Aldehydes 2,4-dinitrophenylhydrazones

A group of Reissert compounds containing various A-acyl groups were subjected to hydrolysis under similar conditions to give the aldehyde-2-,4-dinitrophenylhydrazone. ... 

The ethanol-insoluble mixture of phenylhydrazones was extracted several times with hot chloroform and the solvent removed. The reddish residue was then recrystallized from pyridine yield of levulinic aldehyde, 2,4-dinitrophenylhydrazone, 90.5% melting point, 232° C. Literature melting point, 235-6° C. (5). 

Brady s reagent A solution of 2,4-dinitro-phenylhydrazine sulphate in methanol. Gives characteristic crystalline yellow to deep red 2,4-dinitrophenylhydrazone products with aldehydes and ketones. 

Dinitrophenylhydra2ones usually separate in well-formed crystals. These can be filtered at the pump, washed with a diluted sample of the acid in the reagent used, then with water, and then (when the solubility allows) with a small quantity of ethanol the dried specimen is then usually pure. It should, however, be recrystallised from a suitable solvent, a process which can usually be carried out with the dinitrophenylhydrazones of the simpler aldehydes and ketones. Many other hydrazones have a very low solubility in most solvents, and a recrystallisation which involves prolonged boiling with a large volume of solvent may be accompanied by partial decomposition, and with the ultimate deposition of a sample less pure than the above washed, dried and unrecrystal-lised sample. 

Note. The 2,4-dinitrophenylhydrazones of many higher aldehydes and ketones may be insoluble in most solvents. In this case, Mter them off, wash with ethanol, dry and take the m.p. attempted recrystallisation may cause partial decomposition. (M.ps., pp. 530-540.)... 

The experimental procedure to be followed depends upon the products of hydrolysis. If the alcohol and aldehyde are both soluble in water, the reaction product is divided into two parts. One portion is used for the characterisation of the aldehyde by the preparation of a suitable derivative e.g., the 2 4-dinitrophenylhydrazone, semicarbazone or di-medone compound—see Sections 111,70 and 111,74). The other portion is employed for the preparation of a 3 5-dinitrobenzoate, etc. (see Section 111,27) it is advisable first to concentrate the alcohol by dis tillation or to attempt to salt out the alcohol by the addition of solid potassium carbonate. If one of the hydrolysis products is insoluble in the reaction mixture, it is separated and characterised. If both the aldehyde and the alcohol are insoluble, they are removed from the aqueous layer separation is generally most simply effected with sodium bisulphite solution (compare Section Ill,74),but fractional distillation may sometimes be employed. 

The chiral bicyclic imidazolidine 74 is deprotonated at the 2 position by s-BuLi and the resulting anion adds to alkyl halides, acid chlorides, chlorofor-mates, phenyl isocyanate, and aldehydes. The use of this compound as a chiral formyl anion equivalent seems to be limited, however, since the diastereoselectiv-ity in the addition to aldehydes is poor and hydrolysis of the products 75 to give aldehydes also produces cyclohexane-1,2-diamine, necessitating isolation of the aldehyde as its 2,4-dinitrophenylhydrazone (96SL1109 98T14255). 

The aldehyde R"CHO liberated can be determined quantitatively by means of dinitrophenylhydrazine. In the case of formaldehyde (R" = H) being split in an alcoholic-acid medium, it has been found that the formation of a dinitrophenylhydrazone is a relatively slow process. This seems to suggest that formaldehyde is originally split off in the form of an acetal which gradually yields formaldehyde under action of dinitrophenylhydrazine. 

Imine formation from such reagents as hydroxylamine and 2,4-dinitro-phenylhydrazine is sometimes useful because the products of these reactions— oximes and 2,4-dinitrophenylhydrazones (2,4-DNPs), respectively—are often crystalline and easy to handle. Such crystalline derivatives are occasionally prepared as a means of purifying and characterizing liquid ketones or aldehydes. 

When present in macro quantities, aldehydes and ketones can be determined by conversion to the 2,4-dinitrophenylhydrazone which can be collected and weighed. When present in smaller quantities (10 3M or less), although hydrazone formation takes place, it does not separate from methanol solution, but if alkali is added an intense red coloration develops the reagent itself only produces a slight yellow colour. Measurement of the absorbance of the red solution thus provides a method for quantitative determination. 

The identification and quantification of potentially cytotoxic carbonyl compounds (e.g. aldehydes such as pentanal, hexanal, traw-2-octenal and 4-hydroxy-/mAW-2-nonenal, and ketones such as propan- and hexan-2-ones) also serves as a useful marker of the oxidative deterioration of PUFAs in isolated biological samples and chemical model systems. One method developed utilizes HPLC coupled with spectrophotometric detection and involves precolumn derivatization of peroxidized PUFA-derived aldehydes and alternative carbonyl compounds with 2,4-DNPH followed by separation of the resulting chromophoric 2,4-dinitrophenylhydrazones on a reversed-phase column and spectrophotometric detection at a wavelength of378 nm. This method has a relatively high level of sensitivity, and has been successfully applied to the analysis of such products in rat hepatocytes and rat liver microsomal suspensions stimulated with carbon tetrachloride or ADP-iron complexes (Poli etui., 1985). 

See 2,3-Epoxypropionaldehyde 2,4-dinitrophenylhydrazone See Other 1,2-EPOXIDES, OXIMES, POLYMERISATION INCIDENTS See related ALDEHYDES... 

Unfortunately, there are no universal methods to detect all types of protein oxidation, because the products formed can be so diverse in nature. However, some forms of protein oxidation can be assayed using chemical modification (Davies et al., 1999 Shacter, 2000). In particular, the formation of carbonyl groups on proteins can be targeted using the reagent 2,4-dinitrophenyl-hydrazine (DNPH). This compound reacts with aldehydes to form 2,4-dinitrophenylhydrazone derivatives, which create chromogenic modifications that can be detected at high sensitivity in microplate assays or Western blot analysis (Buss et al., 1997 Winterbourn et al., 1999). 

Carbonyl compounds for instance can be trapped by absorption in a reagent solution containing 2, 4-dinitrophenylhydrazine and hydrogen chloride. Details of this method are extensively described elsewhere (8). The principle of the method is that the carbonyl compounds, in case of rendering plant emission the aldehydes, react with the 2,4-dinitrophenylhydrazine and form 2,4-dinitrophenylhydrazones (2,4-DNPH s) according to the scheme. 

Many organic chemicals are analyzed by RPC. These include various arylhydroxylamines as the N-hydroxyurea derivative with methyl isocyanate (614) alkyl- and alkoxy-disubstituted azoxybenzenes (6t5), n-alkyl-4-nitrophenylcarbonate esters ranging in length from methyl to octyl (616), 4-nitrophenol in the presence of 4-nitrophenyl phosphate (617), ben-zilic acid, and benactyzine-HCI using ion-pair chromatography (618), as well as aniline and its various metabolites (619), stereoisomers of 4,4 -dihydroxyhydrobenzoin (620), and aldehydes and ketones as the 2,4-dinitrophenylhydrazones (621). The technique has also been used to analyze propellants and hydrazine and 1,1-dimethylhydrazine were quantitita-vely determined (622, 623). 

Cyclobutanecarboxaldehyde has been prepared in very low yield by the Rosenmund reduction procedure.6 A 46% yield of the 2,4-dinitrophenylhydrazone derivative has also been reported, with the aldehyde formed as an intermediate, in the reaction of the acid chloride and lithium tri-Mmtoxyaluminum hydride at —78° in diglyme.7... 

The ozonides of choline and ethanolamine phosphatides and triglycerides can be subjected to reduction with triphenylphosphine to yield the corresponding core aldehydes, and further derivatized to the 2,4-dinitrophenylhydrazones (DNP). The core aldehydes and their DNP derivatives can be separated by HPLC and characterized by various techniques, including EI-MS and TS-MS of positive and negative ions . See also Section VHI.E. 

Dinitrophenylhydrazones (DNP) aldehyde determination, 670 core aldehydes, 689 malondialdehyde determination, 669 ozonide reduction, 726... 

To the clear solution obtained by warming 0-5 g. of 2 4-dinitro-phenylhydrazine, 1 ml. of concentrated hydrochloric acid and 8-10 ml. of ethanol, add 0-25 g. of the aldehyde and heat just to boiling. Allow to cool to room temperature, filter off the 2 4-dinitrophenylhydrazone and reorystallise it from ethanol or glacial acetic acid. 

Derivatization is a procedure in which analyte is chemically modified to make it easier to detect or separate. For example, formaldehyde and other aldehydes and ketones in air, breath, or cigarette smoke25 can be trapped and derivatized by passing air through a tiny cartridge containing 0.35 g of silica coated with 0.3 wt% 2,4-dinitrophenylhydrazine. Carbonyls are converted into the 2,4-dinitrophenylhydrazone derivative, which is eluted with 5 mL of acetonitrile and analyzed by HPLC. The products are readily detected by their strong ultraviolet absorbance near 360 nm. 

A convenient synthesis of lonchocarpin (206) and similar compounds is the Knoevenagel condensation of a 6-acetylchromene (207) with benzaldehyde (7iJCS(C)796, 71JCS(C)8U>. Carbonyl groups present in chromenes as aldehydes or ketones form oximes and 2,4-dinitrophenylhydrazones <77HC(31)11). 

The most widely used protective groups for aliphatic and alicyclic aldehydes and ketones are (a) cyclic acetals and (b) cyclic dithioacetals and hemithio-acetals. The use of semicarbazones, oximes and 2,4-dinitrophenylhydrazones (for preparation see Section 9.6.13, p. 1257) is less common but has found application in certain instances where the more vigorous methods required for deprotection are not detrimental. 

A red 2.4 dinitrophenylhydrazone is obtained from the reaction of an unknown with an amine. Of the following four structures, which ketone or aldehyde could have formed this iinine ... 

Oximes, 2,4-dinitrophenylhydrazones, and semicarbazones are often used in qualitative organic chemistry as derivatives for aldehydes and ketones. 

Transfer about 0.2 g of d-camphor, accurately weighed, to a 300-ml glass stoppered flask, and dissolve in 25 ml of aldehyde-free ethanol. Add slowly 75 ml of 2,U-dinitrophenylhydrazine TS while shaking, and heat for U hours on a water bath under a reflux condenser. Cool, add 100 ml of diluted sulfuric acid (1 50), and allow to stand for 2h hours. Collect the precipitate so obtained on a glass filter (G3), wash the residue on the filter with cold water until the washings become neutral, dry for 2 hours at 105° and weigh as the 2,U-dinitrophenylhydrazone of d-camphor (C1gH2(-)N 0 332.36). ... 

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