Ab initio study of C—H bond breaking in olefins. II. GVB computations on propene ↔ H + cis- or trans-propen-1-yl

Maré, George R. De; Evleth, E. M.; Poirier, Raymond A.; Collin, Guy J.

doi:10.1139/v94-156

Cited by 10 publications

(3 citation statements)

References 33 publications

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“…This intuition has long been confirmed by PP calculations. 58,[83][84][85][86][87] We see that CCVB has the tools necessary to treat the rather different situations of low SSC, tightly bound, and high SSC, weakly bound geometries. This suggests that CCVB may well be able to provide a consistently good level of accuracy throughout the PES, and the examples given in the first paper support this idea.…”

Section: Theorymentioning

confidence: 98%

Post-modern valence bond theory for strongly correlated electron spins

Small

Head‐Gordon

2011

Phys. Chem. Chem. Phys.

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We give a pedagogical overview of our recently introduced electronic-structure method, Coupled Cluster Valence Bond (CCVB). We show that CCVB can be viewed as an approximation to the accurate, yet very expensive, Spin Coupled Valence Bond model (SCVB). Both of these models are intended for use on strongly correlated molecular systems, especially when the strong correlations are due to electron spin coupling. Using familiar ideas from electronic-structure theory, we provide definitions for these strong-correlation concepts. We show that CCVB and SCVB generally produce similar results, with more substantial discrepancies occurring for systems displaying electronic resonance. We conclude that CCVB is a useful, inexpensive alternative to SCVB.

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Section: Theorymentioning

confidence: 98%

Post-modern valence bond theory for strongly correlated electron spins

Small

Head‐Gordon

2011

Phys. Chem. Chem. Phys.

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“…The decomposition of 16a can be depicted as an intramolecular β-elimination of either propyne from 21A or allene from 21B (Scheme ). In terms of thermodynamic stability propyne is expected to preferentially form because its experimental heat of formation is more favorable by 5.5–5.6 kJ/mol than that of allene. , Although difficulties have been experienced in obtaining accurate C–H bond dissociation energies of simple alkanes and alkenes, the C–H bond dissociation energy of ethylene is reported to be 91–116 kJ/mol greater than that of the allylic C–H bond of propene at 298 K. , No experimental values for bond dissociation energies for the vinyl C–H bonds of propene have been published, but ab initio STO-3G calculations have suggested that the bond dissociation energies of the vinylic CH 2 bonds of propene are within a few percent of the ethylene value. − These bond dissociation energy values argue for the preferred formation of allene via 21B provided that the decomposition is governed by kinetic control. It is well established that propyne and allene exist as an equilibrium mixture.…”

Section: Results and Discussionmentioning

confidence: 99%

Synthesis of 3,5-Isoxazolidinediones and 1H-2,3-Benzoxazine-1,4(3H)-diones from Aliphatic Oximes and Dicarboxylic Acid Chlorides

et al. 2014

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The synthesis of the title compounds was carried out by reacting dicarboxylic acid chlorides with oximes in the presence of excess triethylamine. Disubstituted malonyl chlorides gave 2-alkenyl-4,4-dialkyl-3,5-isoxazolidinediones (8a–f) and 2,2′-ethylidene-bis[4,4-dialkyl-3,5-isoxazolidinedione]s (9a–f). Compounds 9 were formed from 8 and its N-unsubstituted 3,5-isoxazolidinedione decomposition product. Phthaloyl chlorides reacted with acetone oxime to yield 3-(1-methylethenyl)-1H-2,3-benzoxazine-1,4(3H)-diones (16a–e). Products 16 spontaneously decomposed to give N-unsubstituted 1H-2,3-benzoxazine-1,4(3H)-diones (17a–e) at rates that were dependent on temperature and solvent. Kinetic studies showed that two of the compounds decomposed by zero-order kinetics under neutral conditions. Butanedioyl chloride did not produce a cyclic product.

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“…Comme dans le cas de M (23), la structure la plus basse en tnergie de chaque radical est de symttrie Cs avec un atome d'hydrogkne du groupe mCthyle situt dans le plan et au dessus de la double liaison (angles dikdres H4C3C2C 1 optimisCs = 0,00°) (8). Les rksultats des calculs ne sont pas donnCs ici mais notons que les structures Cs avec l'atome d'hydrogkne du groupe mCthyle dans le plan et ding6 vers I'extCrieur sont des Ctats de transition (maxima d'tnergie) pour la rotation du groupe mCthyle.…”

Section: Calculs Ab Initiounclassified

Évaluation des ruptures de liaison α(C—H) centrale et terminale dans la photolyse du propène gazeux à 184,9 nm

Maré¹,

Collin²,

Deslauriers³

1995

Can. J. Chem.

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valuation des ruptures de liaison a(C-H) centrale et terminale dans la photolyse du propene gazeux a 184,9 nm I George R. De Mare, Guy J. Collin et Helene Deslauriers RCsumC : Nous avons repris l'ttude de la photochimie du propkne gazeux dans la region de l'ultraviolet lointain (A = 184,9 nm) dans le but explicite d'apprtcier les rendements quantiques des rtactions de scission des liaisons a(C-H) situees de part et d'autre de la liaison double. Alors que les reactions de rupture des liaisons P(C-H) et a ( C -4 ) sont de loin les reactions les plus importantes et constituent probablement plus de 95% des fragmentations de la molCcule photoexcitCe, la somme des rendements quantiques des rkactions de scission a(C-H) est de l'ordre de 0,03 avec un avantage marquC (4 pour 1, compare i 1 pour 2 statistiquement) pour la rupture de la liaison C-H centrale : +(H secondaire) = 0,02 + 0.01 et +(H primaire) = 0,005 + 0,003. L'tnergie de la liaison qui se rompt est donc un facteur determinant bien que l'knergie photonique soit nettement supCrieure 2 celle nCcessaire pour rompre ces liaisons. Les paramktres gComCtriques, 1'Cnergie totale et les frCquences des modes normaux des radicaux cis-et trans-propkn-1-yle et propkn-2-yle ont C t t determines en utilisant des mkthodes ab initio 2 plusieurs niveaux de thCorie (bases STO-3G, 3-21G, 6-31G, 6-31G* et 6-3 1G**; methodes UHF, ROHF et GVB). On trouve que le cis-propkn-1 -yle est plus bas en Cnergie (0,61,0 kJ mol-l) que le trans-propkn-1-yle, sauf avec la base minimale STO-3G. Les calculs predisent que le propkn-2-yle est 14 + 3 kJ mol-' plus stable que les radicaux cis-et trans-propkn-1-yle.Mots clis : propkne, reactions unimolCculaires, photochimie, scission a(C-H), radicaux propknyles.Abstract: The minor, a(C-H) photofragmentation processes in the far-UV photolysis of gaseous propene at A = 184.9 nm are investigated. At this wavelength the P(C-H) and a(C-C) photofragmentation processes areof major importance, accounting for more than 95% of the primary reaction process. The total quantum yield of the three a(C-H) bond cleavage processes is close to 0.03. However +(H secondary) = 0.02 2 0.0 1 and the sum of the two +(H primary) cleavages is 0.005 5 0.003. Thus +(H secondary)/+(H primary) = 4: 1 whereas statistically one expects 1:2. Thus the energy of the bond that is breaking is important, even though the photon energy is much higher than that required to break it. The geometrical parameters, total energies, and fundamental frequencies of the cis-and trans-propen-1 -yl and propen-2-yl radicals have been determined by ab initio methods at various levels of theory (STO-3G, 3-21G, 6-31G, 6-31G*, and 6-31G** basis sets; UHF, ROHF, and GVB methods). cis-Propen-1-yl is predicted to be 0.61.0 kJ mol-' lower in energy than transpropen-1-yl, except with the minimal STO-3G basis set. The optimizations predict that propen-2-yl is more stable than the cis-and trans-propen-1-yl radicals by 14 2 3 kJ mol-I.

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Ab initio study of C—H bond breaking in olefins. II. GVB computations on propene ↔ H + cis- or trans-propen-1-yl

Cited by 10 publications

References 33 publications

Post-modern valence bond theory for strongly correlated electron spins

Post-modern valence bond theory for strongly correlated electron spins

Synthesis of 3,5-Isoxazolidinediones and 1H-2,3-Benzoxazine-1,4(3H)-diones from Aliphatic Oximes and Dicarboxylic Acid Chlorides

Évaluation des ruptures de liaison α(C—H) centrale et terminale dans la photolyse du propène gazeux à 184,9 nm

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