| Melting Point | 199–201 °C (lit.) |
| Density | 1.272 g/cm³ at 20 °C |
| Color | Yellow to green |
| Formula Weight | 430.57 |
| Physical Form | Crystal-powder |
| Chemical Name or Material | 2,5-Bis(5-tert-butyl-2-benzoxazolyl)thiophene (purified by sublimation) |
| SMILES String | `CC(C)(C)c1ccc2oc(nc2c1)-c3ccc(s3)-c4nc5cc(ccc5o4)C(C)(C)C` |
| Beilstein | 631803 |
| Assay | 99% |
| Solubility | Toluene: 50 mg/mL |
| CAS Number | 7128-64-5 |
| Storage Temperature | Room temperature |
| EC Number | 230-426-4 |
| Molecular Weight (Mw) | 430.56–430.57 g/mol |
| Empirical Formula | C26H26N2O2S |
| NACRES | NA.47 |
| PubChem Substance ID | 24853416 |
| UNSPSC Code | 12171500 |
| MDL Number | MFCD00005774 |
| Quality Segment | 200 |
| InChI | `1S/C26H26N2O2S/c1-25(2,3)15-7-9-19-17(13-15)27-23(29-19)21-11-12-22(31-21)24-28-18-14-16(26(4,5)6)8-10-20(18)30-24/h7-14H,1-6H3` |
| InChI Key | AIXZBGVLNVRQSS-UHFFFAOYSA-N |
| Extinction Coefficient (ε) | ≥47,000 at 372–374 nm in dioxane |
| Applications | Optical brightener/fluorescent whitening agent for plastics, fibers, and coatings |
Optical Brightener OB is a benzoxazole-based fluorescent compound, chemically 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene, built around a central thiophene ring flanked by two tert-butyl-substituted benzoxazole units. This extended conjugated structure gives the molecule strong UV absorption and efficient blue fluorescence, the combination of properties that defines an optical brightener: it absorbs invisible ultraviolet light and re-emits it as visible blue light, which optically offsets yellowing and makes treated materials appear brighter and whiter to the eye. Supplied by Sarchem Labs as a 99%-assay crystalline powder, it is a well-established, commercially proven brightener known industrially by its Colour Index number, C.I. 184.
As a fluorescent whitening agent, Optical Brightener OB is incorporated into plastics, synthetic fibers, and coatings to counteract natural yellow discoloration and boost perceived whiteness and brightness. Its strong, well-characterized fluorescence also makes it valuable well beyond brightening: it is used as a scintillation-grade fluor for radiation detection, as a component in diagnostic assay manufacturing, and in hematology and histology workflows where a reliable fluorescent signal is needed. In materials research, it also serves as a fluorescence tracer for photoluminescence studies on doped silica films and for visualizing UV-patterned acrylic pressure-sensitive adhesives.
No GHS pictograms, signal word, or H-/P-code statements were present in the reference data reviewed, suggesting a relatively low hazard profile for this compound — confirm against Sarchem’s own current SDS before publishing, since “not listed” is not the same as “confirmed non-hazardous.”
