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Enhanced Mechanistic Understanding Through the Detection of Radical Intermediates in Organic Reactions
Get PDFTwo applications of a radical trap based on a homolytic substitution reaction (SH2\u27) are presented for the trapping of short-lived radical intermediates in organic reactions. The first example is a photochemical cyanomethylation catalyzed by a Ru complex. Two intermediate radicals in the radical chain propagation have been trapped and detected using mass spectrometry (MS), along with the starting materials, products and catalyst degradation fragments. Although qualitative, these results helped to elucidate the reaction mechanism. In the second example, the trapping method was applied to study the radical initiation catalyzed by a triethylboronoxygen mixture. In this case, the concentration of trapped radicals was sufficiently high to enable their detection by nuclear magnetic resonance (NMR). Quantitative measurements made it possible to characterize the radical flux in the system under different reaction conditions (including variations of solvent, temperature and concentration) where modelling was complicated by chain reactions and heterogeneous mass transfer
In situ/In vivo Optical Microspectroscopy to Probe the Emergence of Morphology
Get PDFMorphology governs function. Yet, understanding and controlling the emergence of morphology at the molecular level remains challenging. The difficulty in studying the early stage of morphology formation is due to its stochastic nature both spatially and temporally occurring at the nanoscale. This nature has been particularly detrimental for the application of optical spectroscopy. To overcome this problem, we have been developing new in situ/in vivo optical spectroscopy tools, which are label-free and non-invasive. This account highlights several examples of how optical spectroscopy can become an important tool in studying the birth of morphology
Silylium-Catalyzed Activation of Donor- Acceptor Strained Rings and Annulation with Indoles
Get PDFLeveraging the unique reactivity profile of donor-acceptor aminocyclopropanes and cyclobutanes allows the preparation of complex nitrogen-substituted molecules. While most reports focus on donor-acceptor strained rings with two geminal carbonyl groups as acceptors, mono carbonyl acceptor systems, despite their synthetic relevance, have been considerably less studied. Herein we describe catalytic annulation reactions ofaminocyclopropane and aminocyclobutane monoesters employing silylium catalysis to activate these less reactive donor-acceptor systems
The pKa Values of Water in Water: A Long-Standing, Tiresome, yet Soon Forgotten Issue? Chemical Education
No full textThe pKa values of water and the hydrogen ion (proton) in water are 14 and 0, respectively. Yet, many textbooks of general, organic, and, to a lesser extent, inorganic chemistry provide the incorrect values 15.74 and -1.74, respectively. This column briefly introduces the long-standing issue of these two different pairs of values, the consequences it bears when teaching general chemistry, and expresses the hope that it may be solved soon
Industrial Distillation Aspects of Diketene
Get PDFLarge-scale distillation is a challenge in many respects. Particularly difficult is the purification by distillation of a compound with limited thermal stability. This article describes various aspects of these difficulties with some possible solutions. Special emphasis is placed on the collaboration of different disciplines to find pragmatic solutions to these challenges. The purification of diketene in quantities of several 1000 ta–1 is an excellent example to illustrate the different requirements. Although the distillation of diketene has been carried out by several companies for many years, there are still some aspects that deserve special attention
A New Chapter for Swiss Materials Chemistry: Materials Chemistry Highlights
No full textThe division dedicated to materials chemistry at the Swiss Chemical Society (SCS) has been recently restructured by merging the Division for Polymers, Colloids, and Interfaces (DCPI) with the Materials Chemistry Network (MatChem). This column provides more insights into the process while outlining the vision and activities of the newly established SCS Division of Materials Chemistry (DMC)
From Enigma to Revelation: Unravelling Biological Functions of Ubiquitous Small Ribozymes
Get PDFRNA, widely recognized as an information-carrier molecule, is capable of catalyzing essential biological processes through ribozymes. Despite their ubiquity, specific functions in a biological context and phenotypes based on the ribozymes\u27 activity are often unknown. Here, we present the discovery of a subgroup of minimal HDV-like ribozymes, which reside 3\u27 to viral tRNAs and appear to cleave the 3\u27-trailers of viral premature tRNA transcripts. This proposed tRNA-processing function is unprecedented for any ribozymes, thus, we designate this subgroup as theta ribozymes. Most theta ribozymes were identified in Caudoviricetes bacteriophages, the main constituent (>90%) of the mammalian gut virome. Intriguingly, our findings further suggest the involvement of theta ribozymes in the transition of certain bacteriophages between distinct genetic codes, thus possibly contributing to the phage lysis trigger. Our discovery expands the limited repertoire of biological functions attributed to HDV-like ribozymes and provides insights into the fascinating world of RNA catalysis
