Oxygen types

Another type of chemical change is initiated by light, which may trigger autolytic, that is, free radical (Type I) or singlet oxygen (Type II) reactions. These changes are routinely classified as oxidation. Rancidity in cosmetics, especially those containing unsaturated Hpids, is commonly prevented by use of antioxidants (qv). 

BOD (Biological Oxygen Type of treatment required Dilution... 

In summary, the fragmentary evidence at hand suggests that sulfur was the primordial iron complexing material and that this ligand system was selectively modified by stepwise transition to a mixed sulfur-nitrogen and sulfur-oxygen and, finally, to an all-oxygen type of coordination. 

Y zeolite framework showing oxygen type (0) and non-framework ( ) locations (101). 

The Type 1 copper ions are normally coordinated by three strong ligands, a cysteine and two histidines, and often have one or two weaker ligands such as methionine sulfur or oxygen. Type 3 coppers are usually each coordinated by three histidines, with a bridging ligand such as oxygen or hydroxyl anion. 

In other cases fullerene antibacterial action takes place after photoirradiation of fulleropyrrolidinium salts. It is not yet clear if the photodynamic action implies the participation of superoxide and hydroxyl radicals (type I mechanism) or singlet oxygen (type II mechanism) but the efficacy is really interesting with the death of more than 99.9% of bacterial and fungal cells and a special selectivity for microbes over mammalian cells (Tegos et al., 2005). Also a sulfobutyl fullerene derivative is able to inhibit environmental bacteria after photoirradiation and it exerts its action on E. coli even if incorporated in coated polymer (Yu et al., 2005). 

Sulfur compounds with divalent sulfur functionalities are much more prone to dioxirane oxidation on account of their higher nucleophilicity compared to the above-presented oxygen-type nucleophiles. Examples of this type of dioxirane oxidation abound in the literature. Such a case is the oxidation of thiols, which may be quite complex and afford a complex mixture of oxidation products, e.g. sulfinic acids, sulfonic acids, disulfides, thiosulfonates and aldehydes , and is, therefore, hardly useful in synthesis. Nevertheless, the oxidation of some 9i/-purine-6-thiols in the presence of an amine nucleophile produces n >( -nucleoside analogs in useful yields (equation 19). This reaction also displays the general chemoselectivity trend that divalent sulfur functionalities are more reactive than trivalent sp -hybridized nitrogen compounds P. 

Previous analysis of Uinta Basin bitumens (6,10) have shown that the predominant nitrogen types are pyrollic, amide, and aromatic nitrogen. Predominant sulfur types are sulfide, sulfoxide, and thiophenic sulfur predominant oxygen types are ketones, phenols, carboxylic acids, and possibly appreciable concentrations of furans. The aromatic (basic) nitrogen is expected to participate in irreversible adsorption on acidcracking catalysts (13) and it could require an increased cat-to-oil ratio. Previous analyses (10) have indicated also that Uinta Basin bitumen is high in naphthenic hydrocarbon and low in free paraffins. This is illustrated by the results given in Table II in which over 60% of the saturates... 

U, S. Army used double-base powder for small arms. Linde introduced Oxyliquit, the first explosive of liquid-oxygen type, prepared from charcoal saturated with liquid air and enclosed in an insulating paper wrapper. 

However, in the presence of oxygen, Type II reactions are likely to occur producing and 0 (Eqns 2 and 3) ... 

The two main and most explored mechanisms of sensitised photo-oxidation involve the light-driven formation of radicals between substrate and sensitiser with the subsequent reaction of the radicals with oxygen [Type I reaction (34)] and the sensitiser reacting with oxygen to give singlet oxygen which then reacts with the substrate [Type II reaction (35)]. 

Compound type analysis was not conducted in this work, but it is instructive to look at some literature results. With respect to heteroatoms, tar sand bitumen and petroleum asphaltenes have been variously reported as containing predominantly polar heteroatoms, principally oxygen types (18) or nonpolar heteroatoms, principally nitrogen types (14). The difference in these reported results apparently relates to the method of analysis in which the former is a direct determination, the latter an indirect determination. 

Most work has been in the isoquinoline area, principally because of the usefulness of isoquinoline Reissert compounds in the synthesis of isoquinoline alkaloids. Aside from 5-chloro- and 3-acetylaminomethylquinoline and a few halo, methyl, and carbomethoxyisoquinolines, all the substituted quinoline or isoquinoline Reissert compounds have involved oxygen-type functions in one or more of positions 4-, 5-, 6-, 7-, and 8- of the isoquinoline... 

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