DE931473C - Process for the production of pure 2, 4, 6-Kollidinen from technical 2, 4, 6-Kollidinen - Google Patents

Description

Process for the production of pure 2, 4, 6-collidine from technical 2, 4, 6-Kollidinen The task, on a technical scale, from commercially available 2, 4, Obtaining 6-Kollidinen pure 2, 4, 6-Kollidin presents certain difficulties, since the existing admixtures, in particular 2, 3, 6-collidine and 2, 3-Lutid.in, especially in the mixture, show a boiling ratio that their smooth separation on the Ways of fractional distillation prevented even when using good columns.

One has therefore, inter alia. already proposed the technical mixtures with anhydrous hydrogen chloride approximately corresponding to the content of 2, -1, 6-collidine To treat amount and this in the form of its hydrochloride for separation bring (see the USA.-Patent 2 ..126 442). From the hydrochloride obtained the 2, 4, 6-collidine must then be restored with the aid of aqueous inorganic bases set in freedom and then converted into the anhydrous state. The fact that the desired pure 2, 4, 6-Kollid.in not immediately in anhydrous State obtained can be viewed as a certain disadvantage of this procedure will. Nevertheless, there was a certain need to find new, independent processes, especially those that do not suffer from this disadvantage.

It has now been found that the replacement of hydrogen chloride by Formamide offers such a possibility. The 2, 4, 6-collidine forms namely, what was previously unknown and unforeseeable was extremely specific anhydrous formamide a crystalline molecular compound in the molar ratio i: i, which melts at 4o to 42 °; this adduct becomes procedural from the technical, at least 5o%, but more advantageous from 7oo% 2, 4, 6-Kol'liden by contacting with anhydrous formamide, preferably about equivalent proportions, and by cooling the mixture below room temperature, preferably to -5 to -10 °, deposited.

The above-mentioned molecular compound can after its separation (e.g. B. by suction filtration or centrifugation), as was further found, without application decompose water-containing auxiliaries into their components. For example, you can for this purpose with organic solvents such as benzal, tol-wol, hexane, carbon tetrachloride: substance, treat, in which only the collidine is soluble, and off. of the solution obtained then separate the collidine by distillation. But one becomes more advantageous Molecular compound itself immediately the fractional distillation at reduced Submit pressure, the formamide remaining in the distillation residue and immediately can be used again.

Molecular compounds of formamide with organic bases were previously not named at all. But even after finding the formamide compound of the 2, 4, 6-Kollidins was in no way predictable that the chemically extraordinary related accompanying bases .in contrast to the 2, 4, 6-collidine under process-related Conditions would not form crystalline adducts.

Example a) Precipitation as an adduct 2.2 kg of technical 7oo% 2, 4, 6-collidine and 0.575 kg of technically pure anhydrous formamide are combined, cooled to -6 to -10 ° with stirring and kept at this temperature for several hours creating a thick slurry of crystals. The crystals represent the adduct (i collidine -I- i formamide), mp 40 to 42 °. The adduct is suctioned off or centrifuged off in a cool room and mixed with around 0.35 kg of formamide, which has a temperature of -I- 5 ° was pre-cooled, washed afterwards. Yield about 1.7 kg of formamide-moist adduct, containing about 93.5% pure adduct, corresponding to 75% of theory, based on Reirrkollidin in the technical product.

b) Isolation from the adduct The formamide-moist adduct is broken down in a bubble by vacuum distillation, the collidine passing over at a Kp12 57 to 59 °; 409 kg = 71% of theory, based on pure collidin in the technical product, are obtained. Should the distilled collidine still contain small amounts of formamide, it can be cleaned with 1% (based on collidine) solid caustic soda or with 30/0 conc. Sodium hydroxide solution is added, the mixture is heated to 50 to 150 ° for a few hours while passing a little nitrogen through it and then distilled in vacuo, a small forerunner containing all of the water. The pure collide boils within a smaller temperature range than i °, has 99.9 ° / o colide content and the density D20 = o.91 i.

The A4dukt can also be worked up as follows: 500 g of formamide-2, 4, 6-collidine adduct obtained according to a) are introduced into 500 g of saturated saline solution with vigorous stirring; the adduct breaks down and two layers are formed. In addition to the collidine, the upper layer contains about 100 per cent water and 1.39 per cent formamide. The formamide content can be reduced to about 0.5% by stirring with a further 100 to 500 g of saturated sodium chloride solution, while the water content remains unchanged. To destroy the remaining formamide, the collidine layer is refluxed with 2 to 5 "/ o concentrated sodium hydroxide solution for about 2 hours and then - by distillation at normal or reduced pressure into the azeotropic collidine-water mixture (which will be used for the next adduct decomposition can) and broken down into anhydrous collidine.

c) Recovery of formamide The formamide recovered under b) can be used directly.

The mother liquor and the washing formamide from a) "verden together in the Vacuum distilled, the first fraction being a base mixture (bp12 55 to 65 °) and the formamide, Kp12 ioi to 1o4 °, is obtained as the second fraction.

Claims (1)

. PATENT CLAIM: Process for the production of pure 2, 4, 6-Kollidinen from technical, at least 5oo / oigen 2, 4, 6-Kollidinen, characterized in that the latter with anhydrous formamide, preferably in their content of 2, 4, 6- Kollidine is added in approximately equivalent proportions, the mixture is exposed to low temperatures, preferably from -5 to -io °, the molecular compound separated out in this way is separated off and then broken down into its components by methods known per se, in particular by distillation under reduced pressure.