Phenylhydrazines , oxidation

Other chemical methods such as the NADH oxidation and phenylhydrazine oxidation have been employed to determine dissolved oxygen content (van Dam-Mieras et al., 1992), but are not frequently used. 

Azopyrimidines of Type 1.—Pelizzari was the first investigator who attempted to condense alloxan (I) with phenylhydrazine. He failed owing to the occurrence of an oxidation-reduction reaction in which the alloxan was reduced to alloxantine and the phenylhydrazine oxidized to benzene and nitrogen. By using phenylhydrazine hydrochloride rather than the base, Ktihling succeeded in obtaining alloxan-5-phenylhydrazone... 

In the case of the reaction of substituted hydrazines, such as phenylhydrazine with glucose or certain other carbohydrates, one molecule of phenylhydrazine reacts with the terminal aldehyde group to form a phenylhydrazone. A second molecule of phenylhydrazine oxidizes the penultimate carbinol grouping to a carbonyl and a third molecule of phenylhydrazine converts this second carbonyl to a phenylhydrazone. This class of di-phenylhydrazones is called an osazone, a series of compounds not discussed in the present chapter. 

Add 2 -3 drops of phenylhydrazine to about 2 ml. of Fehling s solution in a test-tube and shake the mixture vigorously nitrogen is evolved and reddish-brown cuprous oxide is precipitated. The reaction proceeds rapidly on gentle warming, more slowly in the cold. 

Dissolve 8 8 g. (9 0 ml.) of cyclohexanone in 50 ml. of glacial acetic acid, add 8 ml. of phenylhydrazine, and boil the solution under reflux for 5 minutes. Cool the solution, when the tetrahydrocarbazole will crystallise out. Filter at the pump, drain well, and recrystallise either from aqueous ethanol or (better) from aqueous acetic acid. The recrystallisation should be performed rapidly, for the tetrahydrocarbazole undergoes atmO" spheric oxidation in hot solutions after recrystallisation, the compound should be dried in a vacuum desiccator and not in an oven. Repeated recrystallisation should be avoided. The tetrahydrocarbazole, after thorough drying, is obtained as colourless crystals, m.p. 118° yield of recrystallised material, 11 g. 

This olionge involves the oxidation of the alcohol grouping of C or C to carbonyl by the action of a second molecule of phenylhydrazine the latter is reduced to aniline and ammonia. Alternative explanations of this reaction have been advanced, but these cannot be discussed here (see, however. Section 111,139,6). 

Hydroxyaminopyridazine 1-oxides are usually formed by catalytic hydrogenation of the corresponding nitro derivatives over palladium-charcoal in methanol, provided that the reaction is stopped after absorption of two moles of hydrogen. 3-Hydroxyaminopyridazine 1-oxide and 6-amino-4-hydroxyamino-3-methoxypyridazine 1-oxide are prepared in this way, while 5-hydroxyamino-3-methylpyridazine 2-oxide and 5-hydroxyamino-6-methoxy-3-methylpyridazine 2-oxide are obtained by chemical reduction of the corresponding nitro compounds with phenylhydrazine. 

Isatin (190) is a compound with interesting chemistry. It can be iV-acetylated with acetic anhydride, iV-methylated via its sodium or potassium salt and O-methylated via its silver salt. Oxidation of isatins with hydrogen peroxide in methanolic sodium methoxide yields methyl anthranilates (81AG(E)882>. In moist air, O-methylisatin (191) forms methylisatoid (192). Isatin forms normal carbonyl derivatives (193) with ketonic reagents such as hydroxylamine and phenylhydrazine and the reactive 3-carbonyl group also undergoes aldol condensation with active methylene compounds. Isatin forms a complex derivative, isamic acid (194), with ammonia (76JCS(P1)2004). 

The isoxazoles (585) were formed regioselectively from the (dioxoalkyl)phosphonium salts (584) with hydroxylamine hydrochloride, the direction of cyclization being different from that of the nonphosphorus-containing 1,3-dioxo compound (see Chapter 4.16). Aqueous sodium hydroxide converted (585) into the isoxazole (586) and triphenylphosphine oxide. Treatment of (585) with n-butyllithium and an aldehyde gave the alkene (587). With hydrazine or phenylhydrazine analogous pyrazoles were formed (80CB2852). 

Phenylhydrazides have been prepared from amino acid esters and phenylhydrazine in 70% yield they are cleaved by oxidation [Cu(OAc)2, 95°, 10 min, 67% yield FeCyi NHCl, 96°, 14 min, 85% yield ]. 

Reactions.— i. Add a few drops of phenylhydrazine to 2 c.c. of water, then a drop or two of copper sulphate solution and excess of caustic soda. Cuprous oxide is precipitated with eftervescence and benzene separates, CbHjNH.NHj-tcCliO- -C HB-t-Nj-t-Cu O-t-HoO. The same reaction takes pkicc if the phenylhydrazine is dissolved in dilute acetic acid and copper sulphaie solution added and warmed. 

Pyridine has been phenylated with the following free-radical sources benzenediazonium chloride with aluminum trichloride the Gomberg reaction " phenylhydrazine and metal oxides A -nitroso-acetanilide dibenzoyl peroxide phenylazotriphenylmethane di-phenyliodonium hydroxide and electrolysis of benzoic acid. ° Although 2-phenylpyridine usually accounts for over 50% of the total phenylated product, each of the three phenyl derivatives can be obtained from the reaction by fractional recrystallization of the... 

Ethyl formate34,52 or orthoformate5 3,54 reacts with two equivalents of phenylhydrazine to yield 1,5-diphenylformazan (11) the reaction takes place under acidic conditions and involves an oxidation. Under basic conditions, ethyl nitrate reacts at the methylene position to yield 3-methyl-1,5-diphenylformazan (37) which can also be obtained from the reaction of phenyl-azoethane (38) with isoamyl nitrite (Scheme 4).8,68 Aryl hydrazines react with a variety of s-triazines (39) to yield 1,5-diaryl formazans with hydrogen, methyl, or phenyl groups in the 3-position as in 40 (Eq. 6).56 Hydrazines have also been reported to react with benzotrichloride55,658 and sym-diamino tetrazine659 to yield formazans. 

Interaction, in presence of diluent below 0°C, with isopropylamine or isobuty-lamine caused separation of explosive liquids, and with aniline, phenylhydrazine and 1,2-diphenylhydrazine, explosive solids [1], In absence of diluents, contact with most aliphatic or non-aromatic heterocyclic amines often leads to uncontrolled oxidation and/or explosions [2], During oxidation of two steroidal dienes in dry pyridine at —35 to —40°C, on one occasion each of the reactions was accompanied by violent explosions [3],... 

The structure of difructose anhydride II has not yet been determined. McDonald and Jackson76 prepared its hexamethyl ether, which proved to be a crystalline compound melting at 73°. The behavior of the product from the acid hydrolysis of this hexamethyl derivative toward phenylhydrazine suggests that two different trimethyl-D-fructoses are present, the identification of which remains to be accomplished. Lately some evidence concerning the structure of this anhydride has been obtained by the use of per-iodic acid oxidation, as described on page 275. 

Interestingly, the Fischer indole synthesis does not easily proceed from acetaldehyde to afford indole. Usually, indole-2-carboxylic acid is prepared from phenylhydrazine with a pyruvate ester followed by hydrolysis. Traditional methods for decarboxylation of indole-2-carboxylic acid to form indole are not environmentally benign. They include pyrolysis or heating with copper-bronze powder, copper(I) chloride, copper chromite, copper acetate or copper(II) oxide, in for example, heat-transfer oils, glycerol, quinoline or 2-benzylpyridine. Decomposition of the product during lengthy thermolysis or purification affects the yields. 

The reaction of these aldehydes, derived from periodate oxidation, with carbonyl reagents has also been investigated. Studies 147 148 were made on oxidized laminarin, a (1 —> 3)-linked polysaccharide, in which only the terminal residues had been oxidized. The addition of phenylhydrazine acetate detached the remainder of the terminal residue as glyoxal phenyl-osazone. When the aldehydic compounds derived from the periodate oxidation of raffinose and trehalose818a were reacted with p-nitrophenylhydrazine, the authors were surprised to find that one molecule of oxidized raffinose, containing six aldehydic functions, reacts with only three molecules of the reagent, and that the four aldehydic functions of the oxidized trehalose molecule react with only two. The reactions of periodate-oxidized carbo-... 

Disubstituted 1,2,3-triazoles are usually minor components in the product mixtures obtained from reactions of triazole with electrophiles (see Section 5.01.5). The few regioselective syntheses of such compounds include a reaction of aminoacetophenones 1235 with hydrazines. The reaction with methylhydrazine proceeds well without any catalysis, but that with phenylhydrazine requires cupric chloride as a catalyst. It is assumed that hydrazone 1236 that forms in the first step is in a tautomeric equilibrium with its azo form 1237. However, it is not clear how bond formation between the nitrogen atoms and oxidation to the triazole system occurs. 4-Aryltriazoles 1238 are obtained in 50-66% yield (Scheme 205) <2003SC3513>. 

Phenylhydrazine Phosgene Phosphine Lead dioxide, oxidizers Aluminum, alkali metals, 2-propanol Air, boron trichloride, bromine, chlorine, nitric acid, nitrogen oxides, nitrous acid, oxygen, silver nitrate... 

A number of 2H-1,2,3-triazole 1-oxides 72 were prepared by chemists at the Cassella Company as potential NO-donors in view of their formal structural similarity with furoxan derivatives [18]. Derivative 72a was studied in depth. It was obtained by cupric sulfate oxidation of intermediate 79, derived from the action of the substituted phenylhydrazine 78 on the oximino acetoacetic acid amide 77 (Scheme 6.13). 

It is interesting to note that a Cu(II) precatalyst gives an active catalyst in the absence of reducing agent (phenylhydrazine, etc.) contrary to observations made with bis(oxazolines) as ligands and to the accepted mechanism of this reaction. This reaction occurs at temperatures as low as 0°C, and contradicts the conventional belief that slow thermal homolytic cleavage of the oxidant (tert-butyl per-benzoate) is responsible for initiation of the catalytic cycle. Clearly, further work on the mechanism of this transformation is warranted. 

The extent of oxidation, when determined by the reaction of the product with phenylhydrazine, is 85%. Hydrolysis of the oxidized xylan should produce approximately equimolar quantities of D-glyceraldehyde and glyoxal. Experimental determination of glyceraldehyde indicates 67 % of the theoretical when the oxidized xylan is distilled with sulfuric acid and the evolved methylglyoxal measured as the phenylosazone. Glyoxal is isolated in 63% yield, when separated as the phenylosazone or as the dioxime. Aldehyde groups in the oxidized xylan may be further... 

Like all hydrazones, osazones lose phenylhydrazine when heated with hydrochloric acid. Naturally, it is not the sugar originally taken which is thus recovered, but an oxidation product, a so-called osone. In the example chosen the osone is ... 

Potassium iodate is a fairly strong oxidizing agent that may be used in the assay of a number of pharmaceutical substances, for instance benzalkonium chloride, cetrimide, hydralazine hydrochloride, potassium iodide, phenylhydrazine hydrochloride, semicarbazide hydrochloride and the like. Under appropriate experimental parameters the iodate reacts quantitatively with both iodides and iodine. It is, however, interesting to observe here that the iodate titrations may be carried out effectively in the presence of saturated organic acids, alcohol and a host of other organic substances. 

Atomic charges, effective charges at reacting centres, and HOMO and LUMO energies have been calculated for nitrobenzene, nitrosobenzene, A-phenylhydrazine, diphenyldiazine, A,A -diphenyldiazine-A-oxide, and A,A -diphenyUiydrazine, compared with kinetic data for the hydrogenation of these compounds, and used to propose a mechanism for the hydrogenation of nitrobenzene. 

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