Accretion in Reactions of Organic Peroxy Radicals

化学学部的环境化学科学项目支持加州理工学院的Paul Wennberg教授和Brian Stoltz教授研究空气中粒子的形成方式。这些颗粒，也被称为气溶胶，使空气变得朦胧（降低能见度），导致在道路、海上或天空中导航的潜在问题。也有重要证据表明，吸入此类颗粒物对人体健康有害。一般来说，这些粒子的一半质量是由碳、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，其中一些含氧碳氢化合物是通过两个较小分子的结合在空气中形成的，这个过程被称为吸积。为了了解是什么促进了这种化学组合反应，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。这项研究不仅对发展对空气质量的基本理解很重要，而且对生物学、人类毒理学、土壤化学和艺术品保存也很重要。温伯格和斯托尔茨小组的学生和工作人员积极致力于将科学带给公众。大气化学为洛杉矶市民提供了一个对话和互动的机会，因为他们直接体验到糟糕的空气质量。这些外展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龄前儿童在室外实验室进行的。研究小组与加州格伦代尔的本杰明富兰克林小学密切合作，与教师合作设计实验，以提高学生参与的科学和数学为基础的学习课程。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。这些大分子的蒸汽压要低得多，可以凝结成气溶胶。关于是什么控制着这些吸积产物形成的速率，人们知之甚少。本研究检验了一种假设，即最初产生的两个过氧自由基络合物中的弱键相互作用决定了这种化学反应的效率。研究了不同有机底物的氧化反应速率。该团队合成了被认为是这些吸积产物特征的化合物，以确认它们的身份。通过与哥本哈根大学kjaerggaard教授的合作，综合实验室研究与计算化学相辅相成。该奖项反映了美国国家科学基金会的法定使命，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.