1,722,547 research outputs found
Proyecto de medio ambiente : estudio sobre Arico
No full textEste es un proyecto de carácter lúdico pensado para los alumnos y basado en ellos porque de ellos dependerá en gran parte el cuidado y conservación de su propio entorno. Dada la importancia que la Reforma Educativa da a la Educación Ambiental, este proyecto trata de colaborar en la inclusión de estos temas en los currículos. Este trabajo fue presentado el curso anterior y se continúa su labor en el presente curso. Entre los objetivos más destacados están: -Fomentar una toma de contacto con la realidad, a través de una percepción subjetiva que recoja aspectos vivenciales. -Desarrollar un sentido crítico que permita participar con responsabilidad y solidaridad en los problemas ambientales. -Adquisición de hábitos que permitan la mejora del entorno. Se han realizado los itinerarios que se habían previsto, con una serie de cuadernos de trabajo para los alumnos así como guías para el profesorado. Entre estos cuadernillos destacan: Itinerarios de: Caserío de Icod; Tabaibal-cardonal; Barranco del río; Camino Real; El contador; El pinar; La costa y Ruta de las iglesias. También se realizaron cuadernos de trabajo de actividades de Lengua para el primer ciclo de secundaria. Diferentes fichas referentes a la flora y fauna del municipio. Cuadernillos específicos sobre las actividades económicas de la zona. Todos estos cuadernillos se ven complementados por la elaboración de materiales audiovisuales: fotografías, diapositivas, vídeo...etc. Participan cuatro centros de EGB de la Villa de Arico, Tenerife. Se concluye valorando los resultados como positivos; se ha logrado la consecución de los objetivos previstos (en la medida que pueden evaluarse a corto plazo este tipo de objetivos). Los alumnos han mostrado un gran interés por los aspectos trabajados, conocen mejor su municipio y lo valoran y respetan más. Han aparecido también muchas dificultades: poca bibliografía sobre el tema, problemas de falta de organización entre el alumnado, escacés de material adecuado y necesario, etc. Se cree conveniente continuar en la misma línea de trabajo para el próximo curso. .Dirección General de Ordenación e Innovación EducativaES
An intracellular target for Helicobacter pylori vacuolating toxin - Response from de Bernard and Arico
No full textno abstract avilabl
IGLESIA DE ARICO [Material gráfico]
Full text linkADQUIRIDA POR EL COLECCIONISTA EN LAS PALMAS G.C.FOTO POSTAL DE VISTA GENERAL DE PUEBLO (ARICO) CON IGLESIA Y PLAZA ATRÁSCopia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201
Analoghi carbonati delle ipriti
Full text linkI gas mostarda o ipriti, bis(2-cloroetil)solfuro e la bis(2-cloroetil)etilammina, sono tristemente conosciuti per il loro impiego come armi chimiche durante la Prima Guerra Mondiale.1 La tossicità delle ipriti è strettamente correlata alla loro elevata reattività. Infatti, questi composti sono in grado di eliminare lo ione cloruro attraverso una sostituzione nucleofila intramolecolare grazie all’effetto anchimerico dello zolfo o dell’azoto vicinale, generando uno ione episolfonico o aziridinico ciclico che è – a sua volta - estremamente reattivo.2 Nonostante la loro ben nota tossicità, questi composti trovano largo impiego nella preparazione di farmaci, nonché come reagenti per la sintesi di intermedi di reazione.3
Nello studio qui presentato, i dialchil carbonati (DAC)4 – noti reagenti e solventi Green – sono stati fatti reagire con alcoli/dioli precursori dei gas mostarda portando ad una nuova classe di composti: le mostarde carbonate. La reattività degli analoghi carbonati delle ipriti è stata successivamente investigata dimostrando che questi composti preservano l’effetto anchimerico dei gas mostarda, ma non presentano alcuna tossicità, nè pericolo per l’operatore o l’ambiente.5 Le reazioni di alchilazione favorite dall’effetto anchimerico delle mostarde carbonate sono state condotte impiegando diversi nucleofili e operando sia in autoclave ad alta temperatura (180 °C) che in neat a temperature inferiori (150 °C) e a pressione atmosferica. Inoltre, recentemente sono state studiate reazioni di alchilazione in one-pot dove la mostarda carbonata è sintetizzata in situ e reagisce immediatamente con il nucleofilo scelto.
Riferimenti
1. a) J. C. Dacre, M. Goldman, Pharmacol. Rev. 1996, 48, 289–326; b) J. Liu, K. L. Powell, H. D. Thames, M. C. MacLeod, Chem. Res. Toxicol. 2010, 23, 488–496.
2. E. Block in Reactions of Organosulfur Compounds, Academic Press, New York, 1978, pp. 141–145.
3. M. C. S. Barnes, H. J. Dennison, S. S. Flack, J. A. Lumley, P. S. Pang, K. C. Spencer, WO2011/27156, 2011.
4. a) P. Tundo, M. Selva, Acc. Chem. Res. 2002, 35, 9, 706; b) Fabio Arico,̀ A. S. Aldoshin, and P. Tundo, ACS Sustainable Chem. Eng.2016, 4, 2843−2851
5. F. Aricò, M. Chiurato, J. Peltier, P. Tundo. Eur. J. Org. Chem. 2012, 3223–322
DIALKYL CARBONATE CHEMISTRY: EXPLORING NEW GREEN, CHLORINE-FREE SYNTHETIC APPROACHES
Full text linkDialkyl carbonates are green solvents and reagents (DACs) extensively investigated as possible alternatives to
chlorine reagents and solvents.[1] Specific areas where Green, chlorine-free synthetic approaches via DAC
chemistry have been exploited include:
Renewables upgrade: Substitution of petroleum-based compounds with renewable substances has been a
focal point in recent research. The US Department of Energy (DOE) has published a list of target molecules
considered of special interest for biorefinery development.[2] Among them D-sorbitol, and HMF derivatives
occupies a top position in the list as they encompass all of the desired criteria for a bio-based platform
compound. In particular, chlorine-free upgrading of D-sorbitol, isosorbide and HMF with DACs has led to
several industrially relevant product.[2]
Heterocycles: DACs chemistry has been proved efficient in the preparation of numerous 5- and 6-membered
heterocycles including: furan systems, pyrrolidines, indolines, isoindolines, 1,4-dioxanes, piperidines and
cyclic carbamates. In these reactions, the selected DAC acts as sacrificial molecule instead of Chlorine-based
compounds.[3] Mustard carbonates:
Mustard carbonate: Carbonate analogues of toxic mustard gases - are a new class of compounds, easily
synthesized via DAC chemistry retaining the reactivity of mustard gases, but that are not toxic for the operators
or the environment. Their reactivity as novel, green electrophiles and their possible potential application as
green reagents have been investigated; applications include synthesis of heterocycles via ring expansion and
macromolecules preparation.[4]
Research conducted in the abovemention areas indicate that DACs can be used to develop a beyond chlorine
chemistry with high efficiency and selectivity
Chlorine-free chemistry via dialkyl carbonates
No full textIn the last decades, due to the increasingly stringent environmental regulations, companies’ priority has become the conservation of high process performances by means of eco-compatible methodologies. In this view, green solvents and reagents dialkyl carbonates (DACs) have been extensively investigated as possible alternatives to some chlorine reagents (methyl and acyl halides, phosgene) and solvents (dichloromethane and chloroform).
In this talk the following aspects and applications of chlorine-free chemistry via DAC will be addressed:
Heterocycles synthesis: DACs chemistry has been proved efficient in the preparation of numerous 5- and 6-membered heterocycles including: furan systems, pyrrolidines, indolines, isoindolines, 1,4-dioxanes, piperidines and cyclic carbamates. In these reactions, the selected DAC acts as sacrificial molecule being completely converted, at the end of the reaction, into CO2 and an alcohol. Chlorine and carbonate moieties can both be used as sacrificial groups in nucleophilic displacements, however the latter do not produce salts and harmful wastes to be disposed of and display low toxicity and high biodegradability.
Renewables upgrade: The reactivity of isosorbide with DMC is an industrially relevant process as it can lead to the formation of dicarboxymethyl isosorbide, a potential monomer for isosorbide-based polycarbonate, and dimethyl isosorbide, a high boiling green solvent. The peculiar reactivity of isosorbide via chlorine-free DMC-based approaches is paving the way to several industrial potential applications.
From war chemicals to green reagents: Mustard gases are vesicant and blistering agents that have been sadly used in several chemical warfare. The toxicity of these compounds is strictly related to their high reactivity. Sulfur and nitrogen (half-)mustard carbonate analogues are a new class of compounds, easily synthesized via DAC chemistry retaining the reactivity of mustard gases, but that are not toxic for the operators or the environment. Their reactivity as novel, green electrophiles and their possible potential application as green reagents will be discussed
Isosorbide as biobased platform chemical: Recent advances
No full textD-sorbitol and isosorbide have been indicated by the US Department of Energy among the 15 target molecules of special interest for biorefinery development. This minireview reports on isosorbide conversion into potential substitutes of petrochemicals. In the last two years, investigations on the peculiar reactivity of isosorbide have been focused on preparation of green solvents, biobased monomers for polymerization reactions, functional materials, synthesis of pharmaceuticals, surfactants, novel organocatalysts, potential flame retardants, and cross-linking agents
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