SU140430A1 - The method of selection of cyclic silazanov - Google Patents

Description

At present, when cyclized silazanes are obtained from the synthesis obtained on the basis of alkylchlorosilanes and ammonia, the silazane solution is prefiltered from the ammonium chloride formed during the reaction, and the precipitate is washed. filter several times with a solvent to remove residual product and then silazane is separated from the filtrate by rectification. The presence of a filtration stage in the process of isolating cyclic silazans creates significant inconveniences regarding the safety of the process and entails the loss of the desired product. In accordance with the proposed method of isolating cyclic silazan, the reaction mixture obtained by reacting the benzene solution of alklchlorosilane with ammonia is treated with water or an aqueous alkali solution at 15-20 °, the supernatant organic layer, which is a solution of silzancil, is processed and treated in a known manner. The implementation of the proposed method makes it possible to eliminate the filtration stage and the loss of the target product associated with it, as well as to improve the working conditions. Example 1. Through a solution containing 129 g of dimethyl dichlorosilane in 1600 ml of benzene, with vigorous movement at a temperature of 15–25 ° C (cooled with an ice bath), ammonia from the cattle JffMhn Mi is delivered to the natural gas stream. The supply of ammonia is then stopped and 80 g of a 13.7% aqueous solution of sodium alkali are introduced into the flask. After dissolving the precipitate, the resulting layers are separated and the benzene solution is dispersed from the Wurtz flask, while after the distillation of benzene, 66.4 g of product, which is a mixture of hexamethylcyclotrisilazane and octamethylcyclotetrasilazane, remain in the flask. The comparative characteristic and the yield of the product isolated by the known and proposed method are given in the table below.

Upon subsequent rectification, the resulting mixture is isolated:

1) hexamethylcyclotrisilazane

m.p. 5274 mm,, 9246. , 4950. Mv 220. Found in%: C-33.01; H-9.8; Si-38.33; N-18.8. Calculated for CeHsiSiaN., In%: C-32.8; H-9.55; Si-38.3; N-19.2;

2) octamethylcyclotepdcylosane MV-294 Found in%: C-33.5; H-9.7; Si-38.9; N-18.4.

Calculated in% for C8H28Si4N4: C-32.8; H-9.55; Si-38.3; N-19.2.

Example 2. Under the conditions of example 1, out of 157 diethyldichlorosilane, 62 g of ammonia and 1750 ml of benzene, 96.7 g of product (nitrogen content 13.42%, nj 1.4690) are obtained, from which the subsequent hexaethylcyclotrisilazane with m.p. 148-15079 mm, Df 0.9324, "2J 1.4690. MV-275.8 Found in%: C-46.9; H-11.0; Si-28.3; N-13.42. Calculated for Ci2H33Si3N3%: C-47.52; H-10.89; Si-27.7; N-13.7. The output of 95.8% compared with 78.8% in the allocation of the product in a known manner.

Example 3. Ammonia is passed through a solution containing 50 g of ethyldih / yrsilan in 250 g of benzene (or gasoline) by intensive displacing and cooling in an ice bath at a rate of 0.7 l / min until the solution is saturated. At the end of the synthesis, 600 g of water are added to the reaction mixture and transferred until the precipitate is completely dissolved. The resulting two layers are separated, the benzene layer is formed with calcium chloride (or silica gel) for 3–4 hours and dispersed from a Würz flask. After distilling off the benzene, the product used for the hydrophobization remains in the flask. The comparative characteristic and the yield of the product isolated by the proposed and known method are shown in the table below.

The product is recovered by the proposed method

Product highlighted using filtering

A method for separating cyclic silazanes from a mixture containing ammonium halide salts, such as ammonium chloride, characterized in that, in order to improve working conditions and reduce product loss, the mixture is treated with water or a weak aqueous alkali solution at 15-20 ° C, followed by processing the organic slurry in a way.

- 3 - № 140430

Subject invention