Description
9,10-Dibromoanthracene is an organic chemical compound containing anthracene with two bromine atoms substituted on its central ring. As a symmetrically brominated anthracene derivative, it is bearing functional groups to extend its conjugation further mainly via C-C bond forming i.e. Stille and Suzuki coupling reactions. It is notable in that it was the first single molecule to have a chemical reaction observed by an atomic force microscope and scanning tunneling microscopy. It is a low-molecular-weight organic semiconductor. It can used as an initiator in visible-spectrum solar-light-mediated benzylic C–H oxygenation through solar light or the blue LED activate[1-2].
Chemical Properties
Yellow to yellow-green fluffy powder. Melting point 226°C. It can be sublimated and oxidized to generate anthraquinone. It is soluble in hot benzene and hot toluene, but only slightly soluble in alcohol, ether, and cold benzene. It is insoluble in water.
Uses
9,10-Dibromoanthracene is a dibrominated polycyclic aromatic hydrocarbon (PAH). 9,10-Dibromoanthracene is often used as an energy acceptor and activator in reactions that produce chemiluminescence.
Preparation
9,10-Dibromoanthracene is synthesized by the bromination of anthracene. The bromination reaction is carried out at room temperature using carbon tetrachloride as a solvent. Using 80-85% anthracene as raw material, adding bromine to react for half an hour, the yield is 83-88%.
Origin
9,10-Dibromoanthracene was first synthesized in 1923 by Ian (formerly Isidor) M. Heilbron and John S. Heaton, chemists working at the University of Liverpool.
Synthesis
A solution of bromine (Br2, 2.90 mL, 56.60 mmol) in trichloromethane (CHCl3, 50 mL) was slowly added dropwise to a solution of anthracene (5.0 g, 28.05 mmol) in trichloromethane (CHCl3, 100 mL) at room temperature. The reaction mixture was stirred continuously for 4 h at room temperature. After completion of the reaction, the solvent was removed by rotary evaporator to give the crude product. The crude product was purified by recrystallization with dichloromethane (CH2Cl2) to give final yellow needle-like crystals of 9,10-dibromoanthracene in 98% yield. The structure of the product was confirmed by the following characterization data: 1H NMR (500 MHz, TMS, CDCl3): δ (ppm) = 8.59-8.56 (m, 4H), 7.64-7.61 (m, 4H); IR (KBr, cm-1): 2920, 2850, 1650, 1560, 1460, 1380, 1260, 926. 746, 579; Elemental analysis (C14H8Br2) calculated: C, 54.04; H, 2.40; measured: C, 53.84; H, 2.36; Mass spectrometry (MS) m/z: Calculated: 336.0; measured: 336.1.
Purification Methods
Recrystallise it from toluene, xylene or CCl4 (yellow needles), and sublime it in a vacuum [Johnston et al. J Am Chem Soc 109 1291 1987]. [Heilbron & Heaton Org Synth Coll Vol I 207 1941, Beilstein 5 H 665.]
References
[1] Santra S, et al. Visible-Spectrum Solar-Light-Mediated Benzylic C–H Oxygenation Using 9,10-Dibromoanthracene As an Initiator. The Journal of Organic Chemistry, 2020; 86: 1164–1171.
[2] Watanabe M. Formation of aligned needle-like crystals of 9,10-dibromoanthracene in small droplets. Journal of Applied Polymer Science, 2023; 140: e54515.
