DE1213832B - Process for the production of ketones - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C 07c

German class: 12 ο -10

Number: 1213 832

File number: B 71109 IVb / 12 ο

Filing date: March 13, 1963

Opening day: April 7, 1966

The invention relates to a process for the preparation of ketones of the general formula

R (R ₁ ) CH-CO-R ₂

in which R, R ₁ and R _{2 are} alkyl radicals.

It is known to produce ketones of the formula given from olefins of the structure

R (R ₁ ) C = C (R ₂ ) H

in which R, R ₁ and R _{2 have} the above meaning, to be prepared by reacting the olefin at elevated temperature with halogens in the presence of water. Mineral acid can be added to the reaction mixture to initiate the reaction. In addition to the desired ketone, hydrohalic acid is also formed during the reaction, which acts as a reaction accelerator in certain concentration ranges, but is otherwise a by-product that can no longer be used in the process.

No process has become known in which the incidental hydrogen halide oxidized and thereby formed free halogen for the production of further ketones from olefin in the circuit is returned because as a result of the extremely high technical effort required (concentration the resulting dilute hydrohalic acid solutions) such a process from the start had to appear unfavorable, if at all commercially exploitable.

It was all the more surprising, therefore, when it was now found that it was under very specific circumstances A sufficient oxidation of the hydrohalic acid with simple conditions is possible to carry out technical means and thereby the way of a reuse of the freed To develop halogen for the production of further ketones.

First, it is important in the process of the invention that the implementation of the Olefins used for the ketone halogen is bromine. The inventive method for production of ketones of the general formula

* R (R ₁ ) CH-CO-R ₂

in which R, R ₁ and R _{2 are} alkyl radicals, by reaction of an olefin of the general formula

R (R ₁ ) C = C (R ₂ ) H

in which R, R ₁ and R _{2 have} the meaning given above, with bromine in the presence of water at elevated temperature, optionally with addition

Process for the production of ketones

Applicant:

The British Petroleum Company Limited, London

Representative:

Dipl.-Chem. Dr. W. Koch and Dr.-Ing. R. Glawe, Patent Attorneys, Munich 22, Liebherrstr. 20th

Named as inventor:

Alan John Maurice Wenham, Sunbury-on-Thames, Middlesex (Great Britain)

Claimed priority:

Great Britain April 5, 1962 (13 146)

set of mineral acids, characterized in that the olefin is reacted with an aqueous solution which contains 0.5 to 1 mol of bromine and 0.5 to 0.6 normal of hydrogen bromide and 0.4 to lnormal on alkali bromide, the reaction mixture after distilling off the ketone with oxygen and nitrogen oxides oxidized and the oxidized solution returned to the reaction without concentration will.

It is an advantage of the process according to the invention that the oxidation of the resulting hydrobromic acid solution can take place without the interposition of a lengthy concentration stage. Another advantage is that the after Solution containing oxidation free bromine without any further treatment or adjustment (apart from the replacement of any, relatively low losses of bromine) are used directly for the conversion of further olefins can be, making the process extremely simple.

If the specified conditions are not adhered to, more than 80% of the amount after distilling off would have to be of the ketone remaining in the aqueous residue are oxidized to bromine, in order to restore the starting bromine-hydrogen bromide solution for the conversion of further olefins.

However, the concentration of hydrobromic acid in the starting solution must not be greater than is given because otherwise undesirable side reactions would occur. On the other hand, it is very difficult, the oxidation of hydrogen bromide

609 557/333

to drive to bromine so far that the concentration of hydrogen bromide in the oxidizing solution up is lowered below normal. This difficulty arises in the method according to the invention overcome that in the solution to be oxidized by the presence of the added alkali metal bromide maintains a relatively high concentration of bromide ions.

Only through the interaction of the features of the method according to the invention is it possible to obtain an aqueous residue of such a composition that by its oxidation the initial Bromination mixture can be easily restored.

The conversion of the olefin to the ketone is preferably carried out by heating the reaction mixture under reflux for 1 to 10 hours. It is advantageous to carry out the reaction with a water to bromine molar ratio in the range from 300: 1 to 50: 1. It is also preferred to carry out the reaction with a starting olefin of the general formula given above, in which R, R ₁ and R _{2 are} alkyl groups having 1 to 4 carbon atoms. 2-Methylpentene- (2) is particularly suitable as the starting substance.

In the process according to the invention, mixtures can also be used as starting material, which contain the olefins defined above.

The method according to the invention is now based on the following exemplary embodiment explained in more detail.

example

The 2-methylpentene (2) one is slowly mixed at about 20 ° C. with vigorous stirring 99.5% purity with a solution of bromine (0.55 molar) in aqueous hydrogen bromide (0.5 normal) and sodium bromide (0.8 normal). The resulting suspension is refluxed for 2 hours left to boil and then subjected to distillation until there are no more organic substances transforms. It is ethyl isopropyl ketone in a yield of 90 percent by weight, based on the used Olefin.

The aqueous residue (1,6N hydrogen bromide, 0.8N sodium bromide) is mixed with oxygen in the presence is oxidized by nitrogen oxides and yields a normal value of 0.5 for hydrogen bromide and 0.5 normal for sodium bromide 0.8 normal solution. A small loss of bromine in the device used is compensated for by adding an appropriate bromine to the oxidized solution. Then it will be the solution obtained is returned and reacted with further olefin fed in.

Claims (4)

Patent claims: 1. Process for the preparation of ketones of the general formula R (R ₁ ) CH-CO-R ₂ in which R, R ₁ and R _{2 are} alkyl radicals, by reaction of an olefin of the general formula R (R ₁ ) C = C (R ₂ ) H in which R, R ₁ and R _{2 have} the meaning given above, with bromine in the presence of water at elevated temperature, optionally with the addition of mineral acids, characterized in that the olefin is reacted with an aqueous solution containing 0.5 to 1 Moles of bromine and 0.5 to 0.6 normal of hydrogen bromide and 0.4 to 1 normal of alkali metal bromide, the reaction mixture is oxidized with oxygen and nitrogen oxides after distilling off the ketone and the oxidized solution is returned to the reaction without concentration. 2. The method according to claim 1, characterized in that the reaction by 1- to 10 hours of refluxing is carried out. 3. The method according to claim 1 and 2, characterized in that the reaction with a Molar ratio of water to bromine of 300: 1 to 50: 1 is carried out. 4. The method according to claim 1 to 3, characterized in that the reaction with 2-methylpentene (2) is carried out. Considered publications:
British Patent No. 458,626. 609 557/333 3.66 ® Bundesdruckerei Berlin