Sugars gold catalysts

The most dramatic results obtained so far with gold catalysts have been with the liquid phase processes. They are conducted with oxygen or air, often using water as solvent, and are therefore felt to be environmentally benign. Particular success has been obtained with reducing sugars (Section 8.3.2) and other aldehydes (Section 8.3.3), and with alcohols and other hydroxy-compounds (Sections 8.3.4-8.3.7). Reactions that use soluble gold complexes to catalyse selective oxidation are reported in Chapter 12. 

One of the most surprising and potentially important aspects of the recent advances in catalysis by gold has been the discovery that many reactions of this type can be successfully accomplished under mild conditions.60 2 It is clearly a requirement that only one of the functions of the molecule should be attacked in the case of the reducing sugars and related alcohols (e.g. D-sorbitol), the aldehyde group or one of the terminal hydroxyl groups can be selectively oxidised by gold catalysts ... 

The alchemists believed that a most minute proportion of the Stone projected upon considerable quantities of heated mercury, molten lead, or other "base" metal, would transmute practically the whole into silver or gold. This claim of the alchemists, that a most minute quantity of the Stone was sufficient to transmute considerable quantities of base" metal, has been the object of much ridicule. Certainly, some of the claims of the alchemists (understood literally) are out of all reason but on the other hand, the disproportion between the quantities of Stone and transmuted metal cannot be advanced as an a priori objection to the alchemists claims, inasmuch that a class of chemical reactions (called "catalytic") is known, in which the presence of a small quantity of some appropriate form of matter — the catalyst — brings about a chemical change in an indefinite quantity of some other form or forms thus, for example, cane-sugar in aqueous solution is converted into two other sugars by the action of small quantities of acid and sulphur-dioxide and oxygen, which will not combine under ordinary conditions, do so readily in the presence of a small quantity... 

The fact that gold is active under very mild conditions means that its potential as a selective oxidation catalyst is high, and many selective oxidation processes are important in the chemical industry [1,2]. Papers have been published on the selective oxidation of propene to propene oxide in the presence of hydrogen, oxidation of sugars and aldehydes to acids, and the oxidation of alcohols and other hydroxyl-compounds. Au-Pd catalysts have been used to oxidize ethene to vinyl acetate in the presence of acetic acid and oxygen and this is a process used by a number of manufacturers worldwide. The selective oxidation of hydrogen to hydrogen peroxide, rather than water, is also catalyzed efficiently by supported Au-Pd catalysts [49]. 

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