The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free-electron laser to directly observe the decreased bonding-antibonding splitting following bond-activation using an ultrashort optical laser pulse.
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http://dx.doi.org/10.1021/acs.jpclett.6b01543 | DOI Listing |
Sci Rep
January 2025
Cellulose and Paper Department, National Research Centre, Cairo, 12622, Egypt.
Compounds containing the piperidine group are highly attractive as building blocks for designing new drugs. Functionalized piperidines are of significant interest due to their prevalence in the pharmaceutical field. Herein, 3-oxo-3-(piperidin-1-yl) propanenitrile has been synthesized, and piperidine-based sodium alginate/poly(vinyl alcohol) films have been prepared.
View Article and Find Full Text PDFJ Prosthet Dent
January 2025
Assistant Professor, Department of Prosthodontic, College of Dental Medicine, Rangsit University, Phatum Thani, Thailand. Electronic address:
Statement Of Problem: Comprehensive data are needed on the performance of chemically activated, chairside hard reline materials when used with computer-aided design and computer-aided manufacturing (CAD-CAM) milled polymethyl methacrylate (PMMA) denture bases and conventionally processed bases. This lack of data affects decisions regarding the chairside reline material to be used for improving the fit and retention of relined complete dentures.
Purpose: The purpose of this in vitro study was to evaluate and compare the shear bond strength (SBS) of 3 chemically activated, chairside hard reline materials on CAD-CAM milled and conventional heat-polymerized PMMA denture bases.
Nat Chem
January 2025
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA.
In view of the high propensity of tertiary alkyl amines to be bioactive, the development of new methods for their synthesis is an important challenge. Transition-metal catalysis has the potential to greatly expand the scope of nucleophilic substitution reactions of alkyl electrophiles; unfortunately, in the case of alkyl amines as nucleophiles, only one success has been described so far: the selective mono-alkylation of primary amines to form secondary amines. Here, using photoinduced copper catalysis, we report the synthesis of tertiary alkyl amines from secondary amines and unactivated alkyl electrophiles, two readily available coupling partners.
View Article and Find Full Text PDFSci Rep
January 2025
Department of Chemistry, Clemson University, 211 S. Palmetto Blvd, Clemson, SC, 29634, USA.
Minimizing the oxidation of lipids remains one of the most important challenges to extend the shelf-life of food products and reduce food waste. While most consumer products contain antioxidants, the most efficient strategy is to incorporate combinations of two or more compounds, boosting the total antioxidant capacity. Unfortunately, the reasons for observing synergistic / antagonistic / additive effects in food samples are still unclear, and it is common to observe very different responses even for similar mixtures.
View Article and Find Full Text PDFNat Commun
January 2025
Department of Chemistry, KAIST, Daejeon, Republic of Korea.
Despite its profound significance, the molecular structural changes near the transition state, driven by the vibronic coupling, have remained largely unexplored, leaving a crucial aspect of chemical reactions shrouded in uncertainty. Herein, the dynamical behavior of the reactive flux on the verge of chemical bond breakage was revealed through the spectroscopic characterization of a large amplitude vibrational motion. Highly excited internal rotor states of S methylamine (CHND) report on the structural change as the molecule approaches the transition state, indicating that the quasi-free internal rotation is strongly coupled to the reaction coordinate as their energies near the maximum of the reaction barrier for the N-D chemical bond predissociation.
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