DE2056343A1 - 2-methyl-3-buten-2-ol prodn - by isomersn of 3-methyl-3-buten-1-ol - Google Patents

Abstract

Prepn. of title cpds. is effected as in parent patent but in the presence of ammonium or alkali(ne earth) metal salts where the anion of the acid and/or the salt is a halide. This almost doubles the speed of isomersn. achieved in the parent patent.

Description

Process for the production of 2-methyl -) - buten-2-ol Addition to patent . ... ... (patent application P 19 25 197.9).

The present invention relates to an improved method for Production of 2-methyl-5-buten-2-ol by isomerization of 3-methyl-3-buten-1-ol.

It is known to produce 2-methyl-3-buten-2-ol by reacting acetone with Acetylene and subsequent partial hydrogenation of the 3-methyl-3-buten-1-ol formed to produce (see, for example, Liebigs Annalen der Chemie, Volume 596 (1955) page 37). However, the process is very expensive because it is in the first stage because of the work With acetylene special precautions are necessary and in the second stage the partial hydrogenation using poisoned catalysts most accurate Requires compliance with the reaction conditions. It is further in the French Patent specification 1 301 882 describes 2-methyl-3-buten-2-ol by radical addition of isopropanol to acetylene to produce under pressure. However, this method provides only unsatisfactory yields.

Subject of the main patent. ... ... (patent application P 19 25197.9) is a process for the preparation of 2-methyl-5-buten-2-ol, in which one relies on 3-methyl-3-buten-1-ol at temperatures from 20 to 250 ° with removal of the 2-methyl-3-buten-2-ol formed allows aqueous acids to act by distilling off.

It has now been found that the isomerization rate can be increased to about double if the isomerization in the presence of ammonium, Alkali or alkaline earth salts is carried out, the anion of the acid and / or that of the salt is a halide ion.

The process according to the invention thus provides 2-methyl -) - buten-2-ol opposite to the process of the main application in a much higher space-time yield.

The same acids can be used to isomerize 3-methyl-D-buten-1-ol as described in the main application. Accordingly, will the reaction in the presence of monobasic or polybasic, preferably up to dibasic, organic or inorganic acids. In general, the aqueous ones Acids have a dissociation constant of at least 1.10-5 aur. In the presence of salts but it is also possible to work with weaker acids, e.g. B. with acids with Dissociation constants of at least 10 6 can of course also be Compounds are used which convert into acids in aqueous medium, such as Aluminum trichloride, boron fluoride, iron trichloride and acetyl chloride. Suitable acids are for example hydrochloric acid, hydrobromic acid, hydriodic acid, Hydrofluoric acid, sulfuric acid, phosphoric acid, p-toluenesulfonic acid, trichloroacetic acid, Dichloroacetic acid, chloroacetic acid, formic acid, oxalic acid, ion exchange resins, which contain sulfonic acid or carboxyl groups, but also acetic acid or mixtures of these acids. Hydrochloric acid, oxalic acid and benzenesulfonic acids are preferred.

Also the concentration of the aqueous acids and the weight ratio from starting material to aqueous acid agree with the corresponding values of the Main registration. The concentration of the aqueous Acids generally 0.01 to 35% by weight. Very strong acids, i. H. Acids with a Dissociation constants greater than about 10 1 are beneficial in concentration from 0.01 to 10% by weight, in particular 0.05 to 2% by weight, is used. Acids with a Dissociation constants less than about 10 are preferred in concentrations from 0.5 to 25 wt., In particular 1 to 10 wt., Used. In general is it is advantageous to use lower acid concentrations when using higher temperatures and to use higher acid concentrations at lower temperatures.

For example, it can be used in the event of an increase in temperature from Z. B. 300C to reduce the acid concentration by about a factor of 0.2 to 0.1.

The weight ratio of starting material to aqueous acid is generally 1: 5 to 5: 1, preferably from 1: 2 to 3: 1.

Suitable salts are in principle those which are at the reaction temperature have sufficient solubility in the reaction mixture and be separated from acids derive, which are suitable as isomerization catalysts. That is, they should be derived from acids whose dissociation constants are at least 10-6 or preferably at least 10 '.

The selection of the salts is to be made in such a way that when used as an acid no hydrofluoric acid is used, the salt halide ions such as fluoride, Must contain chloride, bromide or iodide ion. But also when using hydrohalic acids For example, salts containing halide ions can be used. Suitable salts are Salts of acids with a dissociation constant of at least 10-6 and alkali or alkaline earth metals or the corresponding ammonium salts, in particular alkali, Alkaline earth or ammontum halides. Examples include: sodium chloride, Potassium bromide, calcium iodide, sodium sulfate, sodium phosphate, calcium chloride, magnesium sulfate and sodium oxalate. Since the implementation of the reaction by the choice of the salt is not is decisively influenced, provided that the acid has been chosen accordingly mostly economical, or the use of cheap salts such as sodium chloride, Calcium chloride or sodium sulfate, suggest. But there can also be solutions use of salt mixtures. For example, sea water is one for isomerization suitable medium.

When choosing the salt concentration one is up by the solubility of the salt limited at reaction temperature. Concentrated at reaction temperature Salt solutions are preferred.

When using cheaper salts, it is advisable to occasionally use the Salt content should increase the soluble amount in order to avoid possible dilution to counteract any water introduced with the reactants. More dilute Solutions usually have a lower isomerization rate than more concentrated ones. It is therefore recommended to have a salt concentration from about 7 Weight in the reaction mixture is not to be fallen below. But even with such a small one The concentration range is the isomerization versus that in the absence accelerated by salts by a factor between 1 and 1.5.

The isomerization is, as described in the main application, at Temperatures between 50 and 2000C, preferably 70 to 140 ° C, at atmospheric pressure or reduced or increased pressure, out. It can be discontinuous, but operate continuously with particular advantage. You can also with additional The presence of inert organic solvents can be carried out. Suitable Solvents are, for example, optionally nitrated or halogenated aromatic or aliphatic hydrocarbons such as benzene, toluene, ethylbenzene, chlorobenzene, Cyclohexane, ligroin, trichloroethane. The inert solvents become appropriate In amounts of 10 to 200% by weight, preferably 30 to 80% by weight, based on the mixture from starting material and aqueous acid, used. When using -inerten Solvents it is advantageous for vigorous mixing of the reaction mixture to care.

During the isomerization according to the invention, a mixture is distilled from the desired 2-methyl-3-buten-2-01, unreacted 3-methyl-3-buten-1-01, Isoprene, water and, if necessary, solvents.

This mixture can by customary methods, e.g. by fractionated Distillation, are separated. To do this, you can first use the main amount of water separate, you can also azeotpop the water with the 2-methyl-3-buten-2-ol distill off 'and then separate. The reaction mixture is expedient water supplied to the extent that it distills from the reaction mixture.

For example, 2-methyl-3-buten-2-ol is a valuable intermediate for the production of terpenes.

The parts mentioned in the examples are parts by weight. You behave to parts by volume like kilograms to liters.

Examples 1 - 8 A cylindrical reaction vessel (3 parts by volume) is used with the amounts of water, acid and as shown in the following table Filled with salt, the mixture was heated to boiling temperature and stirred vigorously. The reaction vessel is with a reflux condenser (dephlegmator) operated at 90 to 95 ° C and a provided descending cooler connected to it. While substances in the reflux condenser which boil over 90 to 95 ° C, are largely condensed and from here into the reaction vessel return, the descending cooler is used to condense the reaction product and collect. Water, which is distilled off together with the reaction product and separates in the distillate as the lower phase, is also in the reaction vessel returned. 3-Methyl -) - buten-1-ol is during the specified addition time Reaction vessel fed continuously.

When the addition of methylbutenol has ended, it is completed the reaction held at reaction temperature for a further 2 hours. In the reaction vessel apart from the acidic salt solution used for isomerization, the one from the table remains apparent amount (2 to 10 wt. Based on the starting product) of a high-boiling point water-insoluble oil. The distillate obtained contains essentially that 2-methyl-3-buten-2-ol formed, unreacted starting compound, water and isoprene. The amounts of 2-methyl -) - buten-2-ol and isoprene given in the table were determined by gas chromatography. The mixture of substances obtained can be fractionated by Distillation can be separated very easily.

For this purpose, isoprene is first distilled off and then advantageously the azeotropic mixture of 2-methyl-3-buten-2-ol with water, which already boils at 860c. The starting product remaining as bottom product can be used without further purification in the isomerization will be sent back.

T A B E L L E At- Vol- Weight- Weight- Weight- Addition- Weight- Yield weight- weight game parts parts parts parts time + parts of 2-methyl- parts parts H2O Acid Salt 3-Methyl- Duration d. held 3-buten-2-ol + high-boiling isoprene 3-butene-post-reaction 2-methyl- (% by weight) of the 1-ol tion 3-buten- (hours) 2-ol 1 0.6 0.01 H3PO4 0.4 NaCl 2 3 + 2 0.64 80 0.03 0.10 (conc.) 2 1.2 0.05 Oxal- 0.6 NaCl 2 3 + 2 0.68 87 0.02 0.08 acid 3 0.6 0.01 P-Tol- 0.5 NaCl 2 2 + 2 0.78 76 0.05 0.2 uolsulfonic acid 4 1.2 0.02 H3PO4 0.4 NaBr 2 3 + 2 0.83 80 0.08 0.11 (conc.) 5 0.6 0.01 HCl 0.3 NH4Cl 2 2 + 2 0.77 75 0.08 0.13 (conc.) 6 1.0 0.01 BF3 0.5 NaCl 2 2 + 2 0.65 80 0.04 0.10 O (-C2H5) 2 7 0.6 0.4 CH3 0.3 NaCl 0.5 6 + 2 0.28 83 0.02 0.03 # COOH 8 0.6 0.02 HCL 0.2 Na2SO4 2 3 + 2 0.63 79 0.03 0.11 (conc.) + Related on converted 3-methyl-3-buten-1-ol.

Claims (1)

Claim Process for the preparation of 2-methyl-3-buten-2-ol by isomerization of 3-methyl-3-buten-1-ol under the action of aqueous acids according to the patent. , ...,. (Patent application P 19 25 197.9), characterized in that the isomerization is carried out in the presence of ammonium, alkali or alkaline earth salts, wherein the anion of the acid and / or that of the salt is a halide ion.