CA1075245A - Process for preparation of mercaptobenzothiazole - Google Patents
Process for preparation of mercaptobenzothiazoleInfo
- Publication number
- CA1075245A CA1075245A CA270,762A CA270762A CA1075245A CA 1075245 A CA1075245 A CA 1075245A CA 270762 A CA270762 A CA 270762A CA 1075245 A CA1075245 A CA 1075245A
- Authority
- CA
- Canada
- Prior art keywords
- mercaptobenzothiazole
- benzothiazole
- sulfur
- aniline
- reaction
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D277/00—Heterocyclic compounds containing 1,3-thiazole or hydrogenated 1,3-thiazole rings
- C07D277/60—Heterocyclic compounds containing 1,3-thiazole or hydrogenated 1,3-thiazole rings condensed with carbocyclic rings or ring systems
- C07D277/62—Benzothiazoles
- C07D277/68—Benzothiazoles with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached in position 2
- C07D277/70—Sulfur atoms
- C07D277/72—2-Mercaptobenzothiazole
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Thiazole And Isothizaole Compounds (AREA)
Abstract
IMPROVED PROCESS FOR PREPARATION OF
MERCAPTOBENZOTHIAZOLE
ABSTRACT OF THE DISCLOSURE
In the preparation of 2-mercaptobenzothiazole by the reaction of aniline, sulfur and carbon disulfide, less than desirable yields of 2-mercaptobenzothiazole are obtained and valuable reactants are lost in a tarry by-product residue co-produced. These by-products must be removed from the mercaptobenzothiazole before the material is used commercially as an accelerator for the vulcanization of rubber. An improved process with increased yields of mercaptobenzothiazole of high purity are obtained when the tarry reaction by-product produced in said process is separated from the mercaptobenzothiazole, benzothiazole distilled therefrom and reacted with sulfur and carbon disulfide to produce mer-captobenzothiazole.
MERCAPTOBENZOTHIAZOLE
ABSTRACT OF THE DISCLOSURE
In the preparation of 2-mercaptobenzothiazole by the reaction of aniline, sulfur and carbon disulfide, less than desirable yields of 2-mercaptobenzothiazole are obtained and valuable reactants are lost in a tarry by-product residue co-produced. These by-products must be removed from the mercaptobenzothiazole before the material is used commercially as an accelerator for the vulcanization of rubber. An improved process with increased yields of mercaptobenzothiazole of high purity are obtained when the tarry reaction by-product produced in said process is separated from the mercaptobenzothiazole, benzothiazole distilled therefrom and reacted with sulfur and carbon disulfide to produce mer-captobenzothiazole.
Description
--- 10752~5 Thi~ invention relates to an improved process for pre-paring mercaptobenzothiazole.
U.S. Patent 3,031,073 describes the manufacture of mercaptobenzothiazole wherein aniline, sulfur and carbon di-sulfide are reacted together. In accordance with this patent, the residue left after separation of mercaptobenzothiazole from the crude reaction product, normally by a water immiscible organic solvent, after removal of the solvent, was recycled to an autoclave with fresh reactants. While this is alleged to represent an improvement in the yield of desired mercapto-benzothiazole, purification problems are introduced and the recycle product mercaptobenzothiazole so obtained is difficult to purify because of the continued recycling of the tars and other discolored and undesired reaction products. If the by-products are discarded, there is a loss of valuable materials.
Improvement in this process is desired, particularly the obtainment of maximum amounts of substantially color-free mer-captobenzothiazole from these by-product residues.
According to the invention there is provided in the process for preparing mercaptobenzothiazole by the reaction of aniline, sulfur and carbon disulfide, the improvement comprising separating the mercaptobenzothiazole formed from the other reaction by-products of said reaction, fractionating - said by-products to recover benzothiazole and heating said 1, benzothiazole with sulfur, whereby additional yields of i~ mercaptobenzothiazole are obtained.
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~075Z45 Typically the residue obtained after the 2-mercapto-benzothiazole is separated from the reaction product of aniline, culfur and carbon disulfide is fractionated to provide a fraction containing at least 90~ benzothiazole, which benzo-thiazole iA then heated with sulfur, and carbon disulfide if required to react with any aniline impurity in the benzothia-zole, to provide a high purity substantially color-free 2-mercaptobenzothiazole.
In the preparation of the 2-mercaptobenzothiazole by the reaction of aniline, sulfur and carbon disulfide, usually in about equimolar amounts, after the initial reaction, the crude mercaptobenzothiazole iQ normally solubilized in a caustic solution, which solution is then extracted with a solvent as toluene. The toluene removes the tar and other impurities from the mercaptobenzothiazole. In accordance with this invention this solvent solution is then distilled to remove the toluene and the fractionated to obtain benzo-thiazole. This benzothiazole fraction is then reacted with sulfur, and carbon disulfide if required, to obtain an improved yield of high purity mercaptobenzothiazole having improved color.
When the total by-product is recycled or further -reacted, conversion of this residue to some additional mercaptobenzothiazole is obtained; however, the resulting product is difficult to purify because of color and other impurities. In contrast, the distilled benzothiazole product, which normally contains a small amount of aniline, is readily -converted into 2-mercaptobenzothiazole in improved overall ; yields with the elimination of color and purification problems observed when recycling the total tarry by-product residue.
The impurities from the mercaptobenzothiazole reaction product are readily separated from the mercaptobenzo-thiazole with solvents. Preferably, aromatic solvents are used and those containing one aromatic ring including benzene, xylene, toluene, chlorobenzene, aniline and the like have been found to be useful. Other cyclic solvents such as cyclohexane and methyl cyclohexane may be used as well as halogenated hydrocarbons and less desirably, higher aliphatics such as heptane and octane.
In the separation of the benzothiazole from the other mercaptobenzothiazole by-products, distillation under ; 30 vacuum is the most convenient method. The solvent is readily . . .
removed at lower temperatures. Aniline is removed at about 15 milliliters, normally at about 77C., and benzothiazole ~ - 3 -:.
at about 120 to 121C. Higher boiling impurities such as resinous materials, methyl mercaptobenzothiazole, sulfur and the like remain in the still pot because of much higher boiling points. The benzothiazole distillate used normally has a purity of about 90YO and more preferably, about 95 to 9g%. Small amounts of aniline, as 0.1 up to 10~ or even 15%, and typically up to about 5% can be tolerated as well as 2-anilino-benzothiazole. Less desirable, toluidines, methyl benzothiazole and the like are preferably kept low, below about 1%, and normally do not appear when the by-products are carefully distilled. A typical analysis of the by-product from the aniline, sulfur, carbon disulfide reaction wherein 11.4% by-product tars were isolated from the mercaptobenzothiazole by toluene was aniline, 0.34%, benzothiazole, 5.64%, sulfur, 1.32~,
U.S. Patent 3,031,073 describes the manufacture of mercaptobenzothiazole wherein aniline, sulfur and carbon di-sulfide are reacted together. In accordance with this patent, the residue left after separation of mercaptobenzothiazole from the crude reaction product, normally by a water immiscible organic solvent, after removal of the solvent, was recycled to an autoclave with fresh reactants. While this is alleged to represent an improvement in the yield of desired mercapto-benzothiazole, purification problems are introduced and the recycle product mercaptobenzothiazole so obtained is difficult to purify because of the continued recycling of the tars and other discolored and undesired reaction products. If the by-products are discarded, there is a loss of valuable materials.
Improvement in this process is desired, particularly the obtainment of maximum amounts of substantially color-free mer-captobenzothiazole from these by-product residues.
According to the invention there is provided in the process for preparing mercaptobenzothiazole by the reaction of aniline, sulfur and carbon disulfide, the improvement comprising separating the mercaptobenzothiazole formed from the other reaction by-products of said reaction, fractionating - said by-products to recover benzothiazole and heating said 1, benzothiazole with sulfur, whereby additional yields of i~ mercaptobenzothiazole are obtained.
~ , .
,. ,.~
f~
~075Z45 Typically the residue obtained after the 2-mercapto-benzothiazole is separated from the reaction product of aniline, culfur and carbon disulfide is fractionated to provide a fraction containing at least 90~ benzothiazole, which benzo-thiazole iA then heated with sulfur, and carbon disulfide if required to react with any aniline impurity in the benzothia-zole, to provide a high purity substantially color-free 2-mercaptobenzothiazole.
In the preparation of the 2-mercaptobenzothiazole by the reaction of aniline, sulfur and carbon disulfide, usually in about equimolar amounts, after the initial reaction, the crude mercaptobenzothiazole iQ normally solubilized in a caustic solution, which solution is then extracted with a solvent as toluene. The toluene removes the tar and other impurities from the mercaptobenzothiazole. In accordance with this invention this solvent solution is then distilled to remove the toluene and the fractionated to obtain benzo-thiazole. This benzothiazole fraction is then reacted with sulfur, and carbon disulfide if required, to obtain an improved yield of high purity mercaptobenzothiazole having improved color.
When the total by-product is recycled or further -reacted, conversion of this residue to some additional mercaptobenzothiazole is obtained; however, the resulting product is difficult to purify because of color and other impurities. In contrast, the distilled benzothiazole product, which normally contains a small amount of aniline, is readily -converted into 2-mercaptobenzothiazole in improved overall ; yields with the elimination of color and purification problems observed when recycling the total tarry by-product residue.
The impurities from the mercaptobenzothiazole reaction product are readily separated from the mercaptobenzo-thiazole with solvents. Preferably, aromatic solvents are used and those containing one aromatic ring including benzene, xylene, toluene, chlorobenzene, aniline and the like have been found to be useful. Other cyclic solvents such as cyclohexane and methyl cyclohexane may be used as well as halogenated hydrocarbons and less desirably, higher aliphatics such as heptane and octane.
In the separation of the benzothiazole from the other mercaptobenzothiazole by-products, distillation under ; 30 vacuum is the most convenient method. The solvent is readily . . .
removed at lower temperatures. Aniline is removed at about 15 milliliters, normally at about 77C., and benzothiazole ~ - 3 -:.
at about 120 to 121C. Higher boiling impurities such as resinous materials, methyl mercaptobenzothiazole, sulfur and the like remain in the still pot because of much higher boiling points. The benzothiazole distillate used normally has a purity of about 90YO and more preferably, about 95 to 9g%. Small amounts of aniline, as 0.1 up to 10~ or even 15%, and typically up to about 5% can be tolerated as well as 2-anilino-benzothiazole. Less desirable, toluidines, methyl benzothiazole and the like are preferably kept low, below about 1%, and normally do not appear when the by-products are carefully distilled. A typical analysis of the by-product from the aniline, sulfur, carbon disulfide reaction wherein 11.4% by-product tars were isolated from the mercaptobenzothiazole by toluene was aniline, 0.34%, benzothiazole, 5.64%, sulfur, 1.32~,
2-anilinobenzothiazole, 1.12%; other, 2.98æ. The other impurities include undesirable resinous black materials, and possibly small amounts of toluidines, methylbenzothiazole, methyl mercaptobenzothiazole and other benzothiazole derivatives.
In any event, it is desired to carefully distill the tars so as to obtain primarily benzothiazole of at least 90YO purity.
The presence of small amounts of aniline impurity are not undesirable.
On a molar basis of one mol of benzothiazole, , about an equal or a slight molar excess of sulfur provides excellent yields of the desirable 2-mercaptobenzothiazole.
- While lesser amounts of sulfur as 0.5 mol may be used, lower ; yield of desired product are obtained and with larger amounts of sulfur, as greater than about 1.5 to 2 mols of sulfur, problems may be introduced in removing the excess sulfur, ~`~ 30 often requiring the use of a sulfur solvent. When aniline is pre~ent as an impurity, carbon disulfide is included as a xeactant. Normally about equimolar amounts will be used.
; - 4 -From 0.5 to 2.0 mols/mol of aniline may be used, but the lower amounts provide less desired product and the excess must be removed.
The reactants are mixed together in any standard reactor or autoclave, preferably a pressure autoclave and heated to a temperature greater than about 200C. to about 300C. Better yields are generally obtained in the range of about 220C. to about 280C. for periods of about 2 to 6 hours under autogeneous pressure, although higher pessures may be used and longer times at lower temperatures.
EXAMPLE I
To demonstrate the advantages of this invention, a series of reactions were run to prepare mercaptobenzothiazole by reacting a molar ratio of 1.5 mols each of aniline, ~ 15 sulfur and carbon disulfide at 260C. for 2 hours. The ; resulting reaction products were dissolved in a lN solution of sodium hydroxide and the tars and other by-products extracted with toluene. A toluene extract of tar from these mercaptobenzothiazole reactions was combined and distilled at 13-18 mm mercury and 21-32C. to remove toluene, and 10-17 mm mercury and 110 to 120C. to collect benzothiazole containing about 2~ aniline. 1.46 mols (210 grams) of benzothiazole obtained from the by-product tar along with the 0.04 mol of aniline was heated with 1.5 mols (41.8 grams) of sulfur and 0.04 mol (3 grams) of carbon disulfide for 2 hours at 260C. The reaction product was dissolved in : 850 ml of 2N sodium hydroxide. The resulting solution was free of color. This solution was extracted with a total volume of 1 liter of toluene. The separated aqueous solution, which was substantially colorless, was acidified to a pH of
In any event, it is desired to carefully distill the tars so as to obtain primarily benzothiazole of at least 90YO purity.
The presence of small amounts of aniline impurity are not undesirable.
On a molar basis of one mol of benzothiazole, , about an equal or a slight molar excess of sulfur provides excellent yields of the desirable 2-mercaptobenzothiazole.
- While lesser amounts of sulfur as 0.5 mol may be used, lower ; yield of desired product are obtained and with larger amounts of sulfur, as greater than about 1.5 to 2 mols of sulfur, problems may be introduced in removing the excess sulfur, ~`~ 30 often requiring the use of a sulfur solvent. When aniline is pre~ent as an impurity, carbon disulfide is included as a xeactant. Normally about equimolar amounts will be used.
; - 4 -From 0.5 to 2.0 mols/mol of aniline may be used, but the lower amounts provide less desired product and the excess must be removed.
The reactants are mixed together in any standard reactor or autoclave, preferably a pressure autoclave and heated to a temperature greater than about 200C. to about 300C. Better yields are generally obtained in the range of about 220C. to about 280C. for periods of about 2 to 6 hours under autogeneous pressure, although higher pessures may be used and longer times at lower temperatures.
EXAMPLE I
To demonstrate the advantages of this invention, a series of reactions were run to prepare mercaptobenzothiazole by reacting a molar ratio of 1.5 mols each of aniline, ~ 15 sulfur and carbon disulfide at 260C. for 2 hours. The ; resulting reaction products were dissolved in a lN solution of sodium hydroxide and the tars and other by-products extracted with toluene. A toluene extract of tar from these mercaptobenzothiazole reactions was combined and distilled at 13-18 mm mercury and 21-32C. to remove toluene, and 10-17 mm mercury and 110 to 120C. to collect benzothiazole containing about 2~ aniline. 1.46 mols (210 grams) of benzothiazole obtained from the by-product tar along with the 0.04 mol of aniline was heated with 1.5 mols (41.8 grams) of sulfur and 0.04 mol (3 grams) of carbon disulfide for 2 hours at 260C. The reaction product was dissolved in : 850 ml of 2N sodium hydroxide. The resulting solution was free of color. This solution was extracted with a total volume of 1 liter of toluene. The separated aqueous solution, which was substantially colorless, was acidified to a pH of
3 with 5N sulfuric acid and the precipitated mercaptobenzo-thiazole was filtered and washed with water. A yield of : - 5 _ mercaptobenzothiazole of 89.5% (212 grams) having a melting point of 178-181C. was obtained. After drying this product had only a pale yellow discoloration.
EXAMPLE II
To demonstrate the disadvantages of using recovered by-products as such from the mercaptobenzothiazole reaction, 112 grams of by-product was collected as described in Example I and the toluene distilled off. This material, 0.76 mol equivalent of benzothiazole, 2-anilinobenzothiazole and aniline with the required amount of sulfur and carbon di-sulfide, 0.64 mol of sulfur and 0.11 mol of carbon disulfide and the mixture heated in a rocking autoclave at 260C. for 2 hours. The reactor was vented and the reaction mixture removed from the vessel. The reaction product was dissolved in 1 liter of lN sodium hydroxide. The resulting black mixture containing black suspended matter was treated with 14 grams of activated charcoal and filtered. The resulting filtrate was still black. The filtrate was then extracted ~; three times with 200 ml portions of toluene and the aqueous ~, 20 phase treated again with 20 grams of activated charcoal.
After filtration, the filtrate was still colored. The filtrate was acidified with 5N sulfuric acid to a pH of 3 and the precipitate washed with water and dried. A 70~
yield of mercaptobenzothiazole (89 grams) having a melting - 25 point in the range of 173 to 180C. was obtained. This - product had an undesirable yellowish brown color and could not be used as a compounding ingredient in white rubber - stocks.
2-Mercaptobenzothiazole (MBT) is a valuable com-mercial rubber accelerator, normally used to accelerate the sulfur vulcanization of olefinically unsaturated rubbers such as butadiene acrylonitrile and styrene rubbers, poly-butadiene rubber, polyisoprene, neoprene and the like, as is well known to those skilled in the art.
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., .
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EXAMPLE II
To demonstrate the disadvantages of using recovered by-products as such from the mercaptobenzothiazole reaction, 112 grams of by-product was collected as described in Example I and the toluene distilled off. This material, 0.76 mol equivalent of benzothiazole, 2-anilinobenzothiazole and aniline with the required amount of sulfur and carbon di-sulfide, 0.64 mol of sulfur and 0.11 mol of carbon disulfide and the mixture heated in a rocking autoclave at 260C. for 2 hours. The reactor was vented and the reaction mixture removed from the vessel. The reaction product was dissolved in 1 liter of lN sodium hydroxide. The resulting black mixture containing black suspended matter was treated with 14 grams of activated charcoal and filtered. The resulting filtrate was still black. The filtrate was then extracted ~; three times with 200 ml portions of toluene and the aqueous ~, 20 phase treated again with 20 grams of activated charcoal.
After filtration, the filtrate was still colored. The filtrate was acidified with 5N sulfuric acid to a pH of 3 and the precipitate washed with water and dried. A 70~
yield of mercaptobenzothiazole (89 grams) having a melting - 25 point in the range of 173 to 180C. was obtained. This - product had an undesirable yellowish brown color and could not be used as a compounding ingredient in white rubber - stocks.
2-Mercaptobenzothiazole (MBT) is a valuable com-mercial rubber accelerator, normally used to accelerate the sulfur vulcanization of olefinically unsaturated rubbers such as butadiene acrylonitrile and styrene rubbers, poly-butadiene rubber, polyisoprene, neoprene and the like, as is well known to those skilled in the art.
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Claims (7)
1. In the process for preparing mercaptobenzothiazole by the reaction of aniline, sulfur and carbon disulfide, the improvement comprising separating the mercaptobenzothiazole formed from the other reaction by-products of said reaction, fractionating said by-products to recover benzothiazole and heating said benzothiazole with sulfur, whereby additional yields of mercaptobenzothiazole are obtained,
2. A process of claim 1, wherein said benzothiazole has a purity of at least about 90% and is reacted with about a sub-stantially equal or slight molar excess of sulfur at a temperature greater than about 200°C.
3. A process of claim 2, wherein said benzothiazole contains up to about 10% aniline and said benzothiazole is reacted with sulfur and an amount of carbon disulfide sub-stantially equimolar to said aniline in said benzothiazole at a temperature of about 220 to about 300°C.
4. A process of claim 1, wherein said reaction by-products are separated from said mercaptobenzothiazole by extraction with a solvent, which solvent extract is then distilled to remove the solvent and benzothiazole collected at a pressure and temperature substantially equivalent to about 10 to 17 mm mercury and 110 to 120°C. to a purity of said benzothiazole of greater than 90%.
5. The process of claim 4, wherein said solvent is an aromatic solvent, said benzothiazole has a purity greater than about 95% and is reacted with substantially an equal or slight molar excess of sulfur at a temperature in the range of about 220° to about 300°C.
6. A process of Claim 5 wherein said benzothiazole contains up to about 5% aniline and carbon disulfide in amount substantially equimolar to said aniline is reacted with said sulfur and the benzothiazole.
7. A process of Claim 6 wherein said aromatic solvent is toluene.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US66739876A | 1976-03-16 | 1976-03-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1075245A true CA1075245A (en) | 1980-04-08 |
Family
ID=24678051
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA270,762A Expired CA1075245A (en) | 1976-03-16 | 1977-01-31 | Process for preparation of mercaptobenzothiazole |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS52111568A (en) |
| CA (1) | CA1075245A (en) |
| DE (1) | DE2709989A1 (en) |
| FR (1) | FR2344552A1 (en) |
| IT (1) | IT1076897B (en) |
| ZA (1) | ZA77649B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106243059A (en) * | 2016-07-26 | 2016-12-21 | 濮阳蔚林化工股份有限公司 | A kind of method extracting benzothiazole from 2 benzothiazolyl mercaptans production by-products |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5367082A (en) * | 1990-09-07 | 1994-11-22 | Akzo N.V. | Process for the preparation of 2-mercaptobenzothiazole |
| DE4028473A1 (en) * | 1990-09-07 | 1992-03-12 | Akzo Gmbh | METHOD FOR PRODUCING 2-MERCAPTO-BENZOTHIAZOL |
-
1977
- 1977-01-31 CA CA270,762A patent/CA1075245A/en not_active Expired
- 1977-02-04 ZA ZA770649A patent/ZA77649B/en unknown
- 1977-02-15 IT IT7720311A patent/IT1076897B/en active
- 1977-03-08 DE DE19772709989 patent/DE2709989A1/en active Pending
- 1977-03-14 FR FR7707563A patent/FR2344552A1/en not_active Withdrawn
- 1977-03-16 JP JP2815077A patent/JPS52111568A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106243059A (en) * | 2016-07-26 | 2016-12-21 | 濮阳蔚林化工股份有限公司 | A kind of method extracting benzothiazole from 2 benzothiazolyl mercaptans production by-products |
Also Published As
| Publication number | Publication date |
|---|---|
| ZA77649B (en) | 1977-12-28 |
| JPS52111568A (en) | 1977-09-19 |
| DE2709989A1 (en) | 1977-09-29 |
| IT1076897B (en) | 1985-04-27 |
| FR2344552A1 (en) | 1977-10-14 |
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