Carbonyl phenylhydrazones

Both aldehydes and ketones contain the carbonyl group, hence a general test for carbonyl compounds will Immediately characterise both classes of compounds. The preferred reagent is 2 4-dinilrophenylhydrazine, which gives sparingly soluble phenylhydrazones with carbonyl compounds ... 

Indolization of 3-substituted phenylhydrazone 59 normally gives rise to two isomeric products, 4-substituted indole 60 and 6-substituted indole 61. The ratio of 60 to 61 from the cyclization depends on the nature of the R group, the structure of the carbonyl... 

Reductive cleavage of phenylhydrazones of carbonyl compounds provides a route to amines. The reduction is carried out conveniently in ethanol containing ammonia over palladium-on-carbon. Ammonia is used to minimize formation of secondary amines, derived by addition of the initially formed amine to the starting material (160). Alternatively, a two-phase system of benzene, cyclohexane, toluene, or dioxane and aqueous hydrochloric acid can be used. 

Carbonyl compounds are also rapidly regenerated from the corresponding semicar-bazone and phenylhydrazone derivatives using ammonium persulfate impregnated... 

The band at 280 mp persists in spite of such alterations in the molecule as are caused by inethylation, acetylation and treatment with sodium hydroxide. However, the absorption of the phenylhydrazones of spruce (33) and white Scots pine native lignins 111) are peculiar in that a second maximum occurs at 352 mp. Glading (33) suggests that the carbonyl group in spruce native lignin is highly enolized, and, therefore,... 

McCarron Yes, uncouplers increase the depolarization of evoked Ca2+ transients and slow the rate of decay. This was with CCCP (carbonyl cyanide ///-chloro-phenylhydrazone). 

Experiments.—Being a primary hydrazide (of carbamic acid), semicarbazide reduces ammoniacal silver solutions and Fehling s solution. It reacts readily with aldehydes and ketones with the elimination of water and formation of semicarbazones, which, since they are more easily hydrolysed than are phenylhydrazones and oximes, are to be preferred to the latter for purposes of separation and purification of carbonyl compounds. Shake an aqueous solution of the hydrochloride (prepared as described above) with a few drops of benzaldehyde, isolate the semicarbazone and purify it by recrystallisation from alcohol. Melting point 214° decomp. Benzaldehyde semicarbazone is decomposed into its constituents by gentle warming with concentrated hydrochloric acid. 

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. 

Both esters can be distinguished by their reactions with carbonyl reagents. A phenylhydrazone is formed only by the compound with a free carbonyl group. 

Hajipour and coworkers prepared benzyltriphenylphosphonium peroxymonosulfate (BnPhsPHSOs) in a very high yield (95%) and purity (99%). This new oxidizing reagent was applied successfully in various deprotection reactions such as the conversion of oximes, phenylhydrazones, 2,4-dinitrophenylhydrazones and semicarbazones to the corresponding carbonyl compounds in the presence of bismuth chloride under nonaqueous conditions . Oxidative deprotection of trimethylsilyl ethers, tetrahydropyranyl ethers and ethylene acetals with BnPh3PHS05 under microwave irradiation affords the corresponding carbonyl compounds in very high yields (equation 71). The same reaction also proceeds under nonaqueous conditions ". 

Phenylhydrazone formation indicates a carbonyl compound. Since the negative Tollens test rules out an aldehyde, (A) must be a ketone. A negative iodoform test rules out the CH,C=0 group, and the reduction product, pentane, establishes the C s to be in a continuous chain. The compound is CHjCHjCOCHjCH,. 

One of the most important uses of semicarbazide is as a reagent for identifying aldehydes and ketones [3]. Many semicarbazones have higher melting points and lower solubilities than the corresponding phenylhydrazones. The carbonyl compound is easily recovered by hydrolysis in boiling water. 

Regeneration of carbonyl compounds from certain derivatives. Ketones can be recovered in satisfactory yield from the phenylhydrazones, p-nitrophenyl-hydrazones, tosylhydrazoncs, oximes, and semicarhazones by reaction with 1 equivalent of (C6H,Se0)20. 2,4-Dinilrophenylhydrazones and N,N-dimethyl-hydrazones arc inert under even rather vigorous conditions. The reagent can also be used to regenerate aldehydes from oximes or tosylhydrazones. 

Z = 0, NH), then the carbonyl group not adjacent to the heteroatom is preferentially attacked. Thus, isatin and indoxyl and their O- and 5-analogues (279, 282) react with hydroxylamine, hydrazine, phenylhydrazine, semicarbazide, etc., to give oximes, hydrazones, phenylhydrazones, semicarbazones, etc. (282 — 283 279 — 284). 

The uncoupler carbonyl cyanide p-(trifluoro-methoxy)phenylhydrazone (FCCP) and related compounds are widely used in biochemical studies. Their action can be explained only partially by increased proton conduction. 

Substituents on thiocoumarins behave in predictable fashion for example, 3-nitro compounds afford the 3-amines on reduction, while 3-acyl derivatives readily form normal carbonyl derivatives such as phenylhydrazones, or enoic acids with malonates. These derivatives may frequently be cyclized on to position 4 of a 4-hydroxythiocoumarin to give products such as (119) (equation 59). 

Carbonyl groups can be transformed into amines via formation of their hydrazones followed by transfer hydrogenation. Thus the benzoyl formate shown in Scheme 4.35 was converted into the phenylhydrazone under microwave irradiation in ethylene glycol as solvent. Subsequent reduction using ammonium formate and 10% Pd/C as a catalyst provides the amine in an overall reaction time of 10 min and a total yield of 83%.14... 

Falbe and co-workers have studied carbonylation of unsaturated amides to give imides (34), unsaturated amines to give lactams (37), and unsaturated alcohols to give lactones (38). Rosenthal and co-workers studied carbonylation of aromatic ketoximes, (127), phenylhydrazones (131), semicarbazones (129), azines (129), and nitriles (128) to produce phthalimidines. Horiie (65) has described the carbonylation of azobenzenes to give indazolones or 2,4-dioxo-l,2,3,4-tetrahydroquinazolines. Pritchard (121) and Murahashi et al. (103) have described the carbonylation of Schiff s bases to yield substituted phthalimidines. 

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