Di‐
            <i>t</i>
            ‐Butyl Nitroxide

Hoffmann, Arthur Kentaro; Feldman, Allan M.; Gelblum, Ernestine; Henderson, Alan

doi:10.1002/0471264180.os048.19

Cited by 7 publications

(8 citation statements)

References 2 publications

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“…The energy of activation for direct formation of 15g13 from 9 is higher than those for formation of 14a and of 15a from 9 by 2.75 Ϯ 0. 44 (17) [76] and N,NЈ-diisopropylbenzene-1,4-diamine [77] were prepared according to the literature. Compound 17 was purified by distillation through a Vigreux column at 15 mbar.…”

Section: Resultsmentioning

confidence: 99%

The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

et al. 2002

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Keywords: Cycloaddition / Radicals / Reaction mechanisms / ThermochemistryThe thermal [2+2] cyclodimerisation of (E,Z)-cycloocta-1,3diene (9), which is known to afford the cyclobutane dimers 11, 12, and 13, has been investigated in the presence of the nitroxyls 17 and 18 and of atmospheric dioxygen, all of which are known to be efficient trapping agents for carbon-centred free radicals. The nitroxyls have been found to divert the reaction from formation of the dimers to formation of 2:2 adducts of two molecules of 9 and two molecules of nitroxyl. The rate constant for the formation of the overall sum of the dimers plus the 2:2 adducts in the presence of nitroxyl has been found to equal the rate constant for the formation of dimers in the absence of nitroxyl. This and the molecular structures of the 2:2 adducts prove that two molecules of 9 combine irreversibly to produce the two epimeric bis(allylic) 1,4-diradicals 14 and 15 (meso and rac, respectively) which undergo two competing reactions: ring-closure to dimers 11, 12, and 13, and trapping by nitroxyl to form the 2:2 adducts. Dioxygen, too, was found to trap 14 and 15 efficiently. From the kinetics of the latter trapping reaction, studied at six temperatures between 5 and 55°C, the heights of the activation barriers separating 14 from 11 and 15 from 12 + 13 were estimated at 11.1 ± 1.5 and 10.2 ± 1.5 kcal·mol −1 , respectively, corresponding to diradical lifetimes of ca. 0.5 µs. These unexpectedly high barriers have been verified by MM3 force-field calculations and by an investigation of the kinetics of the gas-phase thermolysis of 12 (to give 13 and 16 which is an epimer of 12 and 13) and of 13 (to give 12 and 16). When the [a]

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Section: Resultsmentioning

confidence: 99%

The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

et al. 2002

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“…We first review the discrete generalization of the Frenet equations [39]. We show by an explicit computation, that the two known integrable discretizations introduced in [35] and [36] coincide [40], by devising an explicit change of variables that maps these models to each other. We then proceed to a discretization of the Zakharov-Shabat recursion relation.…”

Section: Introductionmentioning

confidence: 99%

Energy functions for stringlike continuous curves, discrete chains, and space-filling one dimensional structures

Jiang

Niemi

2013

Phys. Rev. D

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The theory of string-like continuous curves and discrete chains have numerous important physical applications. Here we develop a general geometrical approach, to systematically derive Hamiltonian energy functions for these objects. In the case of continuous curves, we demand that the energy function must be invariant under local frame rotations, and it should also transform covariantly under reparametrizations of the curve. This leads us to consider energy functions that are constructed from the conserved quantities in the hierarchy of the integrable nonlinear Schrödinger equation (NLSE). We point out the existence of a Weyl transformation that we utilize to introduce a dual hierarchy to the standard NLSE hierarchy. We propose that the dual hierarchy is also integrable, and we confirm this to the first non-trivial order. In the discrete case the requirement of reparametrization invariance is void. But the demand of invariance under local frame rotations prevails, and we utilize it to introduce a discrete variant of the Zakharov-Shabat recursion relation. We use this relation to derive frame independent quantities that we propose are the essentially unique and as such natural candidates for constructing energy functions for piecewise linear polygonal chains. We also investigate the discrete version of the Weyl duality transformation. We confirm that in the continuum limit the discrete energy functions go over to their continuum counterparts, including the perfect derivative contributions. * Electronic address: hushuangwei@gmail.com † Electronic address: yjiang@shu.edu.cn ‡ Electronic address: Antti.Niemi@physics.uu.se 1 arXiv:1210.7371v1 [hep-th]

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“…44 (17) [76] and N,NЈ-diisopropylbenzene-1,4-diamine [77] were prepared according to the literature. These singlet gauche diradicals are not trapped by nitroxyl or by dioxygen.…”

Section: Resultsmentioning

confidence: 99%

The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

et al. 2002

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Di‐ t ‐Butyl Nitroxide

Abstract: Di‐ t ‐butyl nitroxide product: di‐ t ‐butyl nitroxide

Cited by 7 publications

References 2 publications

The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

Energy functions for stringlike continuous curves, discrete chains, and space-filling one dimensional structures

The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

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