Phenylhydrazones, 2,4-dinitro

The preparation of crystaUine derivatives, including 2 4-dinitro-phenyl hydrazones, semicarbazones, oximes, phenylhydrazones and p-nitrophenylhydrazones can be carried out as described under Aromatic Aldehydes, Section IV, 135. 

The acetone test reagent consists of a 0 1 per cent, solution of 2 4-dinitro-phenylhydrazine and is prepared as follows Dissolve 0-25 g. of 2 4-dinitrophenyl-hydrazine in 60 ml. of water and 42 ml. of concentrated hydrochloric acid by warming on a water bath cool the clear yellow solution and dilute to 250 ml. with water. The acetone test is considered negative when 5 ml. of the reagent and 4-5 drops of the distillate give no cloudiness or precipitate of acetone 2 4-dinitro-phenylhydrazone within 30 seconds. After a negative test is obtained, it is stron y recommended that the mixture in the flask be refluxed for 5-10 minutes with complete condensation and then to collect a few drops of distillate for another test. If no acetone is now detected, the reduction is complete. 

Auf diese Weise erhalt man innerhalb 12 Stdn. 0,197 g (70% d. Th.), innerhalb 24 Stdn. 0,232 g (82% d.Th.) Benzaldehyd-2,4-dinitro-phenylhydrazon, dessen Menge auch innerhalb 36 Stdn. konstant bleibt. 

Auf ahnliche Weise erhalt man aus Hexansaure (0°) innerhalb 36 Stdn. 98% d.Th. He-xanal-2,4-dinitro-phenylhydrazon. 

Mit dieser Methode erhalt man (als 2,4-Dinitro- phenylhydrazon isoliert) u. a. 

Analog erhalt man z. B. die 2,4-Dinitro-phenylhydrazone der folgenden Aldehyde ... 

Dinitro-phenylhydrazone werden durch Diboran in der Regel nicht angegriffen, so daB sie bei Reduktionen als geschiitzte Form von Oxo-Verbindungen dienen kon-... 

H.Van Langenhove, M.Van Acker, N.Schamp, Quantitative Determination of Carbonyl Compounds in Rendering Emissions by RP-HPLC of the 2,4-dinitro-phenylhydrazones, The Analyst (London), 108, 1983, 329-334. 

Grosjean, D., and K. Fung, Collection Efficiencies of Cartridges and Microimpingers for Sampling of Aldehydes in Air as 2,4- Dinitro-phenylhydrazones, Anal. Chem., 54, 1221-1224(1982). 

Trinitro-3-hydroxy-azobenzene, H0.C6H2(N02)2N N.C6H4.N02 red ndls (from acet ac + w), mp 179° was prepd by heating benzoquinone-( 1,4)-oxime-4,6-dinitro-3-hy droxy-phenylhydrazone with nitric acid (d 1.39) acetic acid (Refs 1 3). No expl props are reported... 

Dinitro-3-hydroxybenzaldehyde gives dark crimson needles of 2,4,6-Trinitro-hydroxy-benzaldehyde- [4-nitro-phenylhydrazone], 02NC6H4NN CC6H(N02)3 0H which explode at 228-30°. Its p-Bromophenylhydrazone, deep olive green crystals with a metallic luster, also explodes violently at 218-20°. The p-nitro-phenylhydrazone derived from 2,6-dinitrohydroxy-benzaldehyde, deep terra cotta crystals, explodes at 240-42°, but the corresponding p-bromophenyl-... 

Xanthone is unreactive towards hydrazine and phenylhydrazine. The oxime is obtained by reaction of xanthione (xanthene-9-thione) with hydroxylamine, or from xanthone and hydroxylamine in pyridine. When the oxime is heated in water with phenylhydrazine, the phenylhydrazone is formed. In acid solution, xanthone reacts normally with 2,4-dinitro-phenylhydrazine but xanthone-1 -carboxylic acid (435) gives the pyridazinone (436), possibly via the hydrazone (57JCS1922). When the oxime is heated with phosphorus pentachloride it undergoes a Beckmann rearrangement to give the amide (437) (70MI22300). 

A]thiophene, and with polymeric chloroacetaldehyde, it leads to 5-ethylthieno[2,3-A]thiophene-2-aldehyde, characterized as its 2,4-dinitro-phenylhydrazone. 

Establishing a criterion for the purity of the product is of particular importance because of the known tendency of ethynyl-carbinols to undergo rearrangement.6 6 The authors have reported that consecutive small fractions of the distillate possess a constant boiling point and refractive index. Further, representative fractions, treated with periodic acid and subsequently with 2,4-dinitrophenylhydrazine, give cyclohexanone 2,4-dinitro-phenylhydrazone in 83% over-all yield in a high state of purity. 

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-dinitro-phenylhydrazone, semicarbazone or dimethone, see Aldehydes and ketones, Section 9.6.13, below). The other portion is employed for the preparation of a 3,5-dinitrobenzoate, etc. (see Alcohols and polyhydric alcohols, Section 9.6.4, p. 1241) it is advisable first to concentrate the alcohol by distillation 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 metabisulphite solution (compare Expt 5.82), but fractional distillation may sometimes be employed. 

Dinitro- phenylhydrazone °C Semicarbazone °C p-Nitro- phenylhydrazone °C Other derivatives °C... 

X-ray crystallography of PQQ [28], (PQQ)2(K) [28], and (PQQ)(Na)2 [29] has been reported. Coordination of the potassium ion involves the 7-carboxyl oxygens as well as the N(6) and 0(5) atoms. In the sodium complex, additional interactions with the 0(4) atom and the 2-carboxyl group are observed. As yet, crystalline preparations of PQQ-heavy metal complexes have not been obtained [28], X-ray crystallographic data of the PQQ acetone adduct [30] and the 2,4-dinitro-phenylhydrazone of PQQ triester [31 ] have also been presented. 

Before spectroscopy, one of the best ways to identify ketones and aldehydes was conversion to crystalline hydrazones, especially phenylhydrazones and 2,4-dinitro-phenylhydrazones (Section 18-16). In his exploratory work on sugar structures, Emil Fischer often made and used phenylhydrazone derivatives. In fact, his constant use of phenylhydrazine ultimately led to Fischer s death in 1919 from chronic phenyl-hydrazine poisoning. 

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