Reduction of odor of monothiocarbonate compound by addition of acidifying agent

Abstract

A method for reducing the odor of a compound having at least one five-membered cyclic monothiocarbonate group, referred to for short as a monothiocarbonate compound, is provided, in which the monothiocarbonate compound is in a liquid phase and is contacted with an oxidizing agent.

Description

Technical Field

[0001] The object of the present invention is a method for reducing the odor of a compound having at least one five-membered cyclic monothiocarbonate group, wherein the organic sulfur compound is in the liquid phase and is contacted with an oxidizing agent.

Background Art

[0002] Organic sulfur compounds are valuable compounds having various desired properties caused by the sulfur content. These can be obtained by chemical reactions involving the use of mercaptans, sulfur or sulfides as reactants.

[0003] However, the resulting organic sulfur compounds often have an unpleasant odor, which is probably due to the presence of unwanted volatile by-products containing sulfur in the form of mercapto groups, or any unreacted starting materials having sulfur atoms.

[0004] An example of an organic sulfur compound is cyclic monothiocarbonate. The appropriate synthesis of cyclic monothiocarbonate is described in WO2019 / 034469A1. However, the resulting monothiocarbonate has an unpleasant or offensive odor caused by sulfur-containing by-products.

[0005] The oxidation of sulfur compounds to the corresponding sulfoxide compounds using hydrogen peroxide is described by A. Devender Rao, CH. Ravishankar, and V. Malla Reddy in Indian J. Pharm. Sci. 1986, 48 (1), pages 13 to 15. Table 1 on page 14 includes linear thiocarbonate compounds (see Compounds II d and II j), and these linear thiocarbonate compounds are easily oxidized.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The object of the present invention is to provide an easy and economical method for reducing the odor of organic sulfur compounds while maintaining the sulfur compounds as they are.

Means for Solving the Problems

[0007] It has now been found that the odor-reduced monothiocarbonate compound can be obtained by a method using a specific oxidizing agent.

[0008] Accordingly, the present invention relates to a method for reducing the odor of a compound having at least one 5-membered cyclic monothiocarbonate group, wherein the organic sulfur compound is in a liquid phase and is brought into contact with an oxidizing agent.

Mode for Carrying Out the Invention

[0009] Monothiocarbonate compound A compound having at least one 5-membered cyclic monothiocarbonate group is abbreviated as a "monothiocarbonate compound".

[0010] Any reference to a "monothiocarbonate compound" includes a mixture of different monothiocarbonate compounds unless otherwise specified or clear from the context.

[0011] One 5-membered cyclic monothiocarbonate group is preferably a ring system having 5 members, 3 of which are those of monothiocarbonate -O-C(=O)-S-, and the other 2 members are carbon atoms closing the 5-membered ring.

[0012] The monothiocarbonate compound can contain, for example, up to 1000, particularly up to 500, preferably up to 100 5-membered cyclic monothiocarbonate groups.

[0013] In a preferred embodiment, the monothiocarbonate compound contains 1 to 10, especially 1 to 5 five-membered cyclic monothiocarbonate groups. In the most preferred embodiment, the monothiocarbonate compound contains 1 to 3, especially 1 or 2 five-membered cyclic monothiocarbonate groups.

[0014] The monothiocarbonate compound can have a molecular weight of up to 500,000 g / mol, for example. Preferred monothiocarbonate compounds have a molecular weight of up to 1000 g / mol. Most preferably, the compound has a molecular weight of up to 500 g / mol.

[0015] In a preferred embodiment, the monothiocarbonate compound does not contain any primary or secondary amino groups.

[0016] In a particularly preferred embodiment, the monothiocarbonate compound does not contain any functional groups other than a monothiocarbonate group, a carboxylic acid ester group or an ether group, or a chloride.

[0017] The term "chloride" as used herein is the common name for a covalently bonded Cl atom.

[0018] Suitable monothiocarbonate compounds having one five-membered cyclic monothiocarbonate group are disclosed in WO2019 / 034470. Preferred monothiocarbonate compounds having one five-membered cyclic monothiocarbonate group are of formula (I):

[0019]

Chemical formula

[0020] Suitable monothiocarbonate compounds having more than one five-membered cyclic monothiocarbonate group are disclosed, for example, in WO2019 / 034473A1. Preferred monothiocarbonate compounds having more than one five-membered cyclic monothiocarbonate group are of formula (II):

[0021] [Chemical formula] [wherein R 1b ~R 4b each independently represents hydrogen or an organic group having up to 50 carbon atoms, or two carbon atoms of R 2b , R 4b and the monothiocarbonate group may together form a 5- to 10-membered carbocyclic ring, and one of the groups R 1b ~R 4b is a linking group to Z, n represents an integer of at least 2, and Z represents an n-valent organic group] is a compound of.

[0022] Various methods are known for the preparation of monothiocarbonate compounds.

[0023] According to U.S. Patent No. 3,072,676 and U.S. Patent No. 3,201,416, ethylene monothiocarbonate can be prepared by a two-step method. In the first step, mercaptoethanol and chloro carboxylate are reacted to obtain hydroxyethylthiocarbonate, which is heated in the presence of a metal salt catalyst in the second step to form ethylene monothiocarbonate.

[0024] According to U.S. Patent No. 3,517,029, alkylene monothiocarbonate is obtained by reacting mercaptoethanol and carbonate diester in the presence of a catalytically active salt of thorium.

[0025] According to the method disclosed in U.S. Patent No. 3,349,100, alkylene monothiocarbonate is obtained by reacting an epoxide with carbonyl sulfide.

[0026] Synthesis using phosgene as a starting material is known from U.S. Patent No. 2,828,318. Phosgene is reacted with hydroxymercaptan.

[0027] Preferably, the monothiocarbonate compound used in the purification method defined above is - Reacting a compound having at least one epoxy group or at least one halohydrin group with phosgene or alkyl formate to obtain an adduct, and - Then reacting the adduct with a compound containing anionic sulfur, - Optionally, subsequently further treating the obtained crude product by extraction or distillation is a compound obtained as a product by a method comprising.

[0028] The above methods are disclosed in WO2019 / 034469A1 (using an epoxy compound in the reaction of the first step) and PCT patent application No. PCT / EP2020 / 051110 (using a halohydrin in the reaction of the first step).

[0029] The obtained monothiocarbonate compound usually contains by-products having a certain sulfur content. Such by-products cause a very unpleasant odor. In many cases, such by-products cannot be completely removed by standard treatments involving method steps such as distillation or one or more extractions, especially extraction with a base such as aqueous NaHCO 3 The odor of the monothiocarbonate compound is usually still bad even after such standard treatments.

[0030] The monothiocarbonate compound used in this method is in the liquid phase.

[0031] The monothiocarbonate compound obtained by the preparation method can be liquid or solid at 21 °C and 1 bar.

[0032] The monothiocarbonate compound that is liquid at 21 °C and 1 bar can be used as it is without using a solvent.

[0033] The monothiocarbonate compound that is solid at 21 °C and 1 bar is preferably used in the form of a solution.

[0034] Solvents suitable for the solid monothiocarbonate compound are protic solvents or, in particular, aprotic solvents.

[0035] Aprotic solvents may be hydrophobic solvents, such as hydrocarbons including aromatic hydrocarbons and chlorinated hydrocarbons, such as toluene, chlorobenzene or dichlorobenzene, chloroform, or hydrophilic solvents, such as acetonitrile or dimethyl sulfoxide, or esters, or ethers such as tetrahydrofuran, dioxane, polyethers or glymes.

[0036] Method Contact the monothiocarbonate compound with an oxidizing agent.

[0037] The term "oxidizing agent" includes a single oxidizing agent or a mixture of different oxidizing agents.

[0038] Suitable oxidizing agents are, in particular, oxygen, ozone, hydrogen peroxide, and any other inorganic compound having a high content of oxygen, such as a nitrogen compound containing oxygen, such as nitrogen dioxide, nitric acid, or any salt thereof or, in particular, an inorganic peroxide.

[0039] Such inorganic peroxides can be metal salts with anions selected from acids or salts, in particular perchlorates, permanganates, chromates, hypochlorites or perborates, preferably perchlorates, permanganates or perborates.

[0040] Particularly preferred oxidizing agents are hydrogen peroxide and nitric acid (HNO 3 ).

[0041] Most preferred is hydrogen peroxide.

[0042] The oxidizing agent is preferably used in the form of a solution, particularly an aqueous solution. The concentration of the oxidizing agent in the aqueous solution is preferably less than 50% by weight, more preferably less than 40% by weight. Preferably, the concentration of the oxidizing agent in the aqueous solution is at least 5% by weight, more preferably at least 10% by weight.

[0043] The oxidizing agent is used in an amount of preferably at least 5 mol, especially at least 10 mol, per 100 mol of the organic sulfur compound.

[0044] The oxidizing agent is used in an amount of preferably at most 40 mol, especially at most 30 mol, more preferably at most 20 mol, per 100 mol of the organic sulfur compound, i.e., the monothiocarbonate compound.

[0045] The oxidizing agent can be contacted with the organic sulfur compound, i.e., the monothiocarbonate compound, in any suitable manner.

[0046] In a preferred embodiment of the method, the oxidizing agent is added to the organic sulfur compound, i.e., the monothiocarbonate compound, which is in the liquid state.

[0047] The contact between the oxidizing agent and the organic sulfur compound, i.e., the monothiocarbonate compound, is preferably carried out at a temperature of at least 20°C, especially at least 30°C, more preferably at least 40°C, most preferably at least 50°C, particularly at least 55°C. Preferably, the temperature is at most 150°C, especially at most 100°C.

[0048] The contact time is preferably from 5 minutes to 10 hours, more preferably from 10 minutes to 6 hours, more preferably from 20 minutes to 3 hours, most preferably from 30 minutes to 2 hours.

[0049] Any solvent used in combination with an organic sulfur compound, i.e., a monothiocarbonate compound, can be removed, for example, by distillation.

[0050] The process of the present invention can be a batch process, a semi - continuous process or a continuous process. In a continuous process, all starting materials are continuously fed into the reactor and all products are continuously withdrawn, whereby the oxidizing agent can be separated from the product stream by conventional means, for example, by distillation, filtration or precipitation as appropriate, or by a decomposition reaction.

[0051] The process of the present invention can be used in combination with other purification and odor reduction methods, for example, extraction methods, such as extraction with a base, such as aqueous NaHCO 3 , adsorption methods using metal oxides as adsorbents, or methods in which by - products are removed by a chemical reaction or converted to non - problematic compounds.

[0052] The monothiocarbonate compounds obtained by this process have a significantly reduced odor. It is clear that the oxidation method has no significant effect on the monothiocarbonate itself, and no oxidation of the monothiocarbonate compound itself was observed. The oxidation method seems to have a major effect only on the undesirable, probably volatile, by - products resulting from the synthesis method. Oxidation of the organic sulfur compound itself is not observed or is hardly observed. Usually, less than 10 mol%, especially less than 5 mol%, most preferably less than 2 mol%, and individually less than 1 mol% of the monothiocarbonate compound reacts with the oxidizing agent itself and migrates into the oxidation products.

[0053] [Examples] Synthesis of 5 - [4 - [(2 - oxo - 1,3 - oxathiolan - 5 - yl)methoxy]butoxymethyl]-1,3 - oxathiolan - 2 - one of the following formula, abbreviated as butanediol dithiocarbonate or BDO - TC.

[0054] [Chemistry]

[0055] This synthesis was carried out according to the method disclosed in WO2019 / 034469A1.

[0056] In the first step of the synthesis, the epoxide 1,4-butanediol diglycidyl ether was reacted with phosgene as described in WO2019 / 034469A1.

[0057] In the second step, the obtained β-chloroalkyl chloroformate ([2-chloro-1-[4-(3-chloro-2-chlorocarbonyloxy-propoxy)butoxymethyl]ethyl] carbonochloridate) (845 g, 2.1 mol) and dichloromethane (2.5 L) were placed into an 8-liter reactor. After cooling the solution to 0 °C, Na 2 S (2.2 equivalents, 15 wt% aqueous solution) was slowly added while maintaining the temperature at 5 °C. After complete addition, the reaction mixture was warmed to room temperature and stirred for 1 hour. The phases were separated, and the aqueous phase was extracted with dichloromethane (1 × 0.5 L). The combined organic phases were extracted with water (3 × 0.5 L), dried over Na 2 SO 4 and filtered through Celite 545 (300 g per 1 kg of the initial chloroformate). The solvent was removed from the organic phase under reduced pressure, and the desired product was obtained as a clear viscous liquid (656 g, 96%).

[0058] The above synthesis was carried out with two different grades of 1,4-butanediol diglycidyl ether.

[0059] One grade is a relatively pure grade with a minor content of other epoxides, especially high molecular weight epoxides.

[0060] The other grade was an industrial grade containing a significant content of other epoxides.

[0061] Therefore, two different products were obtained from the synthesis.

[0062] One product, designated as "pure BDO-TC", has a BDO-TC content of 84.2 area % as measured by gas chromatography.

[0063] The other product, designated as "industrial BDO-TC", has a BDO-TC content of 61.3 area % as measured by gas chromatography.

[0064] Examples 1 - 8 Oxidation Individual BDO-TC (5 g) was dissolved in toluene (10 g), and an aqueous solution of the oxidizing agent (30 wt % H 2 O 2 , 0.1 molar aqueous solution of KMnO 4 ) was added. The mixture was stirred for 30 minutes at individual temperatures. After phase separation, the organic phase was washed twice with water (v / v 1:1) at the same temperature. After the final phase separation, toluene was removed from the organic phase under reduced pressure, and BDO-TC was obtained as a viscous liquid.

[0065] KMnO 4 solution was used in an amount of 1 volume per volume of BDO-TC.

[0066] H 2 O 2 solution was used in an amount of 10 mol of H 2 O 2 per 100 mol of BDO-TC.

[0067] The gas chromatograph of BDO-TC obtained after oxidation showed no additional peaks related to the oxidation products of BDO-TC itself.

[0068] Test The odor of the obtained BDO-TC was tested immediately. The samples were tested at room temperature by three different people. The participants reported their olfactory evaluations according to the following classification scheme.

[0069] 1: Odorless 2: Slight musty odor 3: Slight "mercaptan odor" 4: "Mercaptan odor" 5: Distinct "mercaptan odor"

[0070] Before treatment with the oxidizing agent, pure BDO-TC had an odor classified as 4.

[0071] Before treatment with the oxidizing agent, industrial BDO-TC had an odor classified as 5.

[0072] [Table 1]

[0073] Examples 9 - 12 Combination of oxidation and other treatments a) Combination of oxidation and removal of impurities by chemical reaction (Michael addition to double bonds) Individual BDO-TC (5 g) was dissolved in toluene (10 g), and methyl methacrylate (MMA) was added. The mixture was stirred at 25 °C for 30 minutes. Then, H 2 O 2 (30% aqueous solution) was added at 25 °C, and the mixture was stirred for an additional 30 minutes. After phase separation, the organic phase was extracted with water (v / v 1:1). All volatiles and toluene were removed from the organic phase under reduced pressure to obtain BDO-TC as a viscous liquid.

[0074] b) Combination of oxidation and extraction Individual BDO-TC (5 g) was dissolved in toluene (10 g) and extracted twice with NaHCO 3 aqueous solution (v / v 1:1) at 25 °C, followed by extraction with water (v / v 1:1). Then, H 2 O 2 (30% aqueous solution) was added at 25 °C, and the mixture was stirred for an additional 30 minutes. After phase separation, the organic phase was extracted with water (v / v 1:1). All volatiles and toluene were removed from the organic phase under reduced pressure to obtain BDO-TC as a viscous liquid.

[0075]

Table 2

Chem.

Chem.

Claims

1. A method for reducing the odor of a compound having at least one five-membered cyclic monothiocarbonate group, abbreviated as a monothiocarbonate compound, comprising: the monothiocarbonate compound is in a liquid phase and is contacted with an oxidizing agent, the monothiocarbonate compound is of formula (I): 【Chemical 1】 [wherein R 1a to R 4a each independently represent hydrogen or an organic group having 50 or fewer carbon atoms, or R 2a, R 4a and two carbon atoms of the monothiocarbonate group may together form a 5- to 10-membered carbocyclic ring] a compound of, or formula (II): [Chemical Formula 2] [wherein R 1b to R 4b each independently represent hydrogen or an organic group having 50 or fewer carbon atoms, or R 2b, R 4b and two carbon atoms of the monothiocarbonate group may together form a 5- to 10-membered carbocyclic ring, and one of the groups R 1b to R 4b is a linking group to Z, n represents an integer of at least 2, and Z represents an n-valent organic group] a compound of, or a mixture thereof wherein, the monothiocarbonate compound does not contain a monothiocarbonate group, a carboxylic acid ester group or an ether group, or other functional groups other than chlorides, the monothiocarbonate compound contains 1 to 3 five-membered cyclic monothiocarbonate groups, the oxidizing agent is hydrogen peroxide or an inorganic peroxide, and the inorganic peroxide is a metal salt with an anion selected from perchlorate, permanganate, perchromate, hypochlorite or perborate.

2. The method according to claim 1, wherein n represents an integer of 2 or 3.

3. The organic groups defined as R 1a to R 4a in formula (I), the organic groups defined as R 1b to R 4b in formula (II) and the n-valent organic group defined as Z may each independently contain at least one group selected from the group consisting of a carboxylic acid ester group or an ether group, and a chloride, or may be substituted by at least one group selected from the group consisting of a carboxylic acid ester group or an ether group, and a chloride. The method according to claim 1 or 2.

4. The monothiocarbonate compound is - reacting a compound having at least one epoxy group or at least one halohydrin group with phosgene or alkyl formate to obtain an adduct, and - Subsequently, reacting the adduct with a compound containing anionic sulfur, - Optionally, subsequently further treating the obtained crude product by extraction or distillation, a method according to any one of claims 1 to 3, obtained as a product.

5. The method according to any one of claims 1 to 4, wherein the oxidizing agent is hydrogen peroxide.

6. The method according to any one of claims 1 to 5, wherein the oxidizing agent and the monothiocarbonate compound are contacted at 10 to 100 °C.

7. The method according to claim 6, wherein the contact time is from 5 minutes to 10 hours.

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