Hydrazone with 2,4-dinitrophenylhydrazine

Now, it is worth noting (Table 9.4, 3a) that when the carbonyl group (C=0) in the aldehyde or ketone is unhindered, a second equivalent of carbonyl compound can be added to the hydrazone with the formation of an azine. The aryl-substituted hydrazines, for example, phenylhydrazine (C6H5NHNH2) and in particular 2,4-dinitrophenylhydrazine ( 2,4-DNPH ) (Table 9.4,3b) frequently form crystalline hydrazones. For many years (in a largely pre-spectroscopic era), it had been accepted that if the melting points of two derivatives (e.g., 2,4-DNP and oxime) of an unknown ketone or aldehyde corresponded to values found in published tables or lists of those previously reported, then the ketone or aldehyde had been identified. Generally, the method was successful but clearly dependent on ready access to the appropriate tables or lists. 

Interaction of formaldehyde with 2,4-dinitrophenylhydrazine in acid media causes 2,4-dinitrophenylhydrazone (DNPhydrazone) formaldehyde formation. Gas-chromatographic analysis of 2,4-DNP-hydrazone formaldehyde toluene extract with an electron holding detector makes it possible to detect it at the level of 0,001 mg/dm. Phenol is detected in the form of tribromphenol yield, the hexane extract of which undergoes chromatography with an electron holding detector which provides the level of phenol detection of 0.001 mg/dm (the limit of quantitative detection). 

Dinitrophenylhydrazine reacts with carbonyl groups with the elimination of water to yield hydrazones (I) and with aldoses or ketoses to yield colored osazones (II). 

Secondary alcohols yield ketones on oxidation and these can be reacted with 2,4-dinitrophenylhydrazine to yield the corresponding colored hydrazones. 

Heterocyclics 252, 260, 299,416 n-Hexadecanol esters 63 Hexaporphyrin 102 Hexitols 426 Hexobarbital 254,255 Hexoses 161,202 Hexuronic acid 158 Histamine 294,296, 355 Homogentisic acid 166,167 Horizontal chamber 127 Hotplates 93 ff -, temperature distribution 95 Hydrazines 269,284 Hydrazone formation 71 ff -with 2,4-dinitrophenylhydrazine 71, 72, 274... 

Analysis of mixts contg acetone, ethanol isopropanol) 10)H.A.Iddle C.E. Jackson,AnalChem 6,454-6(1934) (Acet, as well as other carbonyl compds, reacts quantitatively with 2,4—dinitrophenylhydrazine with formation of solid hydrazone. This procedure seems to be only approximate) 11)E.K.Nikitin, ZhPriklKhim 9,1543-6(1936)(in Fr) ... 

Method. The keto acid residue is dissolved in 1.0 ml of 2,4-dinitrophenylhydrazine (prepared by dissolving 500 /rmoles in 100 ml of 2.0 Nhydrochloric acid at 40 °C stable for 2 weeks) and left to stand for 30 min at 30 °C. A minimum of a four-fold molar excess of 2,4-dinitrophenylhydrazine is required for stoichiometric conversion of the keto acid into the hydrazone. The reaction is complete in 5 min for keto monocarboxylic acids, and in ca. 20 min for keto dicarboxylic acids. The hydrazones may be extracted from the reaction mixture with ethyl acetate. An aliquot portion of this solution is subjected to TLC. 

Some commercial samples of precipitated manganese dioxide may be active enough for use directly in an oxidation process. To assess the activity of a sample of manganese dioxide, dissolve 0.25 g of pure cinnamyl alcohol in 50 ml of dry light petroleum (b.p. 40-60 °C) and shake the solution at room temperature for 2 hours with 2g of the sample of manganese dioxide (previously dried over phosphoric oxide). Filter, remove the solvent by evaporation and treat the residue with an excess of 2,4-dinitrophenylhydrazine sulphate in methanolt (Section 9.6.13, p. 1257). Collect the cinnamaldehyde 2,4-dinitrophenyl-hydrazone and crystallise it from ethyl acetate. An active dioxide should give a yield of the derivative, m.p. 255 °C (decomp.), in excess of 0.35 g (60%). 

Dinitrophenylhydrazones (DNPHs) were applied to the GC analysis of keto acids. As with carbonyl compounds, they are prepared by reaction with 2,4-dinitrophenylhydrazine and are also used mainly for the preliminary isolation of keto acids. They can be isolated from a dilute aqueous sample by adsorption on activated carbon and selective desorption [178] hydrazones of aldehydes with a methyl formate-dichloromethane mixture and hydrazones of keto acids with a pyridine-water azeotropic mixture. Hydrazones of acids are released from their pyridine salts with methanol containing hydrogen chloride. After... 

Separation of aldehyde dinitrophenylhydrazines by TLC and column chromatography Excess dinitrophenylhydrazine reagent and the hydrazones of acetone, formaldehyde and acetaldehyde, which occur as contaminants, can be removed prior to preparative TLC by column chromatography. Silicic acid (Merck) columns (3x2.1 cm) may be used with chloroform to elute the aldehyde dinitrophenyl-hydrazones. 

An acidic solution of 2,4-dinitrophenylhydrazine reacts with N-p-chlorophenyl-sulfonyl-3-ethoxy-l,2-thiazetidine 1-oxide to give (80%) the bis-2,4-dinitrophenyl-hydrazone of glyoxal. The adduct of A-sulfinyl-p-chlorophenylsulfonamide with dihydropyran is inert to catalytic hydrogenation and bromination. Treatment of two l,2-thiazetidine-3-one 1-oxides (e.g., 421) with hydriodic acid results in ring-cleavage and loss of sulfur. They are not oxidized to 1,1-dioxides by peracetic acid, ° but m-chloroperbenzoic acid accomplishes this oxidation. The unstable adducts with ketene decompose to amides with loss of hydrogen sulfide and sulfur dioxide or may be trapped by reaction with aromatic amines as shown for thiazetidine 1-oxide 422.An aldol-type condensation has been reported for A -cyclohexyl-1,2 thiazetidine-3-one 1-oxide and p-(A(A"-dimethylamino)benz-aldehyde. " Sulfur monoxide is lost in the flash-vacuum thermolysis of 422a. ... 

In the widely used colorimetric assay of SGOT and SGPT (R2), serum is incubated at 37 °G with phosphate-buffered L-aspartate/a-oxoglutarate or DL-alanine/a-oxoglutarate, respectively, the reaction terminated after a definite interval by addition of 2,4-dinitrophenylhydrazine in dilute HCl, and after a period at room temperature the hydrazones of oxalace-tate or pyruvate so formed are treated with dilute alkali and the optical density measured against water at 505 mp the results are read from standard curves of optical density against transaminase activity. 

Formaldehyde and other aldehydes are receiving increasing attention both as toxic substances and as promoters in the photochemical formation of ozone in the atmosphere. They are released into residential buildings from plywood and particle board, insulation, combustion appliances, tobacco smoke, and various consumer products. Aldehydes are released into the atmosphere in the exhaust of motor vehicles and other equipment in which hydrocarbon fuels are incompletely burned. A sensitive method for analyzing aldehydes and ketones is based on the sorption of these compounds to an SPE sorbent and their subsequent reaction with 2,4-dinitrophenylhydrazine (DNPH) on the sorbent. They are then analyzed as their hydrazones by HPLC (Fig. 7.9). A gradient analysis by HPLC may separate as many as 17 components with detection by ultraviolet (UV) light. 

The milk and cream were centrifuged, and the fat fraction was removed. The fat was extracted with carbonyl free hexane, and the fat extract was immediately reacted with 2,4-dinitrophenylhydrazine. The carbonyl compounds formed respective 2,4-dinitrophenylhydrazones (2,4-DNPH). The hydrazones were separated into monocarbonyls and then further purified using thin layer chromatography (18). Alkanal 2,4-DNPH were analyzed by gas chromatography using a 1.83 m glass column (i.d. 4 mm) packed with 2% OV-1 on acid washed Chromosorb W ( 180-200 mesh) (18,19). ... 

Carbonyl compounds in oxidized lipids are the secondary oxidation products resulting from the decomposition of the hydroperoxides. They can be quantified by the reaction with 2,4-dinitrophenylhydrazine and the resulting colored hydrazones are measured spectrophotometrically at 430-460 nm. The carbonyl value is directly related to sensory evaluation, because many of the carbonyl molecules are those responsible for off-flavor in oxidized oil. The anisidine value is a measure of carbonyl compounds that have medium molecular weight and are less volatile (Frankel 1998). It can be used to discover something about the prior oxidation or processing history of an oil. 

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