Benzalazine

Stir a mixture of 2-4 g. of powdered hydrazine sulphate, 18 ml. of water and 2-4 ml. of concentrated aqueous ammonia (sp. gr. 0-88), and add 4-6 g. (4 4 ml.) of benzaldehyde (free from benzoic acid) dropwise, with stirring, over a period of 30-60 minutes. Stir the mixture for a further hour, collect the solid by suction filtration and wash it with water. RecrystalUse from 8 ml. of rectified spirit. The 3 ield of benzalazine (yellow needles), m.p. 92-93°, is 3-6 g. 

Azines. Aldehydes react w ith h3 drazine to yield azines the reaction cannot usually be arrested at the hydrazone stage. This reaction may be illustrated by the preparation of benzalazine from benzaldehyde ... 

As for cyclopropanation of alkenes with aryldiazomethanes, there seems to be only one report of a successful reaction with a group 9 transition metal catalyst Rh2(OAc)4 promotes phenylcyclopropane formation with phenyldiazomethane, but satisfactory yields are obtained only with vinyl ethers 4S) (Scheme 2). Cis- and trans-stilbene as well as benzalazine represent by-products of these reactions, and Rh2(OAc)4 has to be used in an unusually high concentration because the azine inhibits its catalytic activity. With most monosubstituted alkenes of Scheme 2, a preference for the Z-cyclopropane is observed similarly, -selectivity in cyclopropanation of cyclopentene is found. These selectivities are the exact opposite to those obtained in reactions of ethyl diazoacetate with the same olefins 45). Furthermore, they are temperature-dependent for example, the cisjtrcms ratio for l-ethoxy-2-phenylcyclopropane increases with decreasing temperature. 

Herzog, R. and Leuschner, J. Single and subacute local and systemic toxicity studies of benzalazine, Arzneim. Forsch., 44(12) 1353-1356, 1994. 

Reaction with benzaldehyde in ammonia forms benzalazine ... 

It has been shown that the benzophenone sensitized decomposition of benzoyl peroxide is due in part to formation of the benzophenone ketyl radical, which induces decomposition.98,99 Hydrocarbon sensitized peroxide decomposition is discussed in Section IV.A.4. The formation of benzonitrile from the benzophenone sensitized irradiation of benzalazine, which was originally attributed to hydrogen abstraction by benzophenone,100 actually results from a photooxidation.101... 

Figure 3. Isothermal DSC curves showing crystallization of polymethoxy-benzalazine ether, VII-Cg crystallization temperature is indicated for each curve. (Reprinted with permission from ref. 8. Copyright 1986 Sen-i Gakkaishi.)...

N-[(o-Azidobenzylidene)-H -benzylidene]-hydrozide. See under Benzalazine and Derivatives... 

Basic hydrolysis of 3-phenyl-l,2,4,5-tetrazine (81) led to the isolation of benzalazine (82) in 80% yield (71KGS708). In most other cases studied the isolated product was an aldehyde acylhydrazone (83), indicating that during the basic hydrolysis one carbon atom of the tetrazine ring is reduced from the acid oxidation level to an aldehyde level (78HC<33)1075, p. 1094). A mechanism for the reaction has been proposed by Libmann and Slack (56JCS2253). Benzalazine (82) was also isolated when 3-azido-6-phenyl-l,2,4,5-tetrazine (84) was hydrolyzed by base (71KGS711). 

Treatment of 3-phenyl-l,6-dihydro-l,2,4,5-tetrazin-6-one (94) with base led to the isolation of benzalazine (82) (69KGS566). Alkaline hydrolysis of hexahydro-1,2,4,5-tetrazines (74) gave an aldehyde hydrazone or an aldehyde and hydrazine as with the acidic hydrolysis <78HC(33)1075, p. 1213). 

Benzol ani I in. See Benzylidene aniline Benzalazine. Same as Banzaldehyde Azine... 

Table 6 contains data on the transition parameters for a large series of main-chain mesogen macromolecules. Figure 15 shows scanning calorimetry data for poly(oxy-2,2 -dimethylazoxybenzene-4,4 -diyloxydodecanedioyl), entry 8 in Table 6. These data should be compared to data on low molecular mass p-butyl-p -methoxyazoxy-benzene which are shown in Fig. 12. Similar comparisons are available for two benzalazines (entries 14 and 16 of Table 6). Although the entropies of transition from the liquid crystal to the isotropic melt are small for all polymers listed as expected, they are larger than those of the corresponding nematic small molecules [1.6, 3.35, and 3.26 J/(K mol), respectively for the small molecules corresponding to entries 8, 14, and 16]. The main-chain nematics seem to have a somewhat larger entropy of transition than the side-chain nematics for larger flexible spacers.

Although it has long been known that benzaldehyde reacts with hydrazine in alkaline solution to give a yellow, insoluble precipitate of benzalazine1 and that the latter when steam distilled in the presence of mineral acids is hydrolyzed to give the corresponding hydrazine salts,2 no previous attempt has been made to apply these facts to the recovery of hydrazine residues. This reaction is practically quantitative and can be applied not only to the recovery of residual hydrazine left in solution in the Raschig synthesis (No. 31) but to all solutions where the detection and recovery of hydrazine in the presence of ammonia, or hydroxylamine, are of interest. In the process of formation of hydrazine salts from benzalazine, 95 per cent of the benzaldehyde can be recovered. 

In carrying out the recommended procedure, care must be taken to avoid an excess of benzaldehyde, as benzalazine... 

Residues containing 25 g. of hydrazine sulfate are dissolved in 5 1. of water, and the solution made distinctly alkaline to methyl orange with sodium hydroxide. Forty-one grams of benzaldehyde is added, and the solution shaken thoroughly. The milky suspension that forms is allowed to stand (overnight) until the yellow precipitate has settled out and the supernatant liquid has become clear. The precipitate is filtered, washed thoroughly with water, and dried at room temperature. Yield 39 g. (98 per cent) of benzalazine melting point 93°C. after recrystallization from alcohol. 

Preparation of Hydrazine Dihydrochloride from Benzalazine. One hundred and four grams of benzalazine (0.5 mol) is suspended in 400 ml. of water in a 4-1. round-bottom flask, and 80 ml. of concentrated hydrochloric acid added. The suspension is subjected to- steam distillation until no more benzaldehydef comes over in the distillate. 

One hundred and four grams of crude benzalazine (obtainable from the residual solutions of the Raschig synthesis) is suspended in 400 ml. of water, and 60 ml. of concentrated sulfuric acid added. The solution is steam distilled until no more benzaldehyde comes over and then cooled in an ice-salt mixture to bring about precipitation of the sulfate. Yield 60 g. of N2H4H2SO4 (92 per cent). 

Barium amalgam, 11 by displacement method, 14 by electrolytic method, 12 Barium paraperiodate, 171 Benzalazine, 92... 

Barium hexafluorosilicate, preparation of, for decomposition to silicon tetrafluoride, 4 145 Barium paraperiodate (orthoperiodate), Ba3H4(I06)2, 1 171 Barium dezZro-tartrate, for resolution of tris(ethylenediamine)-cobalt(III) ion, 6 184 Barium thiocyanate, 3 24 Benzalazine, in recovery of hydrazine residues, 1 92 Benzoylacetone, beryllium derivative of, 2 19... 

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