Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF THE TERPINEOL ESTERS"

Abstract

The present invention relates to an improved process for the preparation of terpineol esters. In the process terpinyl esters is prepared from pinenes (α-and ß-pinenes) in a single step. The process gives only one isomer in major amounts i.e. α-terpinyl esters (50-55%) or other esters whereas the other isomers, ß-& y-terpineol esters are formed only in 3.0-7.0% yield. The method involves the treatment of pinenes in an inert solvent with an acetylating agent containing a catalyst selected from the salts of group VIII, IIIA, II B or I B elements under low temperature conditions with vigorous agitation for a given time, separating the resulting reaction product by conventional methods and then separating the terpineols esters by fractionation.

Full Text

The present invention relates to an improved process for preparation of terpinyl esters. This invention particularly relates to an improved process for the preparation of terpinyl esters from pinenes in a single step. More particularly, present invention relates to an improved process for the conversion of a mixture of pinenes (α-and ß-pinenes) into more useful terpineol esters. The process gives only one isomer in major amounts i.e. α-terpinyl esters (50-55%) or other esters whereas the other isomers, ß-&-terpineol esters are formed only in 3.0-7.0% yield.Commercially available terpinyl acetate consists of mainly a-terpinyl acetate but also contains a number of other isomers which are known to perfumers, exist in a number of natural oils.The terpineol acetate currently marketed is the α-isomer containing a variable proportion of 13 & y-isomers. It is used to an enormous extent in synthetic perfumery especially for lavender and bergamot types and in essential oil reconstitution. a-Terpinyl acetate has a sweet herbaceous refreshing odour of the bergamot lavender type and is used in the scenting of soaps and other household products such as cleansers and polishes. The higher terpineol esters like terpinyl propionate and terpinyl butyrate has more stronger odour than acetate and formate and find use as fixatives in bergamot notes. a-Terpinyl acetate or l-p-menthen-8-yl acetate, C12H20O2, M+ 196, bp.140° d20 0.9659; n20 1.4689, [a]20+790. Both enantiomers and the racemate occur in many essential oils like Siberian pine needle oil, cypress oil and cardamom oil in minor amounts. The starting material for the preparation of terpinyl acetate and other esters are the pinenes which occur naturally in turpentine oil. The turpentine oil is the most abundantly available raw-material having largest industrial applications. There are many varieties of turpentine oils which vary in their chemical composition but the average composition of Indian turpentine oil isolated from Pinus roxburghiana, P. khasiya and P. excelsa is as follows:- α-pinene, 20-30%; ß-pinene, 5-10%;  3-carene, 55-65% and some amounts of longifolene and minor terpenes (2-10%). The oil of turpentine is one of the most important basic raw materials for the production of camphor, borneol, pine oil and many other terpene chemicals which are used in a wide range of industries such as adhesives, lubricants, synthetic resins, solvents, plasticizers, paints and varnishes, soaps, perfumery and cosmetics, paper and rubber chemicals. Most of the products used in the above mentioned industries are based on α-and ß-pinenes which can be recovered in high purity from the turpentine oil by fractional distillation. Due to low pinene content, the Indian turpentine oil has found its way as a raw-material in the terpene chemical industry quite late. Terpinyl acetate is normally manufactured from terpineols, Kurt Bauer et al 1990, common Fragrance and Flavour Materials, VCH, D-6940 Weinheim, Germany; Merkel D; 1962 Die Atherischen, vol. III b, Gildemeister, E. & Hoffmann, Fr., Akademie Verlag, Berlin; Bukala, M. et al Chem. Abst, 1969, 70, 68536.Terpineols in turn are manufactured from pinenes by the conventional two step process or through a novel single step process (Sethi et al, Del No. 2643/96). Terpineols are generally prepared from pinenes through terpene hydrate formations which is then subjected to selective dehydration under controlled conditions to afford crude terpineols. The crude terpineols are then fractionated to give a-terpineol. In the conventional process, this a-terpineol is then acetylated in presence of acids to produce terpinyl acetate. This conventional methodology for the preparation of terpineol and its acetate is too cumbersome and time consuming as it employs very strong acidic conditions for the preparation of terpineols. Since terpineols are tertiary alcohols and are liable to undergo dehydrations in acidic medium, so selective conditions have to be maintained to prepare the acetate and other esters. Therefore, the pinene required for the preparation of value added products are separated from the turpentine oil by fractional distillation under reduced pressure. No prior art is available in the literature concerning the single step process for preparation of terpineol esters frome pinene. The main object of the present invention is to provide an improved process for the preparation of terpinyl esters. The objective of the present invention is to develop an improved process for the conversion of pinenes directly into terpinyl esters and to modify the existing process of converting pinenes into/ terpineols followed by careful acetylation of the tertiary alcoholic function. The main object of the present invention is to provide an improved process for the preparation of terpineol esters. Another object of the present invention is to provide a single step process for the manufacture of terpinyl esters from pinenes without the isolation of terpineol as the intermediate product. Accordingly, the present invention provides an improved process for the preparation of terpineol esters which comprises; characterized in that reacting pinene with acylating agent in hydrocarbon solvent and a mineral acid in a ratio in the range of 1 to 175 in presence of an emulsifying agent and a catalyst at a temperature in the range of -10 to 55 C over a period of 2 to 20 hours in an inert atmosphere under vigorous agitation, separating the organic layer and recovering the terpineol esters by the known methods. In an embodiment of the present invention the acylating agent used may be an organic acid or an acid anhydride such as acetic acid, formic acid, phthalic acid, trichloro acetic acid, propionic acid, butyric acid or an anhydride such as acetic anhydride, propionic anhydride, butyric anhydride or their mixtures. The mineral acid used may be selected from sulphuric acid, phosphoric acid or boric acid. The catalyst used in the reaction may be derived from salts of group IB, IIB, IIIA and VIII elements such as CuCl2 HgCl2, ZnCl2, AlCl3, FeSO4, BF3 etherate etc or their mixture. In an another embodiment of the present invention the base used for neutralization of acid may be such as Sodium hydroxide, Sodium carbonate and potassium hydroxide. In yet another embodiment of the present invention the emulsifying agent used may be such as dodecyl benzene sulphonate, Polyoxy ethylene, sorbitan monooleate, Polyglycol monooctadecyl ether. The method involves the treatment of pinenes in an inert solvent with an acetylating agent containing a catalyst selected from the salts of group VIII, IIIA, II B or IB elements under low temperature conditions with vigorous agitation for a given time, separating the resulting reaction product by conventional methods and then separating the terpineols esters by fractionation. In a preferred embodiment of the invention, α-pinene or ß-pinene or mixture of both is subjected to a treatment with an acid like acetic acid, formic acid, phthalic acid, trichloroacetic and propionic acid, butyric acid, propionic anhydride, butyric anhydride, acetic anhydride or oxalic acid or with the an acidic catalyst mixture. The reaction may be effected over a period of about 2 to 20 hours at a temperature range of -10o to 55oC, depending upon the nature of the acid used. The crude product and the unreacted starting material may be isolated from the reaction mixture by diluting the mixture with cold water, neutralising the acid with aqueous base selected from the sodium hydroxide, Potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, calcium hydroxide, barium hydroxide etc. and then separating the oily layer from water. The esters are then separated from the reaction product by fractional distillation under reduced pressure in a fractionating column packed with an efficient packing material like metallic helices/glass beads or metallic rings. In the present invention, the conversion of pinenes into terpineol esters has been achieved within a single step without the isolation of the intermediate terpineol. The end product isolated in this process is a mixture of the terpineol esters alongwith menthadienes which could be finally purified by fractionation in a towers fractionating column under controlled reflux ratio. The final purity of the product is checked by gas chromatography. This invention does not involve the isolation of terpineol because it is formed and selectively esterified simultaneously. The formation of terpineol esters from pinenes is dependent upon time, temperature and concentration of the catalyst. At lower temperature with a particular concentration of the catalyst, the formation of terpineol esters takes place which is also time dependant. But at higher temperatures, the reaction leads to the formation of menthadienes and p-cymene. The optimum concentration of the catalyst is of prime importance as under higher concentrations, the reaction leads to the formation of polymeric products whereas with low concentrations, the reaction doesnot proceed smoothly. Similarly, the reaction time has to be maintained properly for the required yield of the product. Therefore, conditions of time, temperature and amount of catalyst have to be adjusted in such a way that leads mainly to terpineols esters while suppressing the side products. The process of invention is described in details in the examples given below which are proved by way of illustrations only and therefore should not be construed to limit the scope of the invention. Example 1 The pinene fraction (2.01) of 90% purity dissolved in n-hexane (1.01) mixed with an emulsifying agent of the type Polyglycol monoocta decyl ether (20ml) and anhydrous Zinc chloride (lOg) is charged in a flask fitted with an efficient agitator, thermometer, dropping funnel, condenser & a Nitrogen inlet. Acetic acid, acetic anhydride and Sulphuric acid in the ratio of 3.0 litre:0.5 litre 0.05 litre), are cooled and taken in another dropping funnel. Then the agitator is started and nitrogen gas purged in the reaction flask. The acid mixture is then slowly charged into the flask at a rate of the about 20 ml/minute. After the addition of the acid has been completed, the reaction mixture is maintained at a temperature around 15oCfor 7 hours. The reaction mixture is agitated vigorously throughout the reaction period. The stirring is then stopped and mixture allowed to settle. The reaction mixture is poured in a separating funnel and lower acid layer is separated out. The oily layer is washed with water (1.0 1 x 3) and then washed with 2% sodium carbonate solution (500 ml x 2). Finally, the oily layer is washed with water and dried over anhydrous sodium sulphate and concentrated to remove solvent. The GC analysis of the product showed à-terpineol acetate 55%, 6-terpineol acetate 2%, terpineol acetate 2%, menthadienes 15% and unreacted α-pinene 15%. α-Terpineol acetate was separated from the a-pinene, ß-terpeneol acetate and y-terpineol acetate by fractional distillation under reduced pressure. Example 2 In a ten litre round bottom flask are put pinenes (2.0 1) and benzene (1.0 1) alongwith 10 ml of emulsifying agent of the dodecyl benzene sulphonic acid containing cupric chloride:mercuric chloride [5g:5g]. The flask is fitted with a dropping funnel, a mechanical stirrer and a thermometer. A mixture of propionic acid (2.0L), propionic anhydride (1.5 L), sulphuric acid (20 ml) is taken in the dropping funnel and slowly added to the pinenes at a rate of 50 ml/minute. After whole of the acid has been added, the mixture is stirred and the temperature maintained at 25oC. The stirring is continued for around 15 hours. After which the mixture is taken into a separating funnel and diluted with water (1.0 1) and allowed to stand. The oily layer is then separated out and washed with water (1.0 1 x 3) and then given one washing with 5% sodium carbonate solution. Finally, the product is washed with water (one washing) and dried over sodium sulphate and concentrated to remove solvent. The dried oil on GC analysis showed the following composition. a-pinene 20%, a-terpineol propionate 55%; ß-terpineol & 4-terpineol propionate-6% and menthadienes 10-12%.α-Terpineol propionate was separated from the a-pinene, ß-terpineol and y-terpineol esters by fractional distillation under reduced pressure. Example 3 In a round bottom flask fitted with an agitator, thermometer and a dropping funnel are taken boron trifluoride etherate 20 ml., in n-hexane (500 ml) and cooled to -5oC. A mixture of Pinenes (2.5 1) dissolved in n-hexane (1.0 1) and an emulsifier of the type polyglycol monooctadecyl ether (10 ml) added slowly. A mixture of phosphoric acid (1.0 1), butyric acid and, butyric anhydride 2.0 litre are taken into the dropping funnel and added slowly to the pinenes at a controlled rate of (1:1) 50 ml/min with continuous stirring at a temperature of-5oC. After the addition of the acid mixture, the contents of the round bottom flask are stirred for about 12 hours at a constant temperature of 15oC. The reaction product is then poured into a separating funnel and diluted with 500ml of chilled water. The lower acid layer is then separated and discarded. The organic layer of terpineol butyrate is then washed with water (500 ml x 4) and then with 5% sodium carbonate solution (500 ml x 2). The final washing is then made with water to make the layer neutral. The crude terpineol ester is then dried over anhydrous sodium sulphate, concentrated to remove solvent and subjected to GC analysis which recorded the following composition;-α-pinene 15%; menthadienes 12%; a-terpineol butyrate 60%; B-terpineol butyrate-3%; -terpineol 2% a-Terpineol butyrate was separated by fractional distillation under reduced pressure. Example 4 Pinenes (2.0 1) dissolved in n-hexane (1.0 1) alongwith with Cupric Chloride: ferrous Sulphate (3 g:10 g) is placed in a round bottom flask fitted with a mechanical stirrer,thermometer and a dropping funnel. An emulsifying agent (10ml) of the type Polyoxy ethylene sorbitan mono oleate is added to pinene and the cooled acid mixture of formic acid, sulphuric acid (1.5:0.05L) is taken in the dropping funnel. The agitator is then kept on and the acid mixture slowly added at a rate of 50 ml/min. After the addition of acid the reaction mixture is kept at 5®C for 8 hours and stirred vigorously. The reaction product is then cooled and transferred into a separating funnel. The acid layer is separated out and the organic phase washed with water (4 x 500 ml) and then with sodium carbonate (2%; 2 x 500 ml). Finally, the oily layer is washed with water and then dried with anhydrous sodium sulphate and concentrated to remove solvent. GLC analysis of the reaction product gave the following analysis:-a-pinene 15.0%; methadienes 10%; α-terpineol formate 55%; ß-terpineol formate-7%; -terpineol formate 5%. α-Terpineol formate was separated from the a-pinene, B-terpeneol and -terpineol esters by fractional distillation under reduced pressure. Example 5 In a round bottom flask are taken pinenes (1.0 1) in benzene (500 ml) is mixed with an emulsifying agent (5.0 ml) of polyoxy ethylene sorbitan mono oleate. Then a mixture of acid prepared from acetic acid, boric acid, acetic anhydride and sulphuric acid in the ratio of (500 ml: 100 g: 150 ml: 20 ml) is slowly dropped into pinenes at a rate of 50 ml/min. at lOoC. Then the catalyst comprising of anhydrous Zinc Chloride and Aluminium chloride (5g:3g) dissolved is acetic acid is slowly added to the reaction mixture. The temperature is then raised to 15oand mixture agitated vigorously for 8 hours. After attaining the required conditions, the acid layer is separated from the reaction product and organic layer washed with water, 5% sodium carbonate solution and finally with water and then dried with anhydrous sodium sulphate and concentrated to remove solvent. GLC analysis of the reaction product gave the following analysis, α-terpineol acetate 50%; ß-terpineol acetate 6%; y-terpineol acetate 4%.α-Terpineol acetate was separated from the α-pinene, ß-terpeneol and y -terpineol esters by fractional distillation under reduced pressure. Advantages of the present Invention: 1. The conversion of pinenes to terpineol esters is in a single step. 2. It is a one pot reaction and doesnot require terpineol as the starting material. 3. The reaction doesnot involve strong acidic or strong basic conditions for esterification and thus is free from any side reactions like dehydration etc. 4. The reaction involves the use of mild catalysts selected from the salts of group VIII, III A, IIB and IB elements. We Claim: 1. An improved process for the preparation of terpineol esters which comprises; characterized in that reacting pinene with acylating agent in hydrocarbon solvent and a mineral acid in a ratio in the range of 1 to 175 in presence of an emulsifying agent and a catalyst at a temperature in the range of-10 to 55°C over a period of 2 to 20 hours in an inert atmosphere under vigorous agitation, separating the organic layer and recovering the terpineol esters by the known methods. 2. An improved process as claimed in claim 1 wherein the pinenes used consist of a mixture of a-pinene (80-85%) & p-pinene (5-10%). 3. An improved process as claimed in claim 1 & 2 wherein the mineral acid used is selected from phosphoric acid, sulphuric acid, boric acid and acylating agent used is selected from formic acid, phthalic acid, trichloro acetic acid, butyric acid, propionic acid, propionic anhydride, butyric anhydride, acetic acid, orxalic acid and mixture thereof. 4. An improved process as claimed in claims 1 to 3 wherein the pinene is reacted at a preferred temperature rage of -5° to 25°C. 5. An improved process for the preparation of terpineol ester as claimed in claim 1 to 4 wherein the catalyst used is selected from ZnCl2, CuCl2, HgCl2, FeCl3, BF3, FeSO4, AlCl3 and mixture thereof. 6. An improved process as claimed in claims 1 to 5 wherein the emulsifying agent used is selected from dodecyl benzene sulphonate, polyoxy ethylene, sorbitan mono oleate, polyglycol mono octadecyl ether. 7. An improved process as claimed in claims 1 to 6 wherein the organic hydrocarbon solvent is selected from hexane, benzene, petroleum fractions or heptane. 8. An improved process as claimed in claims 1 to 7 wherein the ratio of mineral acid and acylating agent used depends upon the nature of mineral acid used. 9. An improved process for the preparation of terpineol esters substantially as herein described with references to the examples.

Documents:

663-del-2000-abstract.pdf

663-del-2000-claims.pdf

663-del-2000-correspondence-others.pdf

663-del-2000-correspondence-po.pdf

663-del-2000-description (complete).pdf

663-del-2000-form-1.pdf

663-del-2000-form-19.pdf

663-del-2000-form-2.pdf