Oxygen abstraction

Abstract. Oxygen abundances of a large number of metal-rich stars, with and without known planets, were derived from the forbidden line [OI] 6300 A, the OI 7771-5 A triplet and from near-UV OH lines. Non-LTE corrections were calculated and applied to the LTE abundance results derived from the OI 7771-5 A triplet. Spectral synthesis was performed for several OH lines. Results from different indicators are compared. We study abundance trends in planet host and comparison sample stars. We find for all the indicators that, on average, [O/Fe] clearly decreases with [Fe/H], with significantly negative slopes in all the linear fits. 

To explore the mechanism of allylic hydroxylation, three probe substrates, 3,3,6,6-tetradeuterocyclohexene, methylene cyclohexane, and /l-pinenc, were studied (113). Each substrate yielded a mixture of two allylic alcohols formed as a consequence of either retention or rearrangement of the double bond. The observation of a significant deuterium isotope effect (4-5) in the oxidation of 3,3,6,6-tetradeuterocyclohexene together with the formation of a mixture of un-rearranged and rearranged allylic alcohols from all three substrates is most consistent with a hydrogen abstraction-oxygen rebound mechanism (Fig. 4.48). 

Oxygen abstraction reactions from alcohols, ketones, acyl halides and other oxygen-containing compounds by MCI or related derivatives also afforded a route to relatively simple complexes of the oxo halides (Table 24). Thus Nb2Cli0 was found to abstract oxygen from higher ketones to yield, after hydrolysis, alkanes, chloroalkanes or arylalkanes.414... 

NbCls and Tads abstract oxygen from diisopropylmethylphosphonate to yield polymeric complexes [Mo(IMP)3] (IMP = isopropoxymethylphosphonate), which contain M=0 groups and both chelating and bridging phosphonato groups. 

In type 2, the homogeneous redox reaction of the electrogenerated and regenerated redox catalyst consists of a chemical reaction. For oxidations, these reactions may be hydride ion or hydrogen atom abstraction, oxygen transfer, or an intermediate complex or bond formation. For reductions, hydride or car-banion transfer from a metal complex is often observed. In all these cases, very large potential differences between the standard potential of the substrate and the redox catalyst may be overcome. The selectivity can be very high and may... 

The silylene 79 abstracts oxygen or sulfur from isocyanates and isothiocyanates413. Cyclic siloxanes are the products with isocyanates (equation 129) these probably arise by polymerization of the silanone, Ar2Si=0 (83). 

The chlorides and bromides can also abstract oxygen from certain donor solvents (cf. VCL, and M0CI5) to give the oxohalides ... 

An earlier experimental study involved the generation of benzylchlorocarbene, phenylchlorocarbene, methoxy-phenylcarbene, dimethylcarbene, cyclobutylidene, adamantylidene, and fluorenylidene by means of laser flash photolysis and their reactions with oxiranes and thiiranes <1998JA8681>. Absolute rate constants ranging from 10 to 10 ° M s at 22 °C were measured in acetonitrile and cyclohexane. Thermally generated dimethoxycarbene was found to be inefficient at abstracting oxygen or sulfur from an oxirane or a thiirane. 

Reducing Agent. A compound abstracting oxygen easily, such as hydrogen or carbon. 

V(mes)3 (mes = mesityl) abstracts oxygen from epoxides to form VO(mes)3 The use of thiiranes and O2 for oxidation of V(III) organometallic complexes has been studied In situ generated V(II) jS-diketonate complexes also are oxidized by epoxides . ... 

Reaction of Nb2Cli0 with 2 eq of the bifunctional phosphazene salt [H2NPPh2NPPh2NH2]Cl produced the metallacycle (58) (Scheme 10).110 Reaction with 1 eq (Me3SiN=PPh2CFI2)2 produced (59) which abstracted oxygen from thf to yield the nine-membered metallacycle (60).111... 

Deoxygenation. The reagent abstracts oxygen from a diaroyl peroxide to give the diaroyl anhydride and triethyl phosphate. ... 

Laser flash-photolysis investigations have been carried out for benzylchloro-carbene, phenylchlorocarbene, methoxyphenylcarbene and fluorenylidene, and some other carbenes, generated from diazirine, diazo and other precursors, in the presence of oxiranes and thiiranes. These carbenes abstract oxygen or sulfur atoms with bimolecular rate constants in the range 10 to 10 s ... 

Niobium(iv) chloride reacts with a variety of / -keto-enol molecules to give 8-coordinate, tetrakischelate molecules 17 these have one unpaired electron and are not isostructural with analogous Zr and Hf compounds. Tantalum(iv) chloride reacts by abstracting oxygen, and analogous complexes are not obtained. 

The resulting nitric oxide abstracts oxygen from the air, and becomes nitric peroxide —... 

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