RESUMEN
Isocyanates play an essential role in modern manufacturing processes, especially in polyurethane production. There are numerous synthesis strategies for isocyanates both under industrial and laboratory conditions, which do not prevent searching for alternative highly efficient synthetic protocols. Here, we report a detailed theoretical investigation of the mechanism of sulfur dioxide-catalyzed rearrangement of phenylnitrile oxide into phenyl isocyanate, which was first reported in 1977. The DLPNO-CCSD(T) method and up-to-date DFT protocols were used to perform a highly accurate quantum-chemical study of the rearrangement mechanism. An overview of various organic and inorganic catalysts has revealed other potential catalysts, such as sulfur trioxide and selenium dioxide. Furthermore, the present study elucidated how substituents in phenylnitrile oxide influence reaction kinetics. This study was performed by a self-organized collaboration of scientists initiated by a humorous post on the VK social network.
RESUMEN
The research into new pharmaceutical substances based on essential oils, individual biologically active phytochemicals, and plant extracts is a priority in field of pharmaceutical sciences. A novel multicomponent substance based on Melaleuca alternifolia (M. alternifolia) leaf oil (TTO), 1,8-cineole (eucalyptol), and (-)-α-bisabolol with potent synergetic antimicrobial activity was investigated and suggested for the treatment of seborrheic dermatitis (SD) and dandruff. The objective of this research was to establish and validate a specific, accurate, and precise gas chromatography-mass spectrometry (GC-MS) method for further quantitative and qualitative analysis in order to ensure quality control. The main parameters of validation were suitability, specificity, linearity, accuracy, and intermediate precision according to the European Pharmacopoeia (XI edition), Russian Pharmacopoeia (XIV edition), and some parameters of ICH requirements. The peaks of fifteen chemical phytoconstituents were identified in the test sample solution with the prevalence of (-)-α-bisabolol (27.67%), 1,8-cineole (25.63%), and terpinen-4-ol (16.98%). These phytochemicals in the novel substance were chosen for standardization and validation of the GC-MS method. The chosen chromatographic conditions were confirmed for testing of the plant-based substance in a suitability test. It was established that the GC-MS method provides a significant separation, symmetry of peaks and resolution between phytochemicals. The calibration curves of each phytochemical had good linearity (R2 > 0.999) in five concentrations. In the same concertation range, the accuracy of terpinen-4-ol, 1,8-cineol, and (-)-α-bisabolol determination using the method of additives was 98.3-101.60%; the relative standard deviation (RSD) ranged from 0.89% to 1.51% and corresponded to requirements. The intraday and interday precision was ≤2.56%. Thus, the GC-MS method was validated to be specific, sensitive, linear, accurate, and precise. This GC-MS method could be recommended as a routine analytic technique for multicomponent plant-based substances-enriched terpenes.
RESUMEN
Compounds bearing ortho-oriented dialkylamino and boryl groups can serve as efficient reagents to trap difluorocarbene leading to zwitterionic ammonium borates featuring N-CF2-B fragments. The reagents are shelf-stable and can be used as mechanistic probes for reactions proceeding via difluorocarbene.