DE933031C - Process for stabilizing phenylhydrazine - Google Patents

Description

Method of stabilizing phenylhydrazine The best and easiest A characteristic of the degree of purity of phenylhydrazine is its solidification point, and even small changes in the percentage show a considerable decrease. Pure phenylhydrazine, e.g. B. in large quantities for syntheses of pharmaceutical Large-scale industry is required, retains its theoretical freezing point for only a short time of r9.6 °. It soon begins to decline, to only a value of after 6 months to reach about 11 °.

It has now been found that phenylhydrazine can be used for a long time can stabilize that he added hexamethylenetetramine, preferably up to 3 0/0 will. This addition can be made after production has ended or in the course of the purity distillation done by making a warm saturated solution of hexamethylenetetramine in phenylhydrazine lets drip.

A phenylhydrazine stabilized in this way with a0 / 0 hexamethylenetetramine has a freezing point of r9.3 ° and retains decomposition even in the presence of catalytically accelerating metals for more than 6 months at summer temperatures (a5 to 35 °) a freezing point of 19.3 to 18.1 ° (- 1oo0 / a to 98.5% phenylhydrazine) and a lighter color, while the unstabilized slowly darkens.

This stabilized product enables a so far for a longer period of time impossible storage and long-distance shipping in metallic Containers without a significant reduction in salary. The application of stabilized Phenylhydrazine is also when shipped for use as a preliminary product for important drug syntheses always required.

Example In 500 g of freshly distilled phenylhydrazine with a freezing point from 19.5 ° and a percentage of 99.5%, 2% hexamethylenetetramine becomes cold dissolved, a zinc sheet is placed in the clear solution and the whole thing at 25 to 35 ° leave closed in a brown glass stopper bottle. After a certain amount of time Times become samples for the determination of the freezing point and the percentage taken and the results with those from a left under the same conditions, compared to the unstabilized pattern.

The following table gives the freezing points and percentages of both samples as a function of time.

After 7 months, the unstabilized material kept closed has lost about 10% of its effectiveness, while the stabilized material has lost about i% under the same conditions. The rate of decomposition of the stabilized material is thus reduced to about a tenth of that of the unstabilized material after 7 months. An even greater difference is to be expected if there is an increased ingress of air. The same thing Time phenylhydrazine phenylhydrazine unstabilized stabilized (Months) Ep. ° CI % content Ep. ° CI ° / a content 0 19.5 99.5 1 9.3 99.5 18.5 98.5 1 9.0 99.3 2 16.7 97.3 1 8.9 9910 3 14.5 95.7 18; 8 0, 9 4 4.3 94.4 18.7 98.7 5 1 2.5 93.2 18.4 98.6 6 ==, o 9 1 , 7 1 8.1 98.5 7 = o, = 89.5 1 8.0 98.5 also applies depending on rising temperatures.

After one year of storage in the absence of air, the stabilized Phenylhydrazine with a solidification point of 7.3 ° still has a content of 96.1%, while the unstabilized only contains 65.7 fl / o phenylhydrazine.

Claims (1)

PATENT CLAIM: Process for stabilizing phenylhydrazine, thereby characterized in that during the preparation of the phenylhydrazine or thereafter Hexamethylenetetramine, preferably in an amount up to 31 / o-, is added.