DE2115327C3 - Process for the preparation of 3-chloropropanol- (1) - Google Patents

Description

The invention relates to a process for the preparation of 3-chloropropanol- (I) from acrolein by reaction of acrolein with hydrogen chloride and reduction of the chloropropionaldehyde formed

HCl

CH ₁ = CH-CHO

Cl-CH, - CH ₁ -CHO

Cl-CH ₁ -CH, -CH ₁ OH

3-chloropropanol- (l) is the starting material for the production of important compounds, for example of Monoesters of propanediol (1,3), which are used as solvents in the paint industry.

It is known to produce 3-chloropropanol- (1) from acrolein by converting the acrolein with hydrogen peroxide epoxidized, the epoxide hydrogenated to propanediol (1,3) and hydrogen chloride on this alcohol can act. The chloropropanol is obtained from the reaction mixture by multiple fractional distillation obtained (Organic Syntheses [1964], Coll. Vol. I, pages 533 to 534). The procedure is cumbersome and expensive and gives a total yield of only about 40%. It is also known. Sulfur chloride instead Apply hydrogen chloride (Houben - Weyl, Methods of Organic Chemistry [1962], Volume V / 3. Page 857). The yield here is only slightly better.

It is also known that 3-chloropropanol- (I) can be obtained by treating acrolein with hydrogen chloride converts in alcohol and the resulting acetals of chloropropionaldehyde in the presence of ruthenium catalysts Treated reducing (BE-PS 6 34 845). The yield is low. This too Process is unsuitable for economical production of chloropropanol.

There has now been a process for the preparation of 3-chloropropanol- (1) from acrolein by reacting the Acroleins are found with hydrogen chloride and reduction of chloropropionaldehyde, which is characterized is that the reduction is carried out by means of alkali boranate. Using this procedure, 3-chloropropanol- (l) from acrolein in a simple manner suitable for industrial standards with yields of about 85% are generated.

The conversion of an aldehyde into an alcohol by reduction with a hydride is not in itself new. It is surprising, however, that it can take place in the case of chloropropionaldehyde; because it is on the one hand it is known that this aldehyde under the action of hydrides or complex hydrides, like alkali hydrides. Frdalkali hydrides or lithiumalane; it polymerizes, and on the other hand it is known that halogen-containing compounds when treated with alkali boronates already hydrogen halide at room temperature split off (foe is. Newer methods der preparative organic chemistry [196b], volume IV. page 221). In the method according to the invention occurs neither polymerization nor elimination of hydrogen halide to any significant extent.

To carry out the process according to the invention, acrolein is first reacted with hydrogen chloride to form chloropropionaldehyde. For this purpose, the acrolein is preferably placed in an inert organic solvent and the hydrogen chloride is passed in as a gas. The solvents used are, for example, aromatic hydrocarbons such as benzene or toluene, halogenated hydrocarbons such as carbon tetrachloride, trichloromethane or dichloromethane, or in particular aliphatic or cycloaliphatic ethers such as diethyl ether, glycol dimethyl ether, dioxane, tetrahydrofuran or tetrahydropyran. ] e mole of acrolein per mole of hydrogen chloride is required. However, it is advantageous to use a deficit of hydrogen chloride, in particular a deficit of about 5 to 10 mol%. The acrolein expediently contains, as usual, small amounts of polymerization inhibitors, for example hydroquinone or phenothiazine. The reaction is generally carried out at temperatures between -30 and +50 ⁰ C, preferably at temperatures between +30 ⁰ C -lOund executed.
According to the invention, the chloropropionaldehyde is reduced to chloropropanol by means of alkali boronates. Among these, sodium and potassium borate are preferred. In general, it is advisable to take the alkali boronate in the form of an aqueous solution and to introduce the chloropropionaldehyde into this solution.

v> The chloropropionaldehyde is used as such or preferably as a solution in inert organic liquids, the liquids primarily being those solvents which are used in the reaction of acrolein with hydrogen chloride. The reaction mixture obtained in the preparation of the chloropropionaldehyde from acrolein and hydrogen chloride is advantageously used directly for the reduction. However, it can be useful to use the previously unreacted

w) Abort acrolein.

) e moles of chloropropionaldehyde or per mole of converted acrolein are generally 0.20 to 1.00 moles, preferably 0.25 to 0.40 mol, alkali boranate is used. The reduction is expediently at

• ι. "Temperatures between 0 and 50 ⁰ C executed. Particularly suitable is the temperature range between 15 and 35 ° C. The chloropropanol is from the IJmsetziingspemisch with organic solvents.

for example toluene, extracted and removed from the solvent, if necessary after drying the extract with conventional drying agents, such as sodium sulfate, separated by distillation under reduced pressure.

The process according to the invention is illustrated by the following examples. Parts are to be understood as parts by weight.

example 1

70 parts of hydrogen chloride were passed into a mixture of 88 parts of tetrahydrofuran, 2 parts of hydroquinone and 112 parts of acrolein. The temperature of the mixture was 14 to 17 ° C here. The reaction mixture was then added dropwise in the course of 40 minutes to a solution of 20 parts of sodium borate (NaBH ₄ ) in 200 parts of water with stirring. The temperature of the mixture was kept at 25 to 30 ^° C. during this. The reaction was complete after a further 10 minutes. 30 parts of sodium chloride were then added. The reaction mixture was extracted twice with 87 parts of toluene each time. The then remaining aqueous phase was discarded. The extracts were combined; the solvents were first driven off from them under reduced pressure at about 20 torr; then the pure 3-chloropropanol was distilled at 10 torr. A small residue remained, a viscous oil, presumably trimeric chloropropionaldehyde. 146 parts of 3-chloropropanol- (l) were obtained, corresponding to a 77% yield based on the acrolein used. The 3-chloropropanol- (1) had a boiling point (bp.io) of 54 to 57 ° C and a refractive index (n * <S) of 1.4443.

Example 2

In a mixture of 103 parts of 1,4-dioxane, 2 parts of hydroquinone and 112 parts of acrolein ⁰ C were introduced 63 parts of hydrogen chloride at 12 to IS. The excess acrolein was first driven off from the reaction mixture at 15 ° C. under reduced pressure. The reaction mixture was then dissolved into a solution of 20 parts over a period of 30 minutes

ίο Sodium borate in 200 parts of water at 20 to 30 ⁰ C added dropwise. The work-up was carried out as indicated in Example 1. 146 parts of 3-chloropropanol- (l) were obtained, corresponding to a yield of 85% based on the converted acrolein. The chloropropanol had a boiling point (bp) of 56 to 59 ° C and a refractive index (V ?? ") of 1.4443.

Example 3

In a mixture of 112 parts of acrolein and 87 parts toluene 60 parts of hydrogen chloride were introduced at -5 to +5 ⁰ C. The reaction mixture was added dropwise over 30 minutes to a solution of 20 parts of sodium boronate in 200 parts of water, which solution was kept at 20-25 ° C. After a further 10 minutes the phases were separated. The aqueous solution was admixed with 25 parts of sodium chloride and extracted with 87 parts of toluene. The toluene phases were combined. The toluene was driven off ^{at 40 °} C. under reduced pressure. In the subsequent distillation, 142 parts of 3-chloropropanol- (1) were obtained. This corresponds to a yield of 75%, based on the acrolein used. The chloropropanol had a boiling point (bp 12) of 57 to 59 ^D C and a refractive index (n ^) of 1.4449.

Claims (3)

Patent claims: 1. Process for the preparation of 3-chloropropanol- (l) from acrolein by reacting the acrolein with hydrogen chloride and reducing the chloropropionaldehyde, characterized in that the reduction is carried out by means of alkali boronate. 2. The method according to claim 1, characterized in that the sodium or alkali boronate Potassium borate is used. 3. The method according to claim 1 or 2, characterized in that the reduction at 15 to 35 ^: C is carried out.