CHEMISTRY

Academician of the Academy of Sciences of the Latvian SSR G. Ya. VANAG and R. A. ZHAGAT

A COLOR REACTION FOR HYDRAZINE AND SUBSTANCES THAT LIBERATE HYDRAZINE

Few color analytical reactions are known for hydrazine: a poorly specific reaction with dimethylaminobenzaldehyde \((^1)\), picryl chloride \((^{2,3})\), and a fluorescence reaction with salicylaldehyde \((^4)\). The presence of hydroxylamine interferes with the determination of hydrazine by these reactions. A sensitive and specific reaction for hydrazine in the presence of hydroxylamine is the reaction with nitroindandione \((^{5,6})\). In studying the interaction of other derivatives of indandione-1,3 with hydrazine, we found that an even more characteristic reagent for hydrazine is anhydro-bis-indandione, or bindone (I).

Bindone is already known as an analytical reagent for aliphatic and aromatic primary amines \((^7)\) and nitro compounds \((^8)\), and has been included in recent analytical manuals \((^9)\). Recently bindone has been used in industry for determining small amounts of amines in the flotation of potassium salts \((^{10,11})\). When bindone is heated in glacial acetic acid with hydrazine hydrochloride, the solution turns green and a dark-green precipitate forms. Judging from the analysis, and also by analogy with other bindone derivatives, the precipitate is the azine of bindone (II). A more detailed study of it will be given separately.

\[ \begin{array}{c} \mathrm{CO} \\ \diagup \ \ \diagdown \\ \mathrm{C_6H_4} \ \ \ \mathrm{C}=\mathrm{C} \ \ \ \mathrm{C_6H_4} \\ \diagdown \ \ \diagup \ \ \diagdown \ \ \diagup \\ \mathrm{CO} \ \ \ \ \ \ \ \ \ \mathrm{CH_2} \ \ \ \ \ \ \mathrm{CO} \end{array} \]

\[ \text{(I)} \]

\[ \mathrm{C_6H_4} \begin{matrix} & \mathrm{CO} \\ \diagup & & \diagdown \\ \end{matrix} \mathrm{C}=\mathrm{C} \begin{matrix} & \mathrm{C_6H_4} \\ \diagdown & & \diagup \\ \end{matrix} \mathrm{C}=\mathrm{N}-\mathrm{N}=\mathrm{C} \begin{matrix} & \mathrm{C_6H_4} \\ \diagup & & \diagdown \\ \end{matrix} \mathrm{C}=\mathrm{C} \begin{matrix} & \mathrm{CO} \\ \diagdown & & \diagup \end{matrix} \mathrm{C_6H_4} \]

\[ \text{(II)} \]

The green coloration with bindone is very characteristic of hydrazine and its salts and can be used as a sensitive and specific reaction for hydrazine. To carry out the reaction, the substance under examination is dissolved or suspended in glacial acetic acid, bindone is added in solid form (for 3–4 ml of solution, approximately 0.02–0.03 g of bindone; an excess of bindone does not interfere with the reaction), and the mixture is heated for several minutes. In the presence of hydrazine, a green coloration of the solution appears, and at a somewhat higher concentration of hydrazine a dark-green precipitate also forms. The appearance of a green coloration with bindone in glacial acetic acid is observed down to a dilution of a solution of hydrazine hydrochloride of 1:100,000, or approximately 1:200,000 calculated as free hydrazine. If the concentration of hydrazine is very low, after boiling for 3–5 minutes the solution is left to stand; after 20–30 minutes a noticeable green coloration appears.

If hydrazine has to be determined in aqueous solutions, such a solution is diluted with a 4–5-fold amount of glacial acetic acid, bindone is added, the mixture is boiled for 2–3 minutes, and left to stand. A green ...

coloration. The sensitivity of the reaction in this case is lower (1:20,000 with hydrazine hydrochloride). Bindone also gives a green coloration with hydrazine in the presence of hydroxylamine. The latter gives a yellow monoxime with bindone^(12), which does not interfere with the determination of hydrazine. Even in the presence of a 1000-fold excess of hydroxylamine, hydrazine was detected down to a dilution of its hydrochloride of 1:50,000 or, calculated as free hydrazine, approximately 1:100,000.

Since hydrazones and azines of aldehydes and ketones are fairly readily cleaved by hydrochloric acid to hydrazine, they too can be detected with bindone. For this purpose, to the hydrazone or azine in 3–4 ml of glacial acetic acid, 0.02–0.03 g of bindone is added, the mixture is heated to boiling, and 1–2 drops of concentrated hydrochloric acid are added. If no green coloration appears, the mixture is heated for 1 min. Acid hydrazides can be determined in an analogous manner. Thus, for example, benzaldehyde azine was detected down to a dilution of 1:50,000, and benzoic acid hydrazide down to 1:15,000.

There are indications in the literature that semicarbazones are also hydrolyzed to hydrazine^(13,14); therefore they too can be detected with bindone. But since semicarbazones are hydrolyzed by hydrochloric acid with varying ease, although the reaction with bindone is always positive, the limiting dilution at which a green color is still observed varies greatly; thus, for example, for semicarbazide hydrochloride it is 1:25,000, for acetone semicarbazone and cyclohexanone semicarbazone 1:10,000, and for furacilin 1:250. Thiosemicarbazide also gives a positive reaction (1:1000), as do some thiosemicarbazones.

Alkyl- and arylhydrazines (methyl-, ethyl-, phenyl-, acetylphenyl-, dinitrophenyl-) do not give a positive reaction with bindone. The reaction is also negative with hydrazo- and azobenzene, diaminoguanidine, pyrazole, aminopyrazoline, pyramidon, analgin, pyridazines, and others.

On the other hand, derivatives of bindone also do not give a green coloration with hydrazine; for example, methyl-, ethyl-, bromo-, dibromo-, bromomethyl-, bromoethyl-, and dinitrobindones give with hydrazine hydrochloride in glacial acetic acid only yellow solutions. A positive reaction—a green coloration—is given only by the methyl and ethyl esters of the enol form of bindone, but it turns out that in glacial acetic acid these substances are cleaved to bindone.

Thus, hydrazine in turn can be used as a reagent for bindone: to a solution of bindone in glacial acetic acid, a little hydrazine hydrochloride is added and the mixture is heated for 1 min.; immediately or after standing for some time a green coloration appears. By this method bindone can be detected down to a dilution of 1:10,000.

In the presence of primary amines, bindone is not applicable as a reagent for hydrazine, since primary amines give with bindone in glacial acetic acid a violet or blue coloration^(7,9). In such a case preference should be given to 2-nitroindandione-1,3; the reaction with it, although somewhat less sensitive, allows hydrazine to be detected even in the presence of primary amines.

Institute of Organic Synthesis
Academy of Sciences of the Latvian SSR

Received
12 III 1960

CITED LITERATURE

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