Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C319/00—Preparation of thiols, sulfides, hydropolysulfides or polysulfides
  • C07C319/02—Preparation of thiols, sulfides, hydropolysulfides or polysulfides of thiols
  • C07C319/04—Preparation of thiols, sulfides, hydropolysulfides or polysulfides of thiols by addition of hydrogen sulfide or its salts to unsaturated compounds

Definitions

• the present invention relates to a new process for the manufacture of the mercaptocarboxylic acids represented by formula (I):
• R 1 represents hydrogen or HO-C-
• R 2 represents hydrogen or methyl
• mercaptocarboxylic acids are useful as synthesis intermediates towards esters (for example with 2-ethylhexanol, pentaerythritol) used either to obtain the tin salts (PVC stabilizers), or as hardeners or modifiers of epoxy resins (adhesives ), polyurethanes (optical glasses).
• Mercapropropionic acid can also be used to modify acrylic polymers (paper industry, paint).
• a direct route for obtaining mercaptopropionic acid is from acrylic acid, a cheap raw material.
• the other technique, consisting in reacting acrylic acid with CS 3 Na 2 makes it possible to improve the selectivity in mercaptopropionic acid and to operate without pressure of H 2 S.
• the use of CS 2 and methanol as co-solvent weighs down the process, especially with regard to the treatment of effluent
• R 1 R 2 SH A, R 1 , R 2 being as defined below.
• CS 2 plays the role of coreactive and prevents the sulfide from forming:
• the present invention is essentially focused on the beneficial effect of the solubility of H 2 S in the reaction medium which promotes the formation of mercaptan.
• the fact of operating with a supply of H 2 S causes the sulphide S [CH - CH - COOH] 2 to pass directly to the desired mercaptan,
• sulfhydrates are therefore reacted with the unsaturated carboxylic acids, according to the following overall reaction (case where the sulfhydrate is represented by ASH:
• O 0 A alkali metal or ammonium cation
• the present invention therefore relates to a process for the manufacture of a mercaptocarboxylic acid represented by formula (I) as defined above, according to which an unsaturated carboxylic acid of formula (II) is reacted:
• R 1 -CH CR 2 -C-OH (II)
• R 1 and R 2 are as defined above, with a sulfhydrate of formula ASH, A being an alkali metal cation or a cation NR 3 R 4 R 5 R 6+ , R 3 to R 6 each representing H or hydrocarbon radical, or of formula Q (SH) 2 , Q being an alkaline earth metal cation, and the resulting reaction medium is acidified to obtain the research compound (I), characterized in that the reaction is carried out with an addition of H 2 S other than that provided by the neutralization of the acid (II).
• the starting acid (II) is chosen in particular from acrylic acid, methacrylic acid, maleic acid and fumaric acid.
• the reaction according to the invention can be carried out in an aqueous medium, but an improvement in the selectivity can be obtained by using a hydroalcoholic or purely alcoholic medium.
• This alcoholic medium, or the alcohol fraction of the hydroalcoholic medium is formed for example by methanol, propanol, isopropanol or a mixture of these alcohols.
• An important parameter which regulates the selectivity for mercapto carboxylic acid (I) is the molar ratio H 2 S / acid (II) in solution. The higher the concentration of H 2 S in solution, the better the selectivity for acid (I). If one operates without the addition of H 2 S other than that provided by the neutralization of the acid (II), this ratio is 1.
• H 2 S If H 2 S is introduced into the system in reaction, its solubility in the medium reaction depends on several physical factors: dilution of the medium (the actual molar ratio in H 2 S solution / acid (II) will be higher); - use of an alcoholic or hydroalcoholic environment; pressure increase in H 2 S; and to a lesser degree, decrease in temperature; as well as the H 2 S / acid (II) ratio in solution.
• H 2 S into the medium by direct external supply and / or to produce H 2 S in situ by reaction of the sulphhydrate with at least one acid introduced into the medium, according to the following reaction (with ASH):
• This acid can be chosen from saturated organic acids of formula RCOOH, R representing in particular a C 1 -C 4 alkyl residue which can carry substituents such as halogens, and from mineral acids.
• the RCOOH acid is advantageously chosen from acetic acid, propionic acid and 3-chloro-propionic acid. If it is desired to obtain 3-mercapto-propionic acid, the operation is advantageously carried out in the presence of 3-chloro-propionic acid, which will itself lead to the desired 3-mercapto-propionic acid, in accordance with following reactions:
• the operation is advantageously carried out under a H 2 S pressure of at least 8 bars, in particular from 8 to 30 bars.
• the reaction temperature it is advantageously between 10 and 150 ° C. In the case of obtaining 3-mercapto-propionic acid, this temperature is generally from 20 to 100 ° C.
• the concentration of acid (II), expressed in moles per liter of solvent (water or alcohol or water + alcohol), is generally between 0.5 and 4.
• the sulphhydrate ASH or Q (SH) 2 can be prepared a part and injected into the reactor, or else be formed in situ, at least in part, by reaction in aqueous or alcoholic or hydroalcoholic medium of H 2 S with AOH or Q (OH) 2 , A and Q being as defined above above.
• the sulfhydrate can be obtained by reaction of H 2 S with soda, potash, lime, amines, ammonia.
• One of the advantages of the process according to the present invention is that it can be applied in existing industrial installations, already optimized for the synthesis of mercaptocarboxylic acids from chlorinated carboxylic acids (thioglycolic acid for example).
• the process of the invention is carried out in an aqueous or hydroalcoholic or alcoholic medium, without the use of CS 2 and without operating in a large excess of H 2 S.
• Another economic advantage is that of not form one molecule of salt per molecule of mercaptocarboxylic acid if H 2 S from an external source is used, unlike the procedures starting from halogenated carboxylic acids, which, when transformed into mercaptans, form 2 moles of salt to eliminate.
• H 2 S is introduced into the autoclave to keep the pressure constant at 25 bars for the duration of the test.
• the temperature is brought to 40 ° C., and 48 g of acrylic acid, ie 0.66 mol, are introduced into the reactor using a pump.
• thiomalic acid is obtained in solution, at a rate of 1.50 mole, or 225 g. This corresponds to a yield of 75% in thiomalic acid compared to maleic acid.

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• Chemical & Material Sciences (AREA)
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• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 1995
  • 1995-12-11 FR FR9514638A patent/FR2742146B1/fr not_active Expired - Fee Related
• 1996
  • 1996-12-10 EP EP96941731A patent/EP0876339B1/fr not_active Expired - Lifetime
  • 1996-12-10 WO PCT/FR1996/001970 patent/WO1997021672A1/fr not_active Ceased
  • 1996-12-10 JP JP52179697A patent/JP4046353B2/ja not_active Expired - Fee Related
  • 1996-12-10 CA CA002239100A patent/CA2239100C/fr not_active Expired - Fee Related
  • 1996-12-10 DE DE69610335T patent/DE69610335T2/de not_active Expired - Lifetime
• 2000
  • 2000-11-16 US US09/713,189 patent/US6689907B1/en not_active Expired - Fee Related

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