Hydrogen shift reaction

Here is the input file for an optimization of the transition structure for the reaction H3CO —t H2COH (a simple 1,2 hydrogen shift reaction). We specify a UHF calculation (open shell) since the molecular system is a doublet ... 

When 150 is thermolyzed at 230 °C it rearranges to at least three isomers, 155-157, which comprise approximately 75% of the product mixture100. Very likely this process is initiated by two 1,5-hydrogen shift reactions providing the isomer 154 first. Before this can undergo a third 1,5-hydrogen migration process to the most stable isomer 155 — formally... 

It is known" that the 1,2-hydrogen shift reaction is catalyzed by base (triethylamine, alcohols, water). Indeed, the decay of the ylidic adducts of... 

One interesting feature of anion radical photochemical behavior has been described recently by Camps et al. (2001). The anion radical of bromoadamantane loses bromide and gives the adamantyl radical. This photoactivated radical undergoes 1,5-hydrogen shift. Reactions of such kinds were not observed before. 

The aromaticities of symmetry-allowed and -forbidden transition states for electrocyclic reactions and sigmatropic rearrangements involving two, four, and six r-electrons, and Diels-Alder cycloadditions, have been investigated by ab initio CASSCF calculations and analysis based on an index of deviation from aromaticity. The order of the aromaticity levels was found to correspond to the energy barriers for some of the reactions studied, and also to the allowed or forbidden nature of the transition states.2 The uses of catalytic metal vinylidene complexes in electrocycliza-tion, [l,5]-hydrogen shift reactions, and 2 + 2-cycloadditions, and the mechanisms of these transformations, have been reviewed.3... 

The degenerate [1,5] hydrogen shift reaction of (Z)-l,3-pentadiene has been studied by a number of ab intio [67-69] and semiempirical [70-72] methods. Since the energy of concert [73] for this reaction is approximately 40 kcal/mol, there is no doubt that this reaction has a concerted mechanism with an aromatic... 

In fact, the 67 68 rearrangement constitutes the first homo [1,5] hydrogen shift reaction to... 

The simplest sigmatropic hydrogen shift reaction is the degenerate positional migration of a hydrogen atom across the allylic carbon skeleton in propene from C-l to C-3 (1 < 2), and vice versa. 

One of the major problems in determining the PES is the choice of appropriate coordinates, which allow the important features and characteristic points to show up in the PES. In the case of the hydrogen-shift reaction from Cj to C7 in CHT, the position of the migrating hydrogen H , can be described by its distance R from the center of the C1-C7 bond and the angle 0, which describes the rotation aroimd an axis through C4 and the center of the C1-C7 bond (i.e., in the molecular plane and perpendicular to the C7-C7 bond) as indicated in Figure 6.2. 

In the investigation of /BA oligomers, 1,5-hydrogen shift reaction mechanism was explained by a combination of formation of a kinetically favorable six-membered ring stmcture and thermodynamically favorable transfer from secondary to tertiary radical (Fig. 3a) [15],... 

In the case of the radical prepared from the pentamer there are two chances of 1,5-hydrogen shift reaction from the initially generated radical. The initial radical center migrated to form mid-chain radical through six-membered ring stracture and then the mid-chain radical moved to form a radical located at the other end of the pentamer. Since expected spectroscopic features of radicals at... 

Perfluorohexane was the least reactive solvent we could imagine. Low Arrhenius parameters were still obtained for dimethylcarbene in perfluorohexane (Figure 8) but values close to those predicted were obtained for perdeutero-methylcarbene (20-d6). From this we concluded that quantum mechanical tunneling contributes to the 1, 2-hydrogen shift reaction of dimethylcarbene but has a smaller contribution to the rearrangement of the perdeuterated isotopomer. [31]... 

The steam reforming of natural gas is conducted in two stages. The first step is the extraction of carbon monoxide and hydrogen from methane and water under high pressure (15-25 bar) and high temperature (750-1000 °C). A catalyst accelerates the reaction. In the second step, water is added that splits the carbon monoxide into carbon dioxide and hydrogen (shift reaction). 

ABSTRACT. Alkynes, when activated by an electron-rich d Re, Mo or W phosphinic centre, undergo hydrogen shift reactions (to give, e.g., vinylidene species) or oxidatively add to the metal (forming alkynyl--hydrido or alkynyl complexes). These alkyne-derived products undergo 3-protonation to afford a variety of carbyne-fluoro or -chloro complexes, whereas aminocarbynes are obtained upon 3-electrophilic attack (e.g., by a protic or a Lewis acid) at isocyanides when ligating such metal sites. Mechanistic studies, by stopped-flow spectrophotometry, are also indicated. 

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