DE1162365B - Process for the production of silanes - Google Patents

Description

Process for the preparation of silanes The invention relates to a process for the production of silanes, which have both hydrogen and OR groups on the silicon atom contain bonded, where R is an alkyl or aryl radical without active hydrogen, by reacting halosilanes containing SiH groups with alcohols of the formula RAW.

The conversion of halosilanes of the general formula Ra Si Hb X4 - (a + b) where R is an aliphatic or aromatic radical, such as methyl, ethyl, Vinyl or phenyl radical, X denotes a halogen atom, preferably a chlorine atom and a has a value from 0 to 2, b has a value from 1 to 3 and the sum of a + b is less than 4, in the corresponding alk (Ar) oxysilane is according to the known Procedure only unsatisfactorily possible.

The reason for this is mainly to be found in the fact that when alcohols act on hydrogenhalosilanes, hydrogen halide corresponding to the reaction becomes free.

The resulting acid now favors the side reaction thus an undesired elimination of the hydrogen from the hydrogen silane. It would be possible to intercept the resulting acid with bases. However, the use of ammonia, amines or alcoholates as acid scavengers does not lead to success, since the decomposition of the hydrosilane takes place very quickly, especially in the basic range.

It was therefore so far the synthesis of alk (Ar) oxysilanes, the hydrogen contained bonded to the silicon atom, from the corresponding halosilanes with somewhat satisfactory yields only possible in a roundabout way.

It is known to produce methyl diethoxysilane in that one first converts trimethylchlorosilane into trimethylethoxysilane and this after following Equation converted with methyldichlorosilane: 2 (CHa) 3SiOC2H5 + CH3 (H) SiCl2 2 2 (CH3) 3SiCl + CH3 (H) Si (OCaH5) 2-The trimethylchlorosilane produced as a by-product is continuously distilled off from equilibrium.

Another, but complex and therefore not very economical The method consists in treating 2 moles of ethyl orthoformate with methyldichlorosilane or other halosilanes with SiH bonds.

It is also known and described in U.S. Patent 3,008,975, Reacting chlorosilanes directly with alcohols and the hydrogen chlorosilane released in the process to remove from the reaction mixture under reduced pressure. The reaction is but poorly reproducible. In addition, working with negative pressure a disruptive loss of the highly volatile silanes, which as a result of their easy, hydrolytically conditioned gelability to disturbances in the lines, in particular lead into the vacuum pumps.

It has now been found that one can easily and with high yields reaches the corresponding alk (Ar) oxysilanes from the halosilanes with SiH groups, if the hydrogen halide formed in the reaction with alcohols is in statu nascendi binds without increasing the value of the reaction mixture at the same time.

According to the invention, this is achieved by carrying out the reaction in the presence an acid acceptor which is insoluble in the reaction mixture is carried out.

The acid acceptors used are preferably urea and thiourea or melamine. However, the use of ammeline, urotropin, Substitution products of the aforementioned compounds, calcium cyanamide or sodium sulfonamide in good yields. Basic ion exchangers are also extremely useful acid acceptors for the method according to the invention. Prerequisite for the usefulness of these compounds and at the same time the selection principle for the search for further suitable acid acceptors is, in addition to their basicity, their insolubility in the reaction mixture. condition is further that with the corresponding hydrohalic acid no water, ammonia or amine is produced as a by-product.

The resulting salts of the bases with the hydrohalic acids can again easily be broken down into base and acid, so that the process with a limited amount of acid acceptor that is regenerated in the circuit can be.

Often times, the use of an inert solvent can be used for dilution the reaction mixture, to influence its viscosity or to improve it the heat transfer can be an advantage. However, it is assumed that the acid acceptor is insoluble in the solvent used.

The reaction can be carried out at low temperatures. However, the lower reactivity of a higher alcohol, ROH, causes the If higher temperatures are used or if the reaction is to be accelerated, this is the case It is a particular advantage of this process that even then there is a decomposition of the hydrosilane can be avoided with elimination of the hydrogen, since the hydrogen halide formed is immediately removed from the reaction mixture and bound.

Example 1 A mixture of 184.3 g (4 moles) of ethanol, 480 g (8 moles) Finely ground urea and 400 ml of methylene chloride is poured into a three-necked flask given, which is provided with stirrer, dropping funnel and reflux condenser. One lets now within 2 hours with vigorous stirring, 230 g (2 mol) of methyldichlorosilane add dropwise, the mixture boiling under reflux.

The mixture is then stirred for a further hour, followed by the reaction mixture filtered, the residue was washed with methylene chloride and the combined filtrates distilled through a column. The boiling point of the methyl diethoxyhydrogensilane obtained was 97 to 102 ° C; yield 214 g, corresponding to 800 / o of theory.

Example 2 To a suspension of 360 g of urea in a mixture of 600 cc of methylene chloride and 138 g (3 mol) of absolute ethanol is left with stirring 135.5 g (1 mol) of silicochloroform are added dropwise over the course of one hour. During this Time the reaction mixture is cooled by an ice bath, and then is they stored overnight at room temperature, then filtered, the salt residue Washed thoroughly with methylene chloride and finally the combined solutions over a column distilled.

117.2 g (= 71.3% of theory) of triethoxysilane, boiling point 132, are thus obtained up to 135 ° C.

Example 3 A mixture of 376.4 g (2 moles) phenol, 480 g (8 moles) Finely ground urea and 300 cc of methylene chloride is poured into a three-necked flask given, which is provided with stirrer, dropping funnel and reflux condenser. One lets now within 2 hours with vigorous stirring 230 g (2 mol) of methyldichlorosilane, dissolved in 200 cc of methylene chloride, added dropwise, the mixture under reflux boils. The reaction mixture is then allowed to reflux for a further hour. It is left to stand and the one stored overnight at room temperature is filtered Reaction mixture.

The residue is washed thoroughly with methylene chloride. The United Filtrates are distilled, lastly in vacuo using an oil pump.

This gives 360 g of methyldiphenylphenoxyhydrogensilane, Kr 0.4 100 to 104 "C (yield 78.3% of theory). The compound contains 0.450/0 Si-bonded Hydrogen compared to a theoretical value of 0.435%.

Claims (2)

Claims: 1. Process for the production of silanes, which contain both hydrogen and OR groups bonded to the silicon atom, where R is a Is alkyl or aryl radical without active hydrogen, by reaction of SiH groups containing halosilanes with alcohols or phenols of the formula ROH, thereby characterized in that the reaction is carried out in the presence of an insoluble in the reaction mixture Carries out acid acceptor. 2. The method according to claim 1, characterized in that the Carries out reaction in the presence of an inert solvent.