Water oxide tautomerization

By analogy, the formation of a double bond between carbon and phosphorus, which in our opinion, however is improbable, is assumed to be the third stage. Finally, this is followed by the addition of water and tautomeric rearrangement to the primary phosphine. In this way, phosphine, which is present in technical acetylene, and because of its good solubility in actone concentrates in the commercial steel cylinders, forms with acetone, isopropylphosphine oxide and possibly, secondary products... 

The 1-hydroxypyrazoles exist as the neutral structure (151a) and not in the iV-oxide form (151b), although in water there is a small percentage of the latter present. For tautomerism of 2-hydroxyindazole see (82JOC4323). 

The hydrochloride of (3) holds water rather tenaciously, and the infrared spectrum indicates that the water is covalently bound. Mild oxidation of the cation (3) gives 4-hydroxyquinazoline in high yield and ring-chain tautomerism is excluded on the grounds that quinazo-line does not give a positive aldehyde test in acid solution, 2-Methyl-quinazoline also has an anomalous cationic spectrum and a high basic strength (see Table I), but 2,4-dimethylquinazoline is normal in both these respects, which supports the view that abnormal cation formation entails attack on an unsubstituted 4-position. ... 

It is striking that reactions of arsenic(III) with 1-equivalent oxidizing agents take place fairly slowly, while reactions with 2-equivalent partners e.g. with iodine, are fast. To interpret this behaviour it was suggested by Waters that arsenious acid has the tautomeric forms... 

Vasudevan, D. Dorley, P.J. Zhuang, X. (2001) Adsorption of hydroxy pyridines and quinolines at the metal oxide-water interface Role of tautomeric equilibrium. Environ. Sci. 

Recently, Behiman and coworkers discussed the mechanism of the Elbs oxidation reaction and explained why the para product predominates over the ortho product in this oxidation. According to the authors, semiempirical calculations show that the intermediate formed by the reaction between peroxydisulfate anion and the phenolate ion is the species resulting from reaction of the tautomeric carbanion of the latter rather than by the one resulting from the attack by the oxyanion. This is confirmed by the synthesis of the latter intermediate by the reaction between Caro s acid dianion and some nitro-substituted fluorobenzenes. An example of oxidative functionalization of an aromatic compound is the conversion of alkylated aromatic compound 17 to benzyl alcohols 20. The initial step in the mechanism of this reaction is the formation of a radical cation 18, which subsequently undergoes deprotonation. The fate of the resulting benzylic radical 19 depends on the conditions and additives. In aqueous solution, for example, further oxidation and trapping of the cationic intermediate by water lead to the formation of the benzyl alcohols 20 (equation 13) . ... 

Price obtained in the presence of water a crystalline product (m. p. 256—257 °C) and an amorphous material from which Markl could isolate the X -phosphine oxide 158 (m. p. 156-158 °C) and the 4-hydroxy-phosphine oxide 160 (m. p. 239-241 °C) which probably was formed by autoxidation. 158 is also formed by HaO2-oxidation of 147 The tautomeric form of 158 would be the 1-hydroxy-X -phosphorin 159. Indeed, treatment with base affords a bright red anion which probably has the structure 161 (see p. 60 and 87). 

Hydroboration-oxidation of alkynes preparation of aldehydes and ketones Hydroboration-oxidation of terminal alkynes gives syn addition of water across the triple bond. The reaction is regioselective and follows anti-Markovnikov addition. Terminal alkynes are converted to aldehydes, and all other alkynes are converted to ketones. A sterically hindered dialkylborane must be used to prevent the addition of two borane molecules. A vinyl borane is produced with anU-Markovnikov orientation, which is oxidized by basic hydrogen peroxide to an enol. This enol tautomerizes readily to the more stable keto form. 

Nitroparaffins such as nitromethane, nitro-ethane, nitropropane, are mild oxidizers and should not be heated with easily oxidized hydrocarbons. With water, they form nitronic acids as tautomeric forms, which form explosive salts with inorganic bases (Ref 83)... 

Methylnitramine is a strong monobasic acid, very readily soluble in water, alcohol, chloroform, and benzene, less soluble in ether, and sparingly soluble in petroleum ether. It crystallizes from ether in flat needles which melt at 38°. It is not decomposed by boiling in aqueous solution even in the presence of an excess of alkali. On distillation it yields dimethylnitramine, m.p. 57°, methyl alcohol, nitrous oxide and other products. Methylnitramine owes its acidity to the fact that it is tautomeric. 

These reactions are real tautomerization reactions, but the quite common water elimination reactions can also completely change the redox property of a radical. A case in point is the radical derived from ethylene glycol which is a reducing a-hydroxyalkyl radical which is transformed by water elimination into the fomylmethyl radical (see below) whose oxidizing property has been discussed above [reaction (20)]. Similarly, the phenol OH-adduct is a reason-... 

Nitriles are susceptible to hydrolysis via nucleophilic attack of water on the electropositive carbon atom, especially under strongly acidic and basic conditions (Fig. 29). Nitriles hydrolyze to imidic acids, which tautomerize to amides. Amides can be hydrolyzed further to carboxylic acids, although much more slowly. Nitriles are susceptible to oxidation by peroxides under mildly basic conditions (e.g., pH 7.5-8) as has been documented in the case... 

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