Sublimation, solvent-assisted

Starting from 27, cyclo-Cig was prepared in the gas phase by laser flash heating and the neutral product, formed by stepwise elimination of three anthracene molecules in retro-Diels-Alder reactions, was detected by resonant two-photon-ionization time-of-flight mass spectrometry [23]. However, all attempts to prepare macroscopic quantities of the cyclocarbon by flash vacuum pyrolysis using solvent-assisted sublimation [50] only afforded anthracene and polymeric material. 

The design of the precursor as well as the pyrolysis technique have to be optimized to obtain satisfactory selectivities and yields in the thermal conversions. The starting material has to be stable enough to be transferred into the gas phase without decomposition at temperatures up to 400 °C (depending on the vapor pressure and therefore on the molecular weight and structure) but also to possess an inherent reactivity which can be exploited to yield the desired products with high selectivities and yields under conditions as mild as possible. Thus, enthalpies of activation of 200-400 kJ mol 1 [31, 32] are representative for pyrolyses as synthetic procedures with moderate or high yields. Numerous special techniques have been developed to transfer thermally labile products into the gas phase (spray pyrolysis [33], solvent assisted sublimation techniques... 

Subsequent to freeze stabilization, wet books can be thawed and air dried with or without interleaving or they can be vacuum dried in heated chambers (5). The moisture in frozen books can be sublimed by freeze drying (10) or removed by a vacuum/thaw/outgassing process (8), with microwave energy (6, 14), with dielectric energy (6), or by solvent extraction with or without vacuum assistance (5). 

Silver(I)-assisted rearrangement is the mildest method of inducing cyclopropyl to allyl rearrangement of halocyclopropanes. Cases are known where halocyclopropanes prove to be totally unreactive to uncatalyzed solvolysis in different solvents and even survive sublimation at 200°C unchanged however, they can be rearranged in the presence of silver(I) acetate. ... 

The tropolones are crystalline solids, tropolone itself melting at 50°. They dissolve more readily in hydroxylic solvents than in ether or hydrocarbons. They frequently sublime readily, a feature which has sometimes assisted in their purification. 

The fundamental concepts of chemistry can assist in the understanding of the corrosion of ceramics. A ceramic having a basic character tends to be attacked by an environment with an acidic character, whereas a ceramic having an acidic character tends to be attacked by an environment basic in character. Also, ionic materials tend to be soluble in polar solvents whereas covalent materials tend to be soluble in nonpolar solvents, and the vapor pressure of covalent materials is generally greater than that of ionic materials and therefore covalents tend to vaporize or sublime more quickly. 

An aerosol-assisted chemical vapor deposition (AACVD) can also be implemented in the intermediate thermal range between processes B and D, provided that suitable solvents and precursors are used (process C according to the classification made by Vigui6 and Spitz). In proper conditions, the solvent vaporizes first, then the precursor vaporizes (or sublimes) and the vapor reaches the substrate to undergo a heterogeneous solid-gas phase decomposition. Thus, whether or not an aerosol-assisted deposition process may be classified as chemical vapor deposition depends on two factors ... 

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