Pyruvic acid dinitrophenylhydrazone

An improved method for the preparation of A" -3-ketones from 4-bromo compounds was described by Mattox and Kendall. This procedure involves dehydrobromination of the 2,4-dinitrophenylhydrazone and subsequent cleavage of the hydrazone with pyruvic acid ... 

The scope of this reaction was investigated by Djerassi, °° who showed that 4-bromo ketones in the series and 2-bromo ketones in the 5a series give unsaturated 2,4-dinitrophenylhydrazones in 80-90% yield on warming under nitrogen with 1.1 moles of 2,4-dinitrophenylhydrazine in acetic acid. Cleavage with pyruvic acid affords the pure unsaturated ketones in 60-70 % yield. 

Pyridine base eliminations of a-bromo ketones cannot be recommended for general use because of the side reactions already discussed. The semi-carbazone-pyruvic acid method should be employed if strict absence of isomerization is required in the dehydrobromination of 2- or 4-bromo-3-ke-tones. This procedure is not applicable for the preparation of A1,4-3-ketones, due to rearrangement. The use of semicarbazide for the dehydrobromination of 6-bromo-A4-3-ketones is reported to be satisfactory for the preparation of A4,6-3-ketones65 but appears to be a neglected approach. (The corresponding 2,4-dinitrophenylhydrazones cannot be cleaved.)... 

Esters of pyruvic acid 2,6-dinitrophenylhydrazone were described by Bassette et al. 

Pyruvic acid was first found in agar194 and then in several carrageenans.113,195,196 It may be determined quantitatively in the form of its 2,4-dinitrophenylhydrazone,197 but an enzymatic procedure with the available lactate dehydrogenase seems to be more convenient.198... 

In addition, the DNPH (2,4-dinitrophenylhydrazine) [38] and NADH (dihydronicotinamide adenine dinucleotide) [36] studies with purified Iso-4 provided the evidence that the 70 Da moiety was a pyruvate derivative (C3H2O2). In the DNPH study, treatment of Iso-4 with acid and 2,4-dinitrophenylhydrazine produced the 2,4-dinitrophenylhydrazone of the pyruvic acid liberated from Iso-4. In the NADH study, the amount of NAD+... 

A procedure developed by Mattox and Kendall for the liberation of cortisone acetate from the C3 2,4-dinitrophenylhydrazone utilizes a mixture of pyruvic acid, acetic acid, chloroform, and hydrogen bromide and affords the parent compound in 80% yield. For comparison. DePuy° prepared a mixture of 1 g. of A -cholestene-S-one 2,4-DNP with 100 ml. of chloroform and 100 ml. of the usual levulinic-hydrochloric acid and heated it under reflux for 3 hrs. Chromatography afforded pure A -cholestene-3-one in high yield. 

Detection systems for GC are chosen for their sensitivity and selectivity for a particular class of VOCs. Detectors for GC include FID, the BCD, the photoionization detector (PID), the pulsed discharge detector (PDD), and the reduction gas detector (RGD). A variety of mass spectrometers can also be interfaced with a GC for confirmation of molecular structure and quantitation. Singlewavelength ultraviolet-visible detectors (190 to 600 nm) and diode array detectors are used to detect carbonyls as their 2,4-dinitrophenylhydrazone derivatives. The absorption maxima for aliphatic carbonyls, aromatic carbonyls, and dicarbonyls are near 360 nm, 385 to 390 nm, and 415 to 430 nm, respectively. Formic, acetic, and pyruvic acid are detected by ion conductivity. 

Carbonyl products were identified by paper chromatography of the 2,4-dinitrophenylhydrazones (20). The irradiated N-acetylalanine showed only pyruvic acid and acetaldehyde. These were determined quantitatively by the method of Johnson and Scholes (13) with minor modifications. Chloride ion was determined by the method of Luce et al. (15) after Hayon and Allen (12). 

The absorption spectra of equal concentrations of the 2.4-dinitrophenylhydrazones of pyruvic acid and a-oxogtutaric acids, showing an isosbestic point at 431 nm. 

Timmen and Dimick (1972) characterized the major hydroxy compounds in milk lipids by first isolating the compounds as their pyruvic ester-2,.6-dinitrophenylhydrazones. Concentrations as weight percent of the compounds from bovine herd milk lipids were 1,2-DGs 1.43, hydroxyacylglycerols 0.61, and sterols 0.35. Lipolysis tripled the DG content. The usual milk fatty acids were observed, except that the DGs lacked 4 0 and 6 00, again indicating that these lipids were in part intermediates in milk lipid biosynthesis. With the large hydrazone group... 

For the determination of keto-acids, e.g. pyruvic, a-ketoglutaric and oxalacetic acids in mixtures and in biological materials, a method has been proposed employing paper electrophoretic separations of the 2,4-dinitrophenylhydrazones of these acids.< ) After elution, the polarographic wave corresponding to the reduction of the nitro-groups (in the 2,4-dinitrophenylhydrazone formed) was followed in 0-1 N HCl and the first wave at —0T4 V measured. 

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