Accretion in Reactions of Organic Peroxy Radicals

化学系的环境化学科学项目支持加州理工学院的Paul Wennberg和Brian Stoltz教授研究颗粒如何在空气中形成。这些颗粒，也被称为气溶胶，使空气朦胧（降低能见度），造成潜在的问题，在道路上，海上或天空中导航。也有大量证据表明，呼吸这些颗粒物对人体健康有害。通常，这些颗粒的质量约有一半是由碳、氧和氢（含氧碳氢化合物）组成的分子组成的。最近有证据表明，这些含氧碳氢化合物中的一些通过两个较小分子的结合在空气中形成，这一过程被称为吸积。为了了解是什么促进了这种类型的化学结合反应，实验室和计算机计算被用来检查在大气中发现的不同化学物质的效率。 这项研究对于发展对空气质量的基本理解非常重要，对于生物学，人类毒理学，土壤化学和艺术品的保护也很重要。 学生和工作人员从温伯格和斯托尔兹集团大量从事科学带给公众。大气化学为对话和互动提供了一个机会，因为洛杉矶的市民对糟糕的空气质量有直接的体验。这些推广活动在校园和当地学校进行。例如，在校园里，科学项目是与当地小学和学前儿童在户外实验室进行的。研究团队与加州格伦代尔市的本杰明富兰克林小学密切合作，与教师合作设计实验，增强学生参与的科学和数学基础学习课程。有机过氧自由基与其他过氧自由基的反应被认为通过吸积产生更大的分子。这些较大的分子具有低得多的蒸气压，并且可以冷凝形成气溶胶。关于是什么控制着这些吸积产物形成的速率，我们知之甚少。本研究探讨的假设，弱键的相互作用，在最初产生的复合物的两个过氧自由基确定这种化学的效率。这种氧化反应的速率进行了研究，为一组不同的有机底物。该团队合成了被认为是表征这些吸积产物的化合物，以确认它们的身份。通过与哥本哈根大学Kjaergaard教授的合作，综合实验室研究与计算化学相辅相成。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Environmental Chemical Sciences Program of the Chemistry Division supports Professors Paul Wennberg and Brian Stoltz of the California Institute of Technology to study how particles form in air. These particles, also known as aerosols, make the air hazy (reduce visibility) causing potential problems navigating on the roads, at sea or in the sky. There is also significant evidence that breathing such particles is harmful to human health. Generally, about half of the mass of these particles is composed of molecules comprised of carbon, oxygen, and hydrogen (oxygenated hydrocarbons). There is recent evidence that some of these oxygenated hydrocarbons form in the air via the combination of two smaller molecules, a process known as accretion. To learn what promotes this type of chemical combination reaction, laboratory and computer calculations are used to examine the efficiency for different chemicals found in the atmosphere. This research is important for developing an underlying understanding of air quality but also for biology, human toxicology, soil chemistry and the preservation of artwork. Students and staff from the Wennberg and Stoltz groups are heavily engaged in bringing science to the public. Atmospheric chemistry provides an opening for conversation and interaction as citizens of Los Angeles have direct experience with poor air quality. These outreach activities are performed both on campus and in the local schools. On campus,for example, the science program is conducted with local elementary schools and pre-K children in an outdoor lab. The research team works closely with the Benjamin Franklin Elementary School in Glendale, CA to collaborate with the teachers in designing experiments that enhance the science- and math-based learning curriculum in which the students are engaged.Reactions of organic peroxy radicals with other peroxy radicals are thought to produce much larger molecules via accretion. These larger molecules have a much lower vapor pressure and can condense to form aerosol. Little is known about what controls the rates at which these accretion products form. This study examines the hypothesis that weak bonding interactions in the initially produced complex of the two peroxy radicals determine the efficiency of this chemistry. The rates of this oxidative reaction are studied for a diverse set of organic substrates. The team synthesizes compounds that are thought to characterize these accretion products to confirm their identity. The comprehensive laboratory studies are complemented with computational chemistry through a collaboration with Professor Kjaergaard at the University of Copenhagen.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.