Zur Energiedelle des orthogonalen Trimethylenmethans. – 1‐Methylen‐2‐phenylcyclopropan‐Thermolyse

Roth, Wolfgang R.; Winzer, Markus; Lennartz, Hans‐Werner; Boese, Roland

doi:10.1002/cber.19931261222

Cited by 11 publications

(6 citation statements)

References 29 publications

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“…Table collects our best theoretical enthalpies of formation, Δ H f ° [298.15 K], for the complete set of 161 hydrocarbons (corresponding Δ H f ° [0 K] values and ZPE-inclusive atomization energies, E A,0 , in Table S10) and compares them to available experimental data. ,− A second, more recent, experimental value is included if available. The left column reports ATOMIC(hc)/A results in most cases, reverting to ATOMIC(hc)/B 3 for only four molecules ( 124 , 158 , 160 , and 161 , indicated by label B 3 in column “note”), for which full CCSD/cc-pVQZ and CCSD(T)/cc-pVTZ calculations appeared too costly.…”

Section: Atomic(hc): Enthalpies Of Formation For a Large Set Of Hydr...mentioning

confidence: 99%

“…Component uncertainties have been adjusted accordingly. Label “III” indicates that the ATOMIC(hc) CCSD(T) component has been replaced by calculations at the ATOMIC(hc) reference level, in addition to the refinements made for label “II”. e Corrections to thermal enthalpy increments have been applied as described in the text. f Adding 1.2 kcal/mol (this work) to convert from 0 to 298.15 K. g Reference , cycloheptane; ref , heat of hydrogenation. h Reference , combustion; ref sublimation. i Reference , heat of hydrogenation; ref , phenylbutane. j Reference , sublimation; ref , combustion. …”

Section: Atomic(hc): Enthalpies Of Formation For a Large Set Of Hydr...mentioning

confidence: 99%

“…This result has tentatively been rationalized with enhanced conjugation, but our theoretical result (141.5 ± 1.5 kcal/mol) raises some doubts. Enthalpies of formation of 101 and 102 have both been derived from hydrogenation to phenylbutane; , unfortunately only the latter can be reconciled with theory. The experimental value for 105 has been determined from hydrogenation and that of 103 from isomerization ( 105 → 103 ).…”

Section: Atomic(hc): Enthalpies Of Formation For a Large Set Of Hydr...mentioning

confidence: 99%

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Estimating Systematic Error and Uncertainty in Ab Initio Thermochemistry: II. ATOMIC(hc) Enthalpies of Formation for a Large Set of Hydrocarbons

Bakowies

2019

J. Chem. Theory Comput.

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ATOMIC is a thermochemistry protocol geared toward larger molecules with first-row atoms. It implements Pople's concept of bond separation reactions in an ab initio fashion and so enhances the accuracy of midlevel composite models for atomization energies. Recently we have introduced ATOMIC(hc), a model for applications to hydrocarbons, that estimates bias and uncertainty for each of the components contributing to the ATOMIC bottom-ofthe-well atomization energy (Bakowies, D. J. Chem. Theory Comput. 2019, 15, 5230−5251). Here we scrutinize the remaining components of the ATOMIC protocol, including midlevel composite models to approximate the complete-basis set (CBS) limit of CCSD(T) as well as zero-point energies (ZPEs) and thermal enthalpy increments that are evaluated from scaled harmonic MP2 frequencies. Potential errors relating to imperfections in MP2 geometries and ZPEs are estimated using auxiliary information obtained from geometry optimizations and frequency calculations at the density functional (B3LYP) level. Overall corrections to and uncertainties of enthalpies of formation are obtained from summation and error propagation, respectively. The error and uncertainty model is validated with accurate data from the Active Thermochemical Tables (ATcT) and compared to earlier statistical assessments for the G3/99 benchmark. The proposed model is a welcome alternative to statistical assessment, first because it does not depend on comparison with experiment, second because it recognizes the expected scaling of error with system size, and third because it provides a detailed account of the importance of various contributions to overall error and uncertainty. The evaluation of ZPEs from scaled harmonic frequencies expectedly emerges as the leading source of uncertainty if highly accurate composite models are used to treat the electronic problem, but uncertainties are usually balanced with those arising from computationally more attractive B level (B 1 ...B 6 ) models to estimate the CBS limit of CCSD(T). ATOMIC(hc) enthalpies of formation, complete with uncertainty estimates, are reported for 161 hydrocarbons ranging in size from methane (CH 4 ) to [8]circulene (C 32 H 16 ) and tetra-tert-butyltetrahedrane (C 20 H 36 ). Experimental data are available for 127 molecules but cannot be reconciled with theory in 37 cases. Theory helps to identify the more accurate among conflicting experimental values in 11 cases and emerges as a valuable complement to experiment also for larger molecules, provided that fair estimates of uncertainty are available.

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Section: Atomic(hc): Enthalpies Of Formation For a Large Set Of Hydr...mentioning

confidence: 99%

Section: Atomic(hc): Enthalpies Of Formation For a Large Set Of Hydr...mentioning

confidence: 99%

Section: Atomic(hc): Enthalpies Of Formation For a Large Set Of Hydr...mentioning

confidence: 99%

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Estimating Systematic Error and Uncertainty in Ab Initio Thermochemistry: II. ATOMIC(hc) Enthalpies of Formation for a Large Set of Hydrocarbons

Bakowies

2019

J. Chem. Theory Comput.

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“…These distances might be regarded as weak hydrogen bonds. The conformations of the molecules in the crystals must result in each case from energetic compromises between these hydro- 28 [d] 25 [e] [a] Reaction conditions: 1 (3 equiv), [17][18][19][20] www.chemeurj.org gen bonding, conjugation effects, and intramolecular van der Waals interactions between hydrogen atoms and crystalpacking effects. Thus, the angles between the planes of the pyridine and benzene moieties in the more sterically congested compounds 28 b (79.4) and 29 (71.78) are higher than those angles in 28 a, with one bicyclopropyl fragment (55.18).…”

Section: Resultsmentioning

confidence: 99%

Ruthenium‐Catalyzed Hydroarylation of Methylenecyclopropanes through CH Bond Cleavage: Scope and Mechanism

Ackermann

Kozhushkov

Yufit

2012

Chemistry A European J

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Intermolecular hydroarylation reactions of highly strained methylenecyclopropanes 2-phenylmethylenecyclopropane (1), 2,2-diphenylmethylenecyclopropane (2), methylenespiropentane (3), bicyclopropylidene (4), (dicyclopropylmethylene)cyclopropane (5), and benzhydrylidenecyclopropane (6) through C-H bond functionalization of 2-phenylpyridine (7 a) and other arenes with directing groups were studied. The reaction was very sensitive to the substitution on the methylenecyclopropanes. Although these transformations involved (cyclopropylcarbinyl)-metal intermediates, substrates 1 and 4 furnished anti-Markovnikov hydroarylation products with complete conservation of all cyclopropane rings in 11-93 % yield, whereas starting materials 3 and 5 were inert toward hydroarylation. Methylenecyclopropane 6 formed the products of formal hydroarylation reactions of the longest distal C-C bond in the methylenecyclopropane moiety in high yield, and hydrocarbon 2 afforded mixtures of hydroarylated products in low yields with a predominance of compounds that retained the cyclopropane unit. As byproducts, Diels-Alder cycloadducts and self-reorganization products were obtained in several cases from substrates 1-3 and 5. The structures of the most important new products have been unambiguously determined by X-ray diffraction analyses. On the basis of the results of hydroarylation experiments with isotopically labeled 7 a-[D(5)], a plausible mechanistic rationale and a catalytic cycle for these unusual ruthenium-catalyzed hydroarylation reactions have been proposed. Arene-tethered ruthenium-phosphane complex 53, either isolated from the reaction mixture or independently prepared, did not show any catalytic activity.

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“…However, these 2.4 kcal mol Ϫ1 are only a minimum value for the stabilization of the orthogonal diradical 13, because the different steric contributions in the propellanes 2 and 8 and in the reference molecules 15؊17 have to be considered. In contrast to the nonplanar cis-substituted styrene derivatives 15؊17, [2] (phenylmethylene)cyclopropane (14), which serves as a reference molecule for the structure of 2 and 8, is planar [10] and therefore does not show any significant steric interaction between the phenyl group and the vinylic cyclopropane bonds. As a result, 2.4 kcal mol Ϫ1 is only a minimum value for the stabilization of the orthogonal diradical 13.…”

Section: Methodsmentioning

confidence: 96%

The Barrier to Rotation about the Double Bond in Methylenecyclopropane

Roth¹,

Quast²

1998

Eur. J. Org. Chem.

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Activation parameters have been determined in the gas phase for the geometrical isomerization of the double bonds in two phenyl‐substituted methylenecyclopropanes (2 and 8). Comparison with the analogous values for three sterically non‐restricted styrene derivatives (15, 16 and 17) shows that the enthalpies of activation for the methylenecyclopropanes are lower by 3.7 kcal mol−1. This value, which is an upper limit to the amount of strain energy released by pyramidalization of the ring carbon atom in the orthogonal diradical transition state when undergoing geometrical isomerization, is considerably smaller than the value of 12‐14 kcal mol−1 by which the strain energy of methylenecyclopropane is larger relative to that of cyclopropane. Our kinetics experiments thus show that the angle strain, associated with incorporating a trigonal carbon atom into the three‐membered ring, is not responsible for the majority of the additional strain energy of methylenecyclopropane, relative to that of cyclopropane.

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Zur Energiedelle des orthogonalen Trimethylenmethans. – 1‐Methylen‐2‐phenylcyclopropan‐Thermolyse

Abstract: Die in der Gasphase zwischen 160 und 280°C ermittelten Geschwindigkeitskonstanten erster Ordnung zeigen eine Temperaturabhangigkeit, die sich durch die Arrhenius-Gleichungen (l), (2) und (3) beschreiben lassen, wobei die Feh-

Cited by 11 publications

References 29 publications

Estimating Systematic Error and Uncertainty in Ab Initio Thermochemistry: II. ATOMIC(hc) Enthalpies of Formation for a Large Set of Hydrocarbons

Estimating Systematic Error and Uncertainty in Ab Initio Thermochemistry: II. ATOMIC(hc) Enthalpies of Formation for a Large Set of Hydrocarbons

Ruthenium‐Catalyzed Hydroarylation of Methylenecyclopropanes through CH Bond Cleavage: Scope and Mechanism

The Barrier to Rotation about the Double Bond in Methylenecyclopropane

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