Thermolabile Kohlenwasserstoffe, VIII. Thermolysen von 1,2‐Dialkyl‐1,2‐diphenylethanen

Hellmann, G.; Beckhaus, Hans‐Dieter; Rüchardt, Christoph

doi:10.1002/cber.19791120532

Cited by 36 publications

(3 citation statements)

References 61 publications

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“…Correlation of k obs for the decay of the 545 nm absorption as a function of the concentration of TME in pentane gave k add = 1.4 × 10 7 M -1 s -1 for the addition of 2d to TME; cf., Supporting Information Figure S11. This is ∼5 times faster than the corresponding addition of t -BuCCl but ∼130 times slower than the addition of MeCCl to TME …”

Section: Resultsmentioning

confidence: 86%

Tracking “Invisible” Alkylchlorocarbenes by Their σ → p Absorptions: Dynamics and Solvent Interactions

et al. 2007

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Contrary to implications in the literature, the sigma --> p absorptions of alkylchlorocarbenes (RCCl) are readily acquired by laser flash photolysis with UV-vis detection in solution at ambient temperature. Examples include RCCl with R = methyl, benzyl, t-butyl, 1-adamantyl, and cyclopropyl. These absorptions permit direct monitoring of carbene reactions and the formation of carbene-solvent complexes. The kinetics of the reactions of "free" and complexed MeCCl and PhCH2CCl were directly followed with tetramethylethylene and 1-hexene. Particularly effective complexation was provided by anisole and 1,3-dimethoxybenzene, which modulated the rates of intermolecular carbene additions. Computational studies are presented, which aid in understanding the carbene absorption spectra and the nature of the solvent complexes.

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Section: Resultsmentioning

confidence: 86%

Tracking “Invisible” Alkylchlorocarbenes by Their σ → p Absorptions: Dynamics and Solvent Interactions

et al. 2007

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“…24 (tb,27.67 (d,27.67 und 27.41 (t,26.88 (t,23.30 und 22.26 (q,CH,). -MS (70 eV): m/e = 278 (170, M'), 235 (6), 153 (3), 140 (6), 139 (60, M+/2), 138 (79, 126 (6), 124 (7), 112 (9), 110 (6), 97 (53), 83 (IOO), 82 (15), 81 (13), 80 (17), 71 (8), 69 (28), 67 (13), 57 (51), 43 (I@, 41 (30). 251 (l), 168 (6), 167 (37,Mf/2), 166 (loo), 125 (9, 123 (9,112 (4), 111 (39, 110 (32), 109 (6), 98 (5), 97 (69), 96 (6), 95 (6), 85 (16), 84 (111, 83 (24), 82 (ll), 81 (9), 71 (22), 70 (8), 69 (13), 67 (8), 57 (91), 55 (23).…”

Section: Hydrierung Von Diphenylethanenmentioning

confidence: 99%

Thermolabile Kohlenwasserstoffe, XVI. Thermische Stabilität, Spannungsenthalpie und Struktur symmetrisch tetrasubstituierter Ethane

Hellmann

Beckhaus

et al. 1982

Chem. Ber.

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Die Aktivierungsparameter der Thermolyse von 12 symmetrisch tetrasubstituierten Ethanen (C, -C,-Reihe) wurden bestimmt. Produktanalysen belegen, daB im Primarschritt der Thermolyse die zentrale C, -C,-Bindung homolytisch gespalten wird. Aus der Korrelation zwischen AH * und der Abnahme der Spannungsenthalpie im Zuge der Bindungsdissoziation (Kraftfeldrechnungen) folgt, daB im Ubergangszustand der Thermolyse noch ungefahr 20% Restspannung verbleiben. Aus dem Vergleich der Thermolyse von C,-C,-und C,-C,-Ethanen lafit sich 2.3 kcal . mol-als oberer, vermutlich zu hoher Grenzwert fur den Unterschied der Stabilisierungsenergie sek. und tert. Alkylradikale angeben. Der EinfluD der Spannung auf Bindungslangen, Bindungsund Torsionswinkel wird mit den Verhaltnissen in der C, -C,-Ethanreihe verglichen. Thermolabile Hydrocarbons, XVI l)Thermal Stability, Strain Enthalpy, and Structure of Sym. Tetrasubstituted Ethanes" Activation parameters were determined for the thermolysis reaction of 12 sym. tetrasubstituted ethanes (C, -C, series). From product analyses it was concluded that the central C, -C, bond is cleaved in the rate determining step by homolysis. The correlation between AH* and the change in strain enthalpy during the activation process (MM2 calculations) points to nearly 20% residual strain at transition state. From a comparison of the thermolysis data for C, -C, and C, -C, ethanes a 2.3 kcal . mol-I difference in stabilization energy for sek. and tert. alkyl radicals is derived as an upper limiting value. The influence of strain on bond lengths, bond angles, and torsional angles is compared for C, -C, and C, -C, ethanes.Beim Studium der Zusammenhange zwischen Struktur und thermischer Stabilitat von Kohlenwasserstoffenlb) waren charakteristische Unterschiede zwischen tetraalkyliertenlb) und hexaalkylierten Ethanen h b ) erkannt worden. In diesen beiden homologen Reihen, den C, -C,-Alkanen einerseits und den C, -C,-Alkanen andererseits, pragte sich der Einflufi sperriger Gruppen auf die Geschwindigkeit der homolytischen CC-Spaltung und auf die Deformationen des Kohlenstoffgerustes sehr unterschiedlich aus. Wahrend wir uber hexaalkylierte Ethane bereits ausfuhrlich berichteten 1,2), haben wir aufier in zusammenfassender Form lbv3) bisher nur iiber einzelne hochgespannte tetraalkylierte Ethane berichtet: 1,l ,2,2-Tetra-ferf-butylethan4) (17), mesound DL-1 ,2-Di-ferf-butyl-l,2-dicyclohexylethan5) (14 und 13), 1,1,2,2-Tetracy~lohexylethan~) (7). Die Struktur des einfachsten Vertreters dieser C, -C,-Alkanreihe, des 2,3-Dimethylbutans (l), wurde in den vergangenen Jahren eingehend untersucht7). Die Vorzugskonformationen von

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“…These were obtainable either by Wurtz type reactions [26,[36][37][38][39] [20.28,36] [Reaction (c), [36' (d) t Bu-C-N=N-C-t Bu --> t Bu-C-C-t Bu…”

Section: Synthesismentioning

confidence: 99%

Consequences of Strain for the Structure of Aliphatic Molecules

Rüchardt¹,

Beckhaus²

1985

Angew. Chem. Int. Ed. Engl.

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The chemist is accustomed to deriving structures and preferred conformations of organic compounds from rigid molecular models and standard values for bond lengths, bond angles, and torsional profiles. In the case of strained compounds, this rigid structural model has to be abandoned and replaced by a flexible one which takes individual conditions of strain into consideration. It is shown, on the basis of new experimental structural data, that the force field method is suitable and highly reliable for the calculation of structural parameters and preferred conformations of strained compounds. It is, therefore, capable of replacing the rigid molecular model. Furthermore, the systematic analysis of strain induced angle and bond deformation gives a new pivot for the development of a qualitative discussion of deformation in strained molecules and hence for improved conformational analysis.-In the course of this work we were able to isolate two rotamers of D,L-3,4-di(1-adamantyl)-2,2,5,5-tetramethylhexane; this is the first isolation of a rotamer pair of an aliphatic hydrocarbon.

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Thermolabile Kohlenwasserstoffe, VIII. Thermolysen von 1,2‐Dialkyl‐1,2‐diphenylethanen

Cited by 36 publications

References 61 publications

Tracking “Invisible” Alkylchlorocarbenes by Their σ → p Absorptions: Dynamics and Solvent Interactions

Tracking “Invisible” Alkylchlorocarbenes by Their σ → p Absorptions: Dynamics and Solvent Interactions

Thermolabile Kohlenwasserstoffe, XVI. Thermische Stabilität, Spannungsenthalpie und Struktur symmetrisch tetrasubstituierter Ethane

Consequences of Strain for the Structure of Aliphatic Molecules

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