Structure Elucidation of Fluorinated Compounds by NMR March 6, 2020 Nuclear Magnetic Resonance (NMR), ROYALPROBE HFX 0 Introduction Fluorine is increasingly being used in many new drugs As of 2011 there were approximately 200 fluorine containing drugs. [ref 1] Fluoro-organic compounds account for 40% of the new chemical entities entering phase III trials in 2012 and 2013. [ref 2] Fluorine is use in a wide range of drug applications including: Anesthetics, Antacids, Anti-anxiety, Antibiotics, Antidepressants, Anti-fungal antibiotics, Antihistamines, Antilipemics, Anti-malarial, Antimetabolites, Appetite suppressants, Arthritis/anti-inflammatory agents, Psychotropic, Steroids/anti-inflammatory agents. [ref 3] Fluorine is now appearing in illicit and illegal synthetic drugs: These include: Cannabinoids [ref 4], and psychedelic phenethylamines [ref 5] Fluoro Polymers are important to everyday life, for example PTFE (Teflon™) Challenges The potential Fluorine chemical shift range is 500 ppm, 188 kHz at 9.4T (1H 400 MHz) to 282 kHz at 14.1T (1H 600 MHz). 19F-1H j coupling constants up to 60 Hz 19F-13C j coupling constants up to 280 Hz 19F long range J coupling interactions complicate NMR spectra making interpretation difficult These spectral features combine to make 19F difficult to excite and to decouple from other nuclei. For full details: Attached files often contain the full content of the item you are viewing. Be sure and view any attachments. JEOL Structure Elucidation of Fluorinated Compounds by NMR.pdf 1.58 MB Related Articles Development of 19F‐detected 1,1‐ADEQUATE for the characterization of polyfluorinated and perfluorinated compounds Polyfluorinated and perfluorinated compounds in the environment are a growing health concern. 19F‐detected variants of commonly employed heteronuclear shift correlation experiments such as heteronuclear single quantum correlation (HSQC) and heteronuclear multiple bond correlation (HMBC) are available; 19F‐detected experiments that employ carbon–carbon homonuclear coupling, in contrast, have never been reported. Herein, we report the measurement of the 1JCC and nJCC coupling constants of a simple perfluorinated phthalonitrile and the first demonstration of a 19F‐detected 1,1‐ADEQUATE experiment. Analysis of Organogermanium Compounds by Field Desorption (FD) Ionization Organogermanium compounds are organometallics that contain a carbon to germanium chemical bond. Germanium shares group 14 in the periodic table with silicon, tin and lead and the chemistry of organogermanium is somewhat similar to that of organosilicon compounds and organotin compounds. While metallic germanium is widely used in semiconductor devices, infrared light sensors, etc., organogermanium is advocated as a non-toxic alternative to many toxic organotin reagents. In this work, we report the analyses of organogermanium compounds by field desorption (FD) using the JMS-T100GC “AccuTOF-GC” time-of-flight mass spectrometer. Development of Coldspray Ionization Mass Spectrometry (CSI-MS) and Its Application to Labile Organometallic Compounds in Solution Coldspray ionization (CSI) mass spectrometry (MS) has been developed and applied to characterize labile organometallic compounds. While conventional ESI is not applicable to those compounds because of their instability to heat and/or air, CSI affords multiply charged molecular ions with many solvents molecules attached. Here we describe the CSI method and its application to several labile organometallic compounds. Structure Solution of Nano-Crystalline Small Molecules Using MicroED and Solid-State NMR Dipolar-Based Experiments Three-dimensional electron diffraction crystallography (microED) can solve structures of sub-micrometer crystals, which are too small for single crystal X-ray crystallography. However, R factors for the microED-based structures are generally high because of dynamic scattering. That means R factor may not be reliable provided that kinetic analysis is used. Consequently, there remains ambiguity to locate hydrogens and to assign nuclei with close atomic numbers, like carbon, nitrogen, and oxygen. Herein, we employed microED and ssNMR dipolar-based experiments together with spin dynamics numerical simulations. The NMR dipolar-based experiments were 1H-14N phase-modulated rotational-echo saturation-pulse double-resonance (PM-S-RESPDOR) and 1H-1H selective recoupling of proton (SERP) experiments. The former examined the dephasing effect of a specific 1H resonance under multiple 1H-14N dipolar couplings. The latter examined the selective polarization transfer between a 1H-1H pair. The structure was solved by microED and then validated by evaluating the agreement between experimental and calculated dipolar-based NMR results. As the measurements were performed on 1H and 14N, the method can be employed for natural abundance samples. Furthermore, the whole validation procedure was conducted at 293 K unlike widely used chemical shift calculation at 0 K using the GIPAW method. This combined method was demonstrated on monoclinic l-histidine. Analysis of organic compounds on an acrylic plate using JMS-S3000 SpiralTOF™ - MSTips - 251 Industrial materials are often evaluated by surface analysis instruments that provide information on surface elements, bonding states, and functional groups. However, there are limited options for surface analysis techniques that provide molecular weight and molecular structure information for organic compounds present on surfaces. Matrix Assisted Laser Desorption Ionization - Time of Flight Mass Spectrometry (MALDI-TOFMS) is a soft ionization technique that can be used to analyze surfaces in order to estimate elemental compositions with accurate mass measurements, obtain structural information by using MS/MS, and map surface compounds by using MS imaging. MALDI-TOFMS uses a high voltage on the target plate to accelerate the ions into the TOFMS analyzer. Therefore, the target plates are conductive and are typically made of stainless steel. MALDI imaging mass spectrometry is widely used for analyzing organic substances on frozen tissue sections. In this case, a frozen tissue section with a thickness of about 10 μm is placed on a conductive glass slide coated with an indium tin oxide (ITO) film. However, for the analysis of industrial products, the target organic compounds are on nonconductive substrates such as resins with millimeter thicknesses. MALDI-TOFMS surface measurements using nonconductive substrates lead to a reduction in mass resolution and a significant decrease in ion intensity due to surface charging. This problem can be solved by pretreating the surface with gold vapor deposition in order to change it from nonconductive to conductive. This method was previously shown to work well in MSTips No. 204 in which the gold vapor deposition method was applied to the MALDI-MS imaging analysis of inks on paper. In this report, we used gold vapor deposition to look at samples on the surface of a 1 mm thick acrylic plate. Analysis of organic compounds on an acrylic plate using JMS-S3000 "SpiralTOF" Industrial materials are often evaluated by surface analysis instruments that provide information on surface elements, bonding states, and functional groups. However, there are limited options for surface analysis techniques that provide molecular weight and molecular structure information for organic compounds present on surfaces. Matrix Assisted Laser Desorption Ionization - Time of Flight Mass Spectrometry (MALDI-TOFMS) is a soft ionization technique that can be used to analyze surfaces in order to estimate elemental compositions with accurate mass measurements, obtain structural information by using MS/MS, and map surface compounds by using MS imaging. MALDI-TOFMS uses a high voltage on the target plate to accelerate the ions into the TOFMS analyzer. Therefore, the target plates are conductive and are typically made of stainless steel. MALDI imaging mass spectrometry is widely used for analyzing organic substances on frozen tissue sections. In this case, a frozen tissue section with a thickness of about 10 μm is placed on a conductive glass slide coated with an indium tin oxide (ITO) film. However, for the analysis of industrial products, the target organic compounds are on nonconductive substrates such as resins with millimeter thicknesses. MALDI-TOFMS surface measurements using nonconductive substrates lead to a reduction in mass resolution and a significant decrease in ion intensity due to surface charging. This problem can be solved by pretreating the surface with gold vapor deposition in order to change it from nonconductive to conductive. This method was previously shown to work well in MSTips No. 204 in which the gold vapor deposition method was applied to the MALDI-MS imaging analysis of inks on paper. In this report, we used gold vapor deposition to look at samples on the surface of a 1 mm thick acrylic plate. Showing 0 Comment Comments are closed.