Dialkyl peroxides, cyclic

Photochemical synthesis of sulphoxides was reported for the first time by Foote and Peters111 in 1971. They found that dialkyl sulphides undergo smoothly dye-photosensitized oxidation to give sulphoxides (equation 32). This oxidation reaction has been postulated to proceed through an intermediate adduct 63, which could be a zwitterionic peroxide, a diradical or cyclic peroxide, which then reacts with a second molecule of sulphide to give the sulphoxide (equation 33). 

CYCLIC PEROXIDES, DIACYL PEROXIDES DIALKYL PEROXIDES, Z, /-DI(BENZOYLPEROXY)ARYLIODINES DIFLUOROAMINO COMPOUNDS, DIFLUOROAMINOPOLYNITROAROMATIC COMPOUNDS... 

In this Section, we will focus on acyclic dialkyl hydroperoxides and we will not discuss cyclic peroxides. Dioxiranes are discussed in Chapter 14 and dioxetanes in Chapter 15 of this book. 

The dialkyl denomination also includes cyclic peroxides (endoperoxides). The most significant route for peroxide formation is probably that of autoxidation of organic materials, leading to their gradual degradation. Although hydroperoxides are the main products of this process, also peroxyesters are formed, as is the case, for example, of isoprostane bicyclic endoperoxides (25) mentioned in Section II.A.2.C. 

BusSnOOSnBus reacts with alkyl triflates to give symmetrical dialkyl peroxides, and with alkyl bistriflates to give 5-8 membered cyclic peroxides" , but no dialkyl peroxide is produced from f-butylperoxytrimethylsilane. Similarly, symmetrical dialkyl peroxides... 

The allyloxy radicals generated from hydroperoxide, dialkyl peroxide and cyclic peroxide intermediates, in accordance with Reactions 6, 9, and 10, respectively, are converted to allyl alcohol moieties, as shown in Reaction 7. The latter are particularly susceptible to reaction with hydrogen chloride. 

Thus, reactions of carbonyl compounds with hydrogen peroxide and acids lead to products similar to those obtained by the ozonization of olefins (Section III), which also yields 1,2,4-trioxolans and 1,2,4,5-tetroxans. The similarity of the two reactions is understandable, since the intermediates )C+—OO- in the ozonization27a and )C+—OOH in the hydrogen peroxide reactions are related as a conjugate base-acid pair. A number of cyclic peroxides of structure 7 are prepared from bis(hydroperoxy)dialkyl peroxides (5) by reaction with lead(IV) acetate, as described by Criegee et al.la This reaction is also thought to involve a carbonium ion intermediate,31 which reacts with the second OOH group. 

Dialkyl peroxides have the stmctural formula R—OO—R/ where R and R are the same or different primary, secondary, or tertiary alkyl, cycloalkyl, and aralkyl hydrocarbon or hetero-substituted hydrocarbon radicals. Organomineral peroxides have the formulas R Q(OOR) and R QOOQR, where at least one of the peroxygens is bonded directly to the organo-substituted metal or metalloid, Q. Dialkyl peroxides include cyclic and bicycflc peroxides where the R and R groups are linked, eg, endoperoxides and derivatives of 1,2-dioxane. Also included are polymeric peroxides, which usually are called poly(alkylene peroxides) or alkylene—oxygen copolymers, and poly(organomineral peroxides) (44), where Q = As or Sb. 

The alkenyl hydroperoxides and polymeric dialkyl peroxides are fairly stable at ambient temperature but decompose appreciably at the reaction temperatures studied. Thermal stabilities of the alkenyl hydroperoxides and dialkyl peroxides in the olefin solution were determined by heating the solution at 110°C. under nitrogen. The peroxide numbers were plotted vs. time to estimate the half-lives in solution. The thermal decomposition half-lives of these alkenyl hydroperoxides are compared with values from the literature for acyclic and cyclic hydroperoxides in Table IV. Secondary acyclic alkenyl hydroperoxides appear to be less... 

Peroxides in ether solvents. This is one of the commonest causes of explosions in organic chemistry laboratories. Simple dialkyl ethers such as diethyl ether and di-isopropyl ether, and cyclic ethers such as 1,4-dioxane and tetrahydrofuran, form less volatile peroxides on exposure to air and light. If therefore one of these solvents is purified by distillation, the peroxide content in the residue is progressively increased and eventually a violent explosion may occur. In view of this (i) such solvents should not be stored for long periods or in half empty bottles containers should be of dark glass (ii) before the solvents are distilled a peroxide test should be carried out, and, if positive, the peroxide must be removed (Section 4.1.11, p. 402 and Section 4.1.75, p. 404) and (iii) since purified ethers in contact with air rapidly peroxidise again (10 minutes in the case of tetrahydrofuran) they should be retested for peroxides and purified if necessary immediately before use. 

The scope of the transphosphoranylation reaction is enlarged by the availability of cyclic oxyphosphoranes (99) from the reaction of phosphites with certain dialkyl peroxides.14 Several cyclic and acyclic... 

This chapter deals with the formation and behavior of peroxides in which the 0—0 group forms part of a ring. The most important of these heterocycles are peroxides of carbonyl compounds, which may also contain two or three peroxy groups in the same ring ozonides, which are also peroxides of carbonyl compounds, i.e., peroxidic acetals and endoperoxides, as cyclic dialkyl peroxides. 

Only a few cyclic dialkyl peroxides have been prepared by reaction with hydrogen peroxide. The large class formed by the endoperoxides, most of which are prepared by diene synthesis with oxygen, is discussed in Section IV. 

Some attention has been given to the effect of substituents upon the kinetics of dialkyl peroxide decomposition. The data are presented in Table 67. A linear enthalpy-entropy of activation correlation was made for the decomposition of alkyl peroxides (exclusive of the hydroxyalkyl peroxides) using data in solution and in the gas phase. The isokinetic temperature was found to be 483 °K (210 °C) . No rational explanation was advanced for the substituent effects in solution or the gas phase . However, the discussion of the effect of a chain reaction upon the activation parameters, given in the section on gas phase reactions, should be consulted. The large differences in and log A between the alkyl and the hydroxyalkyl peroxides suggests a change in mechanism. This is supported by the products from the hydroxyalkyl peroxides. A cyclic activated complex was suggested , viz. 

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