Oxygen bridge breaking

The increasing addition of a modifier to a given network former leads to the progressive breaking of all oxygen bridges as in (4.2). 

The various types of carbohydrates considered in this chapter are shown in formulas I-XVIII. The two ring forms (II and III) of the aldoses are shown because careful oxidation can produce the lactones X and XI directly without breaking the oxygen bridge. In most cases, however, the products of oxidation have been isolated as salts of aldonic acids (IX) thus the nature of the initial oxidation product, either a lactone having the same ring structure as the sugar, or possibly the free... 

Anthranil (119) and benzyne (from oxidation of 9 with lead tetraacetate) afford acridine (5%)81 depending on the sequence of bond forming and breaking, an oxygen-bridged cycloadduct and/or acridine N-oxide (120) may be intermediates in this reaction (Scheme 15), although 120 is known to react with benzyne in a different sense (Section IX). The addition of benzyne to oxazoles leads, ultimately, to anthracene derivatives in high overall yield.82b... 

The second reaction stage occurs at high pH and consists in breaking of oxygen bridges ... 

When exposed to alkalis, OH" ions break the oxygen bridge bonds, leading to total network disintegration under formation of soluble silicic acid ... 

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