Ketazine

KetaZine Processes. The oxidation of ammonia by chlorine or chloramine in the presence of ahphatic ketones yields hydrazones (36), ketazines (37), or diaziddines (38), depending on the pH, ketone ratios, and reaction conditions (101). 

Peroxide-Ketazine Process. Elf Atochem in France operates a process patented by Produits Chimiques Ugine Kuhhnaim (PCUK). Hydrogen peroxide (qv), rather than chlorine or hypochlorite, is used to oxidize ammonia. The reaction is carried out in the presence of methyl ethyl ketone (MEK) at atmospheric pressure and 50°C. The ratio of H202 MEK NH2 used is 1 2 4. Hydrogen peroxide is activated by acetamide and disodium hydrogen phosphate (117). Eigure 6 is a simplified flow sheet of this process. The overall reaction results in the formation of methyl ethyl ketazine [5921-54-0] (39) and water ... 

Fig. 6. Peroxide—ketazine process flow sheet. MEK = ethyl ketone.

The methyl ethyl ketazine forms an immiscible upper organic layer easily removed by decantation. The lower, aqueous phase, containing acetamide and sodium phosphate, is concentrated to remove water formed in the reaction and is then recycled to the reactor after a purge of water-soluble impurities. Organic by-products are separated from the ketazine layer by distillation. The purified ketazine is then hydrolyzed under pressure (0.2—1.5 MPa (2—15 atm)) to give aqueous hydrazine and methyl ethyl ketone overhead, which is recycled (122). The aqueous hydrazine is concentrated in a final distillation column. 

Comparison to the Raschig Process. The economics of this peroxide process in comparison to the Raschig or hypochlorite—ketazine processes depend on the relative costs of chlorine, caustic, and hydrogen peroxide. An inexpensive source of peroxide would make this process attractive. Its energy consumption could be somewhat less, because the ketazine in the peroxide process is recovered by decantation rather than by distillation as in the hypcochlorite process. A big advantage of the peroxide process is the elimination of sodium chloride as a by-product this is important where salt discharge is an environmental concern. In addition to Elf Atochem, Mitsubishi Gas (Japan) uses a peroxide process. 

The estimated world production capacity for hydrazine solutions is 44,100 t on a N2H4 basis (Table 6). About 60% is made by the hypochlorite—ketazine process, 25% by the peroxide—ketazine route, and the remainder by the Raschig and urea processes. In addition there is anhydrous hydrazine capacity for propellant appHcations. In the United States, one plant dedicated to fuels production (Olin Corp., Raschig process), has a nominal capacity of 3200 t. This facihty also produces the two other hydrazine fuels, monomethyUiydrazine and unsymmetrical dimethyUiydrazine. Other hydrazine fuels capacity includes AH in the PRC, Japan, and Russia MMH in France and Japan and UDMH in France, Russia, and the PRC. 

There are some recent examples of this type of synthesis of pyridazines, but this approach is more valuable for cinnolines. Alkyl and aryl ketazines can be transformed with lithium diisopropylamide into their dianions, which rearrange to tetrahydropyridazines, pyrroles or pyrazoles, depending on the nature of the ketazlne. It is postulated that the reaction course is mainly dependent on the electron density on the carbon termini bearing anionic charges (Scheme 65) (78JOC3370). 

The Piloty-Robinson pyrrole synthesis (74JOC2575,18JCS639) may be viewed as a monocyclic equivalent of the Fischer indole synthesis. The conversion of ketazines into pyrroles under strongly acidic conditions apparently proceeds through a [3,3] sigmatropic rearrange-... 

The important synthesis of pyrazoles and pyrazolines from aldazines and ketazines belongs to this subsection. Formic acid has often been used to carry out the cyclization (66AHQ6)347) and N-formyl-A -pyrazolines are obtained. The proposed mechanism (70BSF4119) involves the electrocyclic ring closure of the intermediate (587) to the pyrazoline (588 R = H) which subsequently partially isomerizes to the more stable trans isomer (589 R = H) (Section 4.04.2.2.2(vi)). Both isomers are formylated in the final step (R = CHO). 

The stabilized phosphonium ylide (601) reacts with aromatic aldehydes to give N-phenacylpyrazoles (602) in good yields (73CC7). Ketone semicarbazones and ketazines react with two moles of phosphorus oxychloride-DMF, the Vilsmeier-Haack reagent, with the formation of 4-formylpyrazoles (603 R = H or PhC=CH2) (70JHC25, 70TL4215). 

In the modified Raschlg process , used by Bayer A.G. and by Mobay Chem. Co. for large scale production of hydrazine, the intermediacy of an oxaziridine could be clearly evidenced (81MI50800). In this process ammonia and hypochlorite are reacted in the presence of acetone to form ketazine (302). Nitrogen-nitrogen bond formation is faster by a factor of about 1000 in the presence of acetone than in its absence. Thus acetone does not merely trap hydrazine after formation, but participates in the N —N bond forming reaction. Very fast formation of oxaziridine (301), which is isolable, is followed by its likewise fast reaction with ammonia. 

Another procedure145 consists of bubbling of sulfur dioxide through a chilled solution of diazomethane in ether146. Evaporation of the solvent leaves the crude thiirane dioxide, which can be further purified by either distillation under reduced pressure or recrystallization. The formation of the thiirane dioxides is usually accompanied by formation of the corresponding olefins, along with small amount of ketazines. 

The stereochemistry of the ring product (17) was rationalized in terms of the attraction and repulsion between the involved substituents98. The accompanying olefins may be formed via carbene intermediates (arising from a-elimination of S02 from sulfene), and the intermediacy of thiadiazoline dioxide (from sulfene and diazoalkane) explains the formation of the ketazine side-products. Thiadiazoline, on its part, may be formed directly by the cyclization of zwitterion 101. 

Simple criss-cross cycloadditions described so far are in fact limited to aromatic aldazines and cyclic or fluorinated ketazines. Other examples are rather rare, including the products of intramolecular criss-cross cycloaddition. The criss-cross cycloadditions of hexafluoroacetone azine are probably the best studied reaction of this type. It has been observed that with azomethine imides 291 derived from hexafluoroacetone azine 290 and C(5)-C(7) cycloalkenes < 1975J(P 1)1902, 1979T389>, a rearrangement to 177-3-pyrazolines 292 competes with the criss-cross adduct 293 formation (Scheme 39). 

A similar reaction sequence allows the preparation of symmetrical and unsymmetri-cal ketazines 318 from hydrazones and diazodiphenylmethane or 2-diazo-l,2-diphenyl- 1-ethanone 293). 

A number of compounds with this ring system (163), including dispiro derivatives, are formed by the catalytic cooligomerization of ketazines or aldazines with butadiene (Scheme 186)249 reactions of this type are analogous to the catalytic cyclotrimerization of butadiene to cyclodecatriene.250... 

Bayer ketazine A process for making hydrazine by the reaction of sodium hypochlorite with ammonia in the presence of acetone. Acetone azine is an intermediate. Never commercialized. See also Raschig (1). 

Keshan disease, selenium and, 22 101 Kessener brush aerators, 26 162 Kestner-Johnson dissolver, 22 672 Kestner process, 2 723 Ketals, aroma chemicals, 3 253 Ketazine processes, 13 576, 579—581 disadvantages of, 13 581 Ketene(s), 10 484... 

Methyl ethyl ether, 10 567 Methyl ethyl ketazine (MEK), 13 582, 583 Methyl ethyl ketone (MEK), 13 700 14 581 adipic acid solubility, l 555t azeotrope with methanol, 8 801 in MEK—MIPK—water system, 22 304-305, 306, 307 peroxide, 14 292... 

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