Organic compounds sublimation pressure

Many organic compounds sublime readily under reduced pressure. When the vapor pressure of the solid equals the applied pressure, sublimation occurs, and the behavior is identical to that shown in Figure 17.1B. The solid phase passes directly into the vapor phase. From the data given in Table 17.1, you should expect camphor, naphthalene, and benzoic acid to sublime at or below the respective applied pressures of 370,7, and 6 mm Hg. In principle, you can sublime p-nitrobenzaldehyde (last entry in the table), but it would not be practical because of the low applied pressure required. 

Generally, the solubihty characteristics of organic compounds depend on several properties of the participating components. For the solute, these properties are the molecular size and structure, polarity, dipole moment, va-por/sublimation pressure, and, in the case of a sohd solute, also its melting characteristics. When using SCCO2 as the solvent, mainly its dipole moment and quadrupole moment influence the solvatation process (Sect. 2.2). 

Jones, A.H. Sublimation pressure data for organic compounds, / Chem. Eng. Data, 5(2) 196-200, 1960. 

An interesting method (88) for the separation of trace amounts of polonium makes use of the volatility of some, as yet unidentified, organic compounds. Polonium complexes with diphenylearbazonc, diphenylear-bazide and diphenylthiocarbazone sublime below 100°C under atmospheric pressure and those with thiourea, 8-hydroxyquinoline, s-diphenylthiourea, thioseinicarbazide and other related compounds sublime below 160°C under the same conditions. Thus trace polonium has been separated from dilute nitric acid in the presence of diphenyl carbazide by steam distillation. 

Sublimation plays an important role in the purification of organic compounds on a micro scale since it involves little loss of material, is convenient and fast, and provides very efficient purification. An essential condition for its application is, however, that the substance has sufficient vapor pressure at the temperature to be used. 

The vapor pressure or the sublimation behavior of organic compounds can by determined conveniently using thermogravimetry. Ashcroft (48), using the Langmuir equation... 

This table gives the sublimation (vapor) pressure of some representative solids as a function of temperature. Entries include simple inorganic and organic substances in their solid phase below room temperature, as well as polycyclic organic compounds which show measurable sublimation pressure only at elevated temperatures. Substances are listed by molecular formula in the Hill order. Values marked by represent the solid-liquid-gas triple point. Note that some pressure values are in pascals (Pa) and others are in kUopascals (kPa). For conversion, 1 kPa = 7.506 mmHg =... 

Steroid Hormones and Other Steroidal Synthetics Sublimation Pressure for Organic Compounds Surface Tension of Liquid Elements Temperature Correction for Barometer Readings Temperature Correction for Glass Volumetric Apparatus Temperature Correction for Volumetric Solutions Temperature Correction, Glass Scale... 

The totally enclosed List sublimation unit Figure 8.33) is provided with selfcleaning heat exchange surfaces and operates semi-continuously under reduced pressure without the aid of a carrier gas. Accumulated impurities are discharged from the sublimator periodically. Batch and continuous modifications of this unit are available (Schwenk and Raouzeos, 1995) and have been successfully applied industrially for the purification of anthraquinone, dyestuffs intermediates, metal-organic compounds and pharmaceuticals with production rates ranging from 300 to 10000 ton/year. 

Davies M (compiler) (1991-92) Sublimation pressure for organic compounds. In Lide DR (ed.) CRC Handbook of Physics and Chemistry, 72nd edn, pp. 5-91. Boca Raton CRC Press. 

The following citations recall the historical development of repertoires and of experimental techniques Bondi, A. Heat of sublimation of molecular crystals. A catalog of molecular structure increments, J. Chem. Eng. Data 1963,8,371-381 Jones, A. H. Sublimation pressure data for organic compounds, J. Chem. Eng. Data 1960,5,196-200 Chickos, J. S. Annunziata, R. Ladon, L. H. Hyman, A. S.. Liebman, J. F. Estimating heats of sublimation of hydrocarbons. A semiem-pirical approach, J. Org. Chem. 1986, 51, 4311-4314 Ouvrard, C. Mitchell, J. B. O., Can we predict lattice energy from molecular structure Acta Cryst. 2003, B59, 676-685 Knauth, R Sabbah, R. Thermochemistry of organic compounds. A review on experimental methods and present-day research activities. Bull. Soc. Chim. Fr. 1990,127, 329-346. 

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