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关键词： biguanide   superbase   ligand   organocatalyst  

摘要： In this minireview, we discuss the chemistry of biguanides and their applications in catalysis. We present their super basicity as a consequence of their structure, the most efficient ways to synthesize symmetric and unsymmetric functionalized biguanides, and their applications in organic catalysis as triazine precursors and ligands in organometallic catalysis.

ISBN: (纸本)9787030647863

关键词： Blue carbon   Coastal vegetated ecosystems   Climate change   Organic chemistry   Diagenesis   CP/MAS C-13 NMR   Australia  

摘要： The high organic carbon (OC) stores in seagrass meadows have led to their recognition as significant Blue Carbon sinks, though the diagenetic conditions that enable OC retention in seagrass soils remain poorly understood. In this study, seagrass soils were sampled from a Posidonia australis meadow in Oyster Harbour (Albany;southwestern Australia) to investigate the preservation of sedimentary OC. We analysed soil characteristics (colour, grain size and redox potential), radiocarbon age, and characterised the soil organic matter (OM) using solid state CP/MAS C-13 NMR spectroscopy to examine the preservation of OM down the soil profile. There was minimal change in organic composition over 1,700 years of accumulation, indicating long-term OM preservation. Primarily, this preservation appears to be driven by the recalcitrance of seagrass detritus buried in anoxic soils. The majority (70-83%) of total sedimentary OM comprised components directly attributable to seagrass origins (lignin, carbohydrate and black carbon-like matter), while the remainder consisted mostly of protein, some of which may have been present in seagrass biomass, along with likely contributions from algae and microbes. Although black carbon originates from organic matter combustion, here we provide evidence that the C-13 NMR signal identified as black carbon-like matter in our soils is possibly associated with seagrass-derived organic matter consisting of degraded lignin products or other non-pyrogenic aromatics. The increase in the relative abundance of this black carbon-like matter with aging suggests its selective preservation. The relative abundances of carbohydrates significantly decreased with age down core (i.e. they appeared to be selectively decomposed), while lignin and protein did not show any quantitative changes in relative abundance (non-selective preservation). These findings demonstrate the exceptional preservation of P. australis derived OC, which contributes to our understanding of

关键词： Second-Year Undergraduate   Organic Chemistry   Problem Solving/Decision Making   Textbooks/Reference Books   Internet/Web-Based Learning   Spectroscopy   Alcohols   Alkenes   Aromatic Compounds   Aldehydes/Ketones  

摘要： A bridge course intended to ease the transition from Organic Chemistry I to II was designed for a January term that spans 2 weeks and features sharply focused topics courses. In the first week, key topics from Organic Chemistry I are revisited to ensure that students have a firm foundation on which to build. During the second week, a selection of Organic Chemistry II material is introduced. The course focuses heavily on interactive problem solving and utilizes an open-access text as well as YouTube videos. Students taking the bridge course were tracked through the second semester against a comparison group with similar Organic Chemistry I grades. Results suggest that the bridge course may lead to better outcomes in Organic Chemistry II.

关键词： General Public   First-Year Undergraduate   Curriculum   Organic Chemistry   Administrative Issues   Nonmajors Courses  

摘要： Educators are constantly looking to improve their pedagogical strategies. This can range from teaching strategies for a specific topic to holistic curriculum changes. Recently, the approach that chemistry departments have chosen to deliver their introductory courses has garnished increasing attention from educators. Our department recently converted our introductory sequence from the traditional two semesters of general chemistry followed by two semesters of organic chemistry to what is often referred to as the 1-2-1 sequence. The 1-2-1 sequence is an introductory sequence in which students take General Chemistry I followed by Organic Chemistry I and II and last General Chemistry II as the fourth introductory course in the introductory sequence. The conversion was motivated by the need to implement a curriculum that more effectively addressed our students' needs and deficiencies and to more effectively utilize department resources to service chemistry majors and the college. The work here highlights the motivation for the conversion, insight into its implementation, and a preliminary investigation on how this change has impacted the Organic Chemistry I class.

关键词： Upper-Division Undergraduate   Laboratory Instruction   Organic Chemistry   Green Chemistry   Microscale Lab   Aqueous Solution Chemistry   Stereochemistry   Synthesis   Student-Centered Learning   Undergraduate Research   Systems-Based Learning  

摘要： Green chemistry metrics and life-cycle analysis (LCA) were used to assess inefficiencies in two current organic chemistry experiments conducted in third-year organic chemistry to synthesize (E)-stilbene from benzaldehyde. An alternative Wittig-based, greener, one-pot experiment using the same starting material was selected as a vehicle to introduce the concepts of green chemistry to students. The original learning objectives for the experiment were maintained with additional learning objectives in green chemistry introduced. The theoretical and experimental calculations of all experiments were compared using the standard univariate and multivariate metrics for LCA analysis, to assess the impact of chemical waste generated on the environment. The LCA metrics showed that the Wittig-based experiment addressed eight principles of green chemistry and possessed fewer environmental hazards, produced less waste (E-factor), and had better isomeric purity, mass, and process efficiency including factors such as global warming potential than the current lab methods. Results from a survey of students who conducted all three experiments indicated an enhanced knowledge of green chemistry and an improved sense of chemical and environmental impact. The research provided a platform to introduce sustainable chemistry practices to organic chemistry students at the undergraduate level.

关键词： First-Year Undergraduate/General   Organic Chemistry   Distance Learning/Self Instruction   Computer-based Learning   Internet/Web-based Learning   Applications of Chemistry   Student/Career Counseling  

摘要： A massive open online course (MOOC), Exploring Everyday Chemistry (eeDc), was delivered four times between 2017 and 2019, attracting a worldwide audience of over 15 000 learners from a wide range of backgrounds. This 4-week course was designed to show a variety of everyday applications of organic chemistry, targeted at high school students seeking to study a chemistry-related degree at university. A mix of video, text, polls, quizzes, and practical activities was incorporated with material designed to build on high school studies, highlighting aspects of university-level teaching and research, as well as showcasing some career opportunities for chemistry graduates. We monitored student attitudes toward this course, finding a consistent enthusiasm for the approach and selection of material. The impact of the course was evident from the significant number of students who mentioned it positively in their university applications.

关键词： Free energy   Chemical structure   Organic compounds   Potential energy   Computer simulations  

摘要： This work combines a machine learning potential energy function with a modular enhanced sampling scheme to obtain statistically converged thermodynamical properties of flexible medium-size organic molecules at high ab initio level. We offer a modular environment in the python package MORESIM that allows custom design of replica exchange simulations with any level of theory including ML-based potentials. Our specific combination of Hamiltonian and reservoir replica exchange is shown to be a powerful technique to accelerate enhanced sampling simulations and explore free energy landscapes with a quantum chemical accuracy unattainable otherwise (e.g., DLPNO-CCSD-(T)/CBS quality). This engine is used to demonstrate the relevance of accessing the ab initio free energy landscapes of molecules whose stability is determined by a subtle interplay between variations in the underlying potential energy and conformational entropy (i.e., a bridged asymmetrically polarized dithiacyclophane and a widely used organocatalyst) both in the gas phase and in solution (implicit solvent).

关键词： 身心发展规律   学科核心素养   化学教材   主要学习内容   章引言   辅助材料   人教版   《有机化学基础》  

摘要： 《普通高中化学课程标准(2017年版)》中提到,化学教材应结合学生的身心发展规律,对"前言"等助读学习辅助材料进行科学、系统、合理的设计,促进学生自主学习和学习方式的转变。教材总引言和章引言是教材和各章内容的引导性材料,是教与学的良好素材,也是培养学科核心素养的重要载体。人教版高中《有机化学基础》教材既有教材总引言还有章引言,但无论是总引言还是章引言,它们都有一个共同特点,就是介绍本教材、本章的主要学习内容以及相应知识在生产生活中的应用。

关键词： 民族院校   生物有机化学   教学改革  

摘要： 生物有机化学作为有机化学向生命科学渗透过程中形成的一个新的学科分支,近20年来取得了令人瞩目的迅速发展。我们在教学实践中,结合生物有机化学学科的发展与民族院校有机化学专业硕士研究生的特点和基础情况,对生物有机化学内容进行优化,突出应用有机化学的知识来解释生命科学中的现象,适当增加或减少一些基础内容,提高了教学效果,获得了学生的好评。