2154-62-3

Upstream product

• 2154-76-9 cyclopropylmethyl 
• 6142-73-0 methylene cyclopropane 
• 287-23-0 cyclobutane 
• 61704-47-0 1,2-di(but-3-en-1-yl)disulfide 
• 22110-53-8 1-adamantyl isocyanide 

Relevant academic research and scientific papers

Alkanethioimidoyl Radicals: Evaluation of β-Scission Rates and of Cyclization onto S-Alkenyl Substituents

Thioimidoyl radicals were generated by addition of alkylsulfanyl radicals to alkyl isonitriles and were characterized by electron paramagnetic resonance (EPR) spectroscopy. The β-scissions of their C·S-C bonds were studied by variable-temperature EPR spectroscopy and the fragmentation rate constants and activation energies were calculated. The scission rates depend on the stability of the released alkyl radicals but in any case, at room temperature, the processes were fast. Data collected on similar oxyimidoyls showed that their fragmentations are slightly slower compared to those of analogous thioimidoyls. The scission rates of selenoimidoyls could not be studied by EPR and were evaluated by theoretical calculations. EPR experiments also enabled both β-scission and 5-exo ring closure rate constants of two S-but-3-enyl-substituted imidoyl radicals to be determined, showing that cyclization prevails only at low temperatures. Density functional theory (DFT) theoretical calculations predicted that the fragmentation process preferentially occurs from the s-cis rotamers (X-C bond) of the imidoyl radicals. Thio- and seleno-imidoyls (but not oxyimidoyls) prefer s-trans conformations so that their fragmentations involve prior rotation about the X-C bond.

Kinetics and equilibrium constants for reactions of α-phenyl- substituted cyclopropylcarbinyl radicals

Laser-flash photolysis methods were used to determine Arrhenius functions for cyclizations of the 4,4-diphenyl-3-butenyl (2) and trans-4- phenyl-3-butenyl (5) radicals to the 1,1-diphenylcyclopropylcarbinyl (1) and 1-phenylcyclopropylcarbinyl (4) radicals, respectively. At 20 °C, the cyclization rate constants are 1.7 x 107 and 5.4 x 106 s-1. Equilibrium constants for the two processes were estimated and evaluated with thermochemical data and via computational methods, and Arrhenius functions for the ring-opening reactions of the cyclopropylcarbinyl radicals were calculated. The cyclization reactions of 2 and 5 are strongly enthalpy controlled. Production of radicals 1 and 2 from the corresponding tert- butylperoxy esters in the presence of Et3SnH gave diphenylcyclopropylmethane and 1,1-diphenyl-1-butene from H-atom trapping of radicals 1 and 2 and 4- phenyl-1,2-dihydronaphthalene which derives from the product radical formed by addition of the radical moiety in 2 to the cis-phenyl group. Rate constants for the latter cyclization of 2 and for reactions of radicals 1 and 2 with Et3SnH were obtained from the indirect kinetic studies.

Small rings, 91: Fragmentation of cyclobutane in a bromine-doped and undoped xenon matrix

Irradiation (λ = 254 nm) of cyclobutane in a bromine-doped xenon matrix leads to ring opening in spite of the fact that cyclobutane does not absorb in this region. The main products are ethene and 1-butene. The same reaction, but less effectively, occurs upon irradiation with a laser (KrF laser, λ = 248 nm) in the absence of the halogen. The difference in the mechanisms of the two fragmentations is discussed. VCH Verlagsgesellschaft mbH, 1996.

Homogeneous Rate Constants for Coupling between Electrochemically Generated Aromatic Anion Radicals and Alkyl Radicals

Rate constants have been measured for the coupling between hexenyl radicals and 2,2-dimethylhexenyl radicals and electrogenerated anion radicals of anthracene, 9,10-diphenylanthracene, benzophenone and quinoxaline.The rate constant for all four reactions in N,N-dimethylformamide is log k2 = 9.1(5), which is in accordance previous results in 1,2-dimethoxyethane for naphthalene and benzophenone anion radicals and 1-hexenyl radicals.The data indicate that the redox potential of the aromatic anion radical has only a minor influence on the rate of coupling with alkyl radicals.The rate constants for anion radicals of 9,10-diphenylanthracene and benzophenone were somewhat lower, 6(1) x 108 M-1 s-1, which for 9,10-diphenylanthracene might be caused by steric hindrance by the two phenyl groups.The conclusion is that the coupling reaction between aromatic anion radicals and alkyl radicals has all the characteristics of a radical-radical coupling.

Calibration of a new horologery of fast radical "clocks". Ring-opening rates for ring- and α-alkyl-substituted cyclopropylcarbinyl radicals and for the bicyclo[2.1.0]pent-2-yl radical

Rate constants have been determined at 37°C for the ring opening of a variety of alkyl-substituted cyclopropylcarbinyl radical "clocks" by nitroxide radical trapping (NRT) using TEMPO. Relative yields of unrearranged and rearranged trialkylhydroxylamines were measured at various TEMPO concentrations, and these data were then combined with absolute rate constants for the reactions of structurally appropriate alkyl radicals with TEMPO as determined by laser flash photolysis. Cyclopropylcarbinyl radicals, including the bicyclo[2.1.0]pent-2-yl radical, were generated by H-atom abstraction from the parent hydrocarbon and, in a few cases, also from the appropriate diacyl peroxide. Twelve substrates yielded sixteen clock reactions because some cyclopropylcarbinyls can undergo two different ring-opening reactions. For six methyl-substituted cyclopropylcarbinyls rate constants ranged from 0.8 × 108 s-1 for 1-methylcyclopropylcarbinyl to 47 × 108 s-1 for pentamethylcyclopropylcarbinyl. Rate constants for the ring opening of cyclopropylcarbinyl, α-methyl- and α,α-dimethylcyclopropylcarbinyl are 1.2, 0.70, and 0.88 × 108 s-1, respectively. Rate constants for H-atom abstraction by tert-butoxyl from various positions in the 12 cyclopropane substrates relative to the rate of H-atom abstraction from cyclopentane have also been determined by using competitive NRT.

Homolytic Reactions of Ligated Boranes. Part 11. Electron Spin Resonance Studies of Radicals Derived from Primary Amine-Boranes

Photochemically generated t-butoxyl radicals react with the primary amine-boranes RNH2->BH3 (R = Me or But) to form, initially, the nucleophilic amine-boryl radical RNH2->BH2, which subsequently abstracts hydrogen from the parent amine-borane to give the more stable isomeric aminyl-borane radical RNH->BH3.The amine-boryl radicals can be intercepted by alkyl bromides or chlorides or by nitriles, with which they react by halogen-atom abstraction or by addition to the CN group to give iminyl radicals, respectively.The e. s. r. spectra of the aminyl-borane radicals show the presence of extensive hyperconjugative delocalisation of the unpaired electron onto the BH3 group .Monoalkylaminyl-borane radicals react readily with alkenes, with arenes, and with conjugated or cumulated dienes to transfer a β-hydrogen atom from boron to give alkyl, cyclohexadienyl, or allyl radicals, respectively.Hydrogen atom transfer to alkenes from the electrophilic MeNH->BH3 takes place with high regioselectivity to give the more stable alkyl radical when two adducts are possible; the rate of transfer increases as the ionisation potential of the alkene decreases along the series CH2=CH2 BH3 to give the isopropyl radical was determined to be ca. 2 x 103 dm3 mol-1 s-1 at 282 K.Competition experiments have been carried out to determine the relative rates of the various reactions undergone by RNH2->BH2 and RNH->BH3.The results are interpreted with the aid of ab initio molecular-orbital calculations at the 6-31G level for RNH2->BH2, RNH->BH3, RNH2->BH3, and RNHBH2 (R = H or Me), together with similar calculations for the isoelectronic organic counterparts in which the NB moiety is replaced by a CC grouping.

A Convenient Method for Kinetic Studies of Fast Radical Rearrangements. Rate Constants and Arrhenius Function for the Cyclopropylcarbinyl Radical Ring Opening

An indirect method for studying the kinetics of radical rearrangements employing N-hydroxypyridine-2-thione esters as radical precursors and hydrogen atom transfer from thiophenol as the basis trapping reaction is demonstrated in a study of an archetypal fast radical reaction, the cyclopropylcarbinyl radical ring opening.Rate constants measured over the temperature range -37 to 50 deg C gave a temperature-dependent function for the ring opening of log(k/s-1)=(13.0+/-0.14)-(6.8+/-0.2)/θ and a rate constant for ring opening at 25 deg C of 1.0E8 s-1.The kinetic values from this work were combined with rate data from low-temperature ESR studies and higher temperature nitroxyl radical trapping studies to give an Arrhenius function of log(k/s-1)=13.15-7.05/θ that is recommended for calculations of rate constants for the title ring opening.