The Kinetics of the Thermal Decomposition of Peresters. III. The Effect of p-Substituents on the Unimolecular Decomposition of t-Butyl Perbenzoates<sup>1</sup>

Blomquist, A. T.; Berstein, I.A.

doi:10.1021/ja01156a009

Cited by 51 publications

(25 citation statements)

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“…Thus our value of 1.3 for the 711 rate ratio at 100" agrees well with the reported values of 1. I (at 13 1 ") and 1.4 (at 100") (14). This enhancement is apparently due to a subtle electronic factor, in which the ground state is either destabilized by electron-donating substituents (this argument is given in ref.…”

Section: Discussionmentioning

confidence: 99%

“…The mixture was stirred 24 h at 25" and was then poured into water and extracted four times with ether and the combined ether layers were washed first with water, then four times with 10% NaOH, and twice with 4These authors also report a moderately greater tendency for decarboxylation of the o,o1-dimethylbenzoyloxy radical, indicating some stabilization of the benzoyloxy radical by conjugation involving the ring. tert-Butyl Permesitoate (8) This was prepared by a procedure analogous to that for 9 and was obtained as a colorless oil after chromatography on Florisil with pentane-chloroform: i. tert-Butyl Pertoluate (7) (14) This was prepared by an analogous procedure.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The decomposition of a series of tert-butyl p-substituted perbenzoates was correlated with o values with p = -0.68 (14). The lower reactivity of the peresters substituted with more electron-withdrawing substituents was attributed (14) to a greater ground state bond strength due to enhanced resonance contributions of the ionic structure with an electron-deficient benzoyloxy group (5). Ortho substituents in aryl peresters (6,15,16) and diacyl peroxides (17) invariably cause enhanced reactivity, however, and these effects are as large as lo6 for highly polarizable substituents such as iodine and sulfur.…”

Section: Introductionmentioning

confidence: 99%

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Steric Crowding and the Reactivity of Substituted tert-Butyl Perbenzoates

Icli¹,

Kandil²,

Thankachan³

et al. 1975

Can. J. Chem.

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SIDDICK ICLI, UNDIL A. KANDIL, C. THANKACHAN, and THOMAS T. TIDWELL. Can. J. Chem. 53,979 (1975).The relative rates of decomposition of peroxyesters in cumene at 100" and their activation parameters AH* (kcal/mol) and ASf (cal deg-I mol-') were tert-butyl perbenzoate (1) 1.0, 34.0, 9.3; tert-butyl pertoluate (7) 1.3, 32.2, 4.8; tert-butyl permesitoate (8) 11, 31.9, 8.4; and tert-butyl2,4,6-tri-tert-butylperbenzoate (9) 29, 32.9, 13.0. Each peroxyester yielded the corresponding acid as one of the products. The reactions are all interpreted as proceeding through a rate-determining scission of the 0-0 bond to yield a benzoyloxy radical, which then undergoes competitive decarboxylation and hydrogen abstraction from the solvent. The small rate acceleration due to apara substituent is interpreted as due to a polar factor and the larger rate enhancing effect of the ortho substituents is interpreted as due to destabilization of the ground state due to twisting of the carboxyl group out of conjugation with the ring. perbenzoate de tert-butyle (9) 29, 32.9, 13.0. Chaque peroxyester conduit entre autre ii l'acide correspondant. On interprete toutes les reactions en fonction d'une Ctape dkterminante de la reaction qui impliquerait la scission du lien 0-0 conduisant au radical benzoyloxy qui subirait ensuite une decarboxylation ou enleverait un hydrogene du solvant. On attribue la petite augmentation de vitesse due ii un substituant en para a des facteurs polaires; par ailleurs l'augmentation importante observee lorsqu'il y a des substituants en position ortho implique une dtstabilisation de 1'6tat fondamental due ii une rotation du groupement carboxyle hors du plan de conjugaison du cycle.[Traduit par le journal]

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Steric Crowding and the Reactivity of Substituted tert-Butyl Perbenzoates

Icli¹,

Kandil²,

Thankachan³

et al. 1975

Can. J. Chem.

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“…Suppose that the reaction can be described bv qg=qm "mo=Cmo(1 _~)n exp {--R~T) (6) A convenient method is to take a value for n and to check after that if the experimental set of (T 1, qg, ~) values obey equation (6). This procedure is repeated until In{qg 9 (1 _~)-n} becomes a linear function of Tll.…”

Section: Thermal Runawaymentioning

confidence: 99%

Thermal runaway in the thermal explosion of a liquid

Verhoeff

Berg

1984

Journal of Thermal Analysis

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To study the thermal explosion of liquids a low pressure autoclave has been built. The first stage of a thermal explosion, the thermal runaway, has been studied. Evaluation of the temperature-time history results in kinetic data. Comparison with other thermal methods shows that the reliability of the method is better than with DTA.Tertiary butylperoxybenzoate has been investigated in the temperature range of 330 K to 440 K. Decomposition starts with a short period of autocatalysis, up to a conversion of about 0.05. The subsequent deco#nposition can be described by a second order process in the first instance and by a first order process in the last resort. Induced decomposition occurs up to a conversion of about 0.95.The description of exploding liquids is usually based on detonation or deflagration. However, many liquids do not detonate when shocked by an explosive and do not deflagrate when ignited by a flame. Yet an explosion can occur after a prolonged period of heating. This is called thermal explosion and is characterized by a considerable degree of self-heating or thermal runaway of the liquid before the larger part of the explosion energy is released. Actually an explosion comparable to a deflagration or detonation does not occur until after a drastic change in the physical state of the liquid by the thermal runaway process.The theory of thermal explosion [1][2][3] is concerned with the competition between heat generation of the reacting system and heat dissipation by conduction, convection and radiation from the reacting mass to the outside. The tendency of the reacting system to rise above the ambient temperature due to self-heating is opposed by both the heat transfer to the surroundings and the heat consumption of the reactant. It is worth noting here that the thermal explosion theory tries to account for the onset of the explosive behaviour of energetic substances during storage or during batch-wise operation. Hence, a continuously stirred tank reactor is not considered.To evaluate the temperature-time history for a thermal explosion and to gather reaction kinetic data a low pressure autoclave has been built. Tertiary butyl peroxybenzoate (TBPB) has been chosen as a model substance [4].

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