Field of invention
This invention relates to a process for production of 1,1,1-trifluoroisopropanol by reduction of 1,1,1-trifluoropropanone using alkali borohydrides in an aqueous medium. After completion of the reaction, azeotrope of water and 1,1,1-trifluoroisopropanol is obtained. Anhydrous 1,1,1-trifluoroisopropanol can be obtained by azeotropic distillation using n-pentane as entrainer.
Background of invention
1,1,1-Trifluoroisopropanol is an important intermediate in the synthesis of agrochemicals. Asymmetry in this compound can be exploited to prepare enantiomeric products. 1,1,1-trifluoroisopropanol has been prepared by a process described by Swarts {Bull. Soc. Chim. Belg. 1929, 38, 99) by reduction of 1,1,1-trifluoropropanone with hydrogen in presence of platinum oxide. This process suffers from the disadvantages that the catalyst is not readily available and is very expensive.
GB621654 teaches a process for preparation of 1,1,1-trifluoroisopropanol by the reduction of 1,1,1-trifluoropropanone with hydrogen in presence of raney nickel at 70-100 °C temperature and 50-100 atmospheric pressure. This process also suffers from the disadvantages of high pressure operations, flammability due to raney nickel operations and lower yields.
The main objective of the present invention is to provide a process for preparation of 1,1,1-trifluoroisopropanol which is easy to perform and does not involve drastic reaction conditions. The reagents required for performing the process of present invention are easily available and convenient to use. The process is conducted at atmospheric pressure and low temperatures removing the necessity of high pressure. The process uses cheap and readily available reagents resulting in cost improvements. There is no catalyst involved in the process. The process is conducted in aqueous medium which improves the purity and recovery of the product. This makes the process much simple and reduces the load on effluent and cost. The process has no organic solvent making it environment friendly. The effluents generated in the process are easily treatable.
Statement of Invention:
Present invention provides a process for preparation of 1,1,1-trifluoropropanol
comprising reacting 1,1,1-trifluoropropanone with an alkali borohydride in aqueous
medium.
Sunmiary of Invention
A process for preparation of 1,1,1-trifluoroisopropanol is disclosed, wherein the process comprises reduction of 1,1,1-trifluoroisopropanone with an alkali borohydride in an aqueous solution. After completion of the reaction, azeotrope of water and 1,1,1-trifluoroisopropanol is obtained. Anhydrous 1,1,1-trifluoroisopropanol can be obtained by azeotropic distillation using n-pentane as entrainer. The process does not utilize any catalyst or organic solvent and is convenient to perform and is cost effective. It is an object of this invention to provide an industrially feasible process, which is operable at easily manageable temperature, pressure and without applying special additives, extreme conditions and costly reagents for the preparation of 1,1,1-trifluoroisopropanol in high yields.
Detailed description of the invention
According to the process of present invention 1,1,1-trifluoroisopropanol can be prepared
by the reduction of 1,1,1-trifluoropropanone using alkali borohydrides in aqueous
medium with greater conversion rate up to 99% and yield greater than 95% without using
any organic solvent and phase transfer catalyst in the reaction.
In an embodiment the reaction is performed by the addition of 1,1,1-trifluoropropanone
to the aqueous alkali borohydride or by the addition of aqueous solution of alkali
borohydride to the 1,1,1-trifluoropropanone. The former way is preferred.
The reaction can be carried out at room temperature or sub-room temperatures. Broadly stating, addition of reactants and reaction can be carried out within the temperature range of-10°C. to-H30°C.
The reaction medium can be water or aqueous alkali hydroxide solution. The use of aqueous alkali hydroxide is preferred. The alkali hydroxides for use in present invention is selected from group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide and cesium hydroxide, preferably sodium and potassium hydroxide. In an embodiment the concentration of alkali hydroxide solution that can be used in the reaction can range from 0.001 to 5 M, preferably from 0.5 to 1.5 M solution. The ratio of amount of water or aqueous alkali hydroxide by weight to that of 1,1,1-trifluoropropanone is in the range of 1:4 to 10:1, preferably from 1:1 to 1:2. The alkali borohydride is selected from a group consisting of Uthium borohydride, sodium borohydride, potassium borohydride or sodium cyano borohydride, all of which can be used in solid or powdered form, or their aqueous or solution in aqueous alkali hydroxide.
In a preferred embodiment, the quantity of alkali borohydride that can be used for performing the process of present invention may range from 0.25 mole equivalent to one mole equivalent preferably 0.3 to 0.5 mole equivalent of 1,1,1-trifluoropropanone. After completion of the reaction product can be isolated by boiling off the reaction mixture as an azeotrope of water and 1,1,1-trifluoroisopropanol. Anhydrous 1,1,1-trifluoroisopropanol can be obtained by azeotropic distillation using n-pentane as entrainer.
The feed to the distillation assembly is a heterogeneous mixture of aqueous alcohol and n-pentane. This mixture suitably contains between 80 and 90% by weight of alcohol, between 5 and 10 by weight of water and between 5 and 10% of n-pentane. The overhead distillate is a ternary azeotrope which separates to organic and aqueous phase at temperature below the boiling point of distillate. By separating the aqueous layer and recycUng the organic followed by removal of n-pentane, anhydrous 1,1,1-trifluoroisopropanol containing not more than 0.1% by weight of water can be recovered from the bottom of the distillation assembly. The invention is further illustrated with but not limiting to the following examples.
Example 1-
Charging solution of sodium hydroxide (200 g, IM) in a round bottom flask attached with a condenser, pressure equalizing funnel and temperature sensor. The whole assembly is kept in an ice bath. Sodium borohydride (12.2g, 0.33 mole) is added to the round bottom flask at 5 deg C. 1,1,1-trifluoropropanone (105g, 0.93 mole) is added drop wise to the reaction mixture using pressure equalizing funnel. The temperature of reaction is maintained below 10 deg C. After completion of reaction 110 g azeotrope of water (5.5% by Karl Fischer method) and 1,1,1-trifluoroisopropanol is distilled off from the reaction mixture.
Example 2-
Charging a solution of sodium hydroxide (200 g, IM) in a round bottom flask attached
with a condenser, pressure-equalizing funnel and temperature sensor. The whole
assembly is kept in an ice bath. Sodium borohydride (9.22g, 0.243 mole) is added to the
round bottom flask at 5 deg C. 1,1,1-trifluoropropanone (105g, 0.93 mole) is added drop
wise to the reaction mixture using pressure-equalizing funnel. After completion of
reaction 107 g azeotrope of water (6.0%) and 1,1,1-trifluoroisopropanol is distilled off
from the reaction mixture.
Example 1 and 2 have been performed with same reaction conditions and quantity of
reagents and the same result.
Example 3-
1,1,1-trifluoroisopropanol azeotrope with 5% water (500g) and n-pentane (75g) were charged to a distillation assembly fitted with the Dean Stark apparatus. The contents were refluxed at 75 deg C. An aqueous layer (36 g) was collected from the Dean Stark apparatus containing 77% water. Thereafter the Dean Stark apparatus was replaced with a reflux divider and the contents were distilled. The first cut from distillation consisted of a fraction containg n-pentane and thereafter pure 1,1,1-trifluoroisopropanol (446g, 99.9% purity by GC) having 0.05% water was collected.

WE CLAIM:
1. A process for preparation of 1,1,1-trifluoropropanol comprising reacting 1,1,1-trifluoropropanone with an alkali borohydride in aqueous medium.
2. The process as claimed in claim 1, wherein alkali borohydride is selected from group consisting of lithium borohydride, sodium borohydride, potassium borohydride and sodium cyano borohydride.
3. The process as claimed in claim 1 or 2, wherein the alkali borohydride is in solid form, powdered form in their aqueous solution or in form of solution in aqueous alkali hydroxide.
4. The process as claimed in claim 1, wherein the ratio of alkali borohydride to that of 1,1,1-trifluoropropanone is in the range from 0.25 mole equivalent to one mole equivalent, preferably 0.3 to 0.5 mole equivalents.
5. The process as claimed in claim 1, wherein the aqueous solution is prepared from water or an aqueous alkali hydroxide.
6. The process as claimed in claim 1, wherein the alkali hydroxides is selected from group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide and cesium hydroxide, preferably sodium and potassium hydroxide.
7. The process as claimed in claim 1, wherein the concentration of alkali hydroxide solution is in range from 0.001 to 5 M, preferably from 0.5 to 1.5 M solution.
8. The process as claimed in claim 1, wherein the ratio of amount of water or aqueous alkali hydroxide by weight to that of 1,1,1-trifluoropropanone is in the range of 1:4 to 10:1, preferably from 1:1 to 1:2.

9. The process as claimed in claim 1, wherein the process is performed at a
temperature range of -10° C. to +30° C.
10. The process as claimed in claim 1, wherein 1,1,1-trifluoroisopropanol obtained is
recovered by azeotropic distillation using n-pentane as entrainer.
11. The process as claimed in claim 10, wherein the feed to distillation assembly is a heterogeneous mixture of aqueous alcohol and n-pentane comprising between 80 and 90% by weight of alcohol, between 5 and 10 by weight of water and between 5 and 10% of n-pentane.
12. The process of preparation of 1,1,1-trifluoroisopropanol such as herein described with reference to foregoing examples.