Application of mass spectrometry to the study of fluoropolymers. II. The copolymer from trifluoronitrosomethane (CF3NO) and tetrafluoroethylene (C2F4)

The techniques of mass spectrometry have been applied to the copolymer from tri-fluoronitrosomethane (CF₃NO) and tetrafluoroethylene (C₂F₄). The copolymer yields spectra of a repetitive nature, typical of the repeating units in the polymer chain. Molecules with masses up to m/e 6400 can be distilled from the unfractionated polymer which is stable up to 220°C. Interpretation of the mass spectrum suggests a linear structure for the regular polymer.     

Slow light in semiconductor quantum wells

We demonstrate slow light via population oscillation in semiconductor quantum-well structures for the first time. A group velocity as low as 9600 m/s is inferred from the experimentally measured dispersive characteristics. The transparency window exhibits a bandwidth as large as 2 GHz.     

Fluorine-Containing Drugs Approved by the FDA in 2018

Over the last two decades, fluorine substitution has become one of the essential structural traits in modern pharmaceuticals. Thus, about half of the most successful drugs (blockbuster drugs) contain fluorine atoms. In this review, we profile 17 fluorine-containing drugs approved by the food and drug administration (FDA) in 2018. The newly approved pharmaceuticals feature several types of aromatic F and CF₃, as well as aliphatic (CF₂) substitution, offering advances in the treatment of various diseases, including cancer, HIV, malarial and smallpox infections.     

Degradation of low-density polyethylene in the presence of water and deuterium oxide

The degradation of low-density polyethylene in the presence of water as the degradative agent was studied at a temperature of 450°C and a pressure greater than 160 atm. The experimental work was conducted in an autoclave of 333-mL capacity. The products (gases, liquids, and solids) were analyzed by microanalytical methods and GC-spectroscopic techniques. The results indicate the presence of paraffins, olefines, dienes, and aromatics in the degradation products. The occurrence of aromatics in the products demonstrates the importance of this degradation procedure for obtaining these valuable materials. The present work (Part 1) is believed to be the first publication to discuss the production of aromatics from polyethylenes degradation.     

A hydrogen-1 nuclear magnetic resonance,mass spectral and extended Hückel study of some olefin complexes of rhodium(I) and iridium(I) and the crystal and molecular structure of η4-2,4-dimethylpenta-1,4-diene(η5-formylcyclopentadienyl)rhodium(I)

A ¹H NMR study of monosubstituted η-cyclopentadienyl-rhodium(I) complexes of type LLRh(C₅H₄X) and -iridium(I) complexes of type L₂Ir(C₅H₄X) (L = ethene, LL = 1,3- or 1,5-diolefin; X = C(C₆H₅)₃, CHO, or COOCH₃) has been carried out. For complexes of both metals in which the neutral ligand is ethene or a non-conjugated diolefin the NMR spectra of the cyclopentadienyl protons are unusual in that H(2), H(5) resonate to high field either at room temperature or below.The corresponding NMR spectra for the cyclopentadienyl ring protons of complexes where the neutral ligand is a conjugated diene are, with one exception, normal.A single crystal X-ray structural analysis of (η⁴-2,4-dimethylpenta-1,4-diene)(η⁵-formylcyclopentadienyl)rhodium(I) (which exhibits an abnormal ¹H NMR spectrum) reveals substantial localisation of electron density in the C(3)C(4) Cp ring bond (1.283(33) Å) which may be consistent with a contribution from an ‘allyl-ene’ rotamer to the ring—metal bonding scheme. An extended Hückel calculation with self consistent charge iteration was performed on this complex.The results predict a greater Mulliken overlap population for the C(3)C(4) bond in the cyclopentadienyl ring and show that the localisation is dependent on both the Cp ring substituent and the nature of the diolefin. The mass spectral fragmentation patterns of some representative diene complexes of iridium(I) and rhodium(I) are presented.     

Untangling two systems of noncrossing curves

We consider two systems (α₁, …, α_m) and (β₁, …,β_n) of simple curves drawn on a compact two-dimensional surface M with boundary.     

A Simple Near-Infrared Fluorescent Probe for the Detection of Peroxynitrite

Herein, we report the evaluation and synthesis of a reaction based fluorescent probe DCM-Bpin for the detection of Peroxynitrite (ONOO−). DCM-Bpin exhibits selective fluorescence off-on response for ONOO⁻ over other reactive oxygen species, including H₂O₂. Moreover, DCM-Bpin is biocompatible and has been used to visualize exogenous ONOO⁻ in HeLa cells.     

Capillary gas chromatographic analysis of amino acids in blood and protein hydrolysates as tert.-butyldimethylsilyl derivatives

A method is given for a one-step derivatization and gas chromatography of amino acids in blood and protein hydrolysates. Blood samples are partially purified by solvent extraction. Protein hydrolysates are neutralized with a triethylamine solution. Then tert.-butyldimethylsilyl derivatives of the amino acids are prepared in a one-step procedure and separated on a 30-m fused-silica SE-30 capillary column. Except for tryptophan and cystine, amino acids are eluted within 30 min. Amino acids are derivatized more rapidly than their corresponding trimethylsilyl derivatives and do not degrade on the long fused-silica columns.