Thermal Unimolecular Decomposition Research Articles

Thermal decomposition of trans-azobenzene in the gas phase

The thermal unimolecular decomposition of trans-azobenzene was investigated. The rate coefficient is given by the expression: k=(4.08 ± 0.53) 1012 exp [(–53.4 ± 2.9) kcal mol–1/RT].

The Very low‐pressure pyrolysis of 2‐phenylethylamine. The enthalpy of formation of the aminomethyl radical

AbstractThe thermal unimolecular decomposition of 2‐phenylethylamine (PhCH2CH2NH2) into benzyl and aminomethyl radicals has been studied under very‐low‐pressure conditions, and the enthalpy of formation of the aminomethyl radicals, ΔH°f, 298K (H2NCH2·) = 37.0 ± 2.0 kcal/mol, has been derived from the kinetic data. This result leads to a value for the C—H bond dissociation energy in methylamine, BDE(H2NCH2—H) = 94.6 ± 2.0 kcal/mol, which is about 3.4 kcal/mol lower than in C2H6 (98 kcal/mol), indicating a sizable stabilization in α‐aminoalkyl radicals.

Thermal unimolecular decomposition of ethyl propionate behind reflected shock waves

The kinetics of the thermal decomposition of ethyl propionate to ethylene and propionic acid behind reflected shock waves have been studied in two single-pulse shock tubes of different design.Between 913 and 1100 K the results from the two sets of experiments are in good agreement with each other, and with the extrapolated results of earlier work using the toluene-carrier method at temperatures between 778 and 875 K.Above 1100 K however, the Arrhenius plot is curved in a manner resembling that previously reported for cyclopropane and cyclobutane.

VLPP unimolecular rate theory

AbstractThe exact theory is derived for the thermal unimolecular decomposition of gas‐phase molecules activated and deactivated exclusively through heterogeneous collisions with the walls of a spherical vessel. This theory is appropriate for the treatment of very‐low‐pressure pyrolysis (VLPP) experiments and other experiments carried out at very low pressures. It is shown, however, that the exact theory is closely approximated by ordinary gas‐phase unimolecular rate theory and that for practical application to experiments the results of both theories are indistinguishable.

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

AbstractThe 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 k(s−1) = (11.04 ± 0.13) − (37.11 ± 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.

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

AbstractThe 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−1) = 11.84 ± 0.29 − (43.57 ± 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.

ChemInform Abstract: THERMOCHEMICAL KINETICS OF NITROGEN COMPOUNDS PART 3, THE UNIMOLECULAR THERMAL DECOMPOSITION OF N‐ALLYLCYCLOHEXYLAMINE IN THE GAS PHASE

Chemischer InformationsdienstVolume 5, Issue 7 Preparative Organic Chemistry ChemInform Abstract: THERMOCHEMICAL KINETICS OF NITROGEN COMPOUNDS PART 3, THE UNIMOLECULAR THERMAL DECOMPOSITION OF N-ALLYLCYCLOHEXYLAMINE IN THE GAS PHASE KURT W. EGGER, KURT W. EGGERSearch for more papers by this author KURT W. EGGER, KURT W. EGGERSearch for more papers by this author First published: February 19, 1974 https://doi.org/10.1002/chin.197407129AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume5, Issue7February 19, 1974 RelatedInformation

The thermochemical kinetics of the retro-‘ene’ reactions of molecules with the general structure (allyl)XYH in the gas phase. Part X. Unimolecular thermal decomposition of diallyl ether

The gas-phase thermal decomposition of diallyl ether (DAE) was investigated in the temperature range 545–627 K. The reaction yields acrolein and propene as the only products and appears to be a homogeneous, unimolecular process. First-order rate constants (determined using the internal standard technique) were insensitive to a 15-fold change in surface:volume ratio, the extent of conversion, and the addition of 5·8-fold excess of toluene or hex-1-ene. The rate constants were also invariant over a 13-fold variation in initial DAE pressure and were found to fit the Arrhenius relationship (i). Conversions obtained on the basis of the products agree with those using the internal log (K1/s–1)=(11·83 ± 0·13)–(40·90 ± 0·35 kcal mol–1)/2·3RT(i) standard method. The thermal decomposition of DAE fits into the general context of retro-‘ene’ reactions involving a concerted [1,5] shift via a six-centre transition state as found for but-3-enols, but-3-enoic acids, and allylamines.

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

AbstractThe gas phase thermal decomposition of triallylamine was studied in the temperature range 531 to 620 K. The major products observed in the reaction were propylene and 3‐picoline. The first order rate constants for depletion of triallylamine, obtained using the internal standard technique, are found to be independent of pressure and conversion, and fit the Arrheniusrelationship The reaction appears to be homogeneous, as a 15‐fold change in thc surface‐to‐volume ratio of the vessel left the rate constants unchanged. The Arrhenius parameters are consistent with a molecular elimination reaction involving a six‐center transition state, yielding propylene and N‐allyl‐prop‐2‐enaldimine. It is proposed that the latter product undergoes a 1,5‐hydrogen transfer, followed by a ring closure reaction to yield dihydropicoline, which in turn reacts forming 3‐picoline via a self‐initiated decomposition reaction.

On the reactivity of organometallic compounds towards functional substrates. Part III. The kinetics of the reaction between tri-isobutylaluminium and benzonitrile

The first-order rate constants for unimolecular thermal decomposition of Bu3iAl–PhCN complex to benzylideneamino(di-isobutyl)aluminium are given at several temperatures. The rate of reduction of PhCN is shown to be independent of the presence of toluene as solvent. For this reaction Ea= 25·0 ± 1·0 kcal mol–1 and A= 1012 s–1; all the data obtained are consistent with the hypothesis that the reduction involves a six-centre transition state. In the presence of an excess of Bu3iAl di-isobutyl-(α-isobutylbenzylideneamino)aluminium is formed. On the basis of the experimental results, possible mechanisms for the addition are discussed.

Thermochemical kinetics of nitrogen compounds. Part III. The unimolecular thermal decomposition of N-allylcyclohexylamine in the gas phase

The thermal, unimolecular gas-phase decomposition of N-allylcyclohexylamine to cyclohexylimine and propene has been studied in the temperature range 562–652 K. The rate constants for the homogeneous depletion of the starting material, using the internal standard technique fit the Arrhenius relationship log k/s–1= 11·44 ± 0·21 –(42·18 ± 0·57 kcal mol–1)/2·303RT and were independent of the initial pressure in the range 15–150 Torr. When toluene or ethylbenzene were added as diluent and potential radical traps, rate constants calculated on the basis of the products formed and the pressure changes observed were consistent with the internal standard results. The homogeneiety of the reaction was demonstrated by the concurring rate constants obtained in a packed reaction vessel with a 15-fold larger surface:volume ratio. The observed activation parameters are consistent with a concerted mechanism involving a cyclic six-centre-transition state and they are in good agreement with those reported for the analogous decompositions of allyl ethyl ether, but-3-en-1-ol, and but-3-enoic acid.

Kinetics of the reactions of silicon compounds. Part VII. Unimolecular gas-phase thermal decomposition of 2,2-difluoroethyltrimethoxysilane

The gas-phase thermal decomposition of 2,2-difluoroethyltrimethoxysilane into vinyl fluoride and trimethoxy-fluorosilane at 242–328 °C and 2–53 Torr initial pressure is a first-order homogeneous reaction insensitive to the presence of radical inhibitors, and is concluded to be a four-centre unimolecular decomposition. The rate constant is given by log10k/s–1=(11·04 ± 0·11)–(152·0 ± 1·2) kJ mol–1/2·303RT

The kinetics of the reactions of silicon compounds. Part IV. Unimolecular gas-phase thermal decomposition of 2,2-difluoroethyltributoxysilane

The gas-phase thermal decomposition of 2,2-difluoroethyltri-n-butoxysilane into vinyl fluoride and tri-n-butoxyfluorosilane shows first-order kinetics at 240–320° and 7–97 torr initial pressure. The reaction is homogeneous and unaffected by the addition of nitric oxide or propene. The first-order rate constant is pressure-independent and given by: log10k(sec.–1)=(10·25 ± 0·26)–(35,055 ± 660)/4·576T.

The Thermal Unimolecular Decomposition of Chlorocyclobutane

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Thermal Unimolecular Decomposition of ChlorocyclobutaneA. T. Cocks and H. M. FreyCite this: J. Am. Chem. Soc. 1969, 91, 27, 7583–7585Publication Date (Print):December 1, 1969Publication History Published online1 May 2002Published inissue 1 December 1969https://doi.org/10.1021/ja50001a008RIGHTS & PERMISSIONSArticle Views34Altmetric-Citations16LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (375 KB) Get e-Alerts Get e-Alerts

The kinetics of the reactions of silicon compounds. Part III. Gas-phase unimolecular thermal decomposition of 2,2-difluoroethylmethyldifluorosilane

The gas-phase thermal decomposition of 2,2-difluoroethylmethyldifluorosilane into vinyl fluoride and methyltrifluorosilane, at temperatures from 182° to 246° and at pressures from 20 to 186 torr, is kinetically of the first order. The reaction is homogeneous, and is unaffected by the addition of nitric oxide and cyclohexene. The first-order rate constant is independent of pressure, and is given by: log10k(sec.–1)=(11·32 ± 0·16)–(32,540 ± 360)/4·576TIt is concluded that the reaction is unimolecular and proceeds by a four-centre β-fluorine elimination similar to that found in other β-fluoroalkylsilicon compounds.

Die unimolekulare thermische Spaltung von Äthylchlorid-2-d3 und Äthylchlorid-2-d1 nach einem Vierzentrenmechanismus

The unimolecular thermal decomposition of chloroethane-2-d3 and chloroethane-2-d1 was studied in a static system at two temperatures and at pressures between 0.1 and 10 mm Hg. The rate constants for the high pressure limit were obtained from these measurements and used to calculate the Arrhenius equations. The decomposition of chloroethane-2-d3 was also studied at high conversions and yielded almost exclusively (97%) DCl and CD2CH2 as shown by mass spectrometric analysis thus proving a molecular elimination mechanism via a four-centered reaction complex.

The Thermal Unimolecular Decomposition of Norbornylene1a

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Thermal Unimolecular Decomposition of Norbornylene1aB. C. RoquitteCite this: J. Phys. Chem. 1965, 69, 4, 1351–1354Publication Date (Print):April 1, 1965Publication History Published online1 May 2002Published inissue 1 April 1965https://doi.org/10.1021/j100888a042RIGHTS & PERMISSIONSArticle Views48Altmetric-Citations16LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (337 KB) Get e-Alerts

A homogeneous unimolecular reaction-the thermal decomposition of acetone in the gaseous state

Unimolecular reactions in gases have a rather exceptional theoretical interest, because they involve, apparently, the spontaneous change of isolated molecules. One example only has been satisfactorily investigated, the thermal decomposi­tion of nitrogen pentoxide, and an examination of the molecular statistics of this reaction leaves a certain mystery about the method by which the mole­cules are caused to decompose. It is unwise to infer too much from what might be a quite special instance; hence we have during the last few years searched for other examples. We now find that the thermal decomposition of acetone vapour satisfies the experimental criteria of a homogeneous, unimolecular reaction. Moreover, the peculiarities of the nitrogen pentoxide decomposition are here reproduced, although the absolute temperature at which the acetone decomposition can be studied is approximately three times as high as that at which nitrogen pentoxide reacts with conveniently measureable speed. Since then this analogy exists between the two reactions, taking place at such different temperatures, we may begin to draw theoretical con­clusions with more confidence. The theoretical discussion is reserved for the last section, after the experimental work has been described, because the conclusions depend very much upon the actual numerical results.