Dinitrogen tetroxide oxidation

Recently, nitration of organolithiums and Grignards with N204 has been developed for the preparation of certain kinds of nitro compounds (Eqs. 2.14 and 2.15).31 The success of this process depends on the reaction conditions (low temperature) and the structure of substrates. For example, 3-nitrothiophene can be obtained in 70% overall yield from 3-bromothiophene this is far superior to the older method. 3-Nitroveratrole cannot be prepared usefully by classical electrophilic nitration of veratrole, but it can now be prepared by direct o>7/ o-lithiation followed by low-temperature N204 nitration. The mechanism is believed to proceed by dinitrogen tetroxide oxidation of the anion to a radical, followed by the radical s combination. 

Phenyl-l,2,4-triazoline-3,5-dione has been prepared by oxidizing 4-phenylurazole with lead dioxide, and with ammoni acal silver nitrate followed by an ethereal solution of iodine. The yields arc low for both methods. 4-Substituted triazoline diones can also be made by oxidation of the corresponding urazole with fuming nitric acid or dinitrogen tetroxide. Oxidation by /-butyl hypochlorite in acetone solution has also been described - it, however, yields an unstable product, even after sublimation. Either dioxane or ethyl acetate are preferred as solvents for the reaction, since the product is obtained in a stable form. The latter solvent is superior since 4-phenylurazole has a greater solubility in it. 

Oxidation of phosphorus and of sulfur compounds. Dinitrogen tetroxide oxidizes trisubstituted phosphates in methylene chloride at dry ice temperature. It oxidizes... 

Reactions.— An observation that dinitrogen tetroxide oxidizes amines to the corresponding alkyl nitrates in low yield has been developed into a useful synthetic method. Conversion of an amine into its trimethylsilyl derivative alters the course of the oxidation permitting isolation of the desired nitrate in high yield (Scheme 118) in a later communication, the use of THF as solvent is reported to obviate the need for prior trimethylsilylation. This reaction seems to be general for primary and secondary amines and, although the mechanism of the reaction is unknown, retention of configuration at carbon is observed the intermediacy of the solvated diazonium salt (192) is invoked when THF is solvent. 

It has been considered that nitric acid was responsible for the oxidation of the nitroso compoimd, but there is recent evidence from the catalysed nitration of p-dimethoxybenzene in carbon tetrachloride that dinitrogen tetroxide is involved ... 

Chemical oxidation with strong acid is reportedly selective at the 6-hydroxyl, either with nitric acid—sulfuric acid—vanadium salts (241) which is claimed as specific for the 6-hydroxyl up to 40% conversion, or with dinitrogen tetroxide ia carbon tetrachloride, with similar specificity up to 25% conversion (242). 

Oxidation under moderate conditions (83) yields soUd products referred to as oxyceUuloses. This general term describes various products that must be qualified by indicating the oxidant employed. Among oxidants used are periodate, dinitrogen tetroxide, and sodium hypochlorite. CeUulose is particularly susceptible to oxidation under alkaline conditions. 

Many other reactions of ethylene oxide are only of laboratory significance. These iaclude nucleophilic additions of amides, alkaU metal organic compounds, and pyridinyl alcohols (93), and electrophilic reactions with orthoformates, acetals, titanium tetrachloride, sulfenyl chlorides, halo-silanes, and dinitrogen tetroxide (94). 

Ammonia can also react violently with a large selection of chemicals including ethylene oxide, halogens, heavy metals, and oxidants such as chromium trioxide, dichlorine oxide, dinitrogen tetroxide, hydrogen peroxide, nitric acid, liquid oxygen, and potassium chlorate. 

The brown nitrogen dioxide gas eondenses to a yellow liquid whieh freezes to eolourless erystals of dinitrogen tetroxide. Below 150°Cthe gas eonsists of moleeules of dinitrogen tetroxide and nitrogen dioxide in equilibrium and the proportion of dinitrogen tetroxide inereases as the temperature falls. Above 150°C nitrogen dioxide dissoeiates into nitrie oxide and oxygen. 

The difluoromethyl group in chlorofluoroalkanes can be oxidized into a carboxylic group by a mixture of chlorine and dinitrogen tetroxide at high temperatures [2] (equation 1)... 

Furazan 1 was first prepared and characterized in 1964 by melting glyoxime 2 with succinic anhydride in 57% yield (64JA1863, 65JOC1854). Its A-oxide, furoxan 3, has been in a focus of attention for chemists for more than a century, but was synthesized only in 1994 by oxidation of 2 with dinitrogen tetroxide in dichloromethane in 45% yield (94MC7) (Scheme 1). The A-oxide cannot be prepared by direct oxidation of furazan. 

Dimethyl sulfide [Methane, thiobis-], 16 Dinitrogen tetroxide [Nitrogen oxide (Na 04)], 65 Disulfide, dimethyl-, 9... 

Determine the correct chemical formulas of potassium permanganate, dinitrogen tetroxide, nickel(II) chloride hexahydrate, sodium hydrogen phosphate, and iron(Itl) oxide. 

C. By Oxidation.—This year s literature has been notable for attempts to study the details of certain phosphine oxidation reactions. In one such investigation nitric acid was found to oxidize phosphines, or phosphine sulphides, to phosphine oxides with inversion of configuration at phosphorus, whereas dinitrogen tetroxide, in the absence of acid, was found to oxidize the same compounds with predominant retention. The partial racemization observed with the latter reagent was probably due to the racemization of the oxides, since methylphenyl-n-propylphosphine oxide... 

This last comment is a warning on the potential risk that dinitrogen tetroxide presents as a reagent vis- i-vis the particular alcohol-acid. The paragraph on hydrocarbons confirms this. This oxide has even caused accidents with saturated hydrocarbons (these can be due to impurities). In any case, there is every chance that oxide will activate the methyl groups of this compound. 

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