Benzothiazole
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| Preferred IUPAC name
1,3-Benzothiazole | |||
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3D model (JSmol)
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| ECHA InfoCard | 100.002.179 | ||
PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |||
| C7H5NS | |||
| Molar mass | 135.1863 g/mol | ||
| Density | 1.238 g/mL | ||
| Melting point | 2 °C (36 °F; 275 K) | ||
| Boiling point | 227 to 228 °C (441 to 442 °F; 500 to 501 K) | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Benzothiazole is an aromatic heterocyclic compound with the chemical formula C
7H
5NS. It is colorless, slightly viscous liquid. Although the parent compound, benzothiazole is not widely used, many of its derivatives are found in commercial products or in nature. Firefly luciferin can be considered a derivative of benzothiazole.
Structure and preparation
Benzothiazoles consist of a 5-membered 1,3-thiazole ring fused to a benzene ring. The nine atoms of the bicycle and the attached substituents are coplanar.
Benzothiazoles are prepared by treatment of 2-mercaptoaniline with acid chlorides:[1]
- C6H4(NH2)SH + RC(O)Cl → C6H4(NH)SCR + HCl + H2O
Uses
Benzothiazole occurs naturally in some foods but is also used as a food additive.[2] It has a sulfurous odor and meaty flavor.[3] The European Food Safety Authority assessment had "no safety concern at estimated levels of intake as a flavouring substance".[4]
The heterocyclic core of the molecule is readily substituted at the unique methyne centre in the thiazole ring. It is a thermally stable electron-withdrawing moiety with numerous applications in dyes such as thioflavin. Some drugs contain this group, examples being riluzole and pramipexole. Accelerators for the sulfur vulcanization of rubber are based on 2-mercaptobenzothiazoles.[5] This ring is a potential component in nonlinear optics (NLO).[6] A benzothiazole derivative is suggested as a dye for arsenic detection.[7]
See also
- Benzothiazoles are related to thiazoles, which lack the fused benzene ring.
- Benzoxazoles, which substitute an oxygen for the sulfur atom.
References
- ^ T. E. Gilchrist "Heterocyclic Chemistry" 3rd Edition, Longman, 1992.
- ^ Lucille Le Bozec, Christopher J. Moody "Naturally Occurring Nitrogen–Sulfur Compounds. The Benzothiazole Alkaloids" Australian Journal of Chemistry 62(7) 639–647.doi:10.1071/CH09126
- ^ "Benzothiazole". The Good Scents Company. Retrieved 2020-10-06.
- ^ "Flavouring Group Evaluation 76, (FGE.76) - Consideration of sulphur-containing heterocyclic compounds evaluated by JECFA (59th meeting) structurally related to thiazoles, thiophene, thiazoline and thienyl derivatives from chemical group 29, miscellaneous". EFSA Journal. 6 (11): 875. 2008. doi:10.2903/j.efsa.2008.875.
- ^ Engels, H.-W., Weidenhaupt, H.-J., Pieroth, M., et al. "Rubber, 4. Chemicals and Additives" in Ullmann's Encyclopedia of Industrial Chemistry 2004, Wiley-VCH, Weinheim. doi:10.1002/14356007.a23_365.pub2
- ^ Hrobarik, P.; Sigmundova, I.; Zahradnik, P.; et al. (2010). "Molecular Engineering of Benzothiazolium Salts with Large Quadratic Hyperpolarizabilities: Can Auxiliary Electron-Withdrawing Groups Enhance Nonlinear Optical Responses?". Journal of Physical Chemistry C. 114 (50): 22289–22302. doi:10.1021/jp108623d.
- ^ Chauhan, Kalpana; Singh, Prem; Kumari, Bhawana; Singhal, Rakesh Kumar (2017-03-16). "Synthesis of new benzothiazole Schiff base as selective and sensitive colorimetric sensor for arsenic on-site detection at ppb level". Analytical Methods. 9 (11): 1779–1785. doi:10.1039/C6AY03302D. ISSN 1759-9679.