Publications

Abstract In the present work the energetic properties of phthalide and phthalic anhydride are assessed experimental and computationally allowing to calculate the standard molar enthalpy of formation, in the gaseous phase, of each compound. These results enabled to analyze and interpret the enthalpic and structural molecular effects of one and two ketone groups in the main structure of phthalan. The high-temperature Calvet microcalorimetry and the static bomb combustion calorimetry were used to measure, respectively, the enthalpy of sublimation and the massic energy of combustion of the two compounds. These data were combined to derive the standard molar enthalpy of formation, in the gaseous phase, of phthalide and phthalic anhydride. The gas-phase enthalpies of formation of phthalide and phthalic anhydride compounds were estimated using the composite G3(MP2)//B3LYP approach together with adequate gas-phase working reactions. The computational study was also extended to phthalan and the reliability of the value obtained for the correspondent gas-phase enthalpy of formation, when compared with the experimental value reported in the literature, contributes to validate the computational methodology used. The good agreement verified between computational and experimental results for the other two phthalan derivatives studied gave us confidence to estimate the gas-phase enthalpy of formation of the 2,5-dihydrofuran that was not studied experimentally. Complementary, natural bond orbital (NBO) calculations were also performed, allowing an advance on the analysis of the structural and reactivity characteristics of this type of compounds.

Abstract The standard ( p degrees = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, of 6-azauracil, 6-azathymine and 6-aza-2-thiothymine at T = 298.15 K, were derived from the standard molar energies of combustion, in oxygen, measured by combustion calorimetry. The standard molar enthalpies of sublimation, at T = 298.15 K, were measured by high temperature Calvet microcalorimetry. For 6-azauracil, the standard molar enthalpy of sublimation, at T = 298.15 K, was determined from the temperature-vapour pressure dependence, obtained by the Knudsen mass-loss effusion method. From the experimental studies, the standard molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, of the 6-azauracil, 6-azathymine and 6-aza-2-thiothymine were derived. The gas-phase enthalpies of formation were also estimated by G3 and G4 calculations which were further extended to the computation of the standard molar enthalpy of formation of 6-aza-2-thiouracil. We compare the values obtained computationally with the experimental data available and find a good agreement between them.

Abstract The standard (p(0) = 0.1 MPa) molar energies of combustion, Delta U-c(m)0, for the crystalline 5-isopropylbarbituric and 2-thiobarbituric acids were determined, at the temperature of 298.15 K, by static bomb or rotating bomb combustion calorimetry, respectively. For 5-isopropylbarbituric acid, the standard molar enthalpy of sublimation, Delta H-g(cr)m(0), at T=298.15 K, was derived by Calvet microcalorimetry. The standard molar enthalpy of sublimation, at T=298.15 K, was derived by the Clausius-Clapeyron equation, from the temperature-vapor pressure dependence, measured by the Knudsen mass-loss effusion method. These experiments allowed the determination of the standard molar enthalpy of formation, in the gaseous phase, at T=298.15 K for 5-isopropylbarbituric acid. For 2-thiobarbituric acid, the gas-phase enthalpy of formation was calculated combining the result derived for the crystalline phase with literature data for the enthalpy of sublimation, at T=298.15 K. These values were compared with estimates obtained from very accurate computational calculations using the G3 and G4 level theory composite methods.

Abstract The standard (p(o) = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, of methyl 1H-indole-3-carboxylate and ethyl 1H-indole-2-carboxylate, at T = 298.15 K, were derived from measurements of the standard massic energies of combustion using a static bomb combustion calorimeter. The Knudsen effusion technique was used to measure the vapour pressures as a function of the temperature, which allowed determining the standard molar enthalpies of sublimation of these compounds. The standard (p(o) = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, were calculated by combining, for each compound, the standard molar enthalpy of formation, in the crystalline phase, and the standard molar enthalpy of sublimation, yielding -(207.6 +/- 3.6) kJ.mol (1) and -(234.4 +/- 2.4) kJ.mol (1), for methyl 1H-indole-3-carboxylate and ethyl 1H-indole-2-carboxylate, respectively. Quantum chemical studies were also conducted, in order to complement the experimental study. The gas-phase enthalpies of formation were estimated from high level ab initio molecular orbital calculations, at the G3(MP2) level, for the compounds studied experimentally, extending the study to the methyl 1H-indole-2-carboxylate and ethyl 1H-indole-3-carboxylate. The results obtained were compared with the experimental data and were also analysed in terms of structural enthalpic group contributions.

Abstract The standard (p(o) = 0.1 MPa) molar enthalpies of formation in the condensed phase, Delta H-f(m)0, of 2,4-dichloro-5-methylpyrimidine, 2,4-dichloro-6-methylpyrimidine, 4,6-dichloro-2-methylpyrimidine and 4,6-dichloro-5-methylpyrimidine were derived from the standard molar energies of combustion, Delta U-c(m)0, in oxygen, to yield CO2 (g), N-2 (g) and HCl center dot 600H(2)O (l), at T = 298.15 K, measured by rotating bomb combustion calorimetry. The standard molar enthalpies of vaporization or sublimation, Delta H-g(cr, l)m(0), for these compounds, at T = 298.15 K were determined by high temperature Calvet microcalorimetry. Combining these values, the following enthalpies of formation in the gas phase, at T = 298.15 K, were then derived: 2,4-dichloro-5-methylpyrimidine, (79.6 +/- 4.1) kJ mol(-1), 2,4-dichloro-6-methylpyrimidine, (70.5 +/- 3.0) kJ mol(-1), 4,6-dichloro-2-methylpyrimidine, (68.7 +/- 3.3) kJ mol(-1), and 4,6-dichloro-5-methylpyrimidine, (78.1 +/- 2.5) kJ mol(-1). The gas-phase enthalpies of formation were also estimated by G3 theoretical calculations, which were extended to the computation of gas-phase enthalpies of formation of the other dichloromethylpyrimidine isomers, namely, 2,5-dichloro-4-methylpyrimidine, 4,5-dichloro-2-methylpyrimidine and 4,5-dichloro-6-methylpyrimidine, whose experimental study was not performed.

Abstract In this work, energetic and structural studies concerning vanillyl alcohol, based both on experimental and computational studies, were developed. The massic energy of combustion and the vapour pressures at different temperatures were measured by static bomb combustion calorimetry and Knudsen mass-loss effusion techniques, respectively. The computational studies were performed using the G3(MP2)//B3LYP method. The combination of experimental and computational data enabled the determination of the enthalpies, entropies and Gibbs energies of sublimation and formation of this compound both in the crystal and gas phase. The intramolecular hydrogen bond energy present in vanillyl alcohol was evaluated, together with the O-H homolytic bond dissociation enthalpy. The new data are very useful for process design and development in the biorefinery. (C) 2016 Elsevier Ltd.

Abstract The main purposes of the research were to know how multimedia was used to teach science and also what methods were chosen to evaluate the pedagogical designs in the Portuguese Education between 2010-2014. A systematic review of literature was conducted. The corpus of analysis consisted of Master dissertations, PhD thesis and conference papers that were retrieved from the online repositories or proceedings. The criteria to include or exclude a given document were the following: (i) the document should report actual cases of pedagogical intervention(s) based on multimedia to teach science (i. e., Biology, Natural Sciences, Physics, Geology, Mathematics and Chemistry); (ii) the interventions should be aimed at the k5-k12 levels and should necessarily include students; (iii) the Master dissertations and PhD thesis should be available at the institutional online repositories and the articles should have been published in the proceedings of the two most important Conferences on Information and Communication Technologies in Portugal. The corpus consisted of 75 works (49% Mathematics; 15% - Physics; 14% - Natural Sciences; 11% - Chemistry; 7% - Biology; 4% - Geology). A content analysis was run. Interventions were coded according to the TPACK framework and the methodological designs were coded as experimental, quasi-experimental or non-experimental. Results showed that a wide range of multimedia was used, including multimedia specifically designed to teach sciences (e.g., simulations) and non-specific multimedia (e.g., Excel). The level of interactivity and openness of the multimedia was also variable (e.g., low interactivity - videos and animations; high interactivity - games and simulations; closed environments - calculator; open environments - wikis) and the affordances of the multimedia were often not fully used. Most pedagogical designs were based on co-constructivist perspectives (43%) or dialogic perspectives (34%), while transmissive perspectives (16%) and constructivist perspectives (7%) were less used. Most research was nonexperimental (case-studies), based on small samples, using non-validated questionnaires and field notes. Mixed methods or qualitative methods were most frequently selected to gather and analyse data. The study is very significant in that it allowed us to map the trends on multimedia research in the particular case of science teaching. These trends revealed an imbalance between non-experimental, exploratory research and alternatives that increase internal validity (such as quasi-experimental or experimental designs) or that allow to explore meaning and pedagogical appropriation of technology associated with the use of multimedia to teach sciences on the long run. It also showed that it is necessary to pay more attention to emergent practices (including mobile technologies and participatory designs). At the same time, this research provides important information also for science teachers that want to improve their performance using best-practices. Current research includes monitoring an online site that gives access to the raw data of the study and allows users to suggest and upload new documents according to an open and participatory science framework.

Abstract The purpose of the research is to identify the most common social representations of chemistry, green chemistry, robotics and sustainability among teenagers as they were engaging in a project that links robotics and green chemistry. Subjects were students from a school in the north of Portugal enrolled in year 9 (n = 163, 73 males and 86 females, 4 missing values, mean age around 15 years-old). Data was collected through a questionnaire that consisted of four open-ended, free association questions. Participants were asked to express their ideas and thoughts on each one of the four mentioned stimuli and asked to draw a robot. Written responses and drawings of robots were submitted to a content analysis. Preliminary results showed that the ten most frequent words associated with chemistry explain around 49% of the semantic field (average of 4.5 words per participant) and largely consist of conceptual elements, e.g., atoms (38), protons (22) and ions (22), experiments (114), laboratory (62) and explosions (19). The ten most frequent words associated with green chemistry explain around 42% of the semantic field of the representation. Participants - which never have learnt about green chemistry at school curriculum - filled their representations (2.8 words per participant) with elements derived from environment (e.g., nature, environment, trees,...). Only 92 participants defined sustainability, many of them associating the concept with earth's natural resources and future. The ten most frequent words associated with robotics (4.1 words per participant) explain around 53% of the semantic field which consists of robots (129), technology (50), electricity (39), metal (33), energy (20), circuits (18) and computers (17): electronics rather than informatics contribute for the representation. Most of the drawings of robots were anthropomorphic resembling more C-3PO than R2-D2 from Star Wars movies. Human elements, such as eyes, mouth and hands are largely present while movement is assured by means of feet or wheels. The significance of the study is that there is a decalage between science and technology developments and teenager audience understanding. From the point of view of the theory of social representations, this gap is not only expected but also understandable. Popular culture although still inspire the representation of chemistry is not as relevant as it would be if participants have not attended physics and chemistry classes for three years. On the other hand, since green chemistry and robotics are not included in the ordinary curriculum until year 9, the concepts are at loose and their meaning must be grounded elsewhere. Despite the impressive and rapid changes that characterize the technology research, its market and advertising, old metaphors and symbols still contribute to build the representations of teenagers about robotics while green chemistry - a relatively new approach - has its poor semantic field rooted in chemistry and environment. School, thus, must act as a medium to help students to build a coherent worldview that is capable of copying with contemporary challenges, strongly affected by science and technology namely regarding sustainability. An ongoing project is designed to introduce green chemistry experiments that involve slow reactions via a programmable robotic arm in the school laboratory to conduct. The planned activities include monitoring experiences by students at home by means of a live webcam.

Abstract In a recent study on oxygen-containing heterocycles, two of the current authors suggested the gas phase enthalpy of formation of 2,5-dihydrofuran in lieu of an experimentally determined quantity. The current study provides new analysis with well-precedented assumptions and literature measurements to result in the value (-63 +/- 4) kJ . mol (1). For the isomeric 2,3-dihydrofuran the value of (-77 +/- 3) kJ . mol (1) is suggested in satisfactory accord with the combustion calorimetric combustion result of (-72.2 +/- 0.4) kJ . mol (1).

Abstract The use of gemini surfactants in gene delivery has been driven by the structural versatility of these compounds, which can be attained by a combination of different spacers, tails, and headgroups. Great efforts have been focused on the inclusion of natural motifs, such as sugars, lipids, and amino acids, to improve their biocompatibility. In this chapter, structural characteristics of gemini surfactants are correlated with their biological impact on cells, in terms of adverse effects produced and capacity to deliver and promote expression of nucleic acids. In the latter process (transfection), emphasis will be given to morphological changes of surfactant-nucleic acid complexes. These are induced by interaction with membranes or triggered by alterations of pH and reducing conditions within the cells, which can play a role in complex dissociation and nucleic acid release. Examples from the literature will illustrate the ability of those complexes to circumvent biological barriers associated with the different steps leading to gene expression, with emphasis on membrane translocation and endosomal escape.