26891-70-3Relevant articles and documents
Rate Constants for Chalcogen Group Transfers in Bimolecular Substitution Reactions with Primary Alkyl Radicals
Curran, Dennis P.,Martin-Esker, Amanda A.,Ko, Sung-Bo,Newcomb, Martin
, p. 4691 - 4695 (2007/10/02)
Rate constants for group transfers of the MeS, PhS, PhSe, and PhTe groups from chalcogen-substituted acetate, acetonitrile, malonate, and malononitrile compounds, from N-(phenylthio)phthalimide and from Me2S2 and Ph2S2 to primary alkyl radicals, have been determined by competition kinetics using PTOC esters as the radical precursors and competing trapping agents.Thio group transfers from malononitrile derivatives are marginally faster than the corresponding group transfer from the symmetrical disulfide, and the rate constant for PhSe group transfer from PhSeSePh isgreater than those from the derivatives studied here.Substituent effects suggest that the chalcogen transfer reactions may be concerted.For three cases in which direct comparisons can be made, the rate constants for reactions of phenylchalcogenides are approximately equal to those for halogen atom transfer when the chalcogen and halide are in the same row of the periodic table and the radical resulting from displacement is the same.The rate constants reported in this work will be useful for the rational design of synthetic schemes based on homolytic group transfer chemistry.
Fast Halogen Abstraction from Alkyl Halides by Alkyl Radicals. Quantitation of the Processes Occurring in and a Caveat for Studies Employing Alkyl Halide Mechanistic Probes
Newcomb, Martin,Sanchez, Robert M.,Kaplan, Jere
, p. 1195 - 1199 (2007/10/02)
Second-order rate constants for halogen atom transfer (kRX) in benzene at 50 deg C were determined for reactions of octyl radical with tert-butyl, isopropyl, and cyclohexyl iodides and bromides and with ethyl iodide, n-butyl bromide, tert-butyl chloride, and carbon tetrachloride using two methods.In method A, an aklyl iodide and tributylstannane were allowed to compete for octyl radical in radical-chain reactions; in method B, an alkyl halide competed with 1-(oxononoxy)-2(1H)-pyridinethione (1) for octyl radical.The values for kRX were calculated from the product distributions, the reactant ratios, and the known rate constants for reaction of tributylstannane or 1 with octyl radical.The possibility that rearranged products can be formed in reactions of alkyl halide mechanistic probes with nucleophiles via a sequence involving radical-chain isomerization that converts the probe halide into a rearranged halide followed by nucleophilic attack on the isomerized halide is discussed as are possible chain-terminating reactions.The conclusion is reached that the percentage of rearranged substitution products formed in reactions of alkyl halide mechanistic probes with nucleophiles can give misleading information about the number of radical-initiating events.
