorohydrins. Based on the novel and revealing discoveries brought by the present work, many insightful suggestions are made towards the improvement of the production of αγ-dichlorohydrin on an industrial scale.

Does Gamma-aminobutyric acid function as a plant resistance mechanism against phytophagous insect activity? /

Gamma-aminobutyric acid (GAB A) is a ubiquitous non-protein amino acid synthesized via the decarboxylation of L-glutamate in a reaction catalyzed by the cytosolic enzyme L-glutamate decarboxylase (GAD). In animals it functions as an inhibitory neurotransmitter. In plants it accumulates rapidly in response to various stresses, but its function remains unclear. The hypothesis that GABA accumulation in leaf tissue may function as a plant resistance mechanism against phytophagous insect activity was investigated. GABA accumulation in response to mechanical stimulation, mechanical damage and insect activity was demonstrated. In wt tobacco (Nicotiana tabacum cv Samsun), mechanical stimulation or damage caused GABA to accumulate within 2 min from mean levels of 14 to 37 and 1~9 nmol g-l fresh weight (FW), respectively. In the transgenic tobacco strain CaMVGAD27c overexpressing Petunia GAD, the same treatments caused GABA to accumulate from 12 to 59 and 279 nmol g-l FW, respectively. In the transgenic tobacco strain CaMVGADilC 11 overexpressing Petunia GAD lacking an autoinhibitory domain, mechanical stimulation or damage caused GABA to accumulate from 180 to 309 and 630 nmol g-l FW, respectively. Ambulatory activity by tobacco budworm (TBW) larvae (Heliothis virescens) on leaves of CaMVGAD27c tobacco caused GABA to accumulate from 28 to 80 nmol g-l FW within 5 min. Ambulatory and leaf-rolling activity by oblique banded leaf roller (OBLR) larvae (Choristoneura rosaceana cv Harris) on wt soybean leaves (Glycine max cv Harovinton) caused GABA to accumulate from 60 to 1123 nmol g-l FW within 20 min. Increased GABA levels in leaf tissue were shown to affect phytophagous preference in TBW larvae presented with wt and transgenic tobacco leaves. When presented with leaves of Samsun wt and CaMVGAD27c plants, TBW larvae consumed more wt leaf tissue (640 ± 501 S.D. mm2 ) than transgenic leaf tissue (278 ± 338 S.D. mm2 ) nine times out of ten. When presented with leaves of Samsun wt and CaMVGAD~C11 plants, TBW larvae consumed more transgenic leaf tissue (1219 ± 1009 S.D. mm2 ) than wt leaf tissue (28 ± 31 S.D. mm2 ) ten times out of ten. These results indicate that: (1) ambulatory activity of insect larvae on leaves results in increased GABA levels, (2) transgenic tobacco leaves with increased capacity for GABA synthesis deter feeding, and (3) transgenic tobacco leaves with constitutively higher GABA levels stimulate feeding.

Synthesis and utilization of guanidine catalysts for applications directed towards the preparation of butenolide and modified amino acid derivatives

Development of guanidine catalysts is explored through direct iminium chloride and amine coupling, alongside a 2-chloro-l,3-dimethyl-IH-imidazol-:-3-ium chloride (DMC) induced thiourea cyclization. Synthesized achiral catalyst N-(5Hdibenzo[ d,t][1,3]diazepin-6(7H)-ylidene)-3,5-bis(trifluoromethyl) aniline proved unsuccessful towards O-acyl migrations, however successfully catalyzed the vinylogous aldol reaction between dicbloro furanone and benzaldehyde. Incorporating chirality into the guanidine catalyst utilizing a (R)-phenylalaninol auxiliary, generating (R)-2-((5Hdibenzo[ d,t] [1,3 ]diazepin-6(7H)-ylidene ) amino )-3 -phenylpropan-l-ol, demonstrated enantioselectivity for a variety of adducts. Highest enantiomeric excess (ee) was afforded between dibromofuranone and p-chlorobenzaldehyde, affording the syn conformation in 96% ee and the anti in 54% ee, with an overall yield of30%. Attempts to increase asymmetric induction were focused on incorporation of axial chirality to the (R)phenylalaninol catalyst using binaphthyl diamine. Incorporation of (S)-binaphthyl exhibited destructive selectivity, whereas incorporation of (R)-binaphthyl demonstrated no effects on enantioselectivity. Current studies are being directed towards identifying the catalytic properties of asymmetric induction with further studies are being aimed towards increasing enantioselectivity by increasing backbone steric bulk.

(A) BODIPY as a versatile fluorophore (B) Synthesis of PNAs via Staudinger reaction

(A) In recent years, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) fluorophores have attracted considerable interest due to their unique photochemical properties. However detailed studies on the stability of BODIPY and analogues under acidic and basic conditions have been lacking. Thus the stability of a series of BODIPY analogues in acidic (di- and trichloroacetic acid) and basic (aqueous ammonium hydroxide) conditions was investigated using 11B NMR spectroscopy. Among the analogues tested, 4,4-diphenyl BODIPY was the most stable under the conditions used in the experiments. It was found that reaction of 4,4-dimethoxy BODIPY with dichloroacetic acid gave mixed anhydride 4,4-bis(dichloroacetoxy) BODIPY in good yields. Treatment of the latter mixed anhydride with alcohols such as methanol and ethanol in the presence of a base afforded corresponding borate esters, whereas treatment with 1,2-diols such as ethylene glycol and catechol in the presence of a base gave corresponding cyclic borate esters. Furthermore treatment of 4,4-difluoro-8-methyl-BODIPY with secondary amines in dihalomethane resulted in carbon–carbon bond formation at the meso-methyl position of BODIPY via Mannich-type reactions. The resulting modified BODIPY fluorophores possess high fluorescent quantum yields. Five BODIPY analogues bearing potential ion-binding moieties were synthesized via this Mannich-type reaction. Among these, the BODIPY bearing an aza-18-crown-5 tether was found to be selective towards copper (II) ion, resulting in a large blue shift in absorption and sharp fluorescent quenching, whereas aza-15-crown-4 analogue was selected towards fluoride ion, leading to effective florescent quenching and blue shift. (B) Peptide nucleic acids (PNA), as mimics of natural nucleic acids, have been widely applied in molecular biology and biotechnology. Currently, the preparation of PNA oligomers is commonly achieved by a coupling reaction between carboxyl and amino groups in the presence of an activator. In this thesis attempts were made towards the synthesis of PNA through the Staudinger ligation reactions between C-terminal diphenylphosphinomethanethiol thioesters and N-terminal α-azido PNA building blocks.

3-O-Demethylation of thebaine and the synthesis of a flacourtia aglycone from benzoic acid.

Two synthetic projects were embarked upon, both fraught with protecting group nuance and reaction selectivity. Transformations of the opiate skeleton remain a valuable tool for the development of new medicines. Thebaine, a biosynthetic intermediate in the expression of morphine, was converted in three steps to oripavine through two parallel modes. Through the use of protecting group manipulations, two irreversible scaffold rearrangements were avoided during aryl methyl ether bond cleavage. This chemistry constitutes a new path in manipulations of the morphinan scaffold through protective groups. A new compound family, the flacourtosides, contains an unusual cyclohexenone fragment. The newly described compounds show in preliminary tests antiviral activity against dengue and chikungunya. This aglycone was approached on three pathways, all beginning with the chemoenzymatic dihydroxylation of benzoic acid. A first attempt from a known vinyl epoxide failed to epimerize and cooperate under deprotective conditions. A second and third attempt made use of a diastereoselective dihydroxylation reaction, which was critical in reaching the correct stereochemistry and oxidation state. The methyl ester of the aglycone was prepared, constituting the first synthesis of the non-trivial natural product framework.

Studies On Supported Cobalt (Ii), Nickel (Ii) and Copper (Ii) Complexes Of O-Phenylenediamine and Schiff Bases Derived from 3-Hydroxyquinoxaline-2-Carboxaldehyde

The thesis deals with the synthesis, characterization and catalytic activity studies of supported cobalt(ii), nickel(II) and copper(II) complexes of O-phenylenediamine and Schiff bases derived from 3-hydroxyquinoxaline -2-carboxaldehyde. Zeolite encapsulation and polymer anchoring was employed for supporting the complexes. The characterization techniques proved that the encapsulation as well as polymer supporting has been successfully achieved. The catalytic activity studies revealed that the activities of the simple complexes are improved upon encapsulation. Various characterization techniques are used such as, chemical analysis, EPR, magnetic measurements, FTIR studies, thermal analysis, electronic spectra, XRD, SEM, surface area, and GC.The present study indicated that the that the mechanism of oxidation of catechol and DTBC by hydrogen peroxide is not altered by the change in the coordination sphere around the metal ion due to encapsulation. This fact suggests outer sphere mechanism for the reactions. The catalytic activity by zeolite encapsulated complex was found to be slower than that by the neat complex. The slowing down of the reaction in the zeolite case is probably due to the constraint imposed by the zeolite framework. The rate of DTBC ( 3,5-di-tert-butylchatechol)oxidation was found to be greater than the rate of catechol oxidation. This is obviously due to the presence of electron donating tertiary butyl groups.

Polystyrene Anchored Vanillin Schiff Base—Complexation and Ion Removal Studies

A set of six new polystyrene anchored metal complexes have been synthesized by the reaction of the metal salt with the polystyrene anchored Schiff base of vanillin. These complexes were characterized by elemental analyses, Fourier transform infrared spectroscopy, diffuse reflectance studies, thermal studies, and magnetic susceptibility measurements. The elemental analyses suggest a metal : ligand ratio of 1 : 2. The ligand is unidentate and coordinates through the azomethine nitrogen. The Mn(II), Fe(III), Co(II), Ni(II), and Cu(II) complexes are all paramagnetic while Zn(II) is diamagnetic. The Cu(II) complex is assigned a square planar structure, while Zn(II) is assigned a tetrahedral structure and Mn(II), Fe(III), Co(II), and Ni(II) are all assigned octahedral geometry. The thermal analyses were done on the ligand and its complexes to reveal their stability. Further, the application of the Schiff base as a chelating resin in ion removal studies was investigated. The polystyrene anchored Schiff base gave 96% efficiency in the removal of Ni(II) from a 20-ppm solution in 15 min, without any interference from ions such as Mn(II), Co(II), Fe(III), Cu(II), Zn(II), U(VI), Na , K , NH4 , Ca2 , Cl , Br , NO3 , NO2 ,and CH3CO2 . The major advantage is that the removal is achieved without altering the pH.

Ni(II) and Ru(II) Schiff base complexes as catalysts for the reduction of benzene

Two new complexes, [MII(L)(Cl)(H2O)2]·H2O (where M=Ni or Ru and L = heterocyclic Schiff base, 3- hydroxyquinoxaline-2-carboxalidene-4-aminoantipyrine), have been synthesized and characterized by elemental analysis, FT-IR, UV–vis diffuse reflectance spectroscopy, FAB-MASS, TG–DTA, AAS, cyclic voltammetry, conductance and magnetic susceptibility measurements. The complexes have a distorted octahedral structure andwere found to be effective catalysts for the hydrogenation of benzene. The influence of several reaction parameters such as reaction time, temperature, hydrogen pressure, concentration of the catalyst and concentration of benzenewas tested. A turnover frequency of 5372 h−1 has been found in the case of ruthenium complex for the reduction of benzene at 80 ◦C with 3.64×10−6 mol catalyst, 0.34 mol benzene and at a hydrogen pressure of 50 bar. In the case of the nickel complex, a turnover frequency of 1718 h−1 has been found for the same reaction with 3.95×10−6 mol catalyst under similar experimental conditions. The nickel complex shows more selectivity for the formation of cyclohexene while the ruthenium complex is more selective for the formation of cyclohexane

Solid acid-catalyzed dehydration/Beckmann rearrangement of aldoximes: towards high atom efficiency green processes

Rare earth metal ion exchanged (La3+, Ce3+, RE3+) KFAU-Y zeolites were prepared by simple ion-exchange methods and have been characterized using different physico-chemical techniques. In this paper a novel application of solid acid catalysts in the dehydration/ Beckmann rearrangement of aldoximes; benzaldoxime and 4-methoxybenzaldoxime is reported. Dehydration/Beckmann rearrangement reactions of benzaldoxime and 4-methoxybenzaldoxime is carried out in a continuous down flow reactor at 473K. 4-Methoxybenzaldoxime gave both Beckmann rearrangement product (4-methoxyphenylformamide) and dehydration product (4-methoxybenzonitrile) in high overall yields. The difference in behavior of the aldoximes is explained in terms of electronic effects. The production of benzonitrile was near quantitative under heterogeneous reaction conditions. The optimal protocol allows nitriles to be synthesized in good yields through the dehydration of aldoximes. Time on stream studies show a fast decline in the activity of the catalyst due to neutralization of acid sites by the basic reactant and product molecules.

Acid base and catalytic properties of Zr02 - Y203 systems

The surface acidity and basicity of mixed oxides of Zr and Y and their mixed oxides have been determined by titration method using Hammett indicators. The acid base properties are evaluated on a common scale of acid strength. Liquid phase reduction of cyclohexanone has been selected as a model reaction to correlate catalytic activity.

Studies on some new Schiff base complexes of ruthenium and neodymium

In the present study an attempt has been made to synthesize some simple complexes of multidentate ligands. Analogous zeolite encapsulated complexes were also synthesized and characterized. Immobilization on to polymer supports through covalent attachment is expected to solve the problem of decomposition of many complexes during catalytic reaction. Hence the work is also extended to the synthesis and characterization of some polymer supported complexes of Schiff base Iigands. All the three types of synthesized complexes, simple, zeolite encapsulated and polystyrene anchored, were subjected to catalytic activity study towards catechol-oxidation reaction. A selected group of complexes were also screened for their catalytic activity towards phenol-oxidation reaction. Biological screening of the synthesized ligands and neat complexes were done with a view to establish the effect of complexation on biological systems.

Zeolite encapsulated complexes of ruthenium: synthesis, characterisation and catalytic activity studies

The work presented in this thesis is mainly centered on the synthesis and characterization of some encapsulated transition metal complexes and the catalytic activity of the synthesized complexes in certain organic reactions.thesis deals with the catalytic activity of ruthenium-exchanged zeolite and the zeolite encapsulated complexes of SSC, SOD, SPD, AA, ABA, DMG, PCO, PCP, CPO and CPP in the hydroxylation of phenol using hydrogen peroxide. The products were analyzed with a GC to determine the percentage conversion and the chromatograms indicate the presence of different products like hydroquinone, catechol,benzoquinone, benzophenone etc. The major product formed is hydroquinone. From the screening studies, RuYSSC was found to be the most effective catalyst for phenol hydroxylation with 94.4% conversion and 76% hydroquinone selectivity. The influence of different factors like reaction time, temperature, amount of catalyst, effect of various solvents and oxidant to substrate ratio in the catalytic activity were studied in order to find out the optimum conditions for the hydroxylation reaction. The influence of time on the percentage conversion of phenol was studied by conducting the reactions for different durations varying from one hour to four hours. There is an induction period for all the complexes and the length of the induction period depends on the nature of the active components. Though the conversion of phenol and selectivity for hydroquinone. increases with time, the amount of benzoquinone formed decreases with time. This is probably due to the decomposition of benzoquinone formed during the initial stages of the reaction into other degradation products like benzophenones. The effect of temperature was studied by carrying out the reaction at three different temperatures, 30°C, 50°C and 70°C. Reactions carried at temperatures higher than 70°C result either in the decomposition of the products or in the formation of tarry products. Activity increased with increase in the amount of the catalyst up to a certain level. However further increase in the weight of the catalyst did not have any noticeable effect on the percentage conversion. The catalytic studies indicate that the oxidation reaction increases with increase in the volume of hydrogen peroxide till a certain volume. But further increase in the volume of H202 is detrimental as some dark mass is obtained after four hours of reaction. The catalytic activity is largely dependent on the nature of the solvent and maximum percentage conversion occurred when the solvent used is water. The intactness of the complexes within the zeolite cages enhances their possibility of recycling and the activities of the recycled catalysts show only a slight decrease when compared to the fresh samples .

Acid-Base. Surface Electron Donatin6 &.Catai.Ytlc Properties Of Some Binary Mixed Oxides Containing Rare Earth Elements

Catalysis research underpins the science of modern chemical processing and fuel technologies. Catalysis is commercially one of the most important technologies in national economies. Solid state heterogeneous catalyst materials such as metal oxides and metal particles on ceramic oxide substrates are most common. They are typically used with commodity gases and liquid reactants. Selective oxidation catalysts of hydrocarbon feedstocks is the dominant process of converting them to key industrial chemicals, polymers and energy sources.[1] In the absence of a unique successfiil theory of heterogeneous catalysis, attempts are being made to correlate catalytic activity with some specific properties of the solid surface. Such correlations help to narrow down the search for a good catalyst for a given reaction. The heterogeneous catalytic performance of material depends on many factors such as [2] Crystal and surface structure of the catalyst. Thermodynamic stability of the catalyst and the reactant. Acid- base properties of the solid surface. Surface defect properties of the catalyst.Electronic and semiconducting properties and the band structure. Co-existence of dilferent types of ions or structures. Adsorption sites and adsorbed species such as oxygen.Preparation method of catalyst , surface area and nature of heat treatment. Molecular structure of the reactants. Many systematic investigations have been performed to correlate catalytic performances with the above mentioned properties. Many of these investigations remain isolated and further research is needed to bridge the gap in the present knowledge of the field.

Propyl Gallate Synthesis Using Acidophilic Tannase and Simultaneous Production of Tannase and Gallic Acid by Marine Aspergillus awamori BTMFW032

Marine Aspergillus awamori BTMFW032, recently reported by us, produce acidophilic tannase as extracellular enzyme. Here, we report the application of this enzyme for synthesis of propyl gallate by direct transesterification of tannic acid and in tea cream solubilisation besides the simultaneous production of gallic acid along with tannase under submerged fermentation by this fungus. This acidophilic tannase enabled synthesis of propyl gallate by direct transesterification of tannic acid using propanol as organic reaction media under low water conditions. The identity of the product was confirmed with thin layer chromatography and Fourier transform infrared spectroscopy. It was noted that 699 U/ml of enzyme could give 60% solubilisation of tea cream within 1 h. Enzyme production medium was optimized adopting Box–Behnken design for simultaneous synthesis of tannase and gallic acid. Process variables including tannic acid, sodium chloride, ferrous sulphate, dipotassium hydrogen phosphate, incubation period and agitation were recognized as the critical factors that influenced tannase and gallic acid production. The model obtained predicted 4,824.61 U/ml of tannase and 136.206 μg/ml gallic acid after 48 h of incubation, whereas optimized medium supported 5,085 U/ml tannase and 372.6 μg/ml of gallic acid production after 36 and 84 h of incubation, respectively, with a 15-fold increase in both enzyme and gallic acid production. Results indicated scope for utilization of this acidophilic tannase for transesterification of tannic acid into propyl gallate, tea cream solubilisation and simultaneous production of gallic acid along with tannase