Jayne C. S. Barboza

Non-edible babassu oil as a new source for energy production-a feasibility transesterification survey assisted by ultrasound.

Ethyl esters of babassu oil were synthesized by alkaline catalysis to make the green production of biodiesel feasible with simple methods and available technology. Babassu oil is a transparent, light yellow oil extracted from the seeds of the babassu palm (Orbinya sp), and due to its high saturated fatty acid composition (83%), it is considered a non-inedible oil. Transesterification using ethanol represents a valid alternative to using methanol because of ethanols lower toxicity and the higher yield on weight compared to methanol. Statistical methodology was applied to optimize the transesterification reaction, which was promoted by ultrasonic waves and mechanical agitation. Nuclear magnetic resonance spectroscopy was used to quantify the conversion attained. Alkaline transesterification assisted by ultrasound produced the best results with respect to reaction time and the phase separation step. The model obtained showed that conversions higher than 97% may be achieved in 10min with correct tuning of the process variables.

Estudo da influência do solvente, carboidrato e ácido graxo na síntese enzimática de ésteres de açúcares

The aim of this work was to gain knowledge of enzymatic processes for the synthesis fatty acid esters of sugar, with the objective to develop an enzymatic process for the preparation of non-toxic biodegradable surface-active agents derived entirely from renewable resources. A wide range of data were collected for reaction conditions involving different sugars (glucose, fructose and sucrose), fatty acids (oleic, palmitic, lauric), solvents (hexane, heptane and t-butanol) and different sources of lipases in both free and immobilized forms. As a solvent t-butanol provided the best conditions to create a catalytic liquid phase in which the reaction occurs. Sugars were preferentially esterified in the following order: fructose > glucose > sucrose, depending on the enzyme preparation. For fructose no influence was found concerning de acyl donor and similar rates were achieved for all tested fatty acids. Ester synthesis was maximized for substrates containing fructose, lauric or oleic acids, t-butanol and lipase from porcine pancreas immobilized on polysiloxane-polyvinyl alcohol particles. Under such conditions molar conversions were higher than 50%.

Thermally-sensitive and Biocompatible Poly(N-vinylcaprolactam): A Kinetic Study of Free Radical Polymerization in Ethanol

Using nuclear magnetic resonance (1H-NMR), a kinetic study on the polymerization of N-vinylcaprolactam (NVCL) was performed under different polymerization conditions. The homopolymers were synthesized by free radical polymerization in ethanol, and azobisisobutyronitrile (AIBN) and 3-mercaptopropionic acid were used as the initiator and chain transfer agent (CTA), respectively. Moreover, the effect of the monomer concentration, initiator concentration and polymerization temperature on the kinetics of the reaction was evaluated. The results revealed that the aforementioned parameters had a significant effect on the polymerization rate (Rp ): as the monomer and initiator concentration increased, an increase in Rp and the overall activation energy was observed. Poly(N-vinylcaprolactam) (PNVCL) is a thermoresponsive and biocompatible polymer that possesses a LCST (low critical solution temperature) near physiological temperature. Thermoresponsive polymers with low molar masses are useful for biomedical applications; thus, the effect of the molar mass on the polymerization rate and the LCST of PNVCL was studied. The number-average molar mass () and the polydispersity of the homopolymers were measured with a gel permeation chromatograph coupled to a triple detector (GPC/SEC/LALS), and the LCST of the PNVCL was determined by UV-visible analyses.

Sonochemical Formation of Iodohydrin and Epoxide from Cyclohexene

Abstract Ultrasonic irradiation substantially improves the reaction of cyclohexene with I2 in aqueous dioxane in the presence of Cu(OAc)2 · H2O to generate the expected iodohydrin in high yield. The product undergoes cyclization to the epoxide by biphasic treatment with either Na2CO3 or KOH in a sonication‐sensitive step.

Redução da massa molecular e funcionalização do poli(3-hidroxibutirato-co-3-hidroxivalerato) (PHBHV) via hidrólise ácida e transesterificação com glicóis

In this work we investigated the reduction in molecular weight of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) with two methods: by acid hydrolysis and transesterification with ethylene and hexyleneglycol. The processing parameters studied were time, temperature and concentration of catalysts. Both methodologies resulted in functionalized biopolymers with hydroxyl and carboxyl end-groups and reduced molecular weight. A comparison of the methodologies allowed us to determine which one was more efficient for the functionalization of PHBHV. The reduction in molecular weight associated with functionalization strategies is extremely useful to induce changes in the degradation rate of materials, thus broadening their applications as biomaterials.

Semi-empirical study of cycloaddition reactions to form β-lactams from 2-amino-β-D-arabine[1′,2′:4,5]oxazoline (ureid) and ketenes

Abstract In this work we studied a ureid system, holding an imine skeleton with an endo (1) or exocyclic (2) double bond. Through a [2 + 2] cycloaddition reaction with ketene it forms β-lactam ring derivatives of spiro (3) or conjugate (4) types. The semi-empirical AM1 method was used to calculate the cycloaddition mechanism. Geometries of the reactants, transition states, intermediates and products were completely optimized and characterized in relation to their minimum or maximum nature on the potential energy surface. The cycloaddition reaction proceeds via non-concerted mechanism with the initial formation of an intermediate with some zwitterionic character. By rotation about the N 1 C 2 bond, this gives a second intermediate which leads to the final product after formation of the C 3 C 4 bond. The second step was found to be rate determining, with an activation energy of 29–33 kcal mol −1 . The reaction involving the endocyclic bond for formation of the conjugate product or the exocyclic bond for formation of the spiro product showed basically the same energy surface, with a slight (1–2 kcal mol −1 ) preference for the spiro product (3).