Shock tube cis-trans isomerization studies. IV

Marley, Wayne M.; Jeffers, Peter M.

doi:10.1021/j100587a002

Cited by 12 publications

(14 citation statements)

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“…We suspect that this is due to the initial product being the trans isomer and that interconversion to the cis compound occurs from this source as opposed to formation directly from 1,2-pentadiene. This cis-trans isomerization of 1,3-pentadiene was studied by Marley and Jeffers [19] many years ago. Results of calculations using their rate constants for cis-trans isomerization where it is assumed that the trans compound is the first product and that the cis compound is formed from it are given in Fig.…”

Section: Rate Expressions For Elementary Processesmentioning

confidence: 94%

1,2‐Pentadiene decomposition

Herzler

Manion

Tsang

2001

Int J of Chemical Kinetics

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1,2-Pentadiene has been decomposed in single pulse shock tube experiments. There appear to be a large number of parallel decomposition and isomerization channels. The following rate expressions for isomerization in the temperature range 1100-1250 K and pressures between 200 and 300 kPa have been obtainedOverall, we estimate the 2σ uncertainty in the absolute rate constants to be about 30%. From detailed balance the rate expression for 1,3 to 1,2-pentadiene isomerization has been found to be k(1,3-pentadiene → 1,2-pentadiene) = 1.2 × 10 15 exp(−42070 ± 900 K/T ) s −1The significance of the 1,3 to 1,2 isomerization process as a bridge between the two-carbon and three-carbon species in high temperature hydrocarbon decomposition systems is discussed. The decomposition processes involve bond breaking and retroene reactions. The rate expression for the latter has been found to be k(1,2-pentadiene → propyne + ethylene) = 6.6 × 10 12 exp(−29240 ± 900 K/T ) sThe rate constants for fission of the C 3 C 4 and C 4 C 5 bonds appear to be close to each other. Our results indicate that the resonance energy of the 1,3-butadiene-2-yl radical is smaller than that of allyl radical by an amount equal to the π bond conjugation energy of butadiene. C 2001

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Section: Rate Expressions For Elementary Processesmentioning

confidence: 94%

1,2‐Pentadiene decomposition

Herzler

Manion

Tsang

2001

Int J of Chemical Kinetics

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“…Upon decomposition of t -PTD the mass-spectral results obtained were very similar to those for the decomposition of the cis-compound. Since the structure oft -PTD precludes IP-hydrogen elimination, then prior isomerization to c-PTD must take place: (2) t-PTD C-PTD -H2 + C~H G The thermal cis -trans interconversion of penta-1,3-diene has been examined previously [6,7,12]. For the trans -cis isomerization log k , (s-l) = 13.3 -52.6/8 and for cis -trans, log k , (s-l) = 13.5 -52.1/8 [6].…”

Section: Resultsmentioning

confidence: 99%

“…(2) t-PTD C-PTD -H2 + C~H G The thermal cistrans interconversion of penta-1,3-diene has been examined previously [6,7,12]. For the transcis isomerization log k , (s-l) = 13.3 -52.6/8 and for cistrans, log k , (s-l) = 13.5 -52.1/8 [6].…”

Section: Resultsmentioning

confidence: 99%

“…Some thermal reactions of penta-1,3-dienes have been examined in conventional static [6] and shock-tube [7] studies, but only kinetic data on the geometrical cis-trans isomerizations have been reported. We report here kinetic data on the formation of hydrogen from cis-and transpenta-1,3-diene (c-PTD and t -PTD) obtained with the VLPP technique.…”

Section: Introductionmentioning

confidence: 99%

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Very low‐pressure pyrolysis (VLPP) of penta‐1,3‐dienes. Kinetics of the unimolecular 1,4‐hydrogen elimination from cis‐penta‐1,3‐diene

Nguyen

King

1982

Int J of Chemical Kinetics

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The thermal unimolecular reactions of cis-and trans-penta-l,3-diene (c-PTD and t-PTD) have been studied over the temperature range of 1002-1235 K using the technique of very low-pressure pyrolysis (VLPP). c-PTD decomposes via 1,4-hydrogen elimination analogous to that previously reported for cis-but-2-ene. RRKM calculations incorporating a six-center transition state show that the experimental rate constants are consistent with the following high-pressure rate expression a t 1100 K: log k , ( s -~) = (13.0 zt 0.6) -(64.5 f 2.0)/19 where 0 = 2.303RT kcai/mol, and the A factor was assumed to be the same as that for cisbut-2-ene. The activation energy is in excellent agreement with that obtained for cis-but-2-ene. t-PTD also undergoes decomposition by Hz elimination presumably via the prior rapid isomerization to c-PTD; the results are in exact agreement with those for c-PTD.

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“…L'isomCrisation cis-trans du penta-1,3-dikne a Ct C maintes et maintes fois observCe et discutke, que ce soit en photosensibilisation (2,3,6), en radiolyse (13), dans des systkmes catalyses (14) ou par voie thermique (15). La photoisomtrisation a 366 nm catalyske par le Pyrex a aussi Ct C observte (1 6), de m&me que la photochimie directe h 253,7 nm (17).…”

Section: ~1 8 4 9 N M (A) Isome'risation De La Mole'cule Photoexcite'eunclassified

La photochimie du cis-penta-1,3-diène, en phase gazeuse à 184,9 et 147,0 nm

Collin¹,

Deslauriers²,

Maré³

1991

Can. J. Chem.

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La photochirnie du cis-penta-1,3-dikne a Ct C CtudiCe a 184,9 et 147,O nrn en phase gazeuse. Les produits majeurs observCs a 184,9 nrn, outre le trans-penta-l,3-dikne, sont le cyclopenta-l,3-diene, et divers radicaux rCvClCs par l'addition d'iodure d'hydrogkne. Le cyclopentadikne est form6 trks probablernent via l'tlirnination successive de deux atornes d'hydrogkne avec isornCrisation concurrente du radical pentadiknyle vers la structure cyclopentknyle : @ o (~y~l~-C 5 H 6 ) --0,25. L'dirnination du radical rnCthyle ( a o = 0,50) est Cgalement importante, I1 y a formation concornitante des radicaux CH,=CHCH=CH*, et dans une rnoindre mesure des radicaux CH,=C=CHCH,*.On n'a cependant pas pu ttablir si ce dernier radical provient de I'isomCrisation du prCcCdent, ou s'il provient d'une moltcule de penta-1,2-dikne** rCsultant de I'isomCrisation de la rnoltcule ehotoexcitCe. On a pu enfin observer une isornCrisation conduisant vers la formation de penta-1,4-dikne ( a 0 = 0,035 2 0,015). A 147,O nrn, on retrouve les rn&mes caractCristiques, avec une fragmentation plus poussCe des intermkdiaires. L'Cnergie supkrieure disponible B cette longueur d'onde explique cette observation. Globalement, la photofragmentation du cis-penta-1,3-diene s'apparente beaucoup plus a la photochirnie des alcknes acycliques et assez peu a celle du buta-1,3-dikne qui passe surtout pas I'isornCrisation vers la structure buta-1,2-dikne.Mots cle's : penta-1,3-dikne, photolyse, UV lointain, rkactions rnonornolCculaires, fragmentation, stabilisation. GUY J. COLLIN, HBLBNE DESLAURIERS, and GEORGE R. DE MARB. Can. J. Chem. 69, 1245 (1991).We have studied the 184.9 and 147.0 nm photochemistry of gaseous cis-1,3-pentadiene: the main products observed at 184.9 nrn are trans-l,3-pentadiene and 1,3-cyclopentadiene. The formation of radicals also occurs as shown through the use of DI as a radical scavenger. Cyclopentadiene is the likely product of successive eliminations of two hydrogen atoms from the photoexcited molecule after rearrangement of the pentadienyl radical to the cyclopentenyl structur;e: @o(cyclo-C5H6) = 0.25.Elimination of methyl radical ( a o --0.50) also occurs, with formation of CH2=CHCH=CH* and, in a lower yield, CH2=C=CHCH2*. However, it is not possible to identify properly the mechanism of the formation of the latter radical. It may be the result of the isomerization of either the first photoexcited molecule or the excited 1,3-butadienyl radicals. A small amount of 1,4-pentadiene formation is also observed ( a o -0.035 2 0.015). At 147.0 nm, the same characteristics are observed, together with higher fragmentation due to the higher energy content of the photoexcited molecules. It appears that the photofragmentation at both wavelengths is more in line with that of acyclic akenes than with that of 1,3-butadiene, which tends to undergo isomerization of the photoexcited molecules to the 1,2-butadiene structure.

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Shock tube cis-trans isomerization studies. IV

Cited by 12 publications

References 1 publication

1,2‐Pentadiene decomposition

1,2‐Pentadiene decomposition

Very low‐pressure pyrolysis (VLPP) of penta‐1,3‐dienes. Kinetics of the unimolecular 1,4‐hydrogen elimination from cis‐penta‐1,3‐diene

La photochimie du cis-penta-1,3-diène, en phase gazeuse à 184,9 et 147,0 nm

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