Drying of solvents

Sodium should never be added to chlorinated solvents because a vigorous or explosive reaction could occur. 

Anhydrous sodium sulphate is a weak drying agent suitable only for drying extracts. It is preferable to magnesium sulphate for drying very acid sensitive compounds. 

Solvents may be dried in individual batches using conventional distillation apparatus (Chapter 11), but it is more convenient to dry common solvents such as dichloromethane, diethyl ether, and THF in continuous stills (Section 5.5). In either case the solvent must be protected from moisture using an inert atmosphere (nitrogen or argon). Rigorously dried solvents must be stored under an inert atmosphere and handled using syringe or cannula techniques (Chapter 6). 

Acetone is completely miscible with water and its susceptibility to acid and base catalysed self condensation makes it particularly difficult to dry. Good results are obtained by drying over 3A sieves (10% w/v) overnight (any 

Distil from the cylinder into a flask cooled to -40°C and fitted with a dry-ice condenser (Chapter 9). Add pieces of sodium until the dark blue colour persists, and then distil the ammonia into your reaction vessel. 

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Hexadecanoic acid (palmitic acid) [57-10-3] M 256.4, m 62-63°, b 215°/15mm, pK 6.46 (50% aq EtOH), 5.0 (H2O). Purified by slow (overnight) recrystn from hexane. Some samples were also crystd from acetone, EtOH or EtOAc. Crystals were stood in air to lose solvent, or were pumped dry of solvent on a vaeuum line. [Iwahashi et al. J Chem Soc, Faraday Trans 1 81 973 1985, pK White J Am Chem Soc 72 1858 1950]. 

In recent years, organic reactions in aqueous media have attracted a great deal of attention, not only because these reactions eliminate the necessity for vigorous drying of solvents and substrates, but also because unique reactiv-... 

Drying of solvents L 4A sieve Equilibrium Thermal swing... 

Instead of either an acid-induced decomposition or acid-catalyzed sulfur compound—hydroperoxide decomposition reaction occurring— formation of alternative active species which catalytically decompose the hydroperoxide is possible, such as SCL, as suggested by Hawkins and Sautter (4). However, under conditions of this work where vigorous drying of solvents was not used, SOL could be converted into the acid which would then induce the acid-catalyzed decomposition of the peroxide. 

Drying of solvents acetonitrile and pyridine should be refluxed and distilled from calcium hydride as required. Before use, store sufficient anhydrous acetonitrile, anhydrous DMF, trimethyl phosphate, anhydrous dioxan, tri-n-butylamine, tri-n-octylamine over activated 3 A sieves. 

FIGURE 14A Compressive stress inside a ceramic green body due to the presence of a polymer after it is dried of solvent. 

Conical Mixer Dryer The conical mixer dryer is a batch-wise operating unit commonly used in the pharmaceutical and specialty chemical industries for the drying of solvent or water wet, free-flowing powders. The process area is a vertically oriented conical vessel with an internally mounted screw. Figure 12-80 shows a schematic of the bottom drive conical mixer dryer. The dryer utilizes the heatable, internal rotating screw to provide agitation of the batch of material and thus improve the heat and mass transfer of the process. Because it rotates around the full circumference of the vessel, the screw provides a self-cleaning effect for the heated vessel walls. 

The use of acidic solutions greatly slows down proton loss [12,133], the rigorous drying of solvents precludes rapid hydroxylation of cationic species [18,134-136], and the use of nonnucleophilic solvents, such as liquid SO2 [137-140], 1,1,1,3,3,3-hexafluoropro-pan-2-ol [141], or CF3COOH/(CF3CO)20, alone [18,142] or mixed with CH2CI2 [12,135,143-146], also permits the formation of several persistent radical cations and dications. For 9,9 -bianthryl even the tetracation has been observed in liquid SO2 [138]. 

Drying of Solvent removal Polymorphic conversion Chemical stability ... 

Trace 0 H HjO Coordinating solvent Electrochemistry in drybox or in high-vacuum cell Nonacidic solvent careful drying of solvent vacuum conditions Change solvent... 

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