Halogen-based Oxidants

Reactions between aquatic HS and halogen-based oxidants, during water chlorination process, can lead to the formation of trihalomethanes, with potential carcinogenic effects. Carvalho et al. (2004) investigated reactions of tropical aquatic fulvic acids (AFA) with chlorine and formation of trihalomethanes through fluorescence spectroscopy. 

The compounds [M(CO)3(NCMe)3] have also been shown to undergo oxidative elimination with a range of other halogen-based oxidants including Br2, ICl, and IBr, to afford analogous seven-coordinate complexes. The reactivity of these compounds has been less extensively investigated than [Mol2(CO)3(NCMe)2]. 

SCHEME 13.144 Stoichiometric oxidation of 1,4-dihydropyridines 563 by halogen-based oxidants [251-257]. 

Oxidation of 1,4-Dihydropyridines to Pyridines with Stoichiometric Oxidants Many of the known stoichiometric oxidants were examined in the oxidation of 1,4-dihydropyridines to the corresponding pyridines. Thus, halogen-based oxidants, such as potassium bromate [251], sodium chlorite [252], calcium hypochlorite [253], iodic acid [254], its anhydride [255], iodine chloride [256], or hypervalent iodine species [257], give good results (Scheme 13.144). 

Behaviour with halogenated solvents, bases, oxidizing acids, amines and aromatic oxygenated solvents can be limited. 

Fluorine is the most energetic oxidizing element and as such is of prime importance in advanced oxidizers. The fluorine-based oxidizers discussed here include elemental fluorine, compounds containing oxygen and fluorine, nitrogen-fluorine compounds, halogen fluorides, and noble gas fluorides. 

Polyolefins When used in conjunction with a halogen-based flame retardant, this zinc borate can partially replace antimony oxide (30%-40%) and still maintain the same fire test performance. In addition, it can improve aged elongation properties, increase char formation, and decrease smoke generation. The B203 moiety in zinc borate can also provide afterglow suppression (Table 9.6). 

The two halogen-based methods that continue to attract organic chemists the most for the oxidative activation of arenois are the Adler oxidation and the Pelter oxidation (vide infra) ... 

Several organoarsenic(III) compounds containing arsenic(III)-transition metal bonds have been oxidized by halogen-based electrophiles or by elemental sulfur to give the corresponding dihalides or sulfides (equations 365 , 366 and 367 - ). 

Tetrachloride and tetrabromide complexes are known for thorium, protactinium, uranium, neptunium, and plutonium. These are similarly produced by halide-based oxidation of metals or hydrides, or by halogenation of oxides. A common structural type is reported for most compounds. The reported structure of thorium tetrachloride reveals that the coordination geometry about the metal is dodecahedral.The compounds are generally volatile and can be sublimed. The gas-phase electron diffraction structure of suggests that the molecule is... 

The aromatization of bicyclo[4.1.0]hept-3-enes gives access to a wide variety of cycloproparenes the substrates are readily available via Diels — Alder reaction of butadienes w ith cyclopropcnes. 1,2-Dihalo- and tetrahalocyclopropenes have been used for this purpose. In the aromatization step, it is important that the halo substituents arc located at Cl and C6 of the bicyclo[4.1. OJhept-3-ene. Halogens at C2 and C5 result in ring enlargement rather than aromatization on reaction with base. Oxidative bis-decarboxylation of bicyclo[4.1.0]hept-3-ene-l, 6-dicarboxylic acid was investigated as an alternative route to cycloproparenes however, the products were derived from carbenium ion capture after monodecarboxylation. 

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