Chemistry Commons^™

Α-Glucosidase Inhibitors From Leaves Of Cannabis Sativa And Cannabinoid Derivatives, Areeba Nayab

Chulalongkorn University Theses and Dissertations (Chula ETD)

Cannabinoids are naturally occurring secondary metabolites with antidiabetic, anti-inflammatory, and anticancer activity because of their enormous interaction efficiency with the human endocannabinoid system. α-glucosidase inhibitory activity guided isolation of Cannabis sativa L. yielded 6 compounds including Δ9-THC, cannabinol (CBN), and cannabichromene (CBC) as major compounds. This study also focused on the study of the structure-activity relationship of Δ9-THC that yielded 4 including 3 new compounds. The structures of isolated and synthesized compounds were elucidated by multiple spectroscopic techniques and with the comparison of previous reports. The isolated and derivatized compounds were evaluated for α-glucosidase inhibition. Among the isolated compounds cannabinol …

Microalgal-Plant Growth Promoting Bacterial Living Biofilters As Soil Amendment For Vegetable Cultivation, Augustine Odibo

Chulalongkorn University Theses and Dissertations (Chula ETD)

This study explored the use of microalgal-plant growth-promoting bacterial co-cultures as living biofilters (Chlorella vulgaris (CV) and Bacillus subtilis (BS) in different ratios) for soil amendment in vegetable cultivation. It aimed to investigate the soil amendment potential of these biofilters on three selected plants (i.e. morning glory, sunflower, and cucumber) over a 20-days plantation in a controlled environment. The highest biomass yields of morning glory, cucumber, and sunflower were 1.3 ± 0.1 g, 2.0 ± 0.3 g, and 1.5 ± 0.2 g when using CV/BS 1:1, CV/BS 3:1, and CV/BS 3:1 respectively. For sunflower, the biomass yield with CV/BS 1:1, …

Synthesis Of Photosensitizers With Aggregation-Induced Emission Properties, Satawat Ngampattrapan

Chulalongkorn University Theses and Dissertations (Chula ETD)

Conventional photosensitizers used in photodynamic therapy often suffer from aggregation-caused quenching (ACQ) due to their planar structure. This study presents the design and synthesis of a donor-acceptor-donor (D-A-D) photosensitizer with aggregation-induced emission (AIE) properties, which effectively eliminates the ACQ problem. The photosensitizers were synthesized using a Suzuki coupling and Knoevenagel condensation reaction, with triphenylamine as the donor and dicyano vinyl and 2-(2,6-dimethyl-4H-pyran-4-ylidene)malononitrile as acceptors. The donor was connected with a thiophene, 2,1,3-benzothiadiazole, and double bond spacers. Novel 7 photosensitizers were obtained with more than 40%yield. Photosensitizers with spacers containing electron-donating or withdrawing effects could enhance the absorption properties of photosensitizers …

Identification Of Volatile Markers In Sweat For Screening Of Covid-19 Infection By Gas Chromatography-Mass Spectrometry, Suriwipa Chuachaina

Chulalongkorn University Theses and Dissertations (Chula ETD)

Due to an outbreak of coronavirus spreading in recent years, there is an urgent need for effective, rapid, and non-invasive diagnostics to detect and differentiate among patients who are infected and uninfected with SARS-CoV-2 for controlling the virus propagation. This study developed an alternative method for COVID-19 screening from volatile analysis of metabolites mainly studied in sweat samples obtained from the populations in Bangkok, Thailand, during December 2020 to April 2022. A total of 140 collected samples tested by RT-PCR; 70 positives and 70 negatives confirmed COVID-19 cases were applied to be separated, detected, and identified as volatile organic compounds …

Intergrated Carbon Dioxide Capture-Conversion By Phthalocyanine-Catalyzed Electrochemical Process, Manatsanan Fangarrom

Chulalongkorn University Theses and Dissertations (Chula ETD)

Carbon dioxide (CO2) is a significant contributor to global warming and climate change. Currently various technologies are available to reduce the CO2 emission. Electrochemical CO2 reduction reaction (CO2RR) in the presence of an appropriate catalyst is a promising approach, but it is limited by ability to scale up the process at reasonable cost. Integrating CO2 capture and conversion into a single process by introducing a CO2-capturing agent in an electrolyte solution used for the CO2RR may help overcome this limitation. This study focused on developing the integrated CO2 capture-conversion by using monoethanolamine (MEA), aminomethyl propanol (AMP) or triethanolamine (TEA) as …

Ultrasonic-Assisted Extraction Of Andrographolide And Bioactive Diterpene Lactones From Andrographis Paniculata, Ayomide Gbadebo

Chulalongkorn University Theses and Dissertations (Chula ETD)

Andrographis paniculata is an herbaceous plant known for its medicinally active diterpene lactones, including andrographolide (AG), neoandrographolide (NAG), 14-deoxy-11,12-didehydroandrographolide (DDHAG), and 14-deoxyandrographolide (DAG). These compounds are typically extracted using polar solvents like methanol and ethanol, yielding ≤4% w/w. This research focused on combining a fairly polar solvent with a highly polar solvent in an ultrasonic-assisted extraction (UAE) process, which is both time and energy efficient. The optimized conditions for the extraction were 40°C, 3 hours, 50% duty cycle, 1:10 solute-solvent ratio using a 6:4 ratio of ethyl acetate to ethanol, and 180W power. Quantitative nuclear magnetic resonance (qNMR) analysis successfully …

Volatile Compound Profiles In Human Sweat For Stress Screening, Teerada Somphot

Chulalongkorn University Theses and Dissertations (Chula ETD)

This research aimed to develop an alternative stress assessment method by analyzing sweat volatile compounds, given the limited access to psychiatric evaluations. Sweat samples were collected from the armpits of 44 male firefighters using cotton rods and analyzed for volatile organic compounds (VOCs). The extraction of VOCs utilized headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS), with identification based on comparing experimental retention indices and mass spectra against the NIST Library database. The results were correlated with perceived stress scores (PSS) from the same 44 firefighters. Significant peaks, chosen for their accuracy and statistical significance, identified potential stress …

การพัฒนาไฮโดรเจลนำไฟฟ้าจากสารเชิงซ้อนพอลิอิเล็กโทรไลต์, ทิชากร สังอรดี

Chulalongkorn University Theses and Dissertations (Chula ETD)

ในงานวิจัยนี้ไฮโดรเจลเมมเบรนของแบคทีเรียเซลลูโลส/สารเชิงซ้อนพอลิอิเล็กโทรไลต์คอมพอสิต ได้ถูกเตรียมเพื่อใช้เป็นตั้วกั้นขั้วอิเล็กโทรด โดยสารละลายสารเชิงซ้อนพอลิอิเล็กโทรไลต์ถูกเตรียมจากการผสม พอลิโซเดียม 4-สไตรีนซัลโฟเนต (พอลิอิเล็กโทรไลต์ประจุลบ) ปริมาณร้อยละ 40-60 โดยโมล กับพอลิ(ไดเมทิลไดอัลลิลแอมโมเนียมคลอไรด์) (พอลิอิเล็กโทรไลต์ประจุบวก) โดยมีเกลือโซเดียมคลอไรด์ทำหน้าที่เป็นชีลด์ดิ้ง เอเจนต์ (เพื่อลดอันตรกิริยาระหว่างประจุลบและประจุบวก) โดยแบคทีเรียเซลลูโลสได้ถูกเตรียมให้อยู่ในรูปของฟองน้ำที่มีรูพรุน 3 มิติ ที่ได้จากการนำแบคทีเรียเซลลูโลสไปปั่นในสารละลายด่าง (โซเดียมไฮดรอกไซด์) ก่อนนำไปผ่านกระบวนการฟรีซ-ธอร์เพื่อให้ได้โครงร่างที่มีรูพรุนจำนวนมาก แล้วจึงนำฟองน้ำแบคทีเรียเซลลูโลสที่เตรียมได้ไปทำการเชื่อมขวางสายโซ่ด้วยกลูตารัลดีไฮด์เพื่อเพิ่มความแข็งแรง จากนั้นนำฟองน้ำแบคทีเรียเซลลูโลสจุ่มลงในสารละลายสารเชิงซ้อนพอลิอิเล็กโทรไลต์ก่อนนำไปกำจัดเกลือโซเดียมคลอไรด์ด้วยการแช่ใน น้ำกลั่น โดยผลิตภัณฑ์ที่ได้ คือ ไฮโดรเจลของสารเชิงซ้อนพอลิอิเล็กโทรไลต์ที่มีแบคทีเรียเซลลูโลสเป็นตัวพยุง จากการทดสอบสมบัติต่างๆ ของไฮโดรเจลเมมเบรนที่เตรียมได้ พบว่า ความทนแรงดึงมีค่าอยู่ในช่วง 56-108 กิโลปาสคาล ความสามารถดูดซึมสารละลายอิเล็กโทรไลต์มีค่าอยู่ในช่วงร้อยละ 413-476 การซึมผ่านของ ไฮดรอกไซด์ไอออนมีค่าประมาณ 2 x 10-2 เซนติเมตร²/นาที การนำไอออนของไฮดรอกไซด์มีค่าระหว่าง 30.9–42.5 มิลลิซีเมนส์/เซนติเมตร ค่าประสิทธิภาพคูลอมบิกจากการทดสอบเก็บประจุ/คายประจุที่ความหนาแน่นกระแส 0.5 แอมแปร์/กรัม จำนวน 2000 รอบ มีค่าระหว่างร้อยละ 84.2-89.1 และการทดสอบการพอกพูน และการละลายสังกะสีในเซลล์สังกะสีแบบสมมาตร ทำให้ขั้วสังกะสีมีการกัดกร่อนน้อยลง และมีการเติบโตของ เดนไดรต์ช้าลงจากการมีประจุทางไฟฟ้าไปชะลอหรือดึงดูดไอออนของสังกะสี จากผลการทดลองแสดงว่า ไฮโดรเจลเมมเบรนของแบคทีเรียเซลลูโลส/สารเชิงซ้อนพอลิอิเล็กโทรไลต์คอมพอสิตที่เตรียมได้สามารถนำไปใช้เป็นแผ่นกั้นขั้วอิเล็กโทรด และเพิ่มความเสถียรในแบตเตอรี่สังกะสีไอออนได้

Development Of Electrochemical Methods For Determination Of Cannabinoids In Cannabis, Tavechai Pholsiri

Chulalongkorn University Theses and Dissertations (Chula ETD)

This thesis focuses on the development of electrochemical devices for the determination of major cannabinoids in various samples obtained from cannabis such as cannabis oil, cannabis flower, and body fluids such as saliva. The developed electrochemical device comprises three distinct platforms, each platform a crucial role in solving the cannabis-related challenges in Thailand. These devices are instrumental in controlling the quality of cannabis products, ensuring the quality of cannabis flowers intended for medical use, and screening individuals who smoke cannabis within legally regulated areas. This thesis can be segmented into three parts, each focusing on addressing specific aspects of the …

ฟลูออเรสเซนต์จากอนุพันธ์ 4-อะมิโน-1,8-แนฟทาลิไมด์บนโซลเจล, ธนเดช นิลเกตุ

Chulalongkorn University Theses and Dissertations (Chula ETD)

ได้สังเคราะห์อนุพันธ์ของ 4-amino-1,8-naphthalimide สองชนิดด้วยร้อยละผลผลิต 49-57 ได้สำเร็จ และศึกษาคุณสมบัติการเรืองแสงตามฟังก์ชันของ pH และปริมาณน้ำในตัวทำละลายอินทรีย์โดยผ่านปฏิกริยาการควบแน่นของอิไมด์และการแทนที่อะโรมาติกของนิวคลีโอฟิล มีจำนวนหน่วย N,N-dimethyl ethylenediamine แตกต่างกัน ความยาวคลื่นการดูดกลืนแสงและการคายพลังงานสูงสุดอยู่ที่ 444 และ 532 นาโนเมตรตามลำดับ เนื่องจากสารละลายที่เป็นน้ำ ความเข้มแสงจะลดลงเมื่อค่า pH เพิ่มขึ้น และปรากฏการณ์นี้จะเกิดขึ้นในรูปแบบที่ผันกลับได้ การตอบสนองของค่า pH ของสารประกอบทั้งสองนี้อาจเป็นผลมาจากกระบวนการถ่ายโอนอิเล็กตรอนที่เกิดจากภาพถ่ายจากการโปรตอนและการสลายตัวของกลุ่มเอมีน ในตัวทำละลายอินทรีย์ส่วนใหญ่สัญญาณเรืองแสงของสารประกอบทั้งสองนี้จะเพิ่มขึ้นตามปริมาณน้ำที่เติมเข้าไป ซึ่งอาจเกี่ยวข้องกับกลไกการให้โปรตอน อย่างไรก็ตาม ความเข้มของฟลูออเรสเซนซ์ของสารประกอบทั้งสองในเตตระไฮโดรฟูแรน (THF) จะสูงสุดเมื่อไม่มีน้ำ และจะอ่อนลงเมื่อปริมาณน้ำเพิ่มขึ้นระหว่าง 0-10% ปรากฏการณ์นี้นำไปสู่การใช้สารประกอบเหล่านี้ในการกำหนดปริมาณน้ำใน THF ซึ่งแสดงความสัมพันธ์เชิงเส้นระหว่างอัตราส่วนการดับเรืองแสงและปริมาณน้ำระหว่าง 0 ถึง 1%

Determination Of Methanol Using Polymers And Mn-Doped Zns Quantum Dots, Sophanat Khenthaphak

Chulalongkorn University Theses and Dissertations (Chula ETD)

This study aimed to develop a method for methanol detection using digital-image colorimetry (DIC). We synthesized and characterized nanomaterials, including gold nanoparticles (AuNPs) and Mn-doped ZnS quantum dots (Mn/ZnS-QDs), to determine their minimum detectable concentration using DIC. We investigated NMPPy-modified Mn/ZnS-QDs, focusing on optimal temperature for the synthesis, and the effects of NMPPy volume, pH, and buffer solution concentration on methanol detection. However, direct methanol detection was not achieved, this research highlights the potential of NMPPy-modified Mn/ZnS-QDs for methanol detection using DIC. Further development is needed to enhance direct methanol detection.

Interactions Of Bioactive Trace Metals In Shipboard Southern Ocean Incubation Experiments, Shannon M. Burns, Randelle M. Bundy, William Abbott, Zuzanna Abdala, Alexa R. Sterling, P. Dreux Chappell, Bethany D. Jenkins, Kristen N. Buck

OES Faculty Publications

In the Southern Ocean, it is well‐known that iron (Fe) limits phytoplankton growth. Yet, other trace metals can also affect phytoplankton physiology. This study investigated feedbacks between phytoplankton growth and dissolved Fe, manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), and cadmium (Cd) concentrations in Southern Ocean shipboard incubations. Three experiments were conducted in September–October 2016 near the West Antarctic Peninsula: Incubations 1 and 3 offshore in the Antarctic Circumpolar Current, and Incubation 2 inshore in Bransfield Strait. Additions of Fe and/or vitamin B₁₂ to inshore and offshore waters were employed and allowed assessment of metal (M) …

Isotopic Evidence For Sources Of Dissolved Carbon And The Role Of Organic Matter Respiration In The Fraser River Basin, Canada, Britta M. Voss, Timothy I. Eglinton, Bernhard Peucker-Ehrenbrink, Valier Galy, Susan Q. Lang, Cameron Mcintyre, Robert G.M. Spencer, Ekaterina Bulygina, Zhaohui Aleck Wang, Katherine A. Guay

OES Faculty Publications

Sources of dissolved and particulate carbon to the Fraser River system vary significantly in space and time. Tributaries in the northern interior of the basin consistently deliver higher concentrations of dissolved organic carbon (DOC) to the main stem than other tributaries. Based on samples collected near the Fraser River mouth throughout 2013, the radiocarbon age of DOC exported from the Fraser River does not change significantly across seasons despite a spike in DOC concentration during the freshet, suggesting modulation of heterogeneous upstream chemical and isotopic signals during transit through the river basin. Dissolved inorganic carbon (DIC) concentrations are highest in …

Systemic Analyses Of Radiocarbon Ages Of Coexisting Planktonic Foraminifera, Jörg Lippold, Julia Gottschalk, Jean Lynch-Stieglitz, Matthew W. Schmidt, Sönke Szidat, Andre Bahr

OES Faculty Publications

We compare radiocarbon (¹⁴C) ages of coexisting planktonic foraminifera species from sediment cores VM12-107 and KNR166-2-26JPC from the Equatorial Atlantic Ocean for three time periods (Holocene, Heinrich Stadial 1, last glacial maximum). We find a maximum inter-species difference of 1200 ¹⁴C yr. On average, the ¹⁴C ages deviate by ∼300 yr between Globigerinoides ruber and other species. In most cases, this exceeds the analytical uncertainty range of the measurements and thus renders the choice of species for generating age models as important as sample weight. While modern stratified water-column profiles imply an increase in ¹⁴C …

What Moves The Needle On Dfw Rates And Student Success In General Chemistry? A Quarter-Century Perspective, Vijay Vyas, Scott A. Reid

Chemistry Faculty Research and Publications

Second-term general chemistry is a key gateway course at our institution for a variety of STEM (Science, Technology, Engineering, and Mathematics) majors. Herein, we examine data on DFW% (i.e., % of D and F grades and withdrawals) in our general chemistry courses over roughly a quarter-century period, focusing on sections taught by the authors. The data are discussed in light of changes in curriculum, pedagogy, and assessments, which included introduction of recitation sections, classroom response systems (clickers), and online homework, restructuring of course content into a modular format, followed by a redesign of the course modules along an anchoring concepts …

Design, Evolution, And Evaluation Of A General Chemistry-Bridging Course, Scott A. Reid

Chemistry Faculty Research and Publications

General chemistry I/II courses are important gateway courses for a variety of STEM majors, as poor performance in these courses is often associated with lower rates of student success and retention. Much research has explored preparatory or remedial strategies to improve student outcomes. In this article, we report a different approach, which involved the development of a bridging or intervention course designed to capture students who are not or have not succeeded in general chemistry I and prepare them to retake the course in the following semester or summer. The course was initially developed as an eight-week module in the …

Symmetry Breaking: A Classic Example Of Quantum Interference Captured By Mixed Quantum/Classical Theory, Kayla Imanzi, Dulat Bostan, Max Mccrea, Josh Featherstone, Mark Brouard, Dmitri Babikov

Chemistry Faculty Research and Publications

The phenomena of propensity and inverse propensity are explored using time-dependent mixed quantum classical theory, MQCT, in which the rotational motion of the molecule is treated quantum mechanically, whereas the scattering process is described classically. Good agreement with the results of accurate full-quantum calculations is reported for a closed shell approximation to the NO + Ar system. It is shown that MQCT reproduces both phenomena in a broad range of the final states of the molecule and for various initial rotational states, offering a unique time-dependent insight. It permits seeing that both propensity and inverse propensity occur due to efficient …

Mixed Quantum/Classical Theory For Rotational Energy Exchange In Symmetric-Top-Rotor + Linear-Rotor Collisions And A Case Study Of The Nd3 + D2 System, Carolin Joy, Bikramaditya Mandal, Dulat Bostan, Dmitri Babikov

Chemistry Faculty Research and Publications

Manifestation of the quantum interference effect in the oscillation of scattering cross section is explored using the N2 + O system as a case study. Calculations are carried out for two electronic PESs of the system, for various initial rotational states of N2, in a broad range of N2 + O collision energies and using three theoretical methods: two versions of the approximate mixed quantum/classical theory (MQCT and AT-MQCT) and the accurate full-quantum coupled-channel method (implemented in MOLSCAT). A good agreement between different methods is observed, especially at high energies. Elastic scattering cross-sections oscillate as a function of collision energy, …

Description Of Quantum Interference Using Mixed Quantum/Classical Theory Of Inelastic Scattering, Dulat Bostan, Bikramaditya Mandal, Carolin Joy, Dmitri Babikov

Chemistry Faculty Research and Publications

Manifestation of the quantum interference effect in the oscillation of scattering cross section is explored using the N₂ + O system as a case study. Calculations are carried out for two electronic PESs of the system, for various initial rotational states of N2, in a broad range of N₂ + O collision energies and using three theoretical methods: two versions of the approximate mixed quantum/classical theory (MQCT and AT-MQCT) and the accurate full-quantum coupled-channel method (implemented in MOLSCAT). A good agreement between different methods is observed, especially at high energies. Elastic scattering cross-sections oscillate as a function of …

Cup Is Essential For Oskar Mrna Translational Repression During Early Drosophila Oogenesis, Livia V. Bayer, Samantha Milano, Stephen K. Formel, Harpreet Kaur, Rishi Ravichandran, Juan A. Cambeiro, Lizaveta Slinko, Irina E. Catrina, Diana P. Bratu

Publications and Research

Study of the timing and location for mRNA translation across model systems has begun to shed light on molecular events fundamental to such processes as intercellular communication, morphogenesis, and body pattern formation. In D. melanogaster, the posterior mRNA determinant, oskar, is transcribed maternally but translated only when properly localized at the oocyte’s posterior cortex. Two effector proteins, Bruno1 and Cup, mediate steps of oskar mRNA regulation. The current model in the field identifies Bruno1 as necessary for Cup’s recruitment to oskar mRNA and indispensable for oskar’s translational repression. We now report that this Bruno1-Cup interaction leads …

C-Glycopyranosyl Aldehydes: Emerging Chiral Synthons In Organic Synthesis, Sandeep Kumar, Vinod Khatri, Priyanka Mangla, Rajni Johar Chhatwal, Virinder S. Parmar, Ashok K. Prasad

Publications and Research

Herein, we have summarized the vast array of synthetic processes that have been developed for the synthesis of C-glycopyranosyl aldehydes and diverse C-glycoconjugates derived from them by covering the literature reported from 1979 to 2023. Notwithstanding its challenging chemistry, C-glycosides are considered stable pharmacophores and are used as important bioactive molecules. The discussed synthetic methodologies to access C-glycopyranosyl aldehydes take advantage of seven key intermediates, viz. allene, thiazole, dithiane, cyanide, alkene, and nitromethane. Furthermore, the integration of complex C-glycoconjugates derived from varied C-glycopyranosyl aldehydes involves nucleophilic addition/substitution, reduction, condensation, oxidation, cyclo condensation, coupling, and …

Molecular Mechanism Behind The Safe Immunostimulatory Effect Of Withania Somnifera, Kriti Kalpana, Shen Yap, Moriya Tsuji, Akira Kawamura

Publications and Research

Withania somnifera (L.) Dunal (family Solanaceae) is a medicinal plant known for, among many pharmacological properties, an immune boosting effect. Our recent study revealed that its key immunostimulatory factor is lipopolysaccharide of plant-associated bacteria. This is peculiar, because, although LPS can elicit protective immunity, it is an extremely potent pro-inflammatory toxin (endotoxin). However, W. somnifera is not associated with such toxicity. In fact, despite the presence of LPS, it does not trigger massive inflammatory responses in macrophages. To gain insights into the safe immunostimulatory effect of W. somnifera, we conducted a mechanistic study on its major phytochemical constituent, …

I. Preparation Of Strategic Synthetic Building Blocks For World Health Organization Essential Medicines. Ii. Applying The Principles Of Process Intensification To The Synthesis Of Fluoroquinolone Antibiotics., Jeffrey M. Noble

Theses and Dissertations

The synthesis of active pharmaceutical ingredients is often a time-consuming and expensive process. Due to the nature of pharmaceutical manufacturing, these costs are carried forward to the final purchase price by the consumer. Although there are many factors which are involved in the final costing of a pharmaceutical, the cost associated with the synthesis is the primary one which can be managed by chemists and engineers.

This work discusses the synthetic routes of four active pharmaceutical ingredients as well as the synthetic techniques and equipment used with an emphasis on how the application of specific techniques can be applied to …

Investigating The Dynamics And Fragmentation Of Nitroaromatic Radical Cations Through Femtosecond Time-Resolved Mass Spectrometry And Computational Chemistry, Hugo Andres Lopez Pena

Theses and Dissertations

Chemists have sought to control molecular dissociation with lasers for decades. Effective control of unimolecular dissociation was only achieved with the development of high-intensity ultrashort pulsed lasers and coherent control techniques that operate on timescales faster than vibrational energy redistribution. In view of this, our lab has specialized in the study of polyatomic radical cations using femtosecond time-resolved mass spectrometry (FTRMS). The interest in radical cations stems from the fact that they are highly reactive species that contribute to many physical, chemical, and biological processes. For instance, radical cations participate in shock initiation of detonated energetic materials used as explosives …

Asymmetric Cuh-Catalyzed Reductive Coupling Of Allenamides With Carbonyl Electrophiles & Development Of Nanocatalysts For Heterogeneously Catalyzed Buchwald-Hartwig Amination, Raphael K. Klake

Theses and Dissertations

Many drugs and natural products contain multiple stereogenic carbons bearing heteroatoms throughout their carbon framework. Therefore, methods that can efficiently install multiple heteroatoms on a molecule are valuable. Reductive coupling reactions have been extensively studied, and the allylation of carbonyls via the reductive coupling approach has been a key method for generating chiral tertiary and secondary allylic alcohols. This work utilizes inexpensive Cu for the asymmetric reductive coupling of allenamides with carbonyls to simultaneously install two heteroatoms (oxygen and nitrogen) on the product. These molecules have a polarity profile that make them difficult to make using traditional methods. Herein, we …

Synthesis And Application Of Redox-Active Covalent Organic Frameworks In Rechargeable Batteries, Mohammad K. Shehab

Theses and Dissertations

Synthesis and Application of Redox-Active Covalent Organic Frameworks in Rechargeable Batteries

Mohammad K. Shehab

Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States

Abstract

In recent years, lithium-ion batteries (LIBs) have been considered the dominant energy storage devices for portable electronics and electric vehicles due to their high energy density, low self-discharge rate, and long cycle life. In LIBs, the traditional positive electrodes employed are mainly derived from metal-containing inorganic compounds composed of cobalt, iron, nickel, or manganese (LiCoO₂, LiMn₂O₄, and LiFePO₄) coupled with graphite as the negative electrode. Despite …

Adiabatic Trajectory Approximation: A New General Method In The Toolbox Of Mixed Quantum/Classical Theory For Collisional Energy Transfer, Bikramaditya Mandal, Carolin Joy, Dulat Bostan, Alexander Eng, Dmitri Babikov

Chemistry Faculty Research and Publications

A new version of the MQCT program is presented, which includes an important addition, adiabatic trajectory approximation (AT-MQCT), in which the equations of motion for the classical and quantum parts of the system are decoupled. This method is much faster, which permits calculations for larger molecular systems and at higher collision energies than was possible before. AT-MQCT is general and can be applied to any molecule + molecule inelastic scattering problem. A benchmark study is presented for H₂O + H₂O rotational energy transfer, an important asymmetric-top rotor + asymmetric-top rotor collision process, a very difficult problem …

Impact Of A Low-Stakes Assessments Model With Retake In General Chemistry: Connecting To Student Attitudes And Self-Concept, Vijay Vyas, Llanie Nobile, James R. Gardinier, Scott A. Reid

Chemistry Faculty Research and Publications

Across a variety of fields, the use of low-stakes assessments has led to reductions in achievement gaps and improved student success. Here, we probe the use of a low-stakes assessment model with a retake option for failed quizzes in a two-semester general chemistry sequence. We find that the quiz-retake rate in general chemistry II was significantly higher for students who had completed a retake in a general chemistry I section, and the percentage of students who failed at least one quiz in general chemistry I but passed all quizzes in general chemistry II was significantly higher for students who had …

Excitonic Coupling In Fluorene-Based Bichromophoric Systems: Vibrational Quenching And The Transition From Weak To Intermediate Coupling, Damian L. Kokkin, Neil Reilly, Maxim V. Ivanov, Rajendra Rathore, Scott A. Reid

Chemistry Faculty Research and Publications

Excimeric systems (i.e., excited dimers) have well served as model compounds for the study of the delocalization of electronic energy over weakly interacting chromophores. However, there remain relatively few isolated systems in which such interactions can be studied experimentally at a level to afford detailed comparisons with theory. In this Article, we examine a series of covalently and noncovalently linked dimers of fluorene, as a model aromatic chromophore, where the formation of excimers requires a π-stacked, cofacial orientation at van der Waals contact. Building upon a series of seminal prior studies that examined vibronic quenching of the excitation interaction in …

Contrasting Seasonal Cycling Of Arsenic In A Series Of Subarctic Shield Lakes With Different Morphometric Properties, Jeremy Harbinson

Theses and Dissertations (Comprehensive)

The subarctic shield near Yellowknife, Northwest Territories (NWT), is populated with thousands of small lakes (<1.5 km²) and several large lakes. Historic mining activities in the region have left a legacy of environmental impacts and widespread arsenic (As) contamination in both aquatic and terrestrial environments. In particular, several small subarctic lakes near Yellowknife have been previously documented to be contaminated with high levels of As. Subarctic lakes are characterized by seasonal ice-cover that can persist for more than half of the year, yet little is known about the under-ice spatial and seasonal dynamics of As cycling. The objective of …