In memory of Klaus Hafner.6-Halo-2-pyridones and their pyridol tautomers show different grades of polarization on their halogen substituents in DFT calculations. This and the fact that the tautomeric equilibrium is affected by the surrounding medium make them interesting candidates for a new platform of halogen bond donors. We therefore probed four simple halopyridones for their halogen bonding properties both in the solid state and in solution.Concurring with hydrogen bonding, halogen bonding indeed is found to be an interaction governing the packing motif in pyridone crystals, which is more pronounced in N-methylated congeners. Solution studies using a halide abstraction reaction, and NMR titrations against bromide salts, however, showed no clear evidence for halogen bonding in solution.[a] M.

The instrumental analysis of reaction mixtures is usually the rate-determining step in the optimization of chemical processes. Traditionally, reactions are analyzed by gas chromatography (GC), high-performance liquid chromatography (HPLC), or quantitative nuclear magnetic resonance (qNMR) spectroscopy on high-field spectrometers. However, chromatographic methods require elaborate work-up and calibration protocols, while high-field NMR spectrometers are expensive to purchase and operate. We herein disclose an inexpensive and highly effective analysis method based on low-field benchtop-NMR spectroscopy. Its key feature is the use of fluorine-labeled model substrates which, due to the wide chemical shift range and high sensitivity of 19F, enables separate, quantitative detection of product and by-product signals even on low-field, permanent magnet spectrometers. An external lock / shim device obviates the need for deuterated solvents, permitting the direct, non-invasive measurement of crude reaction mixtures with minimal work-up. The low field-strength allows a homogeneous excitation over a wide chemical shift range, minimizing systematic integration errors. The addition of the correct amount of the non-shifting relaxation agent Fe(acac)3 minimizes relaxation delays at full resolution, reducing the analysis time to 32 seconds per sample. The correct choice of processing parameters is also crucial. A step-by-step guideline is provided, the influence of all parameters is discussed, and potential pitfalls are highlighted. The wide applicability of the analytical protocol for reaction optimization is illustrated by three examples: a Buchwald-Hartwig amination, a Suzuki coupling, and a C–H functionalization reaction.

Unsaturated fatty acids are attractive alternatives to fossil‐based materials as a source of hydrocarbons, but potential applications are limited by the preset chain length of 16–20 carbon atoms. However, if the double bond can be randomly moved along the chain, subsequent bond‐breaking operations such as ethenolysis or oxidative cleavage will give rise to products with chain lengths ranging from 2 to 18 carbon atoms. A process for the double bond isomerization of rapeseed oil methyl esters in a flow‐through reactor using zeolites as the catalyst is herein disclosed. Using H‐mordenite as the catalyst at a flow of 0.125 mL min−1 at 290 °C, near equilibrium isomerization is reached with up to 49% recovery of linear monomeric products after 5 h and up to 44% after 48 h. The main side products are oligomers (3%–15%) and skeletal isomerization products (10%–23%). Practical applications: With a suitable follow‐up modification addressing the double bond (metathesis, ozonolysis, oxidative cleavage), the product mixtures of double‐bond positional isomers can be used in the production of short‐chain base chemicals. In repetitive combination with metathesis catalysis, biofuels with customized chain length distributions can be generated.