Photochemical Initiation and Reactions of Thiyl Radicals Studied with S2' Radical Traps.

A radical trapping method based on an S2' homolytic substitution reaction was applied to study the mechanism of a photochemical spirocyclisation of indole-ynones in the presence of thiols. Starting material, products and a range of trapped radical intermediates were simultaneously detected in reaction mixtures by mass spectrometry (MS). The trapped intermediates included both initiating and main chain propagating radicals.

Mechanistic study of the atomic layer deposition of cobalt: a combined mass spectrometric and computational approach.

Cobaltcarbonyl--butylacetylene (CCTBA) is a conventional precursor for the selective atomic layer deposition of Co onto silicon surfaces. However, a limited understanding of the deposition mechanism of such cobalt precursors curbs rational improvements on their design for increased efficiency and tuneable selectivity. The impact of using a less reactive internal alkyne instead of a terminal alkyne was investigated using experimental and computational methods.

Enhanced Mechanistic Understanding Through the Detection of Radical Intermediates in Organic Reactions.

Two applications of a radical trap based on a homolytic substitution reaction (SH2') are presented for the trapping of short-lived radical intermediates in organic reactions. The first example is a photochemical cyanomethylation catalyzed by a Ru complex. Two intermediate radicals in the radical chain propagation have been trapped and detected using mass spectrometry (MS), along with the starting materials, products and catalyst degradation fragments.

OptiMS: An Accessible Program for Automating Mass Spectrometry Parameter Optimization and Configuration.

Mass spectrometers have an enormous number of user-changeable parameters that drastically affect the observed mass spectrum. Using optimal parameters can significantly improve mass spectrometric data by increasing signal stability and signal-to-noise ratio, which decreases the limit of detection, thus revealing previously unobservable species. However, ascertaining optimal parameters is time-consuming, tedious, and made further challenging by the fact that parameters can act dependently on each other.

Continuous addition kinetic elucidation: catalyst and reactant order, rate constant, and poisoning from a single experiment.

Kinetic analysis of catalytic reactions is a powerful tool for mechanistic elucidation but is often challenging to perform, limiting understanding and therefore development of these reactions. Establishing order in a catalyst is usually achieved by running several reactions at different loadings, which is both time-consuming and complicated by the challenge of maintaining consistent run-to-run experimental conditions. Continuous addition kinetic elucidation (CAKE) was developed to circumvent these issues by continuously injecting a catalyst into a reaction, while monitoring reaction progress over time.

Microstructural Analysis of Benzoxazine Cationic Ring-Opening Polymerization Pathways.

Herein, an evaluation of the initial step of benzoxazine polymerization is presented by mass spectrometry, with a focus on differentiating the phenoxy and phenolic products formed by distinct pathways of the cationic ring opening polymerization (ROP) mechanism of polybenzoxazine formation. The use of infrared multiple photon dissociation (IRMPD) and ion mobility spectrometry (IMS) techniques allows for differentiation of the two pathways and provides valuable insights into the ROP mechanism. The results suggest that type I pathway is favored in the initial stages of the reaction yielding the phenoxy product, while type II product should be observed at later stages when the phenoxy product would interconvert to the most stable type II phenolic product.

New Approach to the Detection of Short-Lived Radical Intermediates.

We report a new general method for trapping short-lived radicals, based on a homolytic substitution reaction S2'. This departure from conventional radical trapping by addition or radical-radical cross-coupling results in high sensitivity, detailed structural information, and general applicability of the new approach. The radical traps in this method are terminal alkenes possessing a nitroxide leaving group (, allyl-TEMPO derivatives).