Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1994-01-12
1995-01-31
Prescott, Arthur C.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
562581, C07C32352, C07C31900
Patent
active
053860560
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for producing 2-hydroxy-4-methylthiobutanoic acid, which is useful as a feed additive for livestock, for instance.
BACKGROUND ART
A process is known for the production of 2-hydroxy-4-methylthiobutanoic acid which comprises preparing 2-hydroxy-4-methylthiobutyronitrile from acrolein, methanethiol and hydrogen cyanide and hydrating said 2-hydroxy-4-methylthiobutyronitrile in the presence of an excess of sulfuric acid. Since the reactions involved therein can be conducted in a relatively easy manner and give the product in high yields, this process is in use on a commercial scale.
However, the process mentioned above produces waste sulfuric acid and ammonium sulfate in large amounts. Treatment steps for these by-products are thus necessary and much energy is expended in such steps, hence the cost of production of 2-hydroxy-4-methylthiobutanoic acid increases. Discharging large amounts of ammonium sulfate or any other sulfate salt into the natural world is undesirable from the view-point of environmental protection.
Accordingly, it is an object of the invention to provide a process for producing 2-hydroxy-4-methylthiobutanoic acid efficiently and at low cost without causing formation of large amounts of waste.
The following publications may be cited as other prior art with reference to the present invention. Japanese Patent Publication No. 7925/1971 discloses a method of producing 2-hydroxy-4-methylthiobutyronitrile from acrolein cyanohydrin. Japanese Patent Publication No. 28943/1987 discloses a method of producing carboxylic acid esters by reacting a formate ester with a carboxylic acid amide. Japanese Patent Laid-open No. 290653/1989 discloses a method of producing methyl methacrylate using acetone and methyl formate as starting materials. Further, Japanese Patent Laid-open No. 235846/1990 discloses a method of producing methyl formate by dehydrogenating methanol.
However, in these publications is not disclosed a process for producing 2-hydroxy-4-methylthiobutanoic acid which comprises hydrating 2-hydroxy-4-methylthiobutyronitrile, allowing the resulting 2-hydroxy-4-methylthiobutanamide to react with methyl formate to form methyl 2-hydroxy-4-methylthiobutanoate, and hydrolyzing said methyl 2-hydroxy-4-methylthiobutanoate to form 2-hydroxy-4-methylthiobutanoic acid.
DISCLOSURE OF THE INVENTION
The present inventor made intensive investigations to achieve the above object and, as a result, found that 2-hydroxy-4-methylthiobutanoic acid can be obtained very efficiently without causing formation of large amounts of waste when 2-hydroxy-4-methylthiobutyronitrile is hydrated, the resulting 2-hydroxy-4-methylthiobutanamide is then reacted with methyl formate and the thus-formed methyl 2-hydroxy-4-methylthiobutanoate is further subjected to hydrolysis, whereby by-product recycling becomes possible and the use of sulfuric acid is substantially avoided. Based on this finding, the present invention has been completed.
The present invention thus provides a process for producing 2-hydroxy-4-methylthiobutanoic acid which comprises (1) the first step of hydrating 2-hydroxy-4-methylthiobutyronitrile for the formation of 2-hydroxy-4-methylthiobutanamide, (2) the second step of reacting the 2-hydroxy-4-methylthiobutanamide obtained in said first step with methyl formate for the formation of methyl 2-hydroxy-4-methylthiobutanoate and formamide and (3) the third step of hydrolyzing the methyl 2-hydroxy-4-methylthiobutanoate obtained in said second step for the formation of 2-hydroxy-4-methylthiobutanoic acid and methanol.
Hydrogen cyanide obtained by dehydrating said formamide can be utilized as a raw material for said 2-hydroxy-4-methylthiobutyronitrile.
DETAILED DESCRIPTION OF THE INVENTION
A reaction scheme in the process of the present invention is shown as follows, for instance. ##STR1##
2-Hydroxy-4-methylthiobutyronitrile to be used as the starting material in the first step mentioned above can be produced by a conventional method from hydrogen cyanide,
REFERENCES:
patent: 4451486 (1984-05-01), Baker et al.
patent: 4524077 (1985-06-01), Ruest et al.
patent: 4855495 (1989-08-01), Takano
patent: 4912257 (1990-03-01), Hernandez et al.
Daicel Chemical Industries Ltd.
Prescott Arthur C.
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