Process for synthesis of primary or higher alcohol
Filed of the invention
The present invention relates to chemical synthesis of primary or higher alcohols from its corresponding acids.
Background of Invention:
Alcohols are used as a solvent for a wide variety of chemical, textile and medicinal
processes, in organic synthesis and as a chemical intermediate. They are also used as paint thinner and a solvent in other coating applications where it is used as a relatively slow evaporating latent solvent in lacquers and ambient-cured enamels. These alcohols find other uses such as a component of hydraulic and brake aids. It is also used as a base for perfumes, but on its own has a highly alcoholic aroma. Methanol, elhanol, propanol, butanol etc. are considered as a potential biofuel. Butanol at 85 percent strength can be used in cars without any change to the engine and it produces as much power as gasoline. Salts of butanol are chemical intermediates for example alkali metal salts of tert-bulanol are tert-but oxides.
Although at present a huge amount of research is going for green process for production of primary or higher alcohols through fermentation and genetic improvement of organisms still the processes are not economical due to lesser product yield, product inhibition, formation of multiple products and separation of the formed products.
Carboxylic acids have one property that distinguishes them from most other organic compounds -the acidity of these compounds arises from the resonance stabilization of the conjugate Carboxylic acids that undergo hydrogen bonding. However, in carboxylic acids function as a hydrogen bond donor and acceptor in the same molecule as well. These acids thus form highly stable dimers and the same cannot even be broken down by distillation - which explains why the boiling point for these acids is so high. To reduce the stability of these acids, enormous energy is required. This becomes a major

impediment of conversion such acids into corresponding alcohols. Contrary to that, hydrogenation by reducing agent and catalytic hydrogenation of carboxylic acid derivatives can produce various alcohols. However, the existing processes suffer from low yield and conversion due to the selective hydrogenation of carboxylic acid.
US patent 7,179,925 discloses a process for the reduction of an aliphatic, aromatic or heterocyclic organic compound by a hydride and/or a derivative in liquid or dissolved form with at least one hydride derivative or borohydride derivative, in a reactor for a residence time, and optionally isolating the reduced organic compound from the reaction mixture.
US patent 5,091,595 describes the syntheses for the preparation of 2-phenyl-l,3-propanediol, a useful intermediate for the preparation of 2-phenyI-l,3-propanedioI bicarbonate, by selective reduction of diethyl phenylmalonate with the Lewis acid type metal hydrides diisobulylaluminum hydride (DIBAH) or borane dimethylsulfide (BMS) in solution with heterocyclic ethers are disclosed.
U.S. patent 2848459 discloses the preparation of arylpropanediols wherein an ester of an aryl acetic acid, such an benzoylacetic acid, prepared by condensing benzoic acid ester with an ester of acetic acid, employing a basic substance, such as sodium ethoxide, as a catalyst is treated with a chlorinating agent, such as sulfuric chloride, to yield benzoyldichloroacetic acid, ethyl ester.
Benzoyldichloroacetic acid, ethyl ester is subsequently reduced to 2,2-dichloro-l-phenyl-1.3-propanedtol by reduction with lithium aluminum hydride in anhydrous ether.
U.S. patent 2,884,444 depicts the preparation of 2-phenyl-l, 3-propanediol by reduction of the corresponding 2-substituted malonic ester, diethyl phenyl Maloney. with lithium aluminum hydride in ethyl ether. 2-phenyl-l,3-propanediol is an intermediate in the synthesis of 2-phenyi-l,3-propanedioi bicarbonate an important anticonvulsant known generically as Fleabane,

The preparation of 2-phenyl-1.3-propanediol by reduction of diethyl phenyl malonate with lithium aluminum hydride in ethyl ether as taught in U.S. Pat. No. 2,884,444 gives yields ranging from a low of about 30% of product to a high of only about 50% of 2-phenyl-1,3-propanediol.
None of the cited art discloses the conversion of organic acid to its corresponding alcohol using transition metal hydride to promote selective hydrogenation or hydride addhion so that complete utilization of catalyst takes place and facilitate maximum conversion. Also the existing processes suffer from formation of acid intermediate as ester etc.
Object of the present invention;
I'he primary object of the present invention is to develop a process of conversion of organic acids into its corresponding alcohols with higher yield and conversion.
Summary of the invention:
In view of the above said the instant application discloses a process for effective production of organic alcohol from the corresponding acids as chemical resources by using low amount inorganic hydrides in presence of a transition metal catalyst. Sodium borohydride or lithium borohydride is a mild reducing agent with high selectivity. The combination of sodium borohydride with halide lewis acids with cobalt, nickel, iridium, osmium, copper, platinum, titanium, niobium, tantalum and rhodium halides, oxides etc or a transition metal with slightly acidic condition has been employed to reduce functional groups, which are inert to sodium borohydride alone.
Ill the present invention, the presence of a transition metal compound such as cobalt oxide, molybdenum oxide, nickel oxide. nickel nitrate, nickel chloride, tungsten. Iron's soluble sails etc, are used in these processes to produce metal boride to attract and release the hydride selectively to the carbonyl carbon site. In water solution of carboxylic acid gradually the carboxylic acid has been converted completely to alcohol.

Brief description of Figures:
Figure 1 a-b: GC pattern of Butyric acid as blank (a) and converted butanol (b).
Figure 2 a-b: GC pattern of acetic acid as blank (a) and converted elhano) (b).
Figure 3 a-b: GC pattern of propinic acid as blank (a) and converted
propanol(b)
Deatiled descirption of the invention:
Aeerodingly, the present invention provides a process of producing an alcohol from its corresponding acids by reducing an acids using hydride and/or a derivative thereof in the presence of a soluble salt of transition metals, wherein the ratio of hydride and salt of transition metal salt is in the range of 0.5 - 2 to 1 - 9,
In an aspect of the present invention the alcohol is selected from a group comprising ethanol, butanol, propanol.
In an aspect of the present invention the alcohol is butanol.
In another aspect of the present invention the alcohol is ethanol.
In still another aspect of the present invention the alcohol is propanol. In yet another aspect of the present invention the hydride is selected from a group comprising boron hydride, aluminium hydride, tin hydride, silicon hydride, a derivative thereof or a mixture,.
In a further aspect of the present invention the soluble salt of transition metal is selected from a group comprising nickel, molybdenum, cobalt, tungsten. Niobium and iron-In a further more aspect of the present invention the ratio of hydride and metal sah is 1.5 to 6.

In one more aspect of the present invention the reduction reaction is carried out for a period in the range of 3 to 6 hours.
Examples:
The invention is illustrated by the following examples, which are provided to illustrate the invention and should not be construed as limitation in the inventive concept herein.
Example 1:
Conversion of butyric acid to its corresponding alcohol i.e. butanol was carried out by adding transition metal soluble sah as tantalum chloride, with Sodium borohydride / boron trifluoride methanol complex and Butyric acid in water. This reaction step is exothermic and the reaction media comprises 0.7 gm butyric acid in 100 ml solution, 1. 3 equivalent tantalum chloride and 7 equivalents NaBH4 and 1 equivalent of boron trifluoride methanol complex (Sigma Aldrich) in water. The temperature of the reaction maintained at 70"C. Reaction time was 6 hrs. The residue is treated with basic solution of 8% Sodium bicarbonate and extracted several times with dichloromethane. The combined organic layers are washed with water and brine, before being dried and evaporation of solvent, 'fhe alcohol production was measured against time in GC by Porapak Q column. The overall production of butanol is > 95%.as measured by GC.
Example 2:
The reduction was carried out by adding transition metal soluble salt as Niobium chloride, with Sodium borohydride / Iodine and Acetic acid in water is used. This reaction step is exothermic. In this reduction reaction, 0.24 gm acetic acid in 100 ml solution. 1.3 equivalent niobium chloride and 7 equivalents NaBH4 and 1 equivalent of Iodine in water. The temperature of the reaction should not exceed 70 C.
The reaction may deposit a black granular precipitate of boride. The alcohol production was measured against time in GC. The reaction was carried out tor 6 hrs. The residue is treated with basic solution (8% Sodium bicarbonate) and extracted several limes with dichloromethane. The combined organic layers are washed with water and brine, before

being dried and evaporation of solvent. The overall conversion of acetic acid to ethanol is about 75%. The estimation of alcohol done in GC using Porapak Q column.
Example 3:
The reduction was carried out by adding transition metal as iron powder with a very little amount of muriatic acid in presence of Sodium borohydride. In this reduction reaction, 30 mmol propionic acid, 0.4 equivalent fine iron powder and 0.1% muriatic acid in water was used with vigorous stirring (stirrer speed > 420 rpm). The temperature of the reaction was maintained at 40''C. After 4 hours the temperature was elevated to SO^C for the possible conversion of reaction.
The resultant mixture was washed with excess sodium sulfide to remove the iron hydroxide as iron sulfide. After filtration the alcohol production was measured in GC. The overall conversion of propionic acid to propanol is about 18%.

iVe Claim:
1. A process of producing an alcohol from its corresponding acids by reducing an acids using hydride and/or a derivative thereof in the presence of a soluble salt of transition metals, wherein the ratio of hydride and salt of transition metal salt is in the range ofO.5-2 to 1 - 9.
2. A process as claimed in claim 1, wherein the alcohol is selected from a group comprising ethanol, butanol, propanol,
3. A process as claimed in claim 2, wherein the alcohol is butanol.
4. A process as claimed in claim 2, wherein the alcohol is ethanol.
5. A process as claimed in claim 2, wherein the alcohol is propanol.
6. A process as claimed in claim 1. wherein the hydride is selected from a group comprising boron hydride, aluminium hydride, tin hydride, silicon hydride, a derivative thereof or a mixture.,
7. A process as claimed in claim 1, wherein the soluble salt of transition metal is selected from a group comprising nickel, molybdenum, cobalt, tungsten. Niobium and iron.
8. A process as claimed in claim 1, wherein the ratio of hydride and metal salt is 1.5 to 6.
9. A process as claimed in claim 1, wherein the reduction reaction is carried out for a period in the range of 3 to 6 hours.

10. A process of producing an alcohol from its corresponding acids substantially ashereindescribed with reference to the accompanying drawings.