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Sharpless Epoxidation

The conversion of allylic alcohols into epoxides using the chiral catalyst was discovered by K. Barry Sharpless and is known as Sharpless epoxidation. The use of a chiral catalyst enables the formation of one enantiomer of the product in excess. This chiral catalyst is mainly a chiral complex of titanium tetraisopropoxide and tartrate ester (specific stereoisomer). The stereoisomer used in the chiral catalyst dictates the formation of the enantiomer of the product. In other words, the use of...
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Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
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The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on Their Photocatalytic NOx Abatement Performance
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EPOXI en el cometa Hartley 2

Michael F A'Hearn1, Michael J S Belton, W Alan Delamere

  • 1Department of Astronomy, University of Maryland, College Park, MD 20742-2421 USA. ma@astro.umd.edu

Science (New York, N.Y.)
|June 18, 2011
PubMed
Resumen
Este resumen es generado por máquina.

La misión EPOXI estudió el cometa 103P/Hartley 2, revelando que su actividad es impulsada por la desgasificación de dióxido de carbono. Este proceso expulsa trozos de hielo y muestra una variada composición volátil a través del pequeño núcleo activo.

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Área de la Ciencia:

  • * Ciencias planetarias Ciencias planetarias
  • * La astronomía es la astronomía.
  • * Ciencia de los cometas.

Sus antecedentes:

  • * La comprensión de la actividad cometaria es clave para el estudio del sistema solar temprano.
  • * Los cometas proporcionan una visión única de los materiales del sistema solar primordial.
  • * La misión EPOXI apuntó al cometa 103P/Hartley 2 para una observación detallada.

Objetivo del estudio:

  • * Investigar los impulsores de la actividad cometaria en núcleos pequeños y activos.
  • * Para analizar la composición y el comportamiento del cometa 103P/Hartley 2.
  • * Comprender la relación entre las propiedades del núcleo y la desgasificación.

Principales métodos:

  • * La nave espacial EPOXI realizó un sobrevuelo del cometa 103P/Hartley 2.
  • * Las imágenes de alta resolución capturaron el núcleo y la actividad del cometa.
  • * El análisis espectroscópico proporcionó datos sobre la composición volátil del cometa.

Principales resultados:

  • * El núcleo del cometa 103P/Hartley 2 es inusualmente pequeño pero altamente activo.
  • * La desgasificación de dióxido de carbono (CO2) es el principal motor de la actividad, a diferencia de los cometas más grandes.
  • * La sublimación de CO2 expulsa hielo y polvo, creando chorros y actividad.
  • * Se observaron variaciones significativas en la abundancia volátil en diferentes regiones del núcleo.

Conclusiones:

  • * Los núcleos cometarios pequeños y activos pueden estar dominados por la desgasificación de CO2.
  • * Los mecanismos de actividad de los cometas difieren según el tamaño y la composición del núcleo.
  • * Los hallazgos mejoran nuestra comprensión de la evolución cometaria y las primeras condiciones del sistema solar.