4598-47-4Relevant articles and documents
Atmospheric chemistry of 1,4-dioxane. Laboratory studies
Platz,Sehested,Mogelberg,Nielsen,Wallington
, p. 2855 - 2863 (1997)
A pulse radiolysis technique was used to measure the UV absorption spectra of c-C4H7O2 and (c-C4H7O2)O2 radicals over the range 220-320 nm, σ(c-C4H7O2)250 nm = (5.9 ± 0.6) × 10-18 and σ[(c-C4H7O2)O2]240 nm = (4.8 × 0.8) × 10-18 cm2 molecule-1. The observed self-reaction rate constants for the c-C4H7O2 and (c-C4H7O2)O2 radicals, defined as -d[c-C4H7O2]/dt = 2k4[c-C4H7O2]2 and -d[(c-C4H7O2)O2]/dt = 2k5 obs[(c-C4H7O2)O2]2 were k4 = (3.3 ± 0.4) × 10-11 and k5 obs = (7.3 ± 1.2) × 10-12 cm3 molecule-1 s-1. The rate constants for reactions of (c-C4H7O2)O2 radicals with NO and NO2 were k6 (1.2 ± 0.3) × 10-11 and k7 = (1.3 ± 0.3) × 10-11 cm3 molecule-1 s-1, respectively. The rate constants for the reaction of F atoms with 1,4-dioxane and the reaction of c-C4H7O2 radicals with O2, were k3 = (2.4 ± 0.7) × 10-10 and k2 = (8.8 ± 0.9) × 10-12 cm3 molecule-1 s-1, respectively. A relative rate technique was used to measure the rate constant for the reaction of Cl atoms with 1,4-dioxane, k17 = (2.0 ± 0.3) × 10-10 cm3 molecule-1 s-1. A long-pathlength FTIR spectrometer coupled to a smog chamber system was used to show that the sole atmospheric fate of the alkoxy radical (c-C4H7O2)O is decomposition via C-C bond scission leading to the formation of H(O)COCH2CH2OC(O)H (ethylene glycol diformate).
Absolute Rate Constants for the Reactions of tert-Butoxyl with Ethers: Importance of the Stereoelectronic Effect
Malatesta, V.,Scaiano, J. C.
, p. 1455 - 1459 (1982)
Absolute rates of hydrogen atom abstraction by tert-butoxyl from variety of cyclic and acyclic ethers, orthoformates, and acetals have been measured at 27 deg C by laser flash photolysis techniques.High rates of abstraction from the C-H bond adjacent to oxygen and forming small dihedral angle (ca. 30 deg) with the ?-type orbital(s) on the oxygen(s) have been observed.For larger dihedral angles (ca. 90 deg) the rate of C-H abstraction is much lower.Arrehenius parameters have also been measured for a few representative cyclic ethers.
On the mechanism of reaction of radicals with tirapazamine
Shi, Xiaofeng,Mandel, Sarah M.,Platz, Matthew S.
, p. 4542 - 4550 (2007)
Ketyl radicals produced by photolysis of ketones or di-tert-butyl peroxide (DTBP) in alcohol solvents react rapidly with tirapazamine (TPZ). The acetone ketyl radical (ACOH) reacts with TPZ with an absolute second-order rate constant of (9.7 ± 0.4) × 108 M-1 s-1. The reaction kinetics can be followed by monitoring the bleaching of TPZ absorption at 475 nm or the formation of a reaction product which absorbs at 320 and 410 nm. The ACOD radical reacts with TPZ in 2-propanol-OD with an absolute rate constant of (6.7 ± 0.5) × 108 M-1 s -1 corresponding to a kinetic isotope effect (KIE) of 1.4. Deuteration of the radical on carbon (ACOH-d6) retards the reaction of the radical with TPZ even further (absolute rate constant = (4.8 ± 0.04) × 108 M-1 s-1). This result corresponds to a KIE of 2.0. Radicals derived from dioxane and diisopropyl ether by flash photolysis of DTBP in ethereal solvent react with TPZ more slowly than do ketyl radicals. It is concluded that ketyl radicals react, in part, with TPZ in organic solvents by transfer of a hydrogen atom from the OH and CH 3 groups of the ketyl radical to the oxygen atom at the N4 position of TPZ to form acetone or acetone enol and a radical derivative of TPZ (TPZH). The latter species absorbs at 320 and 405 nm, has a lifetime of hundreds of microseconds in alcohol solvents, and decays by disproportionation to form TPZ and a reduced heterocycle. The reduced heterocycle eventually forms a desoxytirapazamine by a polar mechanism. The results are supported by density functional theory calculations. It is proposed that dioxanyl radical will also react, in part, with TPZ by transfer of a hydrogen atom from the carbon adjacent to the radical center to the oxygen atom at the N4 position of TPZ. This produces the enol ether and the previously mentioned TPZH radical. It is further posited that ether radicals react a bit more slowly than ketyl radicals because they lack the second mode of hydrogen transfer (from the OH group) that is present in the ACOH radical. Our data are permissive of the possibility that ether radicals add to TPZ at a rate that is competitive with β-hydrogen atom transfer.
The interplay of electronic, steric and stereoelectronic effects in hydrogen-atom abstraction reactions of SO4-., revealed by ESR spectroscopy
Gilbert, Bruce C.,Smith, John R. Lindsay,Taylor, Philip,Ward, Steven,Whitwood, Adrian C.
, p. 1631 - 1638 (2007/10/03)
Attack by SO4-. (generated by photolysis and one-electron transfer on a number of carbohydrates and some model compounds has been followed directly by ESR spectroscopy. SO4-. is a reactive, electrophilic species but is more selective
