Synthesis of Perdeuteriobenzo [a] pyrene

Abstract

Benzo[a]pyrene is one of the most extensively studied chemical carcinogens"]. There is substantial evidence implicating the electronically excited states of this and other polynuclear aromatic hydrocarbons in the initiation of the neoplastic processC2, ']. When the hydrogens of aromatic hydrocarbons are replaced by deuterium, the photophysical properties are affectedr4]. Perdeuteriated polycyclic arenes may thus be employed to test those hypotheses of chemical carcinogenesis which invoke the intermediacy of electronic excited In one such study it was found that perdeuterio-7,12-dimethylbenz [a]anthracene was approximately twice as carcinogenic as the undeuterated compound[31.Perdeuterated polycyclic arenes are currently prepared by two quite different procedures [6]. A suspension of the arene in D 2 0 is heated in the presence of reduced platinum in an autoclave at about 350°C for several days, or, the exchange can be achieved in a homogeneous catalytic system. In the latter procedure the arene is dissolved in [D6]-benzene, the exchange catalyst C2H5AIC12 is added and the solution is heated at about 90°C for about 7In our procedure, the homogeneous exchange with [D6]-benzene is achieved in 6 h using AIBr3 as a catalyst.Aluminum tribromide is vacuum sublimed and stored under nitrogen. To a 5 ml glass ampoule are added 2 ml of [D6]-benzene and 1 p1 of pure bromine. Approximately 20mg of freshly sublimed AlBr3 is added (in a dry box) to the preweighed reddish-orange solution in the ampoule, whereupon the solution turns yellow. The ampoule is capped and removed from the dry box, cooled in dry ice/acetone and flame sealed. The sealed ampoule is then heated (stirring is not necessary) in an oil bath in which it is immersed to about the liquid content level at 100°C for 2 hours. The ampoule is opened (in a dry box) and its contents transferred by Pasteur pipette or syringe to a second 5 ml ampoule containing 100mg of benzo[a]pyrene. A deep red color develops. The ampoule is sealed as before and heated in an oil bath without stirring at 110°C for 6 h. The ampoule is cooled, opened, and 4-5 drops of distilled water added. The benzene layer is removed and transferred to a small round bottom flask. The reaction flask is washed several times with small additional amounts of benzene and the combined benzene solution evaporated to dryness in vacuo. The brown-yellow residue is transferred to a sublimation apparatus and vacuum sublimed. The light yellow sublimate is removed from the cold finger with a few ml of acetone and the acetone solution evaporated by a stream of nitrogen. The residue (87 mg) consist of pure benzo[a]pyrene containing 94.7 atom percent deuterium.The deuterium content was determined by low voltage (7eV) mass spectrometry using a Hitachi Perkin Elmer RMU7 mass spectrometer coupled with a VG Data ~\~i c t n ;rd;ipted to a PDP8 computer. Appropriate precautions to account for isotopic composition ['] were taken and analysis of the data (Amdahl470 computer) afforded both atom percent and mole percent deuterium...

A convenient preparation of deuterated aromatic compounds

“…The classical procedures for the deuteration of polycyclic aromatics are tortuous and inconvenient,1 involving heating the arene in D20 to 350 °C in the presence of a Pt catalyst or exchange with benzene-de•2 A more convenient procedure for the deuteration of benzo[a]pyrene was recently published. 3 There also exists an excellent method developed by Makabe, but since it was published in Japanese it has not been used widely in the west. 4 Their elegant method uses a mixture of BFa-DsPO* and is useful with a variety of organic compounds.…”