Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-01-24
2001-10-02
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S873000, C568S874000
Reexamination Certificate
active
06297407
ABSTRACT:
This is the National phase Application of PCT/EP99/05933 Application filed Aug. 13, 1999.
This invention relates to a process for preparing alkynediols by reacting ketones with acetylenic hydrocarbons using potassium alkoxides.
A number of processes are known for preparing alkynediols.
Reppe's ethynylation process, reaction of aldehydes such as formaldehyde and acetaldehyde with acetylene over copper acetylide as catalyst, gives secondary alkynemonools and glycols in good yields. In the case of higher aldehydes, however, this method leads to unsatisfactory results.
The preparation of tertiary alkynediols by reacting ketones with acetylenic hydrocarbons using bases is particularly problematical. Most existing processes utilize finely divided, ideally water-free KOH powder in organic solvents such as THF, diisopropyl ether, dioxane, methylal or acetaldehyde dibutyl acetal. The disadvantage with these processes is that they mostly produce mixtures of monoalkynols and alkynediols containing an appreciable proportion of monoalkynols. A further disadvantage is that the suspensions formed in the solvents mentioned become so viscous through the formation of acicular crystalline adducts of KOH and tertiary monoalkynols and alkynediols that stirrability is appreciably compromised. As a result, efficient mixing and hence controlled dissipation of the heat of reaction is compromised or impossible. This leads to safety problems as well as low conversions. A possible use of larger solvent quantities has relatively small effect on the viscosity profile and is generally uneconomical, since the solvents used are costly.
EP-A 0 285 755 describes a process for preparing tertiary alkynediols by reacting ketones with acetylene. In particular, acetylene is reacted with carbonyl compounds and KOH powder as base. Alkyl tertbutyl ethers are used as solvents. The ketone and acetylene are used in a molar ratio of 1:1 to 3:1 and KOH and ketone in a molar ratio of 1:1 to 1.6:1. The solvent used is set to ensure efficiently stirrable reaction mixtures. However, it proved impossible to reproduce the teaching of this application (Comparative Example 2). Another disadvantage with this process is the use of specific, costly solvents, making the process uneconomical.
DE-A 20 08 675 describes the preparation of tertiary alkynediols by reacting ketones with acetylene using potassium alkoxides of primary and secondary alcohols of limited solubility in water. Aliphatic, cycloaliphatic and aromatic hydrocarbons can be used as solvents. Similarly, DE-A 20 47 446 describes the use of potassium alkoxides for preparing alkynediols by reacting alkynemonools with ketones.
In both processes, an increase in the viscosity of the reaction mixture in the course of the reaction is observed. Efficient mixing of the reaction batch and controlled dissipation of the heat of reaction are therefore compromised, so that the aforementioned problems arise in these processes, too.
It is an object of the present invention to provide a process for preparing alkynediols using an economically acceptable amount of a common organic solvent. The reaction mixture shall remain efficiently stirrable during the entire reaction time, ensuring controlled dissipation of the heat of reaction and good conversions.
We have found that this object is achieved by a process for preparing alkynediols by reacting ketones with acetylenic hydrocarbons in an organic solvent in the presence of a base comprising potassium alkoxides of primary and/or secondary alcohols to form adducts of alkynemonools and/or alkynediols and said base which precipitate from the reaction mixture by selecting the stoichiometries for the reaction partners so as to produce gellike adducts having a spherical surface, whereby the reaction mixture remains stirrable during the entire reaction.
The adducts which precipitate are adducts of the base with alkynmonools or alkynediols formed in the course of the reaction. Provided a certain stoichiometry is adhered to for the reaction partners, these adducts are gellike and not acicularly crystalline. A spherical surface for the purposes of the invention is a rounded, preferably spherelike surface of the kind present in gellike adducts. This ensures that there is none of the intermeshing which appreciably compromises stirrability as in the case of crystalline, acicular adducts and that instead the precipitated adducts are able to glide past one another when stirred. This permits the controlled dissipation of the heat of reaction and distinctly better mixing of the reaction partners. As well as having an advantageous effect on the conversions of the reaction, controlled dissipation of the heat of reaction is also desirable for safety reasons. If controlled dissipation of the heat of reaction is not ensured, the decomposition temperature of the substances present in the reaction mixture may be exceeded locally and this may give rise to spontaneous decompositions.
Acetylenic hydrocarbons for the purposes of the present invention are acetylene and monoalkynols prepared from carbonyl compounds and acetylene.
In a preferred embodiment of the process of the invention, acetylene is used as acetylenic hydrocarbon. Owing to the efficient mixing, the stoichiometry for the starting materials can be chosen in such a way that acetylene is used stoichiometrically with regard to the ketone. By stoichiometrically is meant a ratio of ketone to acetylene within the range from 1.9:1 to 2.1:1, preferably a ratio of 2:1. The ratio of potassium alkoxide to ketone is within the range from 0.9:1 to 2.1:1, preferably within the range from 1:1 to 1.5:1, particularly preferably within the range from 1.1:1 to 1.3:1. The alkoxide-to-ketone ratio chosen is an essential factor to ensure reaction mixture stirrability, since, at the ratio chosen, the adducts formed are not acicular but gellike and have a spherical surface.
The concentration of the reaction partners in the reaction mixture may be specified in terms of the weight ratio between ketone and a suspension of solvent and base. The concentration at which the reaction mixture remains efficiently stirrable depends on the reaction conditions and in particular on the ketone, solvent and alkoxide used. In the case of a suspension of potassium isobutoxide in xylene and acetone, the weight ratio between ketone and the suspension is generally not less than 1:2.5, preferably within the range from 1:2.5 to 1:8, particularly preferably 1:6.5.
In a further embodiment, the acetylenic hydrocarbons used are alkynemonools. Alkynemonools can be prepared by reacting acetylene with carbonyl compounds according to literature methods.
The carbonyl compounds used can be aliphatic and aromatic aldehydes and ketones. Preference is given to the use of ketones, with aliphatic ketones being particularly preferred. These can be linear, branched or cyclic. Preference is given to using ketones having from 3 to 8 carbon atoms, particularly preferably having from 3 to 6 carbon atoms, with acetone, methyl isobutyl ketone and cyclohexanone being very particularly preferred.
Accordingly, the acetylenemonools used are particularly preferably methylbutynol, 3,5-methylhex-1-yn-3-ol and 3-cyclohexylprop-1-yn-3-ol.
The ratio of alkynemonool to ketone is within the range from 1:0.8 to 1:1.2, preferably 1:1. The ratio of potassium alkoxide to ketone is within the range from 1.5:1 to 2.2:1, preferably within the range from 1.9:1 to 2.1:1, particularly preferably 2:1. The molar ratios chosen ensure reaction mixture stirrability and thus good conversions and controlled dissipation of heat.
The ketones used for the reaction with acetylenic hydrocarbons can be aliphatic and aromatic ketones. The use of aliphatic ketones is preferred. These can be linear, branched or cyclic. Particular preference is given to using aliphatic ketones having from 3 to 8 carbon atoms, very particularly preferably having from 3 to 6 carbon atoms. Among these, acetone, methyl isobutyl ketone and cyclohexanone are preferred. The use of acetone is very particularly preferred.
Suitable sol
Brunner Melanie
Henkelmann Jochem
Kindler Alois
Tragut Christian
Barts Samuel
BASF - Aktiengesellschaft
Keil & Weinkauf
Price Elvis O.
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