Recrystallization compounds

Put the solid in an Erlenmeyer flask, not a beaker. If you recrystallize compounds in beakers, you may find the solid climbing the walls of the beaker to get at you as a reminder. A 125-ml Erlenmeyer usually works. Your solid should look comfortable in it, neither cramped, nor with too much space. You probably shouldn t fill the flask more than one fifth to one fourth full. 

From this, you should get the idea that it would be good to use a mixed solvent to recrystallize compounds that are soluble in alcohol yet insoluble in water. You see, each solvent alone cannot be used. If the material is soluble in the alcohol, not many crystals come back from alcohol alone. If the material is insoluble in water, you cannot even begin to dissolve it. So, you have a mixed solvent, with the best properties of both solvents. To actually perform a mixed-solvent recrystallization you... 

Gallagher P.M., Coffey M.P., Krukonis V.J., Klasutis N., Gas Antisolvent Recrystallisation New Process to Recrystallize Compounds Insoluble in Supercritical Fluids, ACS Symp. Ser. 406, 1989, 335-54... 

In runs of one-tenth the scale specified, the product obtained by the checkers had a melting point of 50-55° when 3delds above 90% were obtained. The 3delds were about 10% lower when 9-bromophenanthrene of melting point 54-56° was produced. The yield of recrystallized compound, melting at 65-66°, as obtained by the checkers, was 60% of the theoretical. 

Gas Antisolvent Recrystallization New Process To Recrystallize Compounds Insoluble in Supercritical Fluids... 

Gallagher PM, Colfey MP, Krukonis VJ, Klasutis N. Gas antisolvent recrystallization new process to recrystallize compounds insoluble in supercritical fluids. In Penniger JML, ed. Supercritical Fluid Science and Technology. ACS Symposium Series 406. Washington, DC American Chemical Society, 1989 334-354. 

Gallagher PM, Coffey MP, Krukonis VJ, Klasutis N. Gas anti-solvent recrystallization new process to recrystallize compounds insoluble in supercritical fluids. In Johnston KP, Penniger JML, eds. Supercritical Fluid Science and Technology. Washington, DC American Chemical Society, 1989 334-354. Dixon D, Johnston KP, Bodmeier R. Polymeric materials formed by precipitation with a compressed fluid antisolvent. AIChE J 1993 39 127-136. Chattopadhyay P, Gupta RB. Production of griseofulvin nanoparticles using supercritical CO2 antisolvent with enhanced mass transfer. Int J Pharm 2001 228 19-31. 

Compound 264 (Scheme 12.66) was prepared by treating the benzopyranoindo-lizinoquinoline derivative 267 with compound 266 by a known procedure, with methanesulfonic acid and followed by recrystallization.Compound 264 is non-hydroscopic and easy to handle material. 

Purification can be effected by dissolving the wet crystals (total yield of crude product) in 1750 ml. of water at 80 to 85°, cooling to about 15° to effect crystallization, followed by filtration and washing. The recrystallized compound is dried as recommended above. About 140 to 145 g. (72 per cent) of a product with a purity of 98 per cent is obtainable in this manner. 

The high reactivity of the 5-position in 1.3-selenazoles toward electrophilic substitution was also observed on azocoupling. By reacting molar quantities of an aqueous solution of a diazonium salt with an ethanolic solution of a 2-arylamino selenazole. for example, the corresponding 2-arylamino-5 azoselenazoles are formed in a smooth reaction (100). They deposit from the deeply colored solution and form intenselv red-colored compounds after their recrystallization from a suitable solvent (Scheme 36l. 

In the resolution of 1 phenylethylamine using (-) malic acid the compound obtained by recrystallization of the mixture of diastereomeric salts is (/ )... 

Anionic polymerization of vinyl monomers can be effected with a variety of organometaUic compounds alkyllithium compounds are the most useful class (1,33—35). A variety of simple alkyllithium compounds are available commercially. Most simple alkyllithium compounds are soluble in hydrocarbon solvents such as hexane and cyclohexane and they can be prepared by reaction of the corresponding alkyl chlorides with lithium metal. Methyllithium [917-54-4] and phenyllithium [591-51-5] are available in diethyl ether and cyclohexane—ether solutions, respectively, because they are not soluble in hydrocarbon solvents vinyllithium [917-57-7] and allyllithium [3052-45-7] are also insoluble in hydrocarbon solutions and can only be prepared in ether solutions (38,39). Hydrocarbon-soluble alkyllithium initiators are used directiy to initiate polymerization of styrene and diene monomers quantitatively one unique aspect of hthium-based initiators in hydrocarbon solution is that elastomeric polydienes with high 1,4-microstmcture are obtained (1,24,33—37). Certain alkyllithium compounds can be purified by recrystallization (ethyllithium), sublimation (ethyllithium, /-butyUithium [594-19-4] isopropyllithium [2417-93-8] or distillation (j -butyUithium) (40,41). Unfortunately, / -butyUithium is noncrystaUine and too high boiling to be purified by distiUation (38). Since methyllithium and phenyllithium are crystalline soUds which are insoluble in hydrocarbon solution, they can be precipitated into these solutions and then redissolved in appropriate polar solvents (42,43). OrganometaUic compounds of other alkaU metals are insoluble in hydrocarbon solution and possess negligible vapor pressures as expected for salt-like compounds. 

Amino-2-hydroxybenZOiC acid. This derivative (18) more commonly known as 4-aminosa1icy1ic acid, forms white crystals from ethanol, melts with effervescence and darkens on exposure to light and air. A reddish-brown crystalline powder is obtained on recrystallization from ethanol —diethyl ether. The compound is soluble ia dilute solutioas of nitric acid and sodium hydroxide, ethanol, and acetone slightly soluble in water and diethyl ether and virtually insoluble in benzene, chloroform or carbon tetrachloride. It is unstable in aqueous solution and decarboxylates to form 3-amiaophenol. Because of the instabihty of the free acid, it is usually prepared as the hydrochloride salt, mp 224 °C (dec), dissociation constant p 3.25. 

About two-thirds of the carbon tetrachloride is distilled. The solution is cooled, and the crystals of />-nitrophenyl isocyanate are filtered as quickly as possible in order to avoid prolonged exposure of the compound to the moisture of the air. By concentration of the mother liquor a further crop is obtained. The product is recrystallized from dry carbon tetrachloride and is obtained in the form of light yellow needles melting at 56-57° (Note 6). The yield after one recrystallization is 152-170 g. (85-95 P r cent of the theoretical amount) (Note 7). 

The crude product has a disagreeable odor probably due to the presence of a compound of phosphorus. The odor may be eliminated by heating at 120°, followed by several recrystallizations. 

Witt and Kopetschni report a melting point of 295-296° (dec.). This compound may be recrystallized from glacial acetic acid or ethanol. 

Although the first all-sulfur macrocycles were prepared many years ago " the first systematic study of such compounds was initiated by Busch and his coworkers , who were interested in the cation binding properties of such ligands. A sequential synthesis was utilized to produce 1,4,8,11-tetrathiacyclotetradecane [tetrathia-14-crown-4 (70)] . In the first step, 1,3-propanedithiol is metallated using sodium and alkylated with 2-chloroethanol. The diol was then treated with thiourea to form the dimercapto-dithioether compound 9. The latter was once again metallated with sodium and allowed to react with 1,3-dibromopropane. The yield of 70 in the ring closure step, conducted at high dilution in absolute ethanol, was 7.5% after recrystallization. The entire sequence is illustrated in Eq. (6.8) . ... 

Acetoxy-17a-hydroxy-5a-pregnane-3,l 1,20-trione (40) is brominated in acetic acid under equilibrating conditions to give a solution of the 2a,4a-di-bromo compound (41). This is reduced by chromous chloride without further treatment, to the 4a-bromo compound (42). The recrystallized bromo compound (42) is then dehydrobrominated via the semicarbazone (43) which is converted without isolation into cortisone acetate (44) by treatment with pyruvic acid ... 

The chloroform solution from which the insoluble 21-fluoro compound has been removed is concentrated in vacuo and the residue recrystallized twice from 95% alcohol. The resulting oxetanone (46) has mp 272-274° ... 

P,17P-Dihydroxyestr-4-en-3-one 1-acetate. The 6-hydroxy compound is removed from the column with 15-17% acetone. Recrystallization of the crude product (1.92 g) from acetone-hexane gives 1.25 g of crystals melting at 165-166° and 0.13 g melting at 162-164° (12.1% yield). When the analytical sample was prepared from the same solvent mixture, the melting point rose to 192-193° (Lit 166° 189-190°) [a] -59.5° (CHCI3) 2, 236 m/i (fi 14,500). 

---