SU33239A1 - Method of preparing methyl green dyes - Google Patents

Description

The proposed method involves the production of methyl green dyes by the action of toluene methyl ester - para - sulfonic acid on the base of methyl or crystal violet; The methyl toluene-sulfonates formed are converted into methyl chlorides by treatment with sodium chloride in a hydro-acidic medium.

Methyl green is chloromethylated to hexamethyl pararosaniline hydrochloride, i.e. the product of addition of methyl chloride to crystal violet.

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H (SNS) about

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BUT.

CH3-N {CH,) 2

C1

The literature describes two methods for the preparation of methyl green:

1) The effect of methyl nitrate on methyl purple (or crystal violet) with the transfer of the obtained addition product to Berichte 6 chlorite methyl. 825 (1873) 1.

2} By the action of iodide or chlorine 50)

of methyl methyl to a solution of methyl violet or crystal violet in methyl alcohol in the presence of alkali (Monuet et Reverdin, Monit. Sdent. 1878, 124).

The first method has long been abandoned due to the danger of working with methyl nitrate (explosive). As for the second method, it is very complicated in terms of instrumentation, since the methylation reaction proceeds only under pressure in an autoclave.

The author of the present invention has developed a method for preparing methyl green with para-toluyesulfonic acid methyl ester, which is a more reactive substance than haloalkyls and does not require the use of autoclaves.

This method consists in the fact that para-toluenesulfonic acid methyl ester is used for the methylation of a very complex amine.

The reaction is carried out either in a solvent (if proceeding from crystal violet), or by direct fusion of the reagents (in the case of using methyl red violet). The product of the reaction, methyl toluene sulfonate, in the process of salting out with sodium chloride, under the influence of chlorine ion, is converted into chloromethyl, i.e. methyl green.

When working with crystal violet, yields are close to quantitative, and c. If methyl violet is used, they reach 35-55%, depending on the quality of the latter.

Example 1. 50 I crystal violet bases, 27.5 g of toluene-para-sulfonic acid methyl ester and 250 cm of acetone are boiled in a flask with reflux condenser for 8 hours.

Upon cooling, the precipitated methylesyl toluene sulfonate is sucked off, washed with acetone and dissolved in a mixture of 1 liter of water and 45% of 10% hydrochloric acid. To the resulting solution were added 20 t of zinc chloride, 5 g of zinc acetate and 200 g of sodium chloride. Methyl green recovered after salting is sucked off, washed with 5% brine and dried at 60 (yield Up to 95% of theoretical). Acetone is recovered from the acetone mother liquor by distillation and a slight amount of methyl green is obtained from the residue.

Example 2. 50 g of methyl violet base and methyl ga LLP

Toluene-para-sulfonic acid ester was spun for 2 hours in an oil bath at 125-130 ° (in an open vessel). After cooling the alloy is dissolved in water, amyiac is added (before alkaline reaction), the tarred unreacted base of methyl violet is precipitated, filtered, and the filtrate is weakly acidified with hydrochloric acid. Methyl green is salted out of the solution obtained after the addition of zinc chloride and zinc acetate, (theoretical yield).

The subject matter of the invention.

The method of preparing methyl greens from methyl or crystal violet, characterized in that the bases of these dyes are acted with methyl toluene-ether sulfonic acid and the methyltoluene sulfonates formed to convert them. in the usual way