Hydrazone formation with 2,4-dinitrophenylhydrazine

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... 

Hydrazone and substituted hydrazone formation—reactions with hydrazine, phenylhydrazine, and 2,4-dinitrophenylhydrazine [each derivative can form as an (E) or (Z) isomer]... 

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). 

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) ... 

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... 

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. 

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. 

We recall that hydrazine and 2,4-dinitrophenylhydrazine react with carbonyl compounds to give hydrazones. However, monosaccharides do not give simple phenylhydrazone derivatives. After the initial formation of a phenylhydrazone, further reaction occurs to give the osazone, which has two molecules of phenylhydrazine incorporated into it. 

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