Thermochemical Kinetics of Nitrogen Compounds. Part 4. The gas phase unimolecular thermal decomposition of triallylamine

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The kinetics of the thermal decomposition of diallylamine to propylene and prop-2-enaldimine have been studied in the gas phase in presence of an excess of methylamine over the temperature range of 532.7 to 615.6"K, using a static reaction system. Methylamine reacted with the unstable primary product prop-2-enaldimine, forming the thermally stable N-methyl prop-2-enaldimine.First-order rate constants, based on the internal standard technique, fit the Arrhenius relationship log kfs-1) = (1 1.04 f 0.13) -(37.1 1 f 0.33 kcal/mole)/2.303 RT. They were independent on the initial total pressure (46-340 torr), the initial pressure of diallylamine (9.2-65 torr), or methylamine as well as the conversion attained. Despite an apparent surface sensitivity, the reaction is essentially homogeneous in nature as demonstrated by experiments carried out in a packed reaction vessel. The observed activation parameters for the title reaction together with those observed earlier for triallylamine and allylcyclohexylamine are consistent with the proposed concerted reaction mechanism involving a cyclic 6-center transition state. The observed substituent effects suggest a nonsynchronous mode of bond breaking and bond formation. Jn troductionT h e thermal decomposition of diallylamine has been investigated as part of a series of studies on the thermochemical kinetics of N-substituted N-allylamines in a n attempt to obtain more information about the effect of substituents and heteroatoms on the concerted nature of the common reaction mechanism, involving a 6-center transition state complex as indicated in eq. Research, 5303 Wurenlingen, Switzerland. EGGER AND VITINSOf particular interest is the question of the extent of nonsynchronous bond breaking and bond formation, i.e., the amount of polar character in the ground and transition states.To this end we have so far reported measurements on N-allyl-N-cyclohexylamine [ 1 ] and triallylamine [2] and are presently investigating N-allyl-N-methylamine and N-allyl-N-methylaniline, as well as 1,6-hexadiene.Experimental Materials N-diallylamine (DAA) and toluene (T) (used as an internal standard) were obtained from Fluka Chemical Corporation, Buchs, Switzerland. After distillation, DAA was found by gas chromatography (GC) to be 99.0% pure, containing one major light impurity which proved to be thermally stable at the reaction conditions used and did not interfere in the analysis of the product mixture.Two starting mixtures (denoted by A and B ) with mole ratios DAA/T of 0.928 and 0.855, respectively, have been used. The mixtures were stored under nitrogen and gave GC analyses reproducible within =t0.6% over the period of several weeks.Methylamine, supplied by Fluka Chemical Corporation, was purified by distillation and stored as a gas in a 2-1. bulb. GC analyses showed it to be 98% pure. The observed impurities did not affect the analysis of the starting or product mixture. Apparatus and procedureThe static high vacuum system and general procedures used for the kinetic studies were essenti...

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confidence: 99%

Thermochemical kinetics of nitrogen compounds. V. The unimolecular thermal decomposition of diallylamine in the gas phase

Egger¹,

Vitins

1974

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“…This observation might be interpreted with a lower energy nonsynchronous reaction path possible with heteroatoms present in one or more positions of the six reactive centers. This assumption seemed to be supported by the very large rate enhancement observed for vinyl substituents in R' or R2 positions in diallylamine [5] and triallylamine [7].…”

Section: Discussionmentioning

confidence: 92%

“…[2], -CO-131, -NH- (4-61, -K(allyl)- [7] and Y e q u a l s -CH2- [1,6], -CHR- [2,4,5,7], or -0-showed the validity of the concerted H-shift "ene" type mechanism involving a 6-center transition state. For allylalkylethers, which undergo the same type of a decomposition reaction into carbonyl compounds and olefins, Cookson and Wallis [9] reported a limited set of relative rate constants.…”

Section: Introduction Kinetic Investigations Of Reaction Systems Of Tmentioning

confidence: 99%

“…For allylalkylethers, which undergo the same type of a decomposition reaction into carbonyl compounds and olefins, Cookson and Wallis [9] reported a limited set of relative rate constants. Although Arrhenius parameters were not obtained, these data can be used to estimate E,, with a reasonable confidence limit at =43 kcal/mole, based on an estimated value [4][5][6][7]111 for log A of = 11.2.…”

Section: Introduction Kinetic Investigations Of Reaction Systems Of Tmentioning

confidence: 99%

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The thermochemical kinetics of retro‐ “ene” reactions of molecules with the general structure (allyl) XYH in the gas phase. IX. The thermal unimolecular decomposition of ethyallylether in the gas phase

Egger¹,

Vitins

1974

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The thermal decomposition of ethylallylether (EAE) has been studied in the gas phase over the temperature range of 560-648'K.Propylene and acetaldehyde are the only reaction products observed. The reaction is apparently homogeneous in nature and independent of the pressure of EAE and of added foreign gases. The experimetally determined first-order rate constants, using the internal standard technique, fit the Arrhenius relationship log k(s-') = 11.84 + 0.29 -(43.57 =t 0.77 kcal/mole)/2.303RT, Independently the same rate constants are obtained, based on the amounts of products formed. The observed activation parameters are in general agreement with expectations based on the concept of a 6-center 1,5-H-shift retro-"ene" reaction mechanism, and they agree with previous results obtained for the similar reactions involving alkylallylamines and olefins. Previous shown in e q .

“…This table suggests that the ART frequency factor for MAE decomposition would be in the range between 1011. 6 and 1012J sec-' and the Em value would be 41-44 kcal/mol a t 600°K.…”

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confidence: 99%

Unimolecular decomposition of chemically activated methylallylether

Ibuki

Takezaki

1977

The unimolecular decomposition of chemically activated methylallylether (XIAE) formed by the cross combination of methoxymethyl and vinyl radicals was studied in the gas phase. The experimentally determined rate constant was found to be 1.11 X lo8 sec-1 at 9.6"C for the decomposition of MAE into propene and formaldehyde. The decomposition of MAE via the six-center retro-"ene" type transition state is analyzed by using the RRKM unimolecular reaction theory. For the molecular parameter assignments of energized MAE, a model which contains one internal rotational mode is supported, and MAE decomposition is characterized by a tight complex model. The best agreement between experimental and theoretical results was found when a critical energy of 40.1 kcal/mol was used.