Hydroxyl radical-induced oligomerization of ethylene in deoxygenated aqueous solution

Abstract

Deoxygenated aqueous solutions of ethylene (4 x 1 0 -3 ~) and nitrous oxide (9 x 10-3M) were irradiated with y-60Co rays at dose rates of 2.6 x 1 015 and 2.1 x 1 Ofs eV g -l s-l. The most prominent among the 1 9 products determined are butane-l,4-diol, hexane-l,6-diol, and octane-l,8-diol. A satisfactory material balance with respect to primary water radicals was obtained. In the radiolysis of N,O-containing water the major part (ca. 90%) of the primary radicsls are OH radicals which are scavenged by ethylene to give (3-hydroxyethyl radicals. These radicals either combine, butane-1 ,$-dial being the product [reaction (i)], or add to ethylene [reaction (ii)]. The 2 H 0-C H2-C H , H 0-CH ,-( CH,),-C H 2 0 H 0) (ii) HO-CH,-CH, + CH,=CH, + HO-CH2-(CH2),-CH2 self-termination rate constant has been measured by pulse radiolysis [2k(i) = ( 5 f 2) x lo8 I mol-l s-l]. The propagation rate constant [k(ii) = (3 f 2) x lo4 I mot-l s-I] has been derived from the dose rate dependence of G(diols) by computer-aided fitting. The (3-hydroxyethyl radicals are readily oxidized by copper(!!) ions ( 5 x M). The major product is ethylene oxide [reaction (iii)], and little (ca. 3%) ethylene glycol is formed [reaction ( W I .

Towards understanding vacuolar antioxidant mechanisms: a role for fructans?

“…Three main mechanisms are devoted to the direct scavenging of ·OH radicals: electron transfer (·OH+R→OH – +R + ); hydrogen abstraction (RH+·OH→R·+H 2 O) and addition to an aromatic ring or to a double bond yielding an addition product (·OH+R=R→HO-R-R·). If double bonds are present, addition is the preferable reaction (Soylemez and von Sonntag, 1980; Czapski, 1984; Hernandez-Marin and Martínez, 2012). This hypothesis was tested further by comparing dihydrocaffeic acid and caffeic acid, only differing by the presence of a double bond in the side chains of the latter (Supplementary Fig.…”

The basics of oxidants in water treatment. Part A: OH radical reactions

“…Yet, with ethene (Söylemez and von Sonntag, 1980) and benzene, that have a double bond to which the z OH radical can add, H-abstraction is negligible.…”

Oxidation of benzyl radicals by Fe(CN)6 3?

“…This may be one of the reasons why the material balance is poorer at pH 13.7 than at pH 7. The major product, 4-chlorobenzaldehyde cannot be formed uia reactions 2) one might suggest that the radical cation formed in reaction (20) could react with water at the exocyclic methylene group [reaction (21)]. The resulting radical could then be further oxidized by Fe(CN),3-and react with water [reactions (22) and 23)].…”

“…The resulting radical could then be further oxidized by Fe(CN),3-and react with water [reactions (22) and 23)]. This mechanistic proposal can be tested by studying the reaction of 4-chlorobenzyl alcohol with the 'OH radical [reactions ( 25)-( 27)] which will produce to a large extent the same radical as that formed in reaction (21)…”

“…For their identification the radiation products were extracted from the aqueous solutions into diethyl ether with a Ludwig extractor (Normag). After drying (Na,SO,) the diethyl ether extract was concentrated, the residue trimethylsilylated with N,N-bis(trimethylsily1)trifluoroacetamide (BSTFA; Macherey Nagel) to convert phenols into their trimethylsilyl ethers and analy sed by gas chroma t ograp hy-mass spectrometry (Hewle tt -Packard 5971A mass selective detector coupled with an HP 5890 Series I1 gas chromatograph), 12 m x 0.2 mm HP-Ultra 1 (crosslinked silicone gum) column, temperature programmed, 60-270 "C. The mass spectra of the products are characterized by their most abundant m/z (the chlorine-containing ions are indicated with an asterisk): 4-chlorobenzaldehyde (MW = 140): 50 (27%), 75 (38), 11 1 (60), 139 (loo)* and 140 (77)*; 4chloro-2-hydroxytoluene-TMS (MW = 214): 73 (15%), 93 (58), 105 (26), 163 (81), 199 (loo)* and 214 (40)*; 4-chloro-3hydroxytoluene-TMS (MW = 214): 73 (23%), 93 (18), 125 (34), 163 (lo), 199 (loo)* and 214 (45)*; 4-chloro-benzyl alcohol-TMS (MW = 214): 73 (779, 93 (7), 125 (loo), 169 (21), 179 (18), 199 (49)* and 214 (4)*; 4-chloro-2hydroxybenzaldehyde-TMS (MW = 228): 75 (1 373, 1 1 1 (37), 139 (69)*, 169 (46), 213 (loo)* and 228 (5)*.…”