I. Preliminaries1. Introduction. In this Account, we will emphasize that organic molecules undergo a wide range of chemistry in neutral superheated water. Counter to what is traditionally taught in organic chemistry courses, no acids, bases, or catalysts need to be added. In this chemistry, water participates as a catalyst, reactant, and solvent. For example, polyethylene terephthalate (plastic soda bottles), polyurethanes, and other polymers are cleaved to their starting materials at 300 °C. Diaryl ethers cleave rapidly, Diels-Alder reaction selectivities are dramatically enhanced, and several types of deuteration reactions are effected in pure superheated deuterium oxide. Such reactions, and many others, are facilitated by changes in the chemical and physical properties of water as temperature increases. These changes make the solvent properties of water (density, dielectric constant) at high temperature similar to those of polar organic solvents at room temperature, thus facilitating reactions with organic compounds in an environmentally friendly medium. An increase in the dissociation constant by 3 orders of magnitude allows water at

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The applications of functionalised polymers in organic synthesis are outlined. Literature from July 1997 to July 1999 is discussed.

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Diphenyl and methyl phenyl sulfones and sulfoxides and dibenzothiophene sulfone were treated at 460 °C with water, 15% aqueous formic acid, and 15% aqueous sodium formate. Thermal comparisons were run in cyclohexane, and for those compounds and conditions that resulted in fast conversion after 7 min at 460 °C, also at lower temperatures. Sulfoxides are highly reactive, sulfones less so. Reactivity is greatest in 15% aqueous sodium formate followed by formic acid for the sulfones; this reactivity order is inverted for the sulfoxides. In all of the aqueous media, ionic reactions dominate. The sulfoxides are mainly deoxygenated to the corresponding sulfides, while C−S bond cleavage is more important for the sulfones. Product slates are identified and analyzed, and reaction pathways are suggested for the transformations found.

A series of aryl hydrocarbons, aryl N-oxides, and aryl carbonyl compounds were subjected to thermolysis at 460°C in water alone, in 15% aqueous formic acid, in 15% aqueous sodium formate, and, for comparison of purely thermal reactions, in cyclohexane. The runs were carried out initially for 7 min and, in most cases, also for 1 h. The aryl carbonyl substrates underwent mainly carbonyl reduction mainly under reducing conditions, with ring opening only observed in significant amounts for 1,4-naphthoquinone and 3,4-benzocoumarin. The arenes produced mainly reduction products with only low yields of ring-opened products observed. Aryl oximes underwent significant denitrogenation and subsequent reduction with only very little cleavage to simpler aromatic systems. The N-oxides underwent deoxygenation, and in the case of isoquinoline, ring opening of the heterocycle was prevalent. 2-Aminobiphenyl was denitrogenated and cleaved to simpler systems in cyclohexane, but in the aqueous systems it underwent mainly cyclization to yield carbazole with only low yields of denitrogenated products. 2-Phenylphenol was unreactive under aqueous conditions with only low yields of deoxygenated products observed.

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