Sublimation under reduced pressure

Sublimation under reduced pressure. The so-called vacuum sublimation may be carried out in the apparatus of Fig. II, 45, 4. The cold finger is fitted into the larger tube by means of a rubber stopper... 

In addition to distillation (73), BI can be purified by sublimation under reduced pressure (77). 

Anthracene has also been crystd from EtOH, chromatographed through alumina in hot benzene (fume hood) and then vac sublimed in a pyrex tube that has been cleaned and baked at 100°. (For further details see Craig and Rajikan J Chem Soc, Faraday Trans 1 74 292 1978 and Williams and Zboinski J Chem Soc, Faraday Trans 1 74 611 1978.) It has been chromatographed on alumina, recrystd from n-hexane and sublimed under reduced pressure. [Saltiel J Am Chem Soc 108 2674 1986 Masnori et al. J Am Chem Soc 108 1126 1986.] Alternatively, it was recrystd from cyclohexane, chromatographed on alumina with n-hexane as eluent, and recrystd two more times [Saltiel et al. J Am Chem Soc 109 1209 1987]. 

Benzo[6]biphenylene [259-56-3] M 202.2, m dec >250. Purified by sublimation under reduced pressure. 

Dichloroanthracene [605-49-1] M 247.1, m 214-215°. Purified by crystn from MeOH or EtOH, followed by sublimation under reduced pressure. [Masnori and Kocbi J Am Chem Soc 107 7880 1985.]... 

Maleic anhydride [108-31-6] M 98.1, m 54 , b 94-96 /20mm, 199 /760mm. Crystd from benzene, CHCI3, CH2Cl2or CCI4. Sublimed under reduced pressure. [Skell et al. J Am Chem Soc 108 6300 7956.]... 

Ethylmercuric chloride [107-27-7] M 265.1, m 193-194°. Mercuric chloride can be removed by suspending ethylmercuric chloride in hot distilled water, filtering with suction in a sintered-glass crucible and drying. Then crystd from ethanol and sublimed under reduced pressure. It can also be crystd from water. 

Styrene, 8, 84,102 Styrene oxide, 8,102 Sublimation under reduced pressure, 6, 80... 

The hydrogenated carbonate can be recovered free of ruthenium catalyst by sublimation under reduced pressure using a Kugelrohr apparatus (bp 70 °C, 1.5mmHg). 

For synthesis on a larger scale, it has been found that the workup described by Hart et al is impractical, and an alternative has been published.27 This differs in that aryl halide by-products are removed by distillation under reduced pressure. The residue is then refluxed in EtOH, and filtration effects the recovery of crude halogenated terphenyl product. Sublimation under reduced pressure affords the pure product in up to 75% yield. 

Difluoromcthylcnecydopropane (20, R = F 2.30 g, 25.6 mmol) was sealed under vacuum in a thick-walled 165-mL glass tube. The tube was heated to 312 C for 3.5 h, then cooled to liquid N2 temperature when opened and the contents (1.75 g, 76%) were transferred to a cold finger under vacuum. A quantity of polymeric material remained in the tube. The material that collected on the cold finger was thawed and trap-to-trap distilled to yield 0.38 g of a ca. 70 30 mixture of 20 (R = F) and 2,2-difiuoromcthylenecyclo-propane (by I9F NMR) and a white solid residue. The solid residue was sublimed under reduced pressure to give crystalline 21 (R = F) yield 0.68 g (30%) mp 64-65 C. 

Fluorenone [486-25-9] M 180.2, m 82.5-83.0°, 85-86°, b 341°/760mm. Crystd from absolute EtOH, MeOH or benzene/pentane. [Ikezawa JACS 108 1589 1986], Also twice recrystd from toluene and sublimed under reduced pressure [Saltiel JACS 108 2674 1986], Can be distd under high vacuum. 

The greenish-black crystals of Bil3 are composed of a hexagonal close packed array of iodine atoms with bismuth atoms in the interstitial spaces, with six nearest neighbours at 3.07 A. It is prepared by heating the elements in stoichiometric quantities, and purified by subliming under reduced pressure. 

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