US3717664A

US3717664A - Method for the preparation of carboxylic acids by an oxidizing decomposition of organic compounds containing longer carbon chains

Info

Publication number: US3717664A
Application number: US00883642A
Authority: US
Inventors: Nguyen N Dinh; A Raal
Original assignee: Incentive Research and Development AB
Current assignee: Incentive Research and Development AB
Priority date: 1968-12-11
Filing date: 1969-12-09
Publication date: 1973-02-20
Anticipated expiration: 1990-02-20
Also published as: GB1276378A; DE1961895A1; SE349291B

Abstract

Carboxylic acids can be prepared by an oxidizing decomposition of organic compounds having longer carbon chains. The organic compounds are treated with potassium permanganate in acetic acid as solvent, resulting in the long carbon chains being split up to form carboxylic acids having shorter carbon chains.

Description

United States Patent [191 Dinh-Nguyen et al. 1 Feb. 20, 1973 METHOD FOR THE PREPARATION OF [56] References Cited CARBOXYLIC ACIDS BY AN UNITED STATES PATENTS OXIDIZING DECOMPOSITION OF 3,196,182 7/1965 Cox ..260/533 X ORGANIC COMPOUNDS CONTAINING 3,646,078 2/1972 Fanning". LONGER CARBON CHAINS 2,674,613 4 1954 Nelson [7 1 Inventors: g y g y Aino Raal 2,721,149 10/1955 Nelson ..260/4l3 X both of Molndal, Sweden OTHER PUBLICATIONS [73] Assignee: Incentive Research & Development Bar k t et aL, mum, Chem, Soc, 1956, p.

Aktiebolag, Bromma, Sweden 4685-4687,

[22] Flled: 1969 Primary Examiner-Lewis Gotts [21] Appl. No.: 883,642 Assistant Examiner-Ethel G. Love Att0rneyBrumbaugh, Graves, Donohue and [30] Foreign Application Priority Data Raymond Dec. 11, 1968 Sweden ..l6972/68 [57] ABSTRACT Carboxylic acids can be prepared by an oxidizing [52] Cl 260/413 260/ decomposition of organic compounds having longer 51 I t Cl C68]! 17/36 carbon chains. The organic compounds are treated 5 81 11 with potassium permanganate in acetic acid as Solvent,

Field of Search ..260/4l3, 533 R resulting in the long carbon chains being split up to form carboxylic acids having shorter carbon chains.

5 Claims, No Drawings METHOD FOR THE PREPARATION OF CARBOXYLIC ACIDS BY AN OXIDIZING DECOMPOSITION OF ORGANIC COMPOUNDS CONTAINING LONGER CARBON CHAINS The invention is concerned with a method for the preparation of carboxylic acids by an oxidizing decomposition of organic compounds containing longer carbon chains, particularly organic compounds having longer, saturated, non-branched carbon chains.

It is known from the field of analysis that it is possible to determine the position of the double bonds in an unsaturated carbon chain by an oxidizing decomposition of the carbon chain by means of potassium permanganate, and asubsequent identification of the carboxylic acids thus formed. The reaction maybe described in this way:

This reaction can be performed in acetone at normal temperature. It is also known that methylated fatty acids can be decomposed by being boiled in acetone for several days. The carbon chain is split up at the place of branching, and the corresponding methyl ketone is formed.

In these known methods the carbon chain is split up at defined places, viz. at the double bonds or at the places of branching. It has now been found, according to the present invention, that it is possible to obtain an oxidizing decomposition of a saturated, non-branched carbon chain so as to form homologous monocarboxylic and dicarboxylic acids by oxidizing the carbon chain by means of potassium permanganate in acetic acid as solvent, the acetic acid being entirely or nearly free from water. The temperature should preferably be higher than 70 C. and up to the boiling point of the solution at normal pressure.

Alternatively, manganese dioxide and sulphuric acid that the reaction product 'c'drit'aihKar'bi 'li acid methyl esters of various carbon chain lengths. Selected reaction conditions produces a reaction mixture in which carbon chains containing eight carbon atoms are prevailing. It is possible to control, to some extent, the carbon chain length in the final product, by varying the reaction conditions. A shorter reaction time displaces the prevailing carbon chain length towards longer chains. In the oxidizing decomposition of methyl stearate a reduction of the reaction time has resulted, i.a., in the formation of keto acids containing 18 carbon atoms in the carbon chain and having the oxo group situated in the position C6 to C10 or C15 to C17.

Examples of substances which can advantageously be subjected to the oxidizing decomposition of the invention are hexadecanoic acid (palmitinic acid), octadecanoic acid (stearic acid), methyl octadecanoate (stearic acid methyl ester), tripalmitin, beeswax, ntetradecanol- 1 hexadecane, docosane, 2,6,10,15,19,23-hexamethyl tetracosane (squalan), and paraffin wax (melting point 6872 C). The table below gives the reaction conditions, the qualitative composition of the fatty acid components of the final product, and the percentage of material which has not been decomposed after a certain time at the temperature stated.

The oxidizing decomposition in acetic acid at an inhaving an industrial use, such as adipic acid (C6),

pimelic acid (C7), suberic acid (C8), and sebacic acid (C 10).

Reaction conditions Reaction products Ratio Non-destarting Monocar- Dicarcomposed Time, Temp., material boxylic boxylic material Starting material hours C. to KMnO acids acids percent Fatty acids {Hexadecanoic acid... 6 76-78 1:5 C6C15 04-014 32. 4

Octadecanoic acid-.. 48 80 1:5

. 1 80 1:5 2 80 1:5 3 80 1:5 Esters Methyloctadecanoate 4 80 1:5 6 80 1:5 48 80 1:5 18 80 1:3 Glycerides 'Iripalmitin 24 115 1:5 Waxes Beeswax 24 115-120 1:5 Alcohols Tetradecanol1 l8 115-120 1:5

24 115-120 Hexadccana 26 115-120 1 :5 Hydrocarhons Docosane 24 116 1:5 2, 6, 10, 15, 1!), 2'1 lrcxnmcthyltctracosunc.. 12 115-120 1:5 Parallin wax (M.I. (38-72 C.) 24 116420 1:5 C5-C24 C5C18 MnOri-llzSOa can be used as oxidizing agent in lieu of potassium permanganate.

The reaction of the invention is non-specific, because it appears that the carbon chain is split up at random at any place of the chain, resulting in the formation of the entire homologous series of monocarboxylic and dicarboxylic acids, from acids having a chain length of a couple of carbon atoms to acids having the same carbon chain length as the starting material. This can be illustrated by subjecting methyl stearate to the oxidizing decomposition of the invention. An analysis of the reaction product in a gas chromatograph reveals The method of the invention is of a particular interest in the preparation of deuterated organic com pounds. it is known from British Pat. No. 1,103,607 that it is possible to replace the hydrogen of organic compounds completely by deuterium by reacting the organic compounds with heavy water in alkaline conditions by means of a platinum catalyst and in the presence of a promoter consisting of deuterium peroxide. The deuteration process in expensive, and it is therefore desired to. deuterate a long chain compound, and subsequently to split up said deuterated compound to form various deuterated compounds containing shorter carbon chains, instead of deuterating short chain compounds separately. It has not been possible to achieve said desire by splitting the deuterated long chain compounds by the known processes referred to above. This is due to the fact that the reaction solution has received hydroxyl ions:

The presence of hydroxyl ions results in a hydrogen deuterium exchange in the deuterated organic molecules. Consequently, the deuterated compounds suffer a partial loss of their deuterium content. In the reaction of the invention, acetic acid being used as solvent, the reaction solution will have no content of hydroxyl ions, and the deuterated carbon chains do not, therefore, loose any deuterium in the splitting operation. The preparation of deuterated carboxylic acids according to the present invention comprises deuterating a hydrogen-containing organic compound having a comparatively long carbon chain, preferably a carbon chain of at least 12 carbon atoms, with deuterium oxide in the presence of an alkaline, a deuteroxide, a metal catalyst of the platinum group, and a deuterium peroxide promoter, and treating the deuterated compound thus prepared with potassium permanganate and sulphuric acid in acetic acid as solvent, at a temperature of at least 70 C. A preferred process for the preparation of deuterated carboxylic acids comprises deuterating a deuteratable organic compound containing hydrogen, said organic compound having a comparatively long carbon chain, preferably a carbon chain of at least 12 carbon atoms, said deuterating operation involving replacing hydrogen with deuterium by reacting said organic compound with heavy water, as a deuterium source, with the aid of sodium deuteroxide and reduced Adams catalyst (PtO, H O), in the presence of a promoter consisting of deuterium peroxide, and exposing the comparatively long-chained deuterated organic compound, thus prepared, to an oxidizing decomposition by treating it with potassium permanganate and sulphuric acid in acetic acid as solvent, at a temperature of at least 70 C., for a time sufficient to split up the comparatively long carbon chain of the V deuterated organic compound into shorter chains.

EXAMPLE 1: OXIDIZING DECOMPOSITION OF N- 0.100 g docosane (0.323 mole) was placed in a reaction tube, the upper, narrower portion of which could be cooled by means of a cooling means. 2 ml acetic acid, having a purity of 99 100 percent, and 0.5 g pulverized potassium permanganate (3.16 10' mole) was added. The reaction tube was placed in an oil bath, controlled by a thermostat, and was allowed to remain there for- 24 hours at 115 C. 20 percent docosane did, not react. The oxidation products were prepared for a gas chromatographic analysis in this way.

The excess of potassium permanganate ions was reduced by a saturated solution of sodium hydrogen sulfite in water. The mixture was extracted quantitatively with diethyl ether. The ether extracted was separated from the underlying phase. The solvent was evaporated, and the residue was esterified with methanol. When calculating the excess of methanol, the acetic acid having been extracted into the ether phase has to be taken into consideration. The methyl esters were analyzed in a gas chromatograph.

EXAMPLE 2: OXIDIZING DECOMPOSITION OF N- METHYL OCTADECANOATE (METHYL STEARATE, CH (CI-I,), COOCI-I 5 g methyl octadecanoate (16.75 10"mole) were placed in a flask having three necks. The flask was placed in a water bath, controlled by a thermostat, and was provided with a cooler, a thermometer, and a magnetic stirrer. The temperature of the water bath was set at C. ml concentrated acetic acid, having a purity of 98-100 percent, was added to dissolve the stearate. 15 g potassium permanganate (95.10' mole) was added during a period of 10 minutes. The reaction started when approximately half the quantity of permanganate had been added. Samples are taken, first each half hour, later with longer intervals. The samples were prepared for a gas chromatographic analysis as.

has been described in Example 1. 23.5 percent nondecomposed stearate remains after 18 hours at 80 C. The reaction mixture was allowed to stand, while being stirred, for another 3 hours at 1 15 C., resulting in 22.6 22.6 percent methyl octadecanoate being non-decomposed.

EXAMPLE 3: OXIDIZING DECOMPOSITION OF N- I-IEXADECANOIC ACID (palmitic acid), CH (CH CODE.

20 g hexadecanoic acid (78-10' mole) was dissolved in a flask in 400 ml 98 percent acetic acid, and was heated to 70 C. in a water bath, controlled by a thermostat. The flask was provided with a magnetic stirrer and a reflux cooler. 100 g pulverized potassium permanganate (633.10" mole) was added in small quantities during a period of 3 hours, and the temperature was simultaneously increased slowly to 78 C. The mixture was allowed to react for 6 hours, while being stirred, and the heating was now switched off overnight. A sample of 1 ml was taken the next day, and was prepared for a gas chromatograph analysis as described in Example 1. The reaction mixture contained 32.4 percent non-decomposed starting material.

EXAMPLE 4. OXIDIZING DECOMPOSITION OF N TETRADECANOLE, CH (CI-I of concentrated sulfuric acid was added. The reaction tube was allowed to stand in an oil bath for 24 hours at 1 1 5 C.

The reaction product was treated as described in Example 1, including the esterifying operation. It was What is claimed is:

l. A method for the preparation of carboxylic acids by an oxidizing decomposition of organic compounds containing long carbon chains and selected from the group consisting of fatty acids esters, glycerides, waxes, alcohols and hydrocarbons, comprising treating said compounds with potassium permanganate or with manganese dioxide and sulfuric acid, in an acetic acid solvent.

2. A method according to claim 1 wherein the decomposition is carried out at a temperature of between 70 C. and the boiling point of the solution at normal pressure, and wherein the acetic acid solvent is water-free.

3. A method for the preparation of deuterated carboxylic acids by an oxidizing decomposition of deuterated organic compounds having a long carbon chain, and selected from the group consisting of fatty acids,

esters, glycerides, waxes, alcohols and hydrocarbons, comprising treating said compounds with potassium permanganate or with manganese dioxide and sulfuric acid in a water-free acetic acid solvent.

4. A method according to claim 3 wherein the deuterated organic compounds have a carbon chain of at least 12 carbon atoms.

5. A method for the preparation of deuterated carboxylic acids comprising exposing a long chain deuterated organic compound selected from the group consisting of fatty acids, ester, glycerides, waxes, alcohols and hydrocarbons to an oxidizing decomposition by treating it with potassium permanganate and sulfuric acid in a water-free acetic acid solvent, at a temperature of at least C. and for a period of time sufficient to split up the long carbon chain of the deuterated organic compound into shorter chains.

mg? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,717,664 Dated February 20,1973

Inventofls) NGUYEN DINH-NGUYEN and AINO RAAL It is certified that error appears in the. above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 8, after "acid" insert -as the oxidizing agent--;

Column 6, line 4, after "acid" (first occurrence) insert as the oxidizing agent,-;

Column 6, line 13, after "permanganate" insert or withmanganese dioxide-;

Column 6, line 14, after "acid" (first occurrence) insert asthe oxidizing agent- Signed and sealed this 9th day of April 197L (SEAL) Attest:

EDWARD PLFIETCILER,JR. 'MRSHALL DAM:

Attesting Officer oommissioner of Patents

Claims

1. A method for the preparation of carboxylic acids by an oxidizing decomposition of organic compounds containing long carbon chains and selected from the group consisting of fatty acids esters, glycerides, waxes, alcohols and hydrocarbons, comprising treating said compounds with potassium permanganate or with manganese dioxide and sulfuric acid, in an acetic acid solvent.

2. A method according to claim 1 wherein the decomposition is carried out at a temperature of between 70* C. and the boiling point of the solution at normal pressure, and wherein the acetic acid solvent is water-free.

3. A method for the preparation of deuterated carboxylic acids by an oxidizing decomposition of deuterated organic compounds having a long carbon chain, and selected from the group consisting of fatty acids, esters, glycerides, waxes, alcohols and hydrocarbons, comprising treating said compounds with potassium permanganate or with manganese dioxide and sulfuric acid in a water-free acetic acid solvent.