Ketone 2,4-dinitrophenyl hydrazones

The carbonyl group is determined by a reaction with 2,4-dinitrophenyl hydrazine which precipitates the 2,4-dinitrophenyl hydrazone of the aldehyde or ketone, which is then filtered off, dried, and weighed. The reaction is... 

Acid hydrolysis of 5-amino-5-deoxy-l,2-0-isopropylidene-o -D-xy-lofuranose (15) might be expected to afiFord 5-amino-5-deoxy-D-xylose, but instead, at 70 , 3-pyridinol (21) is the main product. If the acid hydrolysis of compound 15 is conducted at room temperature, there is obtained, besides 3-pyridinol (21), the crystalline hydrochloride of l-amino-l,5-anhydro-l-deoxy-D-fhreo-pentulose hydrate (22). The crystalline hydrate exhibits no carbonyl band in its infrared and ultraviolet spectra. The water content cannot be removed without decomposition of the compound, and is, therefore, water of constitution. The nuclear magnetic resonance spectrum of 22 lacks the signal characteristic of an anomeric proton. The free ketone group is, however, detectable by the preparation of a (2,4-dinitrophenyl)-hydrazone. 

Reductive cleavage of 2,4-dinitrophenylhydrazones. Certain 2,4-dinitrophenyl> hydrazones of 3-ketosteroids can be cleaved under mild conditions if the nitro groups are reduced to amino groups by chromous chloride. Thus when the 2,4-DNP of 4,5a-dihydrocortisone 21-acetate in methylene chloride was shaken in a separatory funnel with chromous chloride and dilute hydrochloric acid for 15 min., workup of the organic layer afforded the ketone in 94% yield. Use of a water-immiscible solvent protects the released ketone an inert atmosphere if required can be provided with dry ice. Cortisone 2,4-DNP was cleaved in only 3-5 hrs. and the yield was 60%. DN P derivatives of A -diene-S-ones were completely resistant to hydrolysis. Contributed by Leon Mandell... 

An aldehyde or ketone is converted to the corresponding dinitrophenyl-hydrazone (DNP). The DNP is purified by recrystallization and its melting point compared with those reported in data books. In this way the original carbonyl compound can be identified. 

A soln. of cyclohexanone tosylhydrazone in acetone heated 24 hrs. at 65° in a sealed glass tube cyclohexanone. Y 78%. F. e., also cleavage of phenyl-, 2,4-dinitrophenyl-hydrazones, and oximes, and a-perdeuteriated ketones with acetone d(j, s. S. R. Maynez, L. Pelavin, and G. Erker, J. Org. Chem. 40, 3302 (1975). 

An unknown molecule is known to be a ketone and the 2,4-dinitrophenyl-hydrazone derivative of this ketone is bright yellow. What does this tell you about the structure If the 2,4-DNP derivative had been a dark orange or red, what structural information would that convey ... 

Chromatogram of 2,4-dinitrophenyl-hydrazones of carbonyl compounds in 25% dimethylformamide/cyclohexane (1) formaldehyde, acetaldehyde, and acrolein, (2) formaldehyde, acetaldehyde, -butyraldehyde, and -valer-aldehyde, (3) -hexylaldehyde and w-dodecylaldehyde, (4) diacetyl (mono-hydrazone), cyclopentanone, cyclohexanone, mixture of methylcyclohe-xanones, (5) fural (trans-derivative), fural (cis-derivative), acetaldehyde, acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Spots near the start are due to 2,4- dinitrophenylhydrazine. 

These products were defined as poly(vinyl ketone], diketo-derivatives for methyl cellulose and carboxymethyl cellulose or diketoacid derivatives of carrageenans and chondroitin-4-sulfate, respectively. The oxidation products were isolated and identified by the spectral data and elemental analysis, respectively [98-100]. The keto-derivatives showed broad IR absorption bands at 1730-1760 (broad] cm that characterize the carbonyl groups of ketones. The enhancement of the absorption bands of OH groups in the IR spectra may indicate the complete oxidation of the OH groups to its corresponding keto-derivatives [101]. The products were also confirmed by the reactions with 2,4-dinitrophenyl hydrazine and hydroxylamine to afford the corresponding 2,4-dinitrophenyl hydrazone and oxime derivatives, respectively [67-71]. 

However, in some cases azines can be converted to hydrazones by treatment with excess hydrazine and NaOH. Arylhydrazines, especially phenyl, p-nitrophenyl, and 2,4-dinitrophenyl, are used much more often and give the corresponding hydrazones with most aldehydes and ketones.Since these are usually solids, they make excellent derivatives and are commonly employed for this purpose. Cyclic hydrazones are also known, ° as are conjugated hydrazones. a-Hydroxy aldehydes and ketones and ot-dicarbonyl compounds give osazones, in which two adjacent carbons have carbon-nitrogen double bonds ... 

Ketones 2,4-Dinitrophenyl- hydrazine Formation of colored hydrazones or osazones. It is possible to distinguish between saturated and unsaturated hydrazones using potassium hexa-cyanoferrate(UI) [5]. [3,4]... 

---