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Reactions abstraction

Xi M and Bent B E 1993 Reaction of deuterium atoms with cyclohexane on Cu(111)—hydrogen abstraction reactions by Eley-Rideal mechanisms J. Phys. Chem. 97 4167... [Pg.919]

Maeda K, Terazima M, Azumi T and Tanimoto Y 1991 CIDNP and CIDEP studies on intramolecular hydrogen abstraction reaction of polymethylene-linked xanthone and xanthene. Determination of the... [Pg.1620]

Hemmi N and Suits A G 1998 The dynamics of hydrogen abstraction reactions crossed-beam reaction Cl +... [Pg.2088]

CASREACT (Chemical Abstracts Reaction Search Service) is a reaction database started in 1985 with more than 6.7 million reactions (3 million single-step and 3.7 million multi-step reactions) (March, 2003) derived from 400 000 documents (journals, patents, etc.). The records contain the following information ... [Pg.263]

Hydrogen-abstraction reactions-. Kadical-decomposition reactions-. [Pg.125]

Nevertheless, many free-radical processes respond to introduction of polar substituents, just as do heterolytic processes that involve polar or ionic intermediates. The substituent effects on toluene bromination, for example, are correlated by the Hammett equation, which gives a p value of — 1.4, indicating that the benzene ring acts as an electron donor in the transition state. Other radicals, for example the t-butyl radical, show a positive p for hydrogen abstraction reactions involving toluene. ... [Pg.700]

Intramolecular hydrogen abstraction reactions have also been observed in mediumsized rings. The reaction of cyclooctene with carbon tetrachloride is an interesting case. As shown in the equation below, whereas bromotrichloromethane adds to cyclooctene in a completely normal manner, carbon tetrachloride gives some 4-chloro-l-trichloromethyl-cyclooctane as well as the expected product ... [Pg.719]

The converse of polymerization is heterolytic bond scission leading either to R3Sn+ or R3Sn species. Tricoordinate organotin(IV) cations can readily be synthesized at room temperature by hydride or halide abstraction reactions in benzene or other solvents.For example, with R = Me, Bu or Ph ... [Pg.401]

The first term is of importance in all atom abstraction reactions, however, since the reactions are often highly exothermic with consequent early transition slates, the effect may be small. [Pg.31]

Polar factors can play an extremely important role in determining the overall reactivity and specificity of hotnolytic substitution.97 Theoretical studies on atom abstraction reactions support this view by showing that the transition state has a degree of charge separation.101 10 ... [Pg.31]

A striking illustration of the influence of polar factors in hydrogen abstraction reactions can be seen in the following examples (Figure 1.8) where different sites on the molecule are attacked preferentially according to the nature of the attacking radical.67... [Pg.31]

A simple unifying theory to explain rate and specificity in atom abstraction reactions has yet to be developed. However, as with addition reactions, it is possible to devise a set of guidelines to predict qualitatively the rate and outcome of radical transfer processes. The following are based on those suggested by Tedder 2... [Pg.36]

Stames el al.I7 have provided support for the above mechanism (Scheme 6.29) by determining the unsaturated chain ends (112) in low conversion PVAc by l3C NMR. They were able to distinguish (112) from chain ends that might have been formed if transfer involved abstraction of a vinylic hydrogen. The number of unsaturated chain ends (112) was found to equate with the number of -CH OAc ends suggesting that most chains arc formed by transfer to monomer. Stames et a . 13 also found an isotope effect k kD of 2.0 for the abstraction reaction with CTTpCHOiCCD as monomer. This result is consistent with the mechanism shown in Scheme 6.28 but is contrary to an earlier finding.174... [Pg.318]

It is thus anticipated that compressive stress inhibits while tensile stress promotes chemical processes which necessitate a rehybridization of the carbon atom from the sp3 to the sp2 state, regardless of the reaction mechanism. This tendency has been verified for model ring-compounds during the hydrogen abstraction reactions by ozone and methyl radicals the abstraction rate increases from cyclopropane (c3) to cyclononane (c9), then decreases afterwards in the order anticipated from Es [79]. The following relationship was derived for this type of reactions ... [Pg.105]

The formation of adduct is followed by fragmentation and subsequent H-atom abstraction reaction from the sulfinic acid produced. Strong acid solutions of aromatic sulfoxides like thianthrene 5-oxide (7) or phenothiazine 5-oxide (8) gives rise to ESR signals, which... [Pg.1055]

The abstraction reaction, generally, is not a common feature of sulfonyl radicals,... [Pg.1102]

FIGURE 1.7. The potential energy surface of the CH4 + C1 supersystem for the collinear hydrogen abstraction reaction CH4 + Cl—> CH3 + HC1. The counter lines are given in spaces of 10 kcal/mol and the coordinates in angstroms. [Pg.26]

Abstraction reactions, see Hydrogen abstraction reactions Activation energy, see Free energy, of activation... [Pg.229]

Hydrogen abstraction reactions potential surfaces for, 25-26,26,41 resonance structures for, 24 Hydrogen atom, 2 Hydrogen bonds, 169,184 Hydrogen fluoride, 19-20, 20,22-23 Hydrogen molecules, 15-18 energy of, 11,16,17 Hamiltonian for, 4,15-16 induced dipoles, 75,125 lithium ion effect on, 12... [Pg.232]

We also observe other effects of translational energy in methane which are similar to those found in hydrogen. There is an abstraction reaction for parent ions which also produces a hydronated methane. In studying the reaction... [Pg.131]

Thus we think of the chemical ionization of paraffins as involving a randomly located electrophilic attack of the reactant ion on the paraffin molecule, which is then followed by an essentially localized reaction. The reactions can involve either the C-H electrons or the C-C electrons. In the former case an H- ion is abstracted (Reactions 6 and 7, for example), and in the latter a kind of alkyl ion displacement (Reactions 8 and 9) occurs. However, the H abstraction reaction produces an ion oi m/e = MW — 1 regardless of the carbon atom from which the abstraction occurs, but the alkyl ion displacement reaction will give fragment alkyl ions of different m /e values. Thus the much larger intensity of the MW — 1 alkyl ion is explained. From the relative intensities of the MW — 1 ion (about 32%) and the sum of the intensities of the smaller fragment ions (about 68%), we must conclude that the attacking ion effects C-C bond fission about twice as often as C-H fission. [Pg.180]

Thus, the process of hydride ion abstraction from a primary position is approximately thermoneutral, and hence we must conclude that it is an energetically allowed process, although possibly with a relatively small reaction rate. A process competing with primary H abstraction (Reaction 13) is methide ion abstraction (Reaction 11, loss of CH4 from the... [Pg.186]

Correlated or geminate radical pairs are produced in unimolecular decomposition processes (e.g. peroxide decomposition) or bimolecular reactions of reactive precursors (e.g., carbene abstraction reactions). Radical pairs formed by the random encounter of freely diffusing radicals are referred to as uncorrelated or encounter (P) pairs. Once formed, the radical pairs can either collapse, to give combination or disproportionation products, or diffuse apart into free radicals (doublet states). The free radicals escaping may then either form new radical pairs with other radicals or react with some diamagnetic scavenger... [Pg.58]


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A-hydrogen abstraction reactions

Abstract reaction scheme

Abstraction Reactions of Radicals

Abstraction reaction with organic molecules

Abstraction reaction, cross-linking

Abstraction reactions, energies

Abstraction substitution reactions

Abstraction, multiple reaction paths

Alkyl complexes, hydride abstraction reactions

Amino radicals, abstraction reactions

Atom abstraction reaction

Atom abstraction, photoinitiated reactions

Bromine atoms, abstraction reactions

CASREACT Chemical Abstracts Service Reactions

Carbenes abstraction reactions

Chemical Abstracts Service Reactions System

Chlorine atoms, abstraction reactions

Difluoroamino radicals, abstraction reactions

Ethyl radicals, abstraction reactions

Excited-state reactions ketones, hydrogen abstraction

Fluorine atoms, abstraction reaction

Free radicals hydrogen abstraction reactions

Group 4 metal substituents hydride abstraction reactions

H atom abstraction reaction

H-abstraction reactions

Halide abstraction reactions

Halogen abstraction reactions

Halogen atom abstraction reactions

Hydride abstraction reactions

Hydride abstraction reactions from metal hydrides

Hydride abstraction reactions from organic ligands

Hydride abstraction reactions, group

Hydride complexes abstraction reactions

Hydrocarbons, hydride abstraction reactions

Hydrogen Abstraction (Yang Reaction)

Hydrogen Abstraction and Fragmentation Reactions

Hydrogen Bonds and Proton Abstraction Reactions

Hydrogen abstraction Hammett reaction constants

Hydrogen abstraction chain transfer reactions

Hydrogen abstraction reaction rates

Hydrogen abstraction reactions

Hydrogen abstraction reactions, difluoroamino

Hydrogen abstraction reactions, halogenation

Hydrogen abstraction reactions, reversibility

Hydrogen abstraction, ketones competing reactions

Hydrogen atom abstraction in photochemical reactions

Hydrogen atom abstraction intramolecular reactions

Hydrogen atom abstraction reactions

Hydrogen atom abstraction reactions photochemical

Hydrogen atom abstraction tunneling reactions

Hydroxyl radicals, abstraction reactions

Insertion reactions triplet carbenes, hydrogen abstraction, product

Insertion, Abstraction, and Rearrangement Reactions of Carbenes

Intermolecular Hydrogen-abstraction Reactions

Intramolecular and Intermolecular H-Abstraction Reactions

Intramolecular hydrogen abstraction reaction

Iodine atom abstraction reactions, with

Iodine atoms, abstraction reactions

J Abstract Reaction Systems and Their Models

Metal clusters abstraction reaction

Methoxy radicals, abstraction reactions

Methyl radicals, abstraction reactions

Nitrenes abstraction reactions

Nucleophilic reactions Abstraction

Organic reactions abstracted

Oxygen abstraction reactions

Oxygen atoms, abstraction reactions

Photo-Induced Hydrogen Abstraction and Addition Reactions of Aromatic Compounds

Propyl radicals, abstraction reactions

Proton abstraction reaction

Proton abstraction reaction, solvent effects

Pyruvic acid, hydrogen abstraction reaction

Radical abstraction and addition reactions

Radical abstraction reaction

Radical reactions atom abstraction

Radical reactions hydrogen abstraction

Radical reactions hydrogen atom abstraction

Reaction barriers of radical hydrogen abstractions

Reaction with Free Radicals Hydrogen Atom Abstraction and One- or Three-Electron Bonding

Substitution and Atom Abstraction Reactions

Sulfur atom abstraction reactions

Sulfur atom abstraction reactions structures

Sulfur atom abstraction reactions sulfide

Thermal abstraction reactions

Thermal abstraction reactions atoms

Thermolysis hydrogen abstraction reaction

Third Example Proton Transfer and Hydrogen Abstraction Reactions

Time resolved studies of OH abstraction reactions

Titanium oxygen abstraction reactions

Topic 11.2. Structure-Reactivity Relationships in Hydrogen Abstraction Reactions

Trialkylsilanes, hydrogen abstraction reactions

Trichloromethyl radical proton abstraction reaction

Trichloromethyl radicals, abstraction reactions

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