Preparation, properties and applications of organosilicon peroxides

Water Microdroplets Surrounded by Alcohol Vapor Cause Spontaneous Oxidation of Alcohols to Organic Peroxides

Using real-time mass spectrometric (MS) monitoring, we demonstrate one-step, catalyst-free spontaneous oxidation of various alcohols (ROH) to key reactive intermediates for the formation of ROO- compounds on the surface of water microdroplets surrounded by alcohol vapor, carried out under ambient conditions. These organic peroxides (POs) can act as important secondary organic aerosols (SOA). We used hydrogen-deuterium exchange by spraying D2O instead of H2O to learn about the reaction mechanism, and the results demonstrate the crucial role of the water-air interface in microdroplet chemistry. We find that the formation of POs relies on electron transfer occurring at the microdroplet interface, which generates hydrogen atoms and hydroxyl radicals that lead to a cascade of radical reactions. This electron transfer is believed to be driven by two factors: (1) the emergence of a strong electrostatic potential on the microdroplet's surface; and (2) the partial solvation of ions at the interface. Mass spectra reveal that the formation of POs is dependent on the alcohol structure, with tertiary alcohols showing a higher tendency to form organic peroxides than secondary alcohols, which in turn are more reactive than primary alcohols.

Determination of silyl peroxides by ultra-performance liquid chromatography/electrospray ionisation mass spectrometry

RATIONALE

Residual initiators in polymers are a concern in the case of products that come directly into contact with the human body or food. Due to low concentrations and difficulties in the sample preparation, highly sensitive and selective methods are required.

METHODS

A series of bis-silyl- and alkyl-silyl peroxides were analysed by electrospray ionisation mass spectrometry (ESI-MS) on an ultra-performance liquid chromatography/time-of-flight (UPLC/TOF) instrument. Li, Na, K, and NH₄ acetates were used to promote the formation of [M + Me]⁺ ions. The sample preparation involved only dissolution of the polymer sample in 0.1 mL of acetonitrile, followed by precipitation with 1 mL of water. A portion of 0.1-1 μL of the solution was then analysed without further treatment by UPLC/ESI-MS.

RESULTS

Limits of detection (LODs) were in the range of 0.06-9 pmol, depending on the peroxide structure. On average, the signal intensity increased with the number of phenyl groups in a peroxide and decreased in the order Na > Li > K > NH₄ . Peroxides that did not contain phenyl groups could not be detected. Collision-induced dissociation experiments can be used for structural investigations of alkyl-silyl peroxides. It was possible to detect 2 × 10^-4 % (LOD = 7 × 10^-5 %) of unreacted Ph₃ SiOOt-Bu in the poly(methyl methacrylate) sample.

CONCLUSIONS

The method is suitable for the analysis of trace peroxide initiators in polymers and for other purposes where LODs in the pmol range are required.

Bis(trialkylsilyl) peroxides as alkylating agents in the copper-catalyzed selective mono-N-alkylation of primary amides

The copper-catalyzed selective mono-N-alkylation of primary amides with bis(trialkylsilyl) peroxides as alkylating agents was reported.

Autoxidation of Organoboranes and Related Organometallics: Radicals and their Ramifications

The identification, 50 years ago, of the autoxidation products of organoboranes as organoperoxyboranes, and of the mechanism of the reaction as a radical chain, has had far-reaching consequences in organometallic and organic chemistry in the identification of organic radicals and of other radical reactions, in the use of organoboron compounds in synthesis and catalysis, in the parallel chemistry of other metals (particularly, currently, of zinc), and of the behaviour of metals as hydrogen equivalents. This review traces the course of some of those developments in the radical chemistry of compounds in which oxygen forms a bond with boron and related metals, and summarises the present position.