Although the number of natural fluorinated compounds is very small, fluorinated pharmaceuticals and agrochemicals are numerous. 19F NMR spectroscopy has a great potential for the structure elucidation of fluorinated organic...

No abstract

19F is the focal point of broadband, phase-sensitive 2D NMR experiments that provide 1H, 13C and 19F chemical shifts, values of JHF, JHH, and JFC coupling constants and 13C-induced 19F isotopic shifts to elucidate structures of fluorinated molecules.

To understand peatland carbon-cycling processes ultimately requires the ability to track changes occurring on the molecular-level. In this study, we profile a peat core taken from the world’s largest blanket bog, Flow Country, Scotland, using physicochemical properties, ATR-FTIR, solid/liquid-state NMR, and solid/liquid-state FT-ICR-MS. Air-dried peat and labile and recalcitrant peat extracts, including pore water dissolved organic matter (PW-DOM), are analyzed and the merits of each technique are discussed. Solid-state NMR demonstrated changing distribution of compound classes with core depth and water table, the latter not picked up by IR. Liquid-state NMR and MS both demonstrated variations in molecular composition along the core depth in all phases and extracts. Contrary to previous reports, the composition of PW-DOM varied with depth. Major compounds, some previously unreported, identified by 1D/2D NMR occurred throughout the core, suggesting the existence of hot spots of microbial activity/compound accumulation. Offering complementary views, the techniques provided evidence of gradual molecular level changes with age, zonation due to the water table, and hot spots due to microbial activity. This study provides new insights into the molecular signatures of peat layers and establishes the foundation for examining peat function and health at the molecular-level.

Natural organic matter (NOM) is the product of microbial and abiotic decay of plant and animal remains in terrestrial and aquatic ecosystems. On a molecular level, NOM is a complex mixture of organic molecules, of which the vast majority of structures are unknown. By identifying these molecules, our understanding of the many functions of NOM could be greatly enhanced. However, given that they are chromatographically inseparable and number in the thousands, traditional analytical techniques have proven unable to achieve this goal. A promising approach to enumerate functional groups and elucidate molecular structures within NOM is based on a combination of molecular tagging and high resolution spectroscopic techniques, such as nuclear magnetic resonance spectroscopy and mass spectrometry. Molecular tagging involves the selective modification of particular functional groups, inserting nuclei to act as reporters on their surrounding chemical environment. This allows examination of only the tagged molecules within NOM, thereby reducing the complexity of the mixture. In this review, the effectiveness of molecular tagging methods incorporating carbon, silicon, nitrogen, phosphorus, and deuterium into NOM are discussed. Some potential tagging methods which have not yet been applied to NOM are also presented.