Benzil dihydrazone

Benzidine, N,N -diethyl-, 36, 21 Benzidine dihydrochloride, 36, 22 Bcnzil, 34, 42 Benzil dihydrazone, 34, 42 Benzilic acid, 33, 37 2-Benzimidazolethiol, 30, 56 l,2-Benzo-3,4-dihydrocarbazole, 30, 91 Benzofuran, 3-methyl, 33, 43 Benzofurazan oxide, 31,14, 15 37,1 Benzoguanamine, 33,13 Benzoic acid, 32, 94 37, 21 Benzoic acid, -acetyl-, methyl ester, 32, 81... 

A solution of 105.1 g. (0.5 mole) of benzil (Note 1) in 325 ml. of w-propyl alcohol is prepared in a 1-1. round-bottomed flask which is fitted with an efficient reflux condenser. To this solution 76 g. (1.30 moles) of 85% hydrazine hydrate (Note 2) is added, and the mixture (Note 2) is heated under reflux for 60 hours. The solution is cooled with an ice bath, and the benzil dihydrazone is separated by suction filtration. The crystals are washed with 200 ml. of cold, absolute ethanol and dried (Note 3) on the suction filter for 1 hour. The yield of benzil dihydrazone is 99-106 g. (83-89%), m.p. 150-151.5°. 

Benzil dihydrazone should not be dried in a vacuum desiccator, for it sublimes easily. 

An early procedure used triethyl phosphate directly on the diketone, but better yields are obtained by the oxidation of the corresponding dihydrazone 42 The oxidant may be mercury(n) oxide, which is rather expensive 43 alternatively copper(i) chloride in dichloromethane and pyridine is oxidised with oxygen gas, and the derived complex is then used to oxidise the dihydrazone to the acetylenic group with the evolution of nitrogen.44 The reaction is illustrated by the conversion of benzil dihydrazone into diphenylacetylene (Expt 5.25). 

ACID, ETHYL ESTER, 34, S4 Oxidation, by nitric acid, 30, 48 of aldehyde to carboxyl group, 30, 49 of benzil dihydrazone with mercuric oxide, 34, 42... 

MisceUaneons oxidations, Some aromatic amines (e.g., aniline, p-toluidine, p-chloroaniline) are oxidized by silvei(ll) oxide to the corresponding azo derivative in moderate yield. Hydroquinone is oxidized by AgO rapidly to p-benzoquinone in quantitative yield. Oxidation of benzil dihydrazone with AgO gives dipfaenylacctylene in 95% yield. 

One method for the preparation of diphenylacetylene involves oxidation of benzil dihydrazone with mercuric oxide the intermediate diazo compound loses nitrogen as formed to give the hydrocarbon ... 

Dihydrazones of a-diketones, when treated with mercuric oxide at higher temperatures, yield acetylenes [393, 394, 395, 396], Diphenylacet-ylene is obtained by refluxing benzil dihydrazone with mercuric oxide [396] in benzene or by refluxing benzil monohydrazone with mercurous trifluo-roacetate in ether for 2 h (yield 43%) [405], The oxidation of dihydrazones... 

In the preparation of diphenylacetylene from benzil dihydrazone, this derivative is suspended in benzene in a flask fitted with a stirrer and reflux condenser, and mercuric oxide is added in portions at a rate sufficient to maintain gentle refluxing... 

Oxidation. Newman and Reid found the reagent superior to mercuric oxide for Curtius oxidation of dihydrazones of benzils to give diarylacetylenes. A mixture of benzil dihydrazone and silver trifluoroacetate in 250 ml. of acetonitrile is stirred at room temperature and triethylumine is added in the course of 150 min. The course CtHsC—CC4H5 + 4CF3C02Ag + 4 EtjN—— > C HsCSCCsHs + 2 Nj + 4Ag... 

Curtius et ah206 showed that acetylenes can also be prepared by oxidizing vicinal dihydrazones with yellow mercuric oxide. Diphenylacetylene, for example, is thus obtained in 75% yield from benzil dihydrazone.207 In a variant of the Curtius procedure diacetylenes can be prepared in 80-85% yield by oxi-... 

Fe [FeLaCy-CHsCN, L = A/, A/ -bis[l-(pyridin-3-yl) methylidene]benzil dihydrazone) Heterometal-organic frameworks 353 [173]... 

Bai Y, Gao H, Dang D-B et al (2010) A series of metal-organic frameworks based on polydentate schiff-base ligands derived from benzil dihydrazone synthesis, crystal structures and luminescent properties. CrystEngComm 12 1422... 

---