GB2030138A - Preparation of long-chain carboxylic acids and alcohols and the use of an alcohol as a plant growth regulator - Google Patents

Abstract

A process for the preparation of long-chain carbon compounds comprises: a. reacting a carboxylic acid having 21 to 30 carbon atoms with a chlorinating agent to form the acid chloride; b. separating the acid chloride and reacting it with an enamine (e.g. 1- morpholino-cyclohexene) and a hindered tertiary amine in an organic solvent while maintaining the reaction temperature at 30 DEG to 60 DEG C; c. removing the solvent and recovering the beta-diketone product; d. reacting the beta-diketone with a solution of an alkali metal hydroxide or alkoxide and an alcohol; and e. recovering the precipitated product, the salt of a ketocarboxylic acid. The salt may be converted to the free acid, which may be reduced to the corresponding aliphatic acid and alcohol. A plant growth regulator composition comprises a substantially water-soluble solution of 1-triacontanol dissolved in a polar organic solvent, said polar organic solvent being present in an amount sufficient to render said concentrate water-soluble.

Description

SPECIFICATION Preparation of long-chain carboxylic acids and alcohols and their use as a plant growth regulator.

The present invention relates to the preparation of long-chain carboxylic acids and alcohols. The acids are not only useful in themselves but can be used to produce the alcohol 1 -triacontanol which can be employed to increase crop yields. Thus, the invention is also directed to a chemical formulation comprising 1-triacontanol for use in stimulating the growth of living plants.

To the present date, syntheses of long-chain carboxylic acids containing up to about thirty carbon atoms in a straight chain have not proven to be useful economicallywhen applied to large scale production. Such processes have involved a ketoacid intermediate. Some older processes show very low yields and involve additions of various half esters, half acid chlorides (or halides) to organometallic intermediates or beta-keto esters. While some other methods show good yields, they product contaminated products.

The present invention is directed to the preparation of long-chain carboxylic acids which can be easily converted to alcohols through ester intermediates. In this process, shorter chain acids are converted to the acid chloride which may be further purified. The acid chloride is mixed with an enamine and a hindered tertiary amine in an organic solvent and then acidified to form the beta-diketone after washing the organic phase and removal of the solvent. The beta-diketone is reacted with an organic hydroxide or alkali metal alkoxide and acidified to produce the keto acid which can be readily converted to the respective aliphatic acid and alcohol.

The present invention thus provides a process for the preparation of long-chain carboxylic acids and alcohols which comprises: a. reacting a 21 to 30 carbon carboxylic acid with a chlorinating agent to form the acid chloride; b. separating the acid chloride and reacting it with an enamine and a hindered tertiary amine in an organic solvent while maintaining the reaction temperature at 30 to 60"C.; c. removing the solvent and recovering the betadiketone product; d. reacting the beta-diketone with a solution of an alkali metal hydroxide or alkoxide and alcohol; and e. recovering the precipitated product.

Preferred forms of the invention will now be described.

The preferred starting short-chain acid is lignoceric acid, CH3(CH2)22COOH, which is used to make 7-keto-1 -triacontanoic acid and 1 -triacontanoic acid as well as 1 -triacontanol. Other short-chain acids can be used to prepare different long-chain carboxylic acids and alcohols containing from 28 to 36 carbon atoms such as octacosanoic acid and octacosanol and hexatriacontanoic acid and hexatriacontanol.

In the preferred preparation of long-chain carboxylic acids in accordance with the invention, shorterchain starting acids are first treated with thionyl chloride, phosphorus tri-chloride or phosphorus pentachloride for up to 5 hours at temperatures from 30 to 60"C. in the presence of solvents such as anhydrous chloroform, methylene chloride, orcar- bon tetrachloride. This produces the acid chloride which can be separated from the excess solvent and chlorinating agent with a rotary evaporator or similar means. In a preferred embodiment, the reaction temperature is from 50 to 60"C. Increasing the concentrations of initial reactants will increase the yield.

The acid chloride is then dissolved in an organic solvent such as chloroform which is added to a solution of an enamine and a hindered tertiary amine such as cyclohexyl dimethylamine or tributylamine, also in an organic solvent such as chloroform. The enamine can be 1-morpholine-1cyclopentene, 1 -morpholino-1 -cyclohexene or 1 - morphilino-1-cycloheptene although the six carbon enamine is preferred. The more hindered the tertiary amine, the greater is the yield. Pyridine and other less hindered amines fail to work. The reaction is maintained at 30 to 40"C. with an ice bath or similar means. Higher concentrations of reactants allow higher temperatures of up to about 60 C. and increase the yield.While maintaining this temperature, the resulting complex is stirred and refluxed with hydrochloric acid for 3 to 5 hours, although more rapid stirring will reduce the reaction time. The organic phase is then separated and washed with water with the subsequent recovery of the product beta-diketone.

The beta-diketone is then added to the solution of sodium, potassium or lithium hydroxide in alcohol while keeping the temperature below the boiling point. The yield of this reaction can be increased by substituting an alkoxide for the hydroxide. Sodium hydroxide is the preferred hydroxide among the alkali metal hydroxides which can be used in this reaction. The longer chain alkoxide give greater yields so that sodium propoxide is better than sodium ethoxide. Sodium is again preferred over the lithium or potassium alkoxides. Almost any alcohol of 6 carbons or less is acceptable including ethylene glycol.

After refluxing, the solution is cooled to 5 C. to precipitate out the salt of the keto acid which is readily isolated by filtering and washing. The free acid can be prepared by merely suspending the salt in hot water and adding hydrochloric acid. If further purification is desired, the acid can be dissolved in heated methyl ethyl ketone and then cooled to recrystallize the purified acid.

The keto acid can be readily converted to the respective carboxylic acid and alcohol by a number of different processes. For example, the Huang Minlon reduction can be used to form the carboxylic acid.

The long-chain alcohol 1-triacontanol, CH3(CH2)28CH2OH, which can be prepared in accordance with one of the aspects of this invention, has been studied recently as being a naturaily occuring plant growth stimulant (Ries et al,Science, 193, 1339 (1977)). Field trials have been conducted in an attempt to optimise the conditions under which a chemical formulation of this compound can be applied to plants.

In the research involving the utilization of 1-triacontanol as a plant growth regulator, use has been made of a relatively large amount of surfactants in the chemical formulation in an effort to render the 1-triacontanol soluble in water. As is well known, 1-triacontanol is basically insoluble in water. Of course, the use of a large amount of water is imperative in order to economically and effectively apply the chemical formulation to large areas of growing plants. Accordingly, it is imperative to render the 1 -tria-contanol water-soluble so that it can be properly dispersed in a large quantity of water which is to be subsequently applied to the plants.However, the organic solvents which are presently being utilized to make the 1-triacontanol soluble in water, for example, chloroform and chemical surfactants and also other water-insoluble solvents, have been found to be detrimental to both plant life and to the environment. Thus, it has been found, for example that surfactants coat the plants, thereby preventing entry of the 1 -triacontanol into the plant and consequently, the plant growth properties of the 1-tria-contanol are rendered less effective.

Accordingly, an addition objective of the present invention is to provide an inexpensive and effective means for formulating 1 -triacontanol without the use of surfactants or other large quantities of organic solvents which have been found to adversely affect plant growth. Specifically, the present invention provides a plant growth regulatorformulation containing a polar organic solvent which renders the 1-triacontanol soluble in water and at the same time poses no threat to plant life or to the environment.

The plant grown stimulant, 1-triaconanol, is dissolved in a polar organic solvent in an amount sufficient to form a water-soluble concentrate. Typically, the concentrate can be formed by mixing together one part by weight of 1-triacontanol with up to about 500,000 parts by volume of the polar organic solvent, and advantageously one part by weight of 1-triacontanol to about 1,000 parts by volume of the polar organic solvent. The polar solvent can be any water-soluble solvent or solvent mixture containing one or more functional groups, which renders the resulting 1-triacontanol solution soluble in water, which is the major constituent in the formulation. This solution is then dissolved in a large quantity of water with stirring and/orshaking.

Typically, the 1-triacontanol-polar organic solvent concentrate-water mixture is applied to the growing plants in an amount sufficient to achieve a distribution of at least 1 mg. of 1-triacontanol per acre, advantageously 5 to 20 mg. per acre.

The polar organic solvents which are utilized in the present invention to aid in the solubility of the 1-triacontanol in water include alcohols, ketones, water-soluble ethers, glycols and any other solvent or solvent mixture containing one or more functional groups contained in any one class or classes of said solvents. Suitable polar organic solvents include acetone, methyl ethyl ketone, methanol, isopropa nol, diethylene glycoi, n-butanol, propylene glycol and dioxane.

Typical ratios of the 1 -triacontanol-organic solvent solution, on the one hand, to water, on the other hand, may vary from 1: 10,000 to 1:1 parts by volume, preferably 1: 1,000 to 1:100 parts by volume, depending upon the desired concentration of the 1-triacontanol required or desired in the final solution.

The chemical formulation, according to the pre sent invention can be applied to plant life in any desired manner although the spraying of the grow ing plant life has been found to be particularly effective.

The formulation of the invention, when applied to field and sweet corn, sugar cane, tomatoes, cucum bers, beans, and the like, has been found to increase production in the greenhouse-controlled environ ment in an amount up to about 24% based upon dry weight of the plants. Similartests underfield conditions of 1,000 acres or more have resulted in an increase in crop yield of field corn of from about 6 to 16% measured in terms of bushels per acre.

The following Examples are given merely as illustrative of the present invention and are not to be considered as limiting. Unless otherwise noted, the percentages there are by weight.

Example 7 Lignoceric acid was reacted with 3 equivalents of thionyl chloride for up to 3 hours at 50-60 C. in 300 ml per mole of anhydrous chloroform. Excess sol vent and thionyl chloride was evaporated leaving an amber liquid, which was used without further purifi cation. One mole of the acid chloride was then dissolved in 500 ml an hydrous, alcohol-free chlor oform and added over 2 hours to a solution of one mole of 1-morpholino-1-cyclohexene and one equivalent of triethyl amine (a tertiary amine) in an equal volume (500 ml) of chloroform. The temperature was maintained between 30 and 40"C., and the resulting complex was stirred and refluxed with 500 ml of 3N hydrochloric acid over a 5 hour period. The organic phase was then separated and washed with water.The resultant organic phase was evaporated on a rotary evaporator leaving the beta-diketone as a brown oil.

The entire quantity of beta-diketone was then added to a solution of 3 mols of sodium hydroxide in 1.5 liters of ethanol over 1/2 to 1 hour while maintaining the temperature at less than 80"C. The solution was refluxed for 1 to 2 hours and then cooled to 5"C. The resulting precipitate was filtered and washed with methanol and then dried. The free acid was prepared by suspending the salt in hot water and acidifying to pH 2-3 with hydrochloric acid. After filtering and washing with hot water, the product is 7-keto-1 -triacontanoic acid which can be further purified by recrystallization with methyl ethyl ketone. The crude yield was about 82%.

Example 2 Lignoceric acid was reacted with 3 equivalents of thionyl chloride for 3 hours at 50-60"C. in 300ml per mole of anhydrous chloroform. Excess solvent and thionyl chloride were evaporated leaving an amber liquid, which was used without further purification.

One mole of the acid chloride was then dissolved in 500 ml anhydrous, alcohol-free chloroform and added over 2 hours to a solution of one mole of 1 -morpholino-1 -cyclohexene and one equivalent of tributyl amine (a tertiary amine) in an equal volume (500 ml) of chloroform. The temperature was ma intained between 30 and 40 C., and the resulting complex was stirred and refluxed with 500 ml of 3N hydrochloric acid over a 5 hour period. The organic phase was then separated and washed with water.

The resultant organic phase was evaporated on a rotary evaporator leaving the beta-diketone as a brown oil.

The entire quantity of beta-diketone was then added to a solution of 3 mols of sodium ethoxide in 1.5 liters of methanol over 1/2 to 1 hour maintaining the temperature at less than 80"C. The solution was refluxed for 1 to 2 hours and then cooled to 5-10'C.

The resulting precipitate was filtered and washed with methanol and then dried. The free acid was prepared by suspending the salt in hot water and acidifying to pH 2-3 with hydrochloric acid. After filtering and washing with hot water, the product is 7-keto-1 -triacontanoic acid which can be further purified by recrystallization with methyl ethyl ketone. The crude yield was about 85%.

Example 3 Lignoceric acid was reacted with 2 equivalents of phosphorus pentachloride for 1 hour at 40-50"C. in 300 ml per mole of anhydrous chloroform. Excess solvent was removed by distillation while the acid chloride was then collected after further distillation in vacuo as an amber liquid after cooling. One mole of the acid chloride was then dissolved in 500 ml anhydrous, alcohol-free chloroform and added over 2 hours to a solution of one mole of 1-morpholino- 1-cyclohexene and one equivalent of triethyl amine (a tertiary amine) in an equal volume (500 ml) of chloroform. The temperature was maintained be tween 30 and 40"C., and the resulting complex was stirred and refluxed with 500 ml of 3N hydrochloric acid over a 5 hour period. The organic phase was then separated and washed with water.The resul tant organic phase was evaporated on a rotary evaporator leaving the beta-diketone as a brown oil.

The entire quantity of beta-diketone was then added to a solution of 3 mols of potassium hydrox ide in 1.5 liters of ethanol over 1/2 to 1 hour while maintaining the temperature at less than 80"C. The solution was refluxed for 1 to 2 hours and then cooled to 5"C. The resulting precipitate was filtered and washed with methanol and then dried. The free acid was prepared by suspending the salt in hot water and acidifying to pH 2-3 with hydrochloric acid. After filtering and washing with hot water, the product is 7-keto-1-triacontanoic acid which can be further purified by recrystallization with methyl ethyl I ketone. The crude yield was at least 80%.

Example 4 The sodium salt of the 7-keto-1-triacontanoic acid (such as produced in Examples 1-3 above) in the i amount of 0.9 mol was dissolved in 1 liter of diethylene glycol at 150"C. The temperature was reduced to 130"C.; then 150 ml of hydrazine hydrate was added with the reaction mixture being refluxed for 3 to 4 hours to form the hydrazone. Either at this point or during the previous refluxing, about 200 grams of potassium hydroxide was added to the mixture. After the refluxing, the temperature was raised to 195"C. and refluxing was continued for 4 to 12 hours to decompose the hydrazone to the free acid. The temperature was then reduced to 10000.

and 2 liters of hot water was added whereafter the acid salt was acidified to about pH 2-3 with 6N hydrochloric acid (to form triacontanoic acid) and filtered. The triacontanoic acid can be further purified by recrystallization from methyl ethyl ketone with a yield of 89% at a purity of about 99% after washing with diethyl ether and a second recrystallization.

Example 5 Triacontanol was prepared from triacontanoic acid by suspending 0.1 mol of the acid in 40 ml of anhydrous chloroform followed by the addition of thionyl chloride while maintaining the temperature at 40"C. to 60"C. for 2 hours. Chloroform and excess thionyl chloride were removed in a rotary evaporator, and the resulting acid chloride was reacted with 10 ml of absolute ethanol to form the ester. Excess ethanol was removed in a similar manner, and the ester was dissolved in 100 ml of anhydrous ether.

Powdered lithium aluminium hydride (0.5 mol) was refluxed in 200 ml of anhydrous diethyl ether until most of the solid had dissolved. The solution of the ester was added slowly over 45 min. with vigorous stirring, and the reaction mixture was allowed to reflux overnight. Ethyl acetate (20 ml) was added to react with the unreacted lithium aluminum hydride, and the mixture was decomposed cautiously with 50 ml of 6N HC I with vigorous stirring. To solubilize the resulting alcohol, 50 ml of benzene was added, and the mixture was washed with warm water. The organic layer was filtered through anhydrous sodium sulfate, and an equal volume of acetone was added. Cooling to 5"C., foliowed by filtration, produced 1 -triacontanol at a yield of about 86%.

Example 6 Docosanoic acid was heated with 3 equivalents of thionyl chloride for 3 hours at 50-60 C. in 300 ml per mole of anhydrous chloroform. Excess solvent and thionyl chloride were evaporated leaving an amber liquid, which was used without further purification.

One mole of the acid chloride was then dissolved in 500 ml anhydrous, alcohol-free chloroform and added over 2 hours to a solution of one mole of 1-morpholino-1-cyclohexene and one equivalent of diethyl cyclohexyl amine in an equal violume (500 ml) of chloroform. The temperature was maintained between 30 and 40"C., and the resulting complex was stirred and refluxed with 500 ml of 3N hydrochloric acid over a 5 hour period. The organic phase was then separated and washed with water. The resultant organic phase was evaporated on a rotary evaporator leaving the beta-diketone as a brown oil.

The entire quantity of beta-diketone was then added to a solution of 3 mols of sodium hydroxide in 1.5 liters of ethanol over 1/2 to 1 hour while maintain ing the temperature at less than 80"C. The solution was refluxed for 1 to 2 hours and then cooled to 5"C.

The resulting precipitate was filtered and washed with methanol and then dried. The free acid was prepared by suspending the salt in hot water and acidifying to pH 2-3 with hydrochloric acid. After ! filtering and washing with hot water, the product is 7-keto-1-octacosanoic acid which can be further ;purified by recrystallization with metyl ethyl ketone.

The crude yield was at least 80%.

The 7-keto-1-octacosanoic acid can be converted to 1-octacosanoic acid in the same manner as the 7-keto-l -triacontanoic acid is converted to 1 triacontanoic acid in Example 4 and then to the corresponding alcohol as in Examples 5 and 7.

Example 7 The acid chloride of 1-triacontanoic acid was converted to the ester by adding methanol or ethanol and stirring for to 1 hour. The alcohol was evaporated on a rotary evaporator leaving ethyl-l- triacontanoate. The ester was then reacted in a pressure vessel under about 250 atmospheres of hydrogen in the presence of a powdered copper chromite catalyst for about 12 hours at 250 C. to produce 1 -triacontanol. One part of catalyst was present for every 5 to 10 parts of ester.

Example 8 Al mg quantity of 1-triacontanol was dissolved in 10 ml of boiling acetone (or methyl ethyl ketone) and the solution was cooled to room temperature. This was added to 990 ml of water with vigorous stirring over a 30-second period. The resultant solution may be applied to plant life aerially at a concentration of 10 mg per acre using 10 liters of solution per acre.

The solution may further be diluted with ten parts of water resulting in a concentration of 1 mg per acre.

Example 9 A 10 mg quantity of 1 1-triacontanol was dissolved in 100 ml of methanol. The mixture was added to 900 ml of water heated to 500C. with vigorous stirring.

The concentrate may be diluted with 9 liters of water resulting in a solution containing 1 mg per liter. This solution may be applied as described in Example 8.

Example 10 One mg of 1-triacontanol was dissolved in 25 ml of hot isopropanol and the hot solution was poured into 975 ml of water with vigorous stirring over a one-minute period. This solution may be applied as described above in Example 8.

Example 11 One mg of 1-triacontanol was dissolved in 25 ml of hot diethylene glycol and added to 975 ml of rapidly stirring water. The resulting solutioln may be used as described in Example 8.

Example 12 One mg of 1-triacontanol was dissolved in 10 ml of hot n-butanol and the mixture was added with stirring to 990 ml of water at 60 degrees. The solution was cooled to room temperature before use.

Example 13 Ten mg of 1-triacontanol was dissolved in 100 ml of warm dioxane and added over 60 seconds to 950 ml of warm water. The solution may be used as described in Example 8.

Example 14 One mg of 1-triacontanol was dissolved in 50 ml of hot propylene glycol and added to 950 ml of water with stirring. This solution may be used as described in Example 8.

Claims (21)

1. A processforthe preparation of long-chain carbon compounds which comprises: a. reacting a carboxylic acid having 21 to 30 carbon atoms with chlorinating agent to form the acid chloride: b. separating the acid chloride and reacting it with an enamine and a hindered tertiary amine in an organic solvent while maintaining the reaction tem perature at 30 to 60"C.; c. removing the solvent and recovering the beta diketone product.

d. reacting the beta-diketone with a solution of an alkali metal hydroxide or alkoxide and an alcohol; and e. recovering the precipitated product.

2. The process of claim 1, wherein the carboxylic acid is lignoceric acid.

3. The process of claim 1, wherein the enamine is 1 -morpholino-1 -cyclohexane.

4. The process of claim 2, wherein the enamine is 1 -morpholino-1 -cyclohexene.

5. The process of claim 1, wherein the precipitated product is acidified to form the keto acid.

6. The process of claim 5, wherein the carboxylic acid is lignoceric acid, the enamine is 1-morpholino 1-cyclohexene, and the keto acid is a keto-1tricontanoic acid.

7. The process of claim 5, wherein the keto acid is reduced to form a long-chain carboxylic acid.

8. The process of claim 7, wherein the long-chain carboxylic acid is further reduced to form the respective alcohol.

9. The process of claim 6, wherein the keto-1 - triacontanoic acid is reduced to form triacontanoic acid.

10 The process of claim 9, wherein the triaconta noic acid is further reduced to form triacontanol.

11. A plant growth regulator composition com prising a substantially water-soluble solution of 1-triacontanol dissolved in a polar organic solvent, said polar organic solvent being present in an amount sufficient to render said concentrate water soluble.

12. The plant growth regulator composition of claim 11, wherein the solution comprises one part by weight of 1-triacontanol with up to about 500,000 parts by volume of the polar organic solvent.

13. The plant growth regulator composition of claim 12, wherein the polar organic solvent is selected from alcohols, ketones, water-soluble ethers and glycol.

14. The plant growth regulator composition of claim 11, further containing water in an amount so that the ratio of 1 -triacontanol solution to water is from : 10,000 to :1 parts by volume.

15. The plant growth regulator composition of claim 14, wherein the polar organic solvent is selected from acetone, methyl ethyl ketone, methanol, isopropanol, diethylene glycol,n-butanol, propylene glycol and dioxane.

16. A method for stimulating plant growth which comprises applying the plant growth regulator composition of claim 14to growing plants.

17. The method of claim 16, wherein said plants constitute crops selected from the group consisting of corn, sugar cane, tomatoes, cucumbers and beans.

18. The process of claim 1, substantially as described in any of Examples 1-7.

19. A long chain carbon compound when prepared the process of any of claims 1 to 10 and 18.

20. The plant growth regulator composition of claim 11 substantially as described in any of Examples 8 - 14.

21. The method of claim 16 substantially as described in any of Examples 8 - 14.