Der Mechanismus der Alken‐Ozonolyse – eine kritische Betrachtung

Abstract

The Mechanism of Alkene Ozonolysis ± a Critical Examination Alkene ozonolyses have been carried out in experimental organic chemistry for more than a century, and a lucid description of the underlying reaction mechanism has been developped and integrated in most chemistry textbooks. Nevertheless, there are a great number of exceptions hard to rationalize by the accepted mechanism. Attempts in the past to give more-convincing answers to this problem failed. Therefore, the search for an alternative mechanistic model without contradictions is compelling. The present paper offers a redox model based upon the known properties of ozone both as a strong oxidant and an O-atom-transferring agent, especially when reacted with alkenes of sufficiently high electron density to act as reducing partners. Harries

Guiding the synthesis of pentazole derivatives and their mono- and di-oxides with quantum modeling

“…18 The main proposed mechanism involves as first step a 1,3-dipolar cycloaddition of ozone with the unsaturated bond leading to cyclic C 2 O 3 ozonide. 19 Such a pathway has been searched for starting from 1 but also with the N 5 ring, as indicated by its position above the ring. Final dissociation of 1-PC to form the target product 2 may be accompanied by stabilization of dioxygen to its triplet ground state, leading to a high reaction exothermicity (200 kJ/mol at the B3LYP level).…”

“…18 The main proposed mechanism involves as a first step a 1,3-dipolar cycloaddition of ozone with the unsaturated bond leading to cyclic C 2 O 3 ozonide. 19 Such a pathway has been searched for starting from 1 and 3, however no intermediate including a N 2 O 3 ring could be obtained. Such structures lead in all cases either to separated reactants O 3 and 1/3, or to the disruption of the N 5 ring.…”

“…Scheme 2 Other compounds derived from pentazoles (9-17) and tetrazoles(18)(19)(20)(21)(22)(23) studied in this work.…”

Non-Catalytic Oxidative Desulfurization of Diesel Oil Using Ozone in a Biphasic Oil/Acetonitrile System

“…The oxidation product of BT turned out to be 2-mercaptobenzaldehyde, while the oxidation products of DBT and 4,6-DMDBT were their corresponding sulfones (Figure 4). The oxidation of BT seems to be much like alkene ozonolysis (Schank, 2004), while the ozone oxidation of DBT and DMDBT could be electrophilic reactions, in which the sulfur atom was attacked by ozone to generate the corresponding sulfone. Therefore, the higher reactivity of BT than DBT in the ozone oxidation system was due to their different reaction mechanisms.…”

Dipolar 1,3‐cycloaddition of thioformaldehydeS‐methylide (CH2SCH2) to ethylene and acetylene. A comparison with (valence) isoelectronicO3,SO2,CH2OOandCH2SO

“…Ozonolysis represents one of the most important oxidation reactions of species with unsaturated bonds, 24–26 which are key processes for both organic synthesis 27 and materials chemistry 28 . Nearly all the proposed mechanisms for this reaction involve the initial rate determining 1,3‐dipolar cycloaddition of ozone to the double or triple bond, forming primary ozonides 29 . The description of reactions involving ozone is complicated by its diradical character, which has been estimated around 33% by natural orbital occupation and generalized valence bond (GVB) computations 30–32 .…”