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Peroxyesters decomposition

SCCO2 (full symbols) and of n-lieptane (open symbols) at 50 MPa and various temperatures. The ka data plotted for peroxyesters dissolved in SCCO2 are the experimental values provided by Earner [17]. The rate coefficients for peroxyester decomposition in n-heptane were calculated (for the same temperatures as those selected for the SCCO2 experiments) from the equations reported for kj in n-heptane as a function of pressure and temperature [12, 13]. The dashed lines represent these literature expressions for 50 MPa, whereas the full lines are Arrhenius fits of the measured kj data for decomposition in SCCO2. [Pg.59]

The results of the experimental kj studies into alkyl peroxyester decomposition in CO2 [17] may be summarized as follows at least at pressures up to 100 MPa, which range encompasses the entire area of technical relevance, kj values for peroxyester decomposition in SCCO2 differ by less than 20%, and mostly by less than 10%, from the associated values measured in n-heptane solution. A more detailed inspection of the data reveals that peroxyesters which undergo single-bond scission decompose faster in CO2, whereas, in the case of close-to-concerted two-bond scission, decomposition of the peroxyester seems to occur at a slightly slower rate in CO2 than in solution in n-heptane. [Pg.60]

Peroxyesters, particularly those with a-hydrogens or conjugated double bonds, are susceptible to iaduced decomposition under certain conditions, but they are generally less susceptible than diacyl peroxides. Lower molecular weight peroxyesters that have some water solubiUty can be hydroly2ed. [Pg.225]

Alkyl peroxyesters are much less sensitive to radical-induced decompositions than diacyl peroxides. Induced decomposition is only significant in peroxyesters containingnonhindered a-hydrogens or a, P-unsaturation (213,242). [Pg.130]

Acid-catalyzed, ionic decompositions have been reported for peroxyesters, RC(0)—OOR, in which the R group can form a particularly stable carbonium ion, eg, tropybum ion (213). [Pg.131]

The use of monomers that do not homopolymerize, eg, maleic anhydride and dialkyl maleates, reduces the shock sensitivity of tert-huty peroxyesters and other organic peroxides, presumably by acting as radical scavengers, that prevent self-accelerating, induced decomposition (246). [Pg.131]

The main industrial use of alkyl peroxyesters is in the initiation of free-radical chain reactions, primarily for vinyl monomer polymerizations. Decomposition of unsymmetrical diperoxyesters, in which the two peroxyester functions decompose at different rates, results in the formation of polymers of enhanced molecular weights, presumably due to chain extension by sequential initiation (204). [Pg.131]

The decomposition of peroxyesters has been shown to be strongly catalyzed by Cu(I). The process is believed to involve oxidation of the copper to Cu(II) ... [Pg.724]

Azo-compounds and peroxides undergo photodecomposition to radicals when irradiated with light of suitable wavelength. The mechanism appears similar to that of thermal decomposition to the extent that it involves cleavage of the same bonds. The photodecomposition of azo-compounds is discussed in Section 3.3.1.1.2 and peroxides in Sections 3.3.2.1.2 (diacyl peroxides) and 3.3.2.3.2 (peroxyesters). Specific photoinitiators are discussed in Section 3.3.4. It is also worth noting that certain monomers may undergo photochemistry and direct photoinitiation on irradiation of monomer is possible. [Pg.58]

The rates of decomposition of peroxyesters (38) arc very dependent on the nature of the substituents R and R. The variation in the decomposition rale with R follows the same trends as have been discussed for the corresponding diaeyl peroxides (see 3.3.2.1.1). [Pg.88]

The decomposition of the peroxyketals (53) follows a stepwise, rather than a concerted mechanism. Initial homolysis of one of the 0-0 bonds gives an aikoxy radical and an a-peroxyalkoxy radical (Scheme 3.36).306"08"210 This latter species decomposes by P-scission with loss of either a peroxy radical to form a ketone as byproduct or an alkyl radical to form a peroxyester intermediate. The peroxyester formed may also decompose to radicals under the reaction conditions. Thus, four radicals may be derived from the one initiator molecule. [Pg.91]

Aroyloxy radicals are formed by thermal or photochemical decomposition of diaroyl peroxides (see 3.3.2.1) and aromatic peroxyesters (3.3.2.3) (Scheme 3.78) alkoxycarbonyloxy radicals are similarly produced from peroxydicarbonates (33.2.2). [Pg.125]

Infrared measurement of additive concentrations is a more complex analysis than initially expected, as some additives may undergo a variety of chemical reactions during processing, as shown by Reeder et al. [128] for the FTIR analysis of phosphites in polyolefins. Some further examples of IR work refer to PVC/metal stearates [129], and PE/Santonox R [68,130]. Klingbeil [131] has examined the decomposition of various organic peroxyesters (TBPB, TBPP, TBPA and TBPO) and a peroxidicarbonate (BOPD) as a function of pressure, temperature and solvent by means of quantitative FTIR using an optical high p, T reaction cell. [Pg.318]

The peroxyester explodes with great violence when rapidly heated to a critical temperature. Previous standard explosivity tests had not shown this behaviour. The presence of benzene (or preferably a less toxic solvent) as diluent prevents the explosive decomposition, but if the solvent evaporates, the residue is dangerous [1], The pure ester is also shock-sensitive and detonable, but the commercial 75% solutions are not [2]. However, a 75% benzene solution has been exploded with a detonator, though not by mechanical shock [3],... [Pg.822]

When warmed slightly above its m.p., 10°C, the ester undergoes slow but self-accelerating decomposition, which may become dangerously violent under confinement. Bulk solutions of the peroxyester (45%) in benzene-cyclohexane stored at 5°C developed sufficient heat to decompose explosively after 1 day, and 50-90% solutions were found to be impact-sensitive [1]. The solid is normally stored and transported at below -18°C in loose-topped trays [2],... [Pg.1002]

Alkyl orthophosphate triesters, 79 41 terteAlkyl peroxycarbamates, decomposition of, 78 486 Alkyl peroxyesters, 78 478-487 chemical properties of, 78 480 487 physical properties of, 78 480 primary and secondary, 78 485 synthesis of, 78 478-480 synthetic routes to, 78 479 tert-Alkyl peroxyesters, 78 480 84, 485 as free-radical initiators, 74 284-286 properties of, 78 481-483t uses of, 78 487 Alkylperoxy radical, 74 291 Alkyl phenol ethoxylates, 8 678, 693 ... [Pg.34]

The CIEEL mechanism has been utilized to explain the catalyzed decomposition of several cyclic and linear peroxides, including diphenoyl peroxide (4), peroxyesters and 1,2-dioxetanones. Special interest has focused on this mechanism when it was utilized to explain the efficient excited state formation in the chemiexcitation step of the firefly s luciferin/luciferase bio luminescence. However, doubts have been voiced more recently about the validity of this mechanistic scheme, due to divergences about the... [Pg.1213]

Intensive studies in the field of mechanistic CL by several research groups have resulted in the description of a large variety of peroxides which, in the presence of appropriate activators, show decomposition in an activated CL process and might involve the CIEEL mechanism . Even before the formulation of the CIEEL mechanism, Rauhut s research group obtained evidence of the involvement of electron-transfer processes in the excitation step of the peroxyoxalate CL. Results obtained in the activated CL of diphe-noyl peroxide (4) led to the formulation of this chemiexcitation mechanism , and several 1,2-dioxetanones (a-peroxylactones), such as 3,3-dimethyl-l,2-dioxetanone (9) and the first a-peroxylactone synthesized, 3-ierr-butyl-l,2-dioxetanone (14), have been shown to possess similar CL properties, compatible with the CIEEL mechanism Furthermore, the CL properties of secondary peroxyesters, such as 1-phenethylperoxy acetate (15) , peroxylates (16) , o-xylylene peroxide (17) , malonyl peroxides... [Pg.1232]

During the decomposition of peroxyesters, large amounts of CO2 are formed. The value found for the activation volume can be considered when the mechanism of peroxide decomposition is discussed. The analysis of the gaseous decomposition products by gas chromatography shows large amounts of CO2, whose formation can take place during the decomposition. [Pg.79]

Complications arise in many of these decompositions because of other types of processes that can occur. There are, for example, heterolytic rearrangements of peroxyesters and diacyl peroxides (Equations 9.15 and 9.16), as well as base-catalyzed processes, for example Reaction 9.17. These reactions we mention only... [Pg.476]

For the dimethylamino-substituted peroxyester [29c] a third type of behavior is observed. The corrected chemiluminescence intensity obtained is independent of the structure of the activator. This is just what is expected for simple indirect chemiluminescence where the activator is excited by energy transfer from some first-formed singlet state. As indicated above, the initial excited state in this system is p-dimethylaminobenzoic acid. Evidently, the electron donating p-dimethylamino-substituent renders the peroxybenzoate [29c] sufficiently difficult to reduce that the value of k2 is so small that the bimolecular path is never able to compete successfully with unimolecular decomposition. [Pg.229]


See other pages where Peroxyesters decomposition is mentioned: [Pg.225]    [Pg.115]    [Pg.327]    [Pg.225]    [Pg.3926]    [Pg.881]    [Pg.225]    [Pg.115]    [Pg.327]    [Pg.225]    [Pg.3926]    [Pg.881]    [Pg.223]    [Pg.130]    [Pg.598]    [Pg.614]    [Pg.621]    [Pg.1530]    [Pg.33]    [Pg.685]    [Pg.17]    [Pg.329]    [Pg.697]    [Pg.329]    [Pg.697]    [Pg.1232]    [Pg.223]   
See also in sourсe #XX -- [ Pg.319 ]




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Peroxyesters

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