O biodiesel obtido a partir do óleo de fritura foi proposto como uma temática para abordagem das relações CTS atreladas aos conteúdos, energia de ativação, catalisador, reação de transesterificação, entre outros. A metodologia contemplou as ações do Programa PIBID num contexto escolar que apresenta um modelo de gestão pedagógica inovador. Envolveu a elaboração de questionários, pré e pós-testes, intervenção didática com aulas teóricas e uso de vídeos sobre questões sociais como efeito estufa, aquecimento global e descarte inadequado de óleo de fritura em redes de esgoto; elaboração e aplicação de uma síntese do biodiesel etílico a partir do óleo de fritura doado pelos estudantes. A abordagem CTS proporcionou: evolução conceitual em relação às questões sociais aqui comentadas e relação da temática biodiesel com os conceitos químicos aqui expostos; desenvolvimento de atitudes nos alunos como o recolhimento de óleo de fritura de suas residências. Palavras-chave: Biodiesel, óleo de fritura, reação de transesterificação.

The properties of biodiesel are determined by its oleaginous composition and the alcohol used in the transesterification. This study was performed using palm and palmist oils and methyl, ethyl, isopropyl, and benzyl alcohols to investigate their influence on the cold flow properties, density, and viscosity of the resulting biofuel. The products were also characterized by 1 H nuclear magnetic resonance (NMR) and high-performance liquid chromatography (HPLC) analyses. Biofuel produced from palmist oil had different properties compared to biofuel synthesized from palm oil because of its lower average chain length and lower content of unsaturation. Biodiesel produced with palmist oil and isopropyl alcohol had the lowest values of cold filter plugging point (CFPP) (−16 °C) and density (860 kg/m 3 ). The use of benzyl alcohol yielded a biofuel with high viscosity and density values that do not adhere to any international specifications for biodiesel.

Theoretical studies involving minimization of model 3-propanoylaminopicolinic acids (10d-trans, 10d-cis), methyl ester (10a), and corresponding -N-oxide derivatives (10b, 10c-trans, 10c-cis) using AM1 gave conformations contrary to both sound chemical intuition and experimental data. RHF ab initio calculations using the 6-31G and 6-31G basis sets on the other hand corroborated spectroscopic data. 3-Amidopicolinic acid derivatives (7a-9a, 7b-9b, 7c-9c, 9d) were prepared and studied by NMR and IR spectroscopy. The results show that a strong intramolecular hydrogen bond between amide-H and the 2-carboxyl substituent results in a planar molecular conformation. This is particularly profound in the 3-acylaminopicolinic acid N-oxides (c-series). When the 2-substituent is a methyl ester on the other hand, repulsion between N-oxide and ester functions induces twisting of the carbomethoxy group out of the plane of the aromatic ring. The type of method used in molecular modeling can have profound impact on the final theoretical result in the case of the above-mentioned class of compounds. Our results indicate, that it is advisable to employ ab initio methods for modeling these types of compounds, and further, that the choice of basis set used for such calculations should depend on the type of information required. Thus, for most purposes pertaining to molecular conformation the 6-31G basis set provides sufficiently sound data in relatively short CPU time. For data related to electronic properties such as involvement of the N-oxide function or spectroscopic information such as IR frequencies or (1)H or (15)N NMR chemical shifts, the use of polarization functions as contained in the 6-31G basis set seems to be a must.

No abstract

No abstract

No abstract

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.