Azo Compounds, Hydrazine Derivatives

T0641 Radian International, L.L.C., AquadetoxySoil Vapor Extraction (SVE) 

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Blowing agents Azo compounds, hydrazine derivatives, bicarbonates / carbonates... 

The major types of chemical blowing agents include the azo compounds, hydrazine derivatives, semicarbazides, tetrazoles, and benzoxazines. Table 1.10 shows some of the common blowing agents, their decomposition temperatures, and primary uses. 

All chemical blowing agents may be divided into the following groups carbonates and bicarbonates, nitrites, hydrides, peroxides, oxygen-containing acid derivatives, azo compounds, urea derivatives, hydrazines, semicarba-zides, azides, N-nitroso compounds, and triazols. 

Various substituted N-hiomo- and A/-chloroureas have also been prepared (97). These compounds are useful for synthesis of oxazoUdinones, and also hydrazine, hydrazo, and azo compounds. A/-Bromourea [51918-81 -1] is useful for selective oxidation of sugar derivatives (98). 

Azo compounds and hydrazines, azo alkanes, azo aromatics, aminoazobenzenes, dia-zonium salts, diazomethane, hydrazine and its methyl derivatives... 

Types of compounds are arranged according to the following system hydrocarbons and basic heterocycles hydroxy compounds and their ethers mercapto compounds, sulfides, disulfides, sulfoxides and sulfones, sulfenic, sulfinic and sulfonic acids and their derivatives amines, hydroxylamines, hydrazines, hydrazo and azo compounds carbonyl compounds and their functional derivatives carboxylic acids and their functional derivatives and organometallics. In each chapter, halogen, nitroso, nitro, diazo and azido compounds follow the parent compounds as their substitution derivatives. More detail is indicated in the table of contents. In polyfunctional derivatives reduction of a particular function is mentioned in the place of the highest functionality. Reduction of acrylic acid, for example, is described in the chapter on acids rather than functionalized ethylene, and reduction of ethyl acetoacetate is discussed in the chapter on esters rather than in the chapter on ketones. 

The most extensively investigated 1,2-diazocines are 3,4,5,6,7,8-hexahydro derivatives, of interest in connection with studies on the properties of cyclic azo compounds. These compounds are obtained from the hydrazines (159) usually not isolated, by oxidation with yellow mercury(II) oxide. 3,8-Diaryloctahydrodiazocines are prepared by reduction of the azines dialkyl and unsubstituted derivatives are obtained by hydrolysis of the N,N-bis(ethoxycarbonyl) compounds (69JA3226,70JA4922). Cyclization of 2,7-diaminooctane with IFs gave the 3,3,8,8-tetramethyl compound (78CB596). 

Among the oxidative procedures for preparing azo compounds are oxidation of aromatic amines with activated manganese dioxide oxidation of fluorinated aromatic amines with sodium hypochlorite oxidation of aromatic amines with peracids in the presence of cupric ions oxidation of hindered aliphatic amines with iodine pentafluoride oxidation of both aromatic and aliphatic hydrazine derivatives with a variety of reagents such as hydrogen peroxide, halogens or hypochlorites, mercuric oxide, A-bromosuccinimide, nitric acid, and oxides of nitrogen. 

Since A,A -disubstituted hydrazines are readily available from a variety of sources (see Volume I, Chapter 14), their dehydrogenation constitutes a widely applicable route to both aliphatic and aromatic azo compounds. Such oxidative procedures are of particular value in the aliphatic series because so many of the procedures applicable to aromatic compounds, such as the coupling with diazonium salts, have no counterpart. The oxidation reactions permit the formation not only of azoalkanes, but also of a host of azo compounds containing other functional groups, e.g., a-carbonyl azo compounds [83], a-nitrile azo compounds [84], azo derivatives of phosphoric acid [85], phenyl-phosphoric acid derivatives [86],... 

There are two examples where compound 3 or a derivative (269) opens without recyclization. With excess phosphorus pentachloride at 230°C compound 3 reacts to give pentachloropyridine.260 Treatment of 2-phenyl-triazolopyridinium fluoroborate with a base gives an N-formylpyridyl-hydrazine, which on oxidation gives the azo compound 270. 

Thiadiazolyl-5-hydrazines show the expected reducing action towards ammoniacal silver nitrate, and yield ketonic derivatives.176 3-Methylthio-5- (to -phenylhydrazino)-l,2,4-thiadiazole (290) is oxidized by yellow mercuric oxide in ethanol to the azo compound 291.198... 

Azo or diazene compounds possess the —N=N— grouping. Aliphatic azo compounds of the type R—N=N—H appear to be highly unstable and decompose to R—H and nitrogen. Derivatives of the type R—N=N—R are much more stable and can be prepared as mentioned above by oxidation of the corresponding hydrazines. Aromatic azo compounds are available in considerable profusion from diazo coupling reactions (Section 23-IOC) and are of commercial importance as dyes and coloring materials. 

These conformational changes, which take place during the transformation of neutral hydrazines or bicyclic azo compounds into cation radicals, have also been observed in a wide range of derivatives. These changes seemingly have a general character (Williams et al. 1988 Nelsen, Rumack, Meot-Ner 1988). 

The aldehyde or ketone can now desorb, leading to the initial copper(I) hydrazide complex 13 which re-enters the catalytic cycle. The replacement of DEAD-H2 12 by DEAD 19 can be easily understood when considering this catalytic cycle. Indeed, several entries to the main catalytic cycle are possible, either via the hydrazino copper species 13 or via the direct formation of the ternary loaded complex 18 from the azo-derivative 19, Phen CuCl 3 and the alcohol 1. The key-role played by the hydrazine or azo compounds can also be readily appreciated when considering the proposed mechanistic rationale. The hydrazide, not only helps in reducing the copper(II) salt to the copper(I) state but, by virtue of its easy passage into the azo derivative, it also acts as a hydrogen acceptor, allowing the efficient oxidation of the alcohol into the carbonyl compound. 

Moreover, we believe that the azo form helps in stabilizing several of the reactive copper complexes involved in this catalytic cycle such as the hydroxy copper complex 17. Thus, we surmise that this novel catalytic, aerobic oxidation procedure for alcohols into carbonyl derivatives proceeds via a dehydrogenation mechanism and relies on the effective role of hydrazine or azo compounds as hydrogen shuttles and stabilizing ligands for the various copper complexes (20). 

Simple and complex hydrazides, with the general formula RCONHNHCOR, were readily dehydrogenated by DIB to the corresponding azo compounds, some of which were used as dienophiles for in situ Diels-Alder reactions [65,66]. Hydrazine itself in the form of its hydrate was similarly converted into diimide, NH — NH, which served for some in situ hydrogenations [67], Further reactivity accompanied by solvent participation was observed in some cyclic derivatives of hydrazine, i.e. pyrazolones. At low temperature these underwent ffagmentive loss of dinitrogen to give either methyl alkynoates or allenic esters [68] ... 

Efficient dehydrogenation occurred in some N-H containing compounds of various types, e.g. in hydrazine derivatives to azo compounds accompanied by cyclization [38] and in tetrahydroquinoxaline derivatives to quinoxalines [39]. 

The usual Kjeldahl procedure works for a large variety of nitrogen compounds such as amines, amino acids, and alkaloids, but fails for nitrates, nitrites, azo compounds, cyanides, and derivatives of hydrazine. For nitrates a method involving the addition of salicylic acid may be used. Azo compounds give quantitative results if first reduced by refluxing with tin(II) chloride and hydrochloric acid. Hydrazine derivatives are decomposed by heating with formaldehyde, zinc dust, and hydrochloric acid, followed by tin(II) chloride, prior to the usual Kjeldahl digestion. ... 

Reductive alkylation has also been carried out on nitro, nitroso, azo, and other compounds that are reduced in situ to primary or secondary amines. Azo compounds react with aldehydes, in the presence of proline, and subsequent reduction with NaBH4 gives the chiral hydrazine derivative. ... 

The hydrazo-compounds, in contrast with the azoxy-, and especially with the intensely coloured azo-compounds, are colourless. They are derived from hydrazine, NH2—NHj, in which one hydrogen atom of the two amido-groups has been replaced by a hydrocarbon radical. The... 

Aryl Azo Compounds. Alkyl- (including tert-butyl) and aryllithium reagents add to azo benzene to give trisubstituted hydrazines in fair to excellent yields (see Eqs. 44 and 45) alkylation of the intermediate anion in situ leads to tetra-substituted hydrazines.211 Benzyl and heteroarylmethyl (see Eq. 54) anions and the enolate of phenylacetamide add to azo benzene in fair to excellent yields.212 Aromatic Grignard reagents are reported to reduce azo benzene and its derivatives to the hydrazo compounds (cf. also Eq. 20).213 The only other aryl azo compound investigated in animations appears to be benzo[c]cinnoline.214... 

Bicyclic azo-compounds have been converted into the corresponding congested hydrazines, for example (83) the relative thermodynamic stability and kinetics of decomposition of the derived radical cations have been compared with data from less congested analogues.The reaction of (77a) with phthalimidonitrene gives the azimine (84) and the conversions of (85) ... 

The further fate is not explicitly known, but molecule rearrangements and/or the addition of O2, NO c and NO3 is possible. From secondary amines, azo compounds or organic hydrazines (derived from hydrazine N2H4) can be given ... 

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