High pressure studies.  XV.  Effects in aliphatic perester decomposition

Neuman, Robert C.; Pankratz, Richard P.

doi:10.1021/ja00806a027

Cited by 13 publications

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“…Unfortunately, rate data for the pressure and temperature range as in the present study have only been reported for TBPD [14]. Comparison with the TBPiB data provided by Neuman und Pankratz [15] requires some extrapolation beyond the temperature range of the present study.…”

Section: Discussionmentioning

confidence: 80%

“…The pre-exponential is distinctly lower with the "tertiary" and "secondary" peroxyesters than with the "primary" TB peroxyesters. Literature data of activation energy are available for TBPProp [3,5], for TBPiB [15,16], and for TBPD [13,14]. Actually, in most cases activation enthalpies, ∆H ϶ , have been reported which are converted into activation energies, E A , according to the relation: E A ϭ ∆H ϶ ϩ RT.…”

Section: Peroxidementioning

confidence: 99%

“…Literature data for ∆V ϶ obs have been reported for TBPD [13,14] and for TBPiB [15] only. The ∆V ϶ obs value given by Luft et al for decomposition of TBPD in iso-dodecane is 6.1 cm 3 mol Ϫ1 [13].…”

Section: Plotted Inmentioning

confidence: 99%

“…It can not be ruled out that this discrepancy is due to the difference in solvent, although it is not overly likely that the minor solvent variation, iso-dodecane vs. n-heptane, may lead to a significant difference in ∆V ϶ obs . For TBPiB decomposition in cumene solution at 90°C, Neuman and Pankratz [15] report ∆V ϶ obs to be 1.6 cm 3 mol Ϫ1 at around 1000 bar and 3.2 cm 3 mol Ϫ1 in the pressure range 3000 to 5000 bar. The pressure-independent ∆V ϶ obs value of …”

Section: Plotted Inmentioning

confidence: 99%

“…The activation energy is reported to be close to 100 kJ mol Ϫ1 and the measured activation volume is around 6 cm 3 mol Ϫ1 with these parameters, however, being derived from a relatively small number of experiments. For TBPiB, rate coefficients as a function of pressure have been measured by Neuman and Pankratz [15] in cumene solution at 90°C. The activation volume is reported to be slightly pressure-dependent: ∆V ϶ obs ϭ 1.6 cm 3 mol Ϫ1 at 1000 bar and 3.2 cm 3 mol Ϫ1 at 5000 bar.…”

Section: Introductionmentioning

confidence: 99%

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Pressure and Temperature Dependence of the Decomposition Rate of Aliphatic tert-butyl Peroxyesters

Buback¹,

Sandmann²

2000

Zeitschrift Für Physikalische Chemie

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Peroxides / Chemical Kinetics / Spectroscopy, Infrared / High PressureThe thermal decomposition in solution of n-heptane of several aliphatic tert-butyl peroxyesters RC(O)OOTB : TB peroxypropionate, TB peroxy-n-butyrate, TB peroxy-iso-butyrate, TB peroxy-2-methylbutyrate, TB peroxy-2-ethylhexanoate, TB peroxy-3,5,5-trimethylhexanoate, and TB peroxy-neo-decanoate has been investigated at pressures up to 2500 bar and temperatures up to 185°C. The experiments were carried out in a tubular reactor at residence times up to 140 s. Peroxide concentration was monitored via quantitative FT-IR spectroscopic analysis of the pressurized medium under continuous flow conditions. For each peroxide first-order decomposition kinetics were observed over several half-lives. The type of carbon atom (in the R moiety) that is in A-position to the carbonyl group controls decomposition kinetics. The observed first-order rate coefficient, k obs , is smallest in situations where this particular C-atom is primary and is largest when it is tertiary. The "primary" TB peroxyesters are associated with the higher activation energies, around 145 kJ mol Ϫ1 . The activation energies, EA, of the "tertiary" and "secondary" TB peroxyesters are around 120 und 130 kJ mol Ϫ1 , respectively, with the individual EA's being proportional to the stability of the particular free-radical species Rᠨ. The activation volumes, ∆V ϶ obs , of the "secondary" and "tertiary" TB peroxyesters are in the narrow range 3.0 Ϯ 1.5 cm 3 mol Ϫ1 . ∆V ϶ obs of the "primary" TB peroxyesters is above 10 cm 3 mol Ϫ1 and, in addition, is slightly pressure-dependent. Both observations demonstrate that the "primary" aliphatic TB peroxyesters decompose via single-bond scission with this result being supported by modelling dissociation dynamics in the compressed fluid state. The "secondary" and "tertiary" TB peroxyesters decompose via concerted two-bond scission associated with the immediate formation of CO 2 . These results are fully consistent with evidence from the literature and from our preceding detailed study into TB peroxyacetate and TB peroxypivalate dissociation kinetics. The mode of primary bond dissociation, via single-bond or via concerted two-bond scission, largely affects the initiation efficiency of TB peroxyesters in free-radical polymerization. For each TB Brought to you by | provisional account Unauthenticated Download Date | 6/25/15 4:48 PM 584 M. Buback and J. Sandmann peroxyester, rate expressions for k obs (p,T ) are presented. This data for decomposition in compressed n-heptane should be highly suitable for simulation and optimization of technical high-pressure polymerization processes.

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Section: Discussionmentioning

confidence: 80%

Section: Peroxidementioning

confidence: 99%

Section: Plotted Inmentioning

confidence: 99%

Section: Plotted Inmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Pressure and Temperature Dependence of the Decomposition Rate of Aliphatic tert-butyl Peroxyesters

Buback¹,

Sandmann²

2000

Zeitschrift Für Physikalische Chemie

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Organische Peroxide, XIX. Zur Frage der Stabilität und Reaktivität von Kohlenstoffradikalen

1975

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Aryl-, Alkyl-, Cycloalkyl-, Polycycloakyl-und Benzyl-Radikale wurden aus PerGureestern 1 oder (Ary1azo)triphenylmethan durch Thermolyse in CC14/BrCC13 erzeugt; ihre Selektivitat bei der konkurrierenden Halogenubertragung von BrCCl, und CC14 wurde durch gaschromatographische Produktanalyse bestimmt. Die Konkurrenzkonstanten r sinken in der Reihe Benzyl-> Alkyl-> Aryl-> Briickenkopf-Radikal, wofur das Selektivitiitsprinzip verantwortlich gemacht wird.Sterische und polare Effekte besinflussen die Konkurrenzkonstanten ebenfalls deutlich. Es besteht keine einfache Beziehung zwischen der Bildungsgeschwindigkeit der Radikale aus den Perestern und ihrer Selektivitat. -Der Anteil an Kafigrekombination bei der Thermolyse von Cycloalkanpercarbonsaureestern mit 5 -12 Ringgliedern sinkt parallel mit zunehmender Masse dcr beteiligten Radikale. Organic Peroxides, XIX') Relations between Stability and Selectivity of CarbonAryl, alkyl, cycloalkyl. polycycloalkyl, and benzyl radicals were generated by thermolysis of peresters 1 or (ary1azo)triphenylmethanes in CC14/BrCC13. The selectivity of the competing halogen transfer from BrCCl, and C C 4 was determined by gaschromatography of the products. The selectivity relationship lo) is made responsible for the decreasing of the competition constants r in the series benzyl > alkyl > aryl > bridgehead radicals. In addition steric and polar effects determine the size of the competition constants. No relationship is recognized between the rate of radical production from peresters 1 and their selectivity. -The yields of cage recombination product in the thermolysis of tert-butyl cycloalkanepercarboxylates (n = 5 -12) in CC14 decrease regularly with increasing mass of the cycloalkyl radicals. I) Diese Aussage ist in der Polanyi-Evans-Beziehung zwischen Aktivierungsenergie und Reaktionsenthalpie enthalten. M. G. Evans und M . Polmlyi, Trans. Faraday SOC. 34. 1 1 (1938); J . A. Kerr, Chem. Rev. 66,465 (1966). ' ) '*) R. S. Davidson, Quart. Rev. 1%7, 249. -6b) A . A . Zavitsas und J . A . Pinto, J. Amer. Chem. Soc. 94, 7390 (1972), und zit. Lit. -") W A . Pryor, W H . Davis und J . P . Stanley, ebenda 95, 4754 (1973). -6d) J . A. Howard und J . H . B. Chenier, ebenda 95,3054 (1973). -R. C. Neumann und R. P. Pankratz, ebenda 95, 8372 (1973). -" I J . P. Engstrom und J . C . Du Bose, J. Org. Chem. 38, 3817 (1973). -6g)

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Organische Peroxide, XXI. Zum Käfigeffekt bei der Peresterfragmentierung

Rüchardt

Grundmeier

1975

Chem. Ber.

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Die Ausbeute an substituierten Benzyl-terr-butyllthern 3ai, den Produkten der Kafigrekombination bei der Thermolyse substituierter Phenylperessigsaure-tert-butylester 1 ai in n-Octan wird durch Substituenten in o-und p-Stellung nur geringfugig beeinfluBt. Bei Solvensvariation steigt die Ausbeute an 3 mit der Viskositiit des Solvens, aber weitgehend unabhangig von dessen Natur entsprechend den von Noves und Koenig abgeleiteten Beziehungen an. Auch bei der Thermolyse der Phenylperessigsaure-tert-alkylester 4a -f andert sich der Anteil der Kafigrekombination kaum. Die Perester 4b -e zerfallen konkurrierend homolytisch und heterolytisch. Der Anteil der beiden Zerfallswege lien sich durch kinetische Radikalabfangversuche und quantitative Produktanalysen bestimmen. Elektronische und sterische Effekte haben in den untersuchten Beispielen keinen wesentlichen EinfluC auf die Radikalrekombinationsrate. Organic Peroxides, XXI')The Cage Effect in Homolytic Perester Fragmentations2)The yields of substituted benzyl tert-butyl ethers 3a -i obtained as products of cage recombination in the thermoiysis of substituted tert-butyl phenylperacetates 1 a -i in n-octane depend only little on the substitution pattern of the phenyl ring. The influence of solvent variation on the yields of 3 is determined mainly by solvent viscosity according to the equations of Noyes and Koenig, and only to a minor degree by the nature of the solvent. The proportion of cage recombination in the homolytic fragmentation of tert-alkyl phenylperacetates 4a -f is also quite independent of the tert-alkyl group. The peresters 4be decompose competitively in homolytic and heterolytic fashion. Therefore radical counting experiments and quantitative product analyses were required for obtaining a quantitative estimate of the cage effect. The rate ofcage recombination of tert-alkoxy-benzyl radical pairs proved to be quite independent of steric and electronic effects.Zu den schnellsten Reaktionen organischer Radikale zahlt ihre Dimerisierung, deren Geschwindigkeit in Losung oft durch die Geschwindigkeit der Diffusion gesteuert wird 4. 5 ) . Wahrend in neuerer Zeit absolute Geschwindigkeitskonstanten der Reaktionen zweier Radikale rniteinander in groI3erer Zahl bekannt wurden 4 * ' ), diskutierte man den EinfluB d e r Struktur auf die Dimerisierung lange ausschlieDlich anhand der Konkurrenz von ') XX. Mitteil.: H. Lanqhals und C. Riichardr, Chem. Ber. 108, 2156 (1975. 2' Aus der Dissertation M. Grundmeier, Univ. Munster 1972.

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High pressure studies. XV. Effects in aliphatic perester decomposition

Cited by 13 publications

References 9 publications

Pressure and Temperature Dependence of the Decomposition Rate of Aliphatic tert-butyl Peroxyesters

Pressure and Temperature Dependence of the Decomposition Rate of Aliphatic tert-butyl Peroxyesters

Organische Peroxide, XIX. Zur Frage der Stabilität und Reaktivität von Kohlenstoffradikalen

Organische Peroxide, XXI. Zum Käfigeffekt bei der Peresterfragmentierung

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