We report findings from the qualitative evaluation of nuclear magnetic resonance (NMR) reaction monitoring techniques of how each relates to the kinetic profile of a reaction process. The study highlights key reaction rate differences observed between the various NMR reaction monitoring methods investigated: online NMR, static NMR tubes, and periodic inversion of NMR tubes. The analysis of three reaction processes reveals that rates derived from NMR analysis are highly dependent on monitoring method. These findings indicate that users must be aware of the effect of their monitoring method upon the kinetic rate data derived from NMR analysis. Copyright © 2015 John Wiley & Sons, Ltd.

This Letter describes the development of a method for the Pd-catalyzed electrochemical acetoxylation of C–H bonds. The oxidation step of the catalytic cycle is probed through cyclic voltammetry and bulk electrolysis studies of a pre-formed palladacycle of 8-methylquinoline. A catalytic system for C–H acetoxylation is then developed and optimized with respect to the cell configuration, rate of oxidation, and chemistry at the counter electrode. This transformation is then applied to substrates containing various directing groups and to the acetoxylation of both C(sp2)–H and C(sp3)–H bonds.

Permeability development in magmas controls gas escape and, as a consequence, modulates eruptive activity. To date, there are few experimental controls on bubble growth and permeability development, particularly in low viscosity melts. To address this knowledge gap, we have run controlled decompression experiments on crystal-free rhyolite (76 wt. % SiO 2 ), rhyodacite (70 wt. % SiO 2 ), K-phonolite (55 wt. % SiO 2 ) and basaltic andesite (54 wt. % SiO 2 ) melts. This suite of experiments allows us to examine controls on the critical porosity at which vesiculating melts become permeable. As starting materials we used both fine powders and solid slabs of pumice, obsidian and annealed starting materials with viscosities of ~10 2 to ~10 6 Pa s. We saturated the experiments with water at 900˚ (rhyolite, rhyodacite, and phonolite) and 1025˚C (basaltic andesite) at 150 MPa for 2-72 hours and decompressed samples isothermally to final pressures of 125 to 10 MPa at rates of 0.25-4.11 MPa/s. Sample porosity was calculated from reflected light images of polished charges and permeability was measured using a bench-top gas permeameter and application of the Forchheimer equation to estimate both viscous (k 1 ) and inertial (k 2 ) permeabilities. Degassing conditions were assessed by measuring dissolved water contents using micro-Fourier-Transform Infrared (-FTIR) techniques.All experiment charges are impermeable below a critical porosity ( c ) that varies among melt compositions. For experiments decompressed at 0.25 MPa s -1 , we find the percolation threshold for rhyolite is 68.3 ± 2.2 vol.%; for rhyodacite is 77.3 ± 3.8 vol.%; and for K-phonolite is 75.6 ± 1.9 vol.%. Rhyolite decompressed at 3-4 MPa s -1 has a percolation threshold of 74 ± 1.8 vol.%. These results are similar to previous experiments on silicic melts and to high permeability thresholds inferred for silicic pumice. All basaltic andesite melts decompressed at 0.25 MPa s -1 , in contrast, have permeabilities below the detection limit (~10 -15 m 2 ), and a maximum porosity of 63 vol.%. Additionally, although the measured porosities of basaltic andesite experiments are ~10-35 vol. % lower than calculated equilibrium porosities, -FTIR analyses confirm the basaltic andesite melts remained in equilibrium during degassing. We show that the low porosities and permeabilities are a consequence of short melt relaxation timescales during syn-and post-decompression degassing. Our results suggest that basaltic andesite melts reached  c > 63 vol. % and subsequently degassed; loss of internal bubble pressure caused the bubbles to shrink and their connecting apertures to seal before quench, closing the connected pathways between bubbles. Our results challenge the hypothesis that low viscosity melts have a permeability threshold of ~30 vol. %, and instead support the high permeability thresholds observed in analogue experiments on low viscosity materials. Importantly, however, these low viscosity melts are unable to maintain high porosities once the percolation threshold is ...

Awareness of best safety practices in the industrial sector will allow students in chemistry and chemical engineering programs to apply these approaches to their own safety assessments. Process safety is a critical function within the pharmaceutical industry to ensure safety when performing reactions. An introduction to process safety and a series of case studies illustrating how safety is routinely considered within the pharmaceutical industry is presented. The concepts presented herein are applicable to multiple industries, academic research, and chemical reactions conducted on all scales. The case studies include examples where a synthesis was redesigned to afford a triazole intermediate without forming potentially explosive byproducts, an exothermic reaction was controlled by understanding the heat output with time and developing a portion-wise addition procedure, and a reaction that displayed extremely fast gas evolution was managed by using an alternative solvent and controlling the rate of reagent addition.