Aldehydes reaction with phenylhydrazine

D-Arabotetrahydroxybutylbenzo[/]quinoxaline fails to undergo similar reactions with phenylhydrazine. However the 3-aldehyde 37 yields the benzopyrazoloquinoxaline 38 on reaction with phenylhydrazine in acid... 

Phenylhydrazones are best prepared in dilute acetic acid solution use of more concentrated acetic acid can lead to formation of 1-acetyl-1-phenyl-hydrazine, m.p. 130-131° (corr.) if there is a neighboring hydroxyl group, which can lead to osazone formation, and if this is to be avoided, then any acidity is unfavorable and the reaction should be carried out as near the neutral point as possible. Condensation usually occurs in the cold, and almost always on short warming on the water-bath. A solvent is often unnecessary. <%,/ -Unsaturated aldehydes and ketones may cyclize to pyrazole derivatives on reaction with phenylhydrazine. 

Derivatives of the Carbonyl Group. Not many reactions of the aldehyde or keto group of sugars are observed, because the carbonyl forms of sugars comprise only a fraction of one percent in the equilibrium mixture. They can be trapped, however, in a few reactions, e.g. by oximfe formation. Important for the identification of sugars is the reaction with phenylhydrazine or with substituted phenylhydrazines (E. Fischer), which involves two carbon atoms and results in osazones ... 

Another reaction that is characteristic of a-hydroxy aldehydes or ketones, which has been found of value for the characterisation of sugars, is the formation of osazones with phenylhydrazine. This reagent reacts with either an aldose... 

The Sn2 reaction of quinazolinone 147 with phenylhydrazine was followed by rearrangement of the tautomerized intermediate 148 <00T7987>. The loss of both ammonia and aniline was followed by the addition of a second equivalent of phenylhydrazine to the resulting imine to produce quinazolinone hydrazone 149. Subsequent Fischer indolization of 149 followed by condensations with aldehydes led to 7-azarutacarpines. 

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... 

HYDRAZONES. The products of the reaction between an aldehyde or a ketone with phenylhydrazine arc termed hsdrazone.s. Sometimes the compounds are referred to as phenylhydrazones. 

Reaction CXXVlil. Action of Phenylhydrazine, etc., on Aldehydes and Ketones.—Phenylhydrazones of aldehydes and ketones are generally formed by warming these substances in aqueous-alcoholic solution with phenylhydrazine, phenylhydrazine acetate or phenylhydrazine hydrochloride in presence of excess sodium acetate. Derivatives of phenylhydrazine (e.g., p-nitro-phenylhydrazine) also react in a similar manner. 

When unknown compounds are identified without the aid of spectroscopy classification tests are used. Reacting the carbonyl in a ketone or aldehyde with an amine (2,4 dinitro-phenylhydrazine) to form an inline is the easiest way to detect a ketone or aldehyde (Reaction l). The iinine that forms is a highly colored solid. The color of the solid also helps to indicate structural characteristics. Ketones and aldehydes with no conjugation tend to form itnines with yellow to orange colors, while highly conjugated ketones or aldehydes form imines with red color. 

Given the structure or name of an aldehyde or ketone, write an equation for its reaction with the following nucleophiles alcohol, cyanide ion, Grignard reagent or acetylide, hydroxylamine, hydrazine, phenylhydrazine, 2,4-dinitrophenylhydrazine, primary amine, lithium aluminum hydride, and sodium borohydride. 

Reaction of phenylhydrazine with the /J-keto ester (64) gives the pyrazolone (65).55 The hydantoin (66) has been obtained by the action of potassium cyanide and ammonium carbonate on ferrocenecarbox-aldehyde.67-69 The potentiometric titration64 of hydantoin (67) has been reported. 

The accuracy and precision of an enzyme assay usually depend on the underlying chemical basis of techniques that are used. For example, if an assay involving reaction of an enzymatically produced aldehyde with phenylhydrazine to yield a phenylhydrazone product is carried out in buffer of the wrong pH, that is, a pH significantly above 6.0, the observed rate of phenylhydrazone formation will not accurately reflect the rate of enzymatically produced aldehyde, but rather the chemical rate of phenylhydrazone formation. The accuracy of an assay is a reflection of... 

Solid-phase synthesis of substituted pyrazolones 550 from polymer-bound /3-keto esters 549 has been described (Scheme 68) <2001EJ01631>. Trisubstituted pyrazole carboxylic acids were prepared by reaction of polymer-bound arylidene- or alkylidene-/3-oxo esters with phenylhydrazines <1999S1961>. 2-(Pyrazol-l-yl)pyrimi-dine derivatives were prepared by cyclocondensation of ethyl acetoacetate and (6-methyl-4-oxo-3,4-dihydropyrimi-din-2-yl)hydrazine with aromatic aldehydes <2004RJC423>. Reactions of acylated diethyl malonates with hydrazine monohydrochloride in ethanol afforded 3,4-disubstituted-pyrazolin-5-ones <2002T3639>. Reactions of hydrazines with A -acetoacetyl derivatives of (45 )-4-benzyloxazolidin-2-one (Evans oxazolidinone) and (2R)-bornane-10,2-sultam (Oppolzer sultam) in very acidic media gave pyrazoles retaining the 3(5)-chiral moiety <1999S157>. 

The reaction of phenylhydrazine with oxysucrose was found to be similar to that described for oxidized monosaccharide derivatives above, as only two molecules of the base reacted with the four potential aldehyde groups the product was assigned structure (89). Mester found that this derivative forms an amorphous bis(diphenylformazan) with benzenediazonium chloride, and so he assigned structure (90) to it. Acetylation of the formazan gave an amorphous product, identical with the formazan prepared from... 

As aldehydes, aldoses react with phenylhydrazine to form phenylhydrazones. If an excess of phenylhydrazine is used, the reaction proceeds further to yield products known as osazones, which contain two phenylhydrazine residues per molecule a third molecule of the reagent is turned into aniline and ammonia. (Just how the —OH group is oxidized is not quite clear.)... 

Most classes of VOCs found in indoor environments are sampled onto sorbents by adsorption but highly reactive VOCs like carbonyl compounds are sampled by chemical reactions with the sorbent. Thus aldehydes and ketones are sampled by their reactions with sorbent gels coated with 2,4-dinitro-phenylhydrazine to form stable hydrazones [38-40]. Similarly, formaldehyde has been sampled by its reaction with N-benzylethanolamine to give 3-benzyl-oxazolidine [41,42]. 

Condensation of o-phenylenediamine with methylglyoxal, aldohexoses and aryl or alkyl acyloins gave the corresponding quinoxalines 76. Indoloquinoxalines were obtained from isatin. Carbethoxymethylation of isatin and then reaction with o-phenylenedimine gave the respective indoloquinoxalines 77, whereas hydrazide was condensed with aromatic aldehydes and monosaccharides. L-Ascorbic acid or D-isoascorbic acid were oxidized with iodine and then reacted with o-phenylenediamine and phenylhydrazine to give quinoxalinones 78, which were cyclized to pyrazolyl-quinazolinones . ... 

The reaction of 4-formyl-3,5-dimethylisothiazole (175) (R = CHO) with sodium borohydride and organometallic compounds (R MgX or R sAl) gives the alcohols (175) (R = CH20H) and (175) (R = CHR OH), respectively. The Wittig reaction on the aldehyde yields the alkenes (175) (R = CH=CHR ) <88JHC235>. 2-Alkyl-5-aroylisothiazolin-3-ones are debenzoylated with sodium hydroxide (see Section 3.05.9.2.1) <87H(25)569>. On heating 2-alkyl-5-aroylisothiazolin-3-ones with phenylhydrazine in ethanol the 3-phenylhydrazono-3-aroylpropionamides are formed (see Section... 

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