Reactions recrystallization

Szilard-Chalmers reaction, recrystallization and, 1 290-292 HoxN protein, 47 287 HoxW protein, 47 288 —HoxX protein, 47 290 hoxY gene product, 38 409-410 HjPOj-, 33 106... 

Ethoxy-l-oxa-l-cyclopentenium fluoroborate (O-ethylbutyrolactonium fluoroborate 2-ethoxy-l-oxolenium fluoroborate) 216 Triethyloxonium fluoroborate (95 g, 0.5 mole) is added to dry butyrolactone (43 g, 0.5 mole). The salt dissolves to a clear solution, which, however, soon discolors and separates into two layers. After 3 days the lower layer is separated off it crystallizes in a freezing mixture and is then filtered off with cooling and exclusion of moisture. This gives 87 % (88 g) of crude product that is pure enough for further reaction. Recrystallization can be effected from / -tolunitrile below 50° the m.p. is then 42°. 

Background. The phosphate minerals apatite, monazite and xenotime have strongly variable retention properties for Pb under crustal conditions. The mechanisms by which the daughter product can be lost include dissolution/reprecipitation reactions, recrystallization, and diffusive loss. The latter mechanism is likely a common source of discrepancy between a mineral date and the age of the rock from which it formed. 

N-Aminophthalimide is available from Fluka AG or may be prepared from phthalimide and hydrazine. The quality is important the m.p. should be 199-202° with subsequent resolidiiication of the melt due to thermal reaction. Recrystallization, if necessary, can be carried out in ethanol. The checkers observed that with one batch of recrystaDized material, the solid never really did melt, but seemed to sinter at 200°. 

The most exciting enantioselective photochemical conversion of a a-oxoamide to a P-lactam has been found in the case of N,N-diisopropylbenzoylformamide (96) which gives P-lactam 97. In the photocyclization of plain 96 in the solid state, optically active P-lactam 97 of high optical purity was obtained in high chemical yield. Thus no optically active host compound is necessary for the enantioselective reaction Recrystallization of 96 from benzene afforded colorless prisms. That each crystal is chiral was shown by photochemical conversion into the optically active 97. Crystals of 96 which gave (-t-)- and (—)-97 on photocyclization have been tentatively identified as (- -)- and (—)-crystals of 96, respectively. Large amounts of the - -)- and (—)-crystals of 96 can easily be prepared by seeding with finely powdered (-1-)- and (—)-... 

The Duthaler aldol reaction [21] utilizes the transmeta-lation of relatively stable lithium enolates of tert-butyl acetate with chloro(cyclopentadienyl)-bis(l,2 5,6-di-0-isopropylidene-a-D-glucofuranos-3-0-yl)titanate. The so-obtained titanium enolate adds to the re-side of aldehydes and can be converted under acid or basic conditions into its corresponding acid. As often performed for the Braun aldol reaction, recrystallization of the primary aldol product is used as a convenient way for purification and improvement of selectivities. 

Phenylacetic acid. Use 5 0 g. of magnesium, 25 g, (23 ml.) of redistilled benzyl chloride (Section IV,22) and 75 ml. of sodium-dried ether. Allow the reaction mixture to warm to 15° and then decompose it with dilute hydrochloric or sulphuric acid. Filter off the crude acid and recrystallize it from water. The yield of pure phenylacetic acid, m.p. 76-77°, is 11 g. 

Once the reaction mix has cooled after reflux, 500mL of room temperature dHsO can be added and the whole solution extracted with DCM. The DCM layer is separated and the solvent removed by distillation to give the li-nitropropene as an oil of all things. This oil can then be recrystallized in hot methanol just like the crystalline form was [38]. 

The way the chemist knows that she has methylamine and not ammonium chloride is that she compares the look of the two types of crystals. Ammonium chloride crystals that come from this reaction are white, tiny and fuzzy. The methylamine hydrochloride crystals are longer, more crystalline in nature and are a lot more sparkly. The chemist leaves the methylamine crystals in the Buchner funnel of the vacuum filtration apparatus and returns the filtrate to the distillation set up so it can be reduced one last time to afford a second crop. The combined methylamine hydrochloride filter cake is washed with a little chloroform, scraped into a beaker of hot ethanol and chilled. The methylamine hydrochloride that recrystallizes in the cold ethanol is vacuum filtered to afford clean, happy product (yield=50%). 

The cinnamate ester prepared as above (23.2 g. 79 mmol) was added as a solid slowly to refluxing xylene (500 ml) over a period of 3 h at a rate that prevented accumulation of unreacted azidocinnamate in the solution (monitored by gas evolution through a gas bubbler). The solution was refluxed for an additional 2 h after gas evolution ceased. The reaction mixture was cooled and the solvent removed in vacuo. The residue was recrystallized from methanol to give pure product (20.7 g, 99% yield). 

Phenyl-3-oxopropanoic acid (25 mmol) and EtjN (87.5 mmol) were dissolved in THF (150 ml) and cooled to —40°C. Ethyl chloroformate (27.5 mmol) was added dropwise to this solution and then the reaction mixture was stirred for 30 min at —20°C. Di-n-hexylamine (27.5 mmol) was added to the suspension and it was stirred at room temperature for an additional hour. The reaction mixture was diluted with water (100 ml) and extracted with ether (400 ml). The extract was washed with aq. 5% HCl (100 ml) and brine (2 X 100 ml) and dried over NajSO. The crude amide was obtained by removal of the solvent in vacuo and phenylhydrazine (25 mmol) was added. The mixture was heated to 100°C for 30 min. The residue was held in vacuo to remove the water formed and then powdered ZnCl2 (125 mmol) was added. The mixture was heated at 170"C with manual stirring for 5 min. The cooled residue was dissolved in acetone (100 ml) and diluted with ether (500 ml). Water (100 ml) was added. The organic layer was separated and washed successively with 5% aq. HCl (100 ml) and brine (2 x 100 ml) and dried over NajSO. The solvent was removed in vacuo, and the residue was recrystallized from EtOAc-hexane. The yield was 79%. 

A solution of 6-bromoindole (O.lOmol) in toluene (200 ml) was treated with Pd(PPh3)4 (5mol%) and stirred for 30 min. A solution of 4-fluorophenyl-boronic acid (0.25 M, 0.15 mol) in abs. EtOH was added, followed immediately by sal aq. NaHCOj (10 eq.). The biphasic mixture was refluxed for several hours and then cooled to room temperature. The reaction mixture was poured into sat. aq. NaCl (200 ml) and the layers separated. The aq. layer was extracted with additional EtOAc (200 ml) and the combined organic layers dried (Na2S04), filtered and concentrated in vacuo. The solution was filtered through silica gel using hexane-CHjCl -hexanc for elution and evaporated. Final purification by recrystallization gave the product (19 g, 90%). 

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. 

Ammonium fluorosulfate is produced from ammonium fluoride by reaction with sulfur trioxide, oleum, or potassium pyrosulfate, 1 2820 (48). Solutions of ammonium fluorosulfate show Htfle evidence of hydrolysis and the salt may be recrystallized from hot water. Ammonium fluorosulfate absorbs anhydrous ammonia to form a series of Hquid amines that contain 2.5—6 moles of ammonia per mole of salt (77). 

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. 

The oxidation reactor effluent and methanol ate sent to the esterification reactor, which operates at up to 250°C and a pressure sufficient to maintain the Hquid phase. This latter is about 2500 kPa (25 atm). The oxidation products are converted to methyl -toluate and dimethyl terephthalate without a catalyst. Excess methanol is suppHed, and steam and vaporized methanol ate removed and enter a methanol recovery column. The esterification products flow to a cmde ester column, which separates the toluate from the terephthalate. The overhead stream of methyl -toluate is returned to the oxidation reactor, and the bottoms stream of dimethyl terephthalate goes to a primary distillation. The distillate is dissolved in methanol, crystallized, and sohd dimethyl terephthalate is recovered. The dimethyl terephthalate can then be either recrystallized or distilled to yield the highly pure material needed for the polyesterification reaction. 

The reaction takes place at atmospheric pressure. For stable control of the reaction rate, the reaction is first carried out at a temperature of 50°C and then at 60°C. Overall, this batch reaction takes about 9 hours. After completion of reaction, the slurry is diluted to about 70% sulfuric acid solution, and cmde sulfamic acid crystals are separated by centrifuge. The crystals are dissolved in mother Hquor to make a saturated solution at 60°C and the solution is concentrated under vacuum at 40°C. Purified sulfamic acid is obtained by recrystallization. 

Ar = 1 — naphthyl and l-CH -l-naphthyl). When At was 2-CH C H the product was di-2-tolylbismuthinic acid [124066-74-6] rather than the ester. The reaction was unsuccessful when At was l-ClCgH, 3-CF3C3H4, or 2-thienyl. The methyl esters underwent ester exchange when recrystallized from ethyl or isopropyl alcohols. Methyl diphenylbismuthinate [124066-62-2] was readily hydrolyzed in water to diphenylbismuthinic acid [124066-70-2],... 

Amino alcohols can be resolved by a number of pathways including hydrolysis, esterification, and transesterification. For example, hydrolysis of Ai,0-diacet5l-2-amino-l-butanol with PPL followed by recrystallization results in (80a) with 95% ee (108). Hydrolysis of racemic acetates or butyrates of 2-[(aLkoxycarbonyl)amino]-l-aLkanols with PFL gives (R)-alcohol (81) with 95% ee (109). (3)-(81) can be obtained by transesterification of the racemic (81) with ethyl acetate which also serves as the reaction medium (109). 

Ethyl 4,5-Dlbenzamldopent-4-enoate (2) Ethyl 3-lmidazol-4(5)-ylpropanoale 1 (9.2 g, 54 mmol) In ElOAc (140 mL) was treated with benzoyl chloride (15 7 g, 112 mmol) In ElOAc (40 mL) and 1M NaHCOa (380 mL) added simultaneously In 1 h under Ice-cooling. The reaction mixture was stirred for 1 h, then a further portion of benzoyl chloride (IS 7 g, 112 mmol) in ElOAc) and iM NaHCOa (280 mL) was added m the same manner, followed by an additional portion o( 1M NaHCOa (200 mL) The reaction mixture was stirred for 24 h, then the organic layer was separated, concentrated, and the residue dissolved in THF (300 mL) The THF solution was stirred with 10% NaHCOa (600 mL) for 24 h to decompose any N-lormyl intermediate and to remove benzoic acxl Extraction with EtOAc, drying (Na2S04), solvent evaporation and recrystallization of the residue from EtOAc hexane afforded 16 24 g of 2 (84%), mp 128-129°C... 

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