Integrating reaction and analysis: investigation of higher-order reactions by cryogenic trapping

Abstract

SummaryA new approach for the investigation of a higher-order reaction by on-column reaction gas chromatography is presented. The reaction and the analytical separation are combined in a single experiment to investigate the Diels–Alder reaction of benzenediazonium-2-carboxylate as a benzyne precursor with various anthracene derivatives, i.e. anthracene, 9-bromoanthracene, 9-anthracenecarboxaldehyde and 9-anthracenemethanol. To overcome limitations of short reaction contact times at elevated temperatures a novel experimental setup was developed involving a cooling trap to achieve focusing and mixing of the reactants at a defined spot in a fused-silica capillary. This trap functions as a reactor within the separation column in the oven of a gas chromatograph. The reactants are sequentially injected to avoid undefined mixing in the injection port. An experimental protocol was developed with optimized injection intervals and cooling times to achieve sufficient conversions at short reaction times. Reaction products were rapidly identified by mass spectrometric detection. This new approach represents a practical procedure to investigate higher-order reactions at an analytical level and it simultaneously provides valuable information for the optimization of the reaction conditions.

Ruthenium Nanoparticles in High‐Throughput Studies of Chemoselective Carbonyl Hydrogenation Reactions

“…These observations confirm that the selectivity and activity of the Ru nanoparticles is mainly based on their nature, size, and stabilization in the polymeric matrix. This makes our high‐throughput micro‐flow‐reactor system comparable with a classical batch reactor system and allows the fast reaction screening of various catalytic systems …”

“…This makes our high-throughput micro-flowreactors ystemc omparable with ac lassical batch reactor system and allowst he fast reactions creening of various catalytic systems. [10][11][12][13][14][15][16] We furtheri nvestigated the activity of the Ru nanoparticle system in various hydrogenation reactions and studied their reaction kinetics. Based on the Langmuir-Hinshelwood mechanism, we calculated the activation parameters DG°, DH°,a nd DS°as well as the reaction rate constants by using af irstorder reaction rate law.T he calculation was performedu sing temperature-dependent measurements.…”

“…In this study, we used our established strategy of on‐column reaction gas chromatography (ocRGC) to investigate in detail the dependence of the catalyzed reaction on the temperature, the pressure of the reactive carrier gas (H 2 ), the catalyst loading, and the length of the active catalyst capillary. The utilization of the chromatographic technique described here allows us to perform high‐throughput experiments and achieve the direct separation and quantification of the reaction mixture, which provides easy access to kinetic data and, therefore, improves our understanding of catalysis in quasi‐homogeneous systems . This experimental setup was already used by Trapp et al.…”

“…The utilization of the chromatographic technique described herea llows us to perform high-throughput experiments and achievet he direct separation and quantificationo ft he reactionm ixture, which provides easy access to kinetic data and, therefore, improves our understanding of catalysis in quasi-homogeneous systems. [10][11][12][13][14] This experimental setup was already used by Trapp et al for detailed studies of palladium. [15,16] There are various procedures to prepare, characterize,a nd apply Ru nanoparticles.…”

Comparison of a Molecular and an Immobilized Gadolinium(III)‐tris[(1R,4S)‐3‐heptafluorobutanoyl‐camphor] as Catalyst in the Asymmetric Danishefsky‐Hetero‐Diels‐Alder‐Reaction

“…[28][29][30][31][32][33] Thus, our intention of using immobilized catalysts is not only to recycle the material, but to create rapid screening platforms, 34 where catalysts are prepared by complexing metals to the immobilized ligand at an analytical level, which lowers costs in the highthroughput screening of new catalysts and reactions. [35][36][37][38][39]…”