39 research outputs found
Gas phase hydration of methyl glyoxal to form the gemdiol
No full textMethylglyoxal is a known oxidation product of volatile organic compounds (VOCs) in Earth’s atmosphere. While the gas phase chemistry of methylglyoxal is fairly well understood, its modeled concentration and role in the formation of secondary organic aerosol (SOA) continues to be controversial. The gas phase hydration of methylglyoxal to form a gemdiol has not been widely considered for water-restricted environments such as the atmosphere. However, this process may have important consequences for the atmospheric processing of VOCs. We will report on spectroscopic work done in the Vaida laboratory studying the hydration of methylglyoxal and discuss the implications for understanding the atmospheric processing and fate of methylglyoxal and similar molecules
Gas phase hydration of methyl glyoxal to form the gemdiol
No full textMethylglyoxal is a known oxidation product of volatile organic compounds (VOCs) in Earth’s atmosphere. While the gas phase chemistry of methylglyoxal is fairly well understood, its modeled concentration and role in the formation of secondary organic aerosol (SOA) continues to be controversial. The gas phase hydration of methylglyoxal to form a gemdiol has not been widely considered for water-restricted environments such as the atmosphere. However, this process may have important consequences for the atmospheric processing of VOCs. We will report on spectroscopic work done in the Vaida laboratory studying the hydration of methylglyoxal and discuss the implications for understanding the atmospheric processing and fate of methylglyoxal and similar molecules.Made available in DSpace on 2017-01-26T21:39:35Z (GMT). No. of bitstreams: 4
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Previous issue date: 2016-06-2
Ultraviolet study of the gas phase hydration of methylglyoxal to form the gemdiol
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Previous issue date: 6Methylglyoxal is a known oxidation product of volatile organic compounds (VOCs) in Earth’s atmosphere. While the gas phase chemistry of methylglyoxal is fairly well understood, its modeled concentration and role in the formation of secondary organic aerosol (SOA) continues to be controversial. The gas phase hydration of methylglyoxal to form a gemdiol has been shown to occur in infrared studies but has not been widely considered for water-restricted environments such as the atmosphere. However, this process may have important consequences for the atmospheric processing or VOCs. We have recorded UV spectroscopic measurements following the hydration of methylglyoxal and have compared these measurements to calculated spectra of the electronic transitions of methylglyoxal and methylglyoxal diol. We will report on these measurements and discuss the implications for understanding the atmospheric processing and fate of methylglyoxal and similar molecule
Hydrating Aldehydes in the Gas Phase: Atmospheric Consequences
No full textAtmospheric organics originate from biogenic and anthropogenic sources including volatile organic compounds (VOCs) and oxidation products of these VOCs. In the atmosphere, the organics can be processed and become important components of atmospheric aerosols. Methylglyoxal (CH3COCHO) is a known oxidation product of VOCs and has been observed in field studies and incorporated into atmospheric models. While the gas-phase chemistry of methylglyoxal is fairly well understood, its modeled concentration and role in the formation of secondary organic aerosols (SOA) remains controversial. In this thesis, I investigate aqueous chemistry of methylglyoxal to better understand the link between VOCs and the formation of SOA. The gas-phase hydration is a process not previously considered to occur in water-restricted environments, such as the atmosphere, but could have important consequences for the atmospheric processing of organics. Methylglyoxal is an interesting molecule for studying gas-phase hydration of because it contains both a ketone and an aldehyde group. This allows for the simultaneous analysis of the effect of gas-phase hydration on both carbonyl groups. I examine the gas-phase hydration of methylglyoxal leading to diol and hydrates (water clusters), and examine their water and photon mediated chemistry. The gas-phase hydration of methylglyoxal has important consequences to its atmospheric processing. Methylglyoxal diol and its hydrates have a lower vapor pressure than the parent aldehyde and a tendency to form intermolecular hydrogen bonds. The ability to more readily form hydrogen bonds can increase the diol and diol hydrate contributions to aerosol growth by partitioning more readily into the aqueous phase. This would increase methylglyoxal content in aerosols and affect the organic content of aqueous-phase aerosols and cloud droplets. Additionally, hydration of methylglyoxal to form the diol can alter the electronic state of the parent aldehyde. Formation of methylglyoxal diol will eliminate the n→π* transition of the aldehyde carbonyl, which undergoes near-ultraviolet (UV) photochemistry. This allows for methylglyoxal diol to form new products via UV photochemistry through its remaining ketone carbonyl and opens the way for other photochemistry through excitation of the OH vibrational overtone in the near-infrared (IR). To examine the hydration of methylglyoxal and the formation of methylglyoxal diol I employed a variety of spectroscopic techniques including, Fourier transform IR spectroscopy (FTIR), cavity ringdown spectroscopy (CRDS), incoherent broad band cavity enhanced absorption spectroscopy (IBBCEAS), UV-visible spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. The FTIR and CRD are used to observe and characterize the formation of methylglyoxal diol and its hydrates. The IBBCEAS was used to investigate the changes in the UV absorption cross section of methylglyoxal with increasing relative humidity. UV-visible and NMR spectroscopy was used to analyze the aqueous-phase hydration of methylglyoxal and its photolysis products. These results may impact the understanding of the atmospheric fate and processing of methylglyoxal and the role of organics in atmospheric chemistry. Hydration of aldehydes such as methylglyoxal has implications for modification of atmospheric radical production and provides important degradation pathways of potential SOA precursors
Hydrating Aldehydes in the Gas Phase: Atmospheric Consequences
No full textAtmospheric organics originate from biogenic and anthropogenic sources including volatile organic compounds (VOCs) and oxidation products of these VOCs. In the atmosphere, the organics can be processed and become important components of atmospheric aerosols. Methylglyoxal (CH3COCHO) is a known oxidation product of VOCs and has been observed in field studies and incorporated into atmospheric models. While the gas-phase chemistry of methylglyoxal is fairly well understood, its modeled concentration and role in the formation of secondary organic aerosols (SOA) remains controversial. In this thesis, I investigate aqueous chemistry of methylglyoxal to better understand the link between VOCs and the formation of SOA. The gas-phase hydration is a process not previously considered to occur in water-restricted environments, such as the atmosphere, but could have important consequences for the atmospheric processing of organics. Methylglyoxal is an interesting molecule for studying gas-phase hydration of because it contains both a ketone and an aldehyde group. This allows for the simultaneous analysis of the effect of gas-phase hydration on both carbonyl groups. I examine the gas-phase hydration of methylglyoxal leading to diol and hydrates (water clusters), and examine their water and photon mediated chemistry. The gas-phase hydration of methylglyoxal has important consequences to its atmospheric processing. Methylglyoxal diol and its hydrates have a lower vapor pressure than the parent aldehyde and a tendency to form intermolecular hydrogen bonds. The ability to more readily form hydrogen bonds can increase the diol and diol hydrate contributions to aerosol growth by partitioning more readily into the aqueous phase. This would increase methylglyoxal content in aerosols and affect the organic content of aqueous-phase aerosols and cloud droplets. Additionally, hydration of methylglyoxal to form the diol can alter the electronic state of the parent aldehyde. Formation of methylglyoxal diol will eliminate the n→π* transition of the aldehyde carbonyl, which undergoes near-ultraviolet (UV) photochemistry. This allows for methylglyoxal diol to form new products via UV photochemistry through its remaining ketone carbonyl and opens the way for other photochemistry through excitation of the OH vibrational overtone in the near-infrared (IR). To examine the hydration of methylglyoxal and the formation of methylglyoxal diol I employed a variety of spectroscopic techniques including, Fourier transform IR spectroscopy (FTIR), cavity ringdown spectroscopy (CRDS), incoherent broad band cavity enhanced absorption spectroscopy (IBBCEAS), UV-visible spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. The FTIR and CRD are used to observe and characterize the formation of methylglyoxal diol and its hydrates. The IBBCEAS was used to investigate the changes in the UV absorption cross section of methylglyoxal with increasing relative humidity. UV-visible and NMR spectroscopy was used to analyze the aqueous-phase hydration of methylglyoxal and its photolysis products. These results may impact the understanding of the atmospheric fate and processing of methylglyoxal and the role of organics in atmospheric chemistry. Hydration of aldehydes such as methylglyoxal has implications for modification of atmospheric radical production and provides important degradation pathways of potential SOA precursors
Examining Interdisciplinary Sustainability Institutes at Major Research Universities: Innovations in Cross-Campus and Cross-Disciplinary Models.
No full textThis is a study of the distinctive characteristics, activities, challenges and opportunities of a specific type of sustainability institute, one that spans the many disciplines of the University and, to do so, reports to upper administration (Provost or Vice President.) Among research universities within the Association of American Universities (AAU), 19 are identified and 18 agreed to participate in this study. Directors were sent a 71-question survey in January 2017 that covered issues of Governance, Research, Education, Engagement, Campus Operations and Best Practiceshttps://deepblue.lib.umich.edu/bitstream/2027.42/136638/1/1366_Hoffman.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136638/4/1366_Hoffman_June2017.pdfDescription of 1366_Hoffman_June2017.pdf : June 2017 revisio
Advancing Model Systems for Fundamental Laboratory Studies of Sea Spray Aerosol Using the Microbial Loop
No full textSea spray aerosol (SSA) particles
represent one of the most abundant
surfaces available for heterogeneous reactions to occur upon and thus
profoundly alter the composition of the troposphere. In an effort
to better understand tropospheric heterogeneous reaction processes,
fundamental laboratory studies must be able to accurately reproduce
the chemical complexity of SSA. Here we describe a new approach that
uses microbial processes to control the composition of seawater and
SSA particle composition. By inducing a phytoplankton bloom, we are
able to create dynamic ecosystem interactions between marine microorganisms,
which serve to alter the organic mixtures present in seawater. Using
this controlled approach, changes in seawater composition become reflected
in the chemical composition of SSA particles 4 to 10 d after the peak
in chlorophyll-a. This approach for producing and varying the chemical
complexity of a dominant tropospheric aerosol provides the foundation
for further investigations of the physical and chemical properties
of realistic SSA particles under controlled conditions
VIBRATIONAL SPECTROSCOPY OF PHOTOREACTIVE MOLECULES IN ATMOSPHERIC CHEMISTRY
No full textAuthor Institution: Department of chemistry and Biochemistry, University of Colorado, Boulder, CO 80309Vibrational overtone spectra of oxidized atmospheric chromophores are presented and analyzed to energies where chemistry through vibrational overtone pumping is possible. Experimental near infrared and visible spectra complemented by dynamical theory are presented to elucidate the light initiated reaction dynamics of pyruvic and of glyoxilic acid photo-decarboxylation. The role of water is investigated by making use of vibrational spectra of hydrates of the title compounds. Consequences of water and sunlight mediated chemistry to formation of secondary organic aerosol in the atmosphere will be discussed.\\ \\ \noindent K. L. Plath, J. L. Axson, G. C. Nelson, K. Takahashi, R. T. Skodje and V. Vaida {em React. Kineti. Catal. Lett.} \textbf{96}, 209 (2009)\\ V. Vaida {\em J. Phys. Chem. A} \textbf{113}, 5 (2009)\\ K. Takahashi, K. L. Plath, R. T. Skodje and V. Vaida {\em J. Phys. Chem A} \textbf{112} 7321 (2008
Gas Phase water mediated equilibrium between methylglyoxal and its geminal diol
No full text[[sponsorship]]原子與分子科學研究所[[note]]已出版;[SCI];有審查制度;具代表性[[note]]http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Drexel&SrcApp=hagerty_opac&KeyRecord=0027-8424&DestApp=JCR&RQ=IF_CAT_BOXPLO
