Crystallization recrystallization

Materials. Supercritical fluids offer many opportunities in materials processing, such as crystallization, recrystallization, comminution, fiber formation, blend formation, and microceUular (foam) formation. 

B) Add to a suspension of 34 g of 3-acetoxy-7-chloro-1,3-dihydro-5-phenyl-2H-1,4-benzo-diazepin-2-one in 80 ml of alcohol, 6 ml of 4N sodium hydroxide. Allow to stand after complete solution takes place to precipitate a solid. Redissolve the solid by the addition of 80 ml of water. Acidify the solution with acetic acid to give white crystals. Recrystallize from ethanol to obtain 7-chloro-1,3-dihydro-3-hydroxy-5-phenyl-2H-1 4-benzodiazepin-2-one, melting point 203°Cto 204°C. 

Benzoyl-6-deoxy-6-iodo-2,3-0-isopropylidene-a-i, - xylohexulofura-nose (47). A solution of 15 grams (31.3 mmole) of 46 in butanone (200 ml.) containing dry sodium iodide (9.3 grams, 62 mmole) was refluxed for 24 hours. The reaction mixture was cooled, the sodium tosylate removed by filtration, and the filtrate concentrated to dryness. The residue was partitioned between water (50 ml.) and chloroform (2 X 50 ml.) the combined chloroform solutions were washed with water, dried over sodium sulfate and concentrated to a colorless sirup which spontaneously crystallized. Recrystallization from aqueous methanol afforded pure material in two crops (11.6 grams, 85%), m.p. 115°-117°C, [ ]D24 + 36.0° (c, 5.3). Anal Calcd. for C16H1906 C, 44.2 H, 4.4 I, 29.3. Found C, 44.3 H, 4.5 I, 29.4. 

Hydroxy-B-methoxy-B-nitrostyrene. A solution of freshly distilled 2-hydroxy-3-methoxybenzaldehyde (5g), 2.5 ml of nitromethane and 2 g of ammonium acetate in 20 ml of glacial acetic acid is refluxed for two hours. Cool and pour the dark brown mixture into water and allow the gummy product to crystallize. Recrystallize from benzene with the acid of Norit. Yield 2.3 grams of yellow needles melting at 115-122°. This is also to be reduced to an active compound as described in JACS, 72, 2781. 

Considerable geochemical and isotopic evidence has accumulated supporting the concept that many parts of the mantle have experienced a complex history of partial melting, melt emplacement, crystallization, recrystallization, deformation, and metasomatism. A result of this complex history is that the mantle is chemically and isotopically heterogeneous. 

It should be recognized that a seemingly completed precipitation process can be subject to secondary reactions, designated in the overall scheme as aging, which may involve dehydration, crystallization, recrystallization, ripening, etc. of the original particles. 

The pooled extracts of the CH2CI2 washings of the acidified aqueous phase above gave, upon removal of the solvent under vacuum, a brownish residue that crystallized. Recrystallization of this from MeOH gave 0.44 g of N-ethylmelatonin as a white crystalline solid. IR (in cm-1) 790, 829, 929, 1031, 1068,1108, 1182, 1199. MS (in m/z) 173 (100%) indolemethylene+ 160 (67%) parent ion 260 (14%). This amide proved extremely difficult to hydrolyze. 

SYNTHESIS (from MDA) To a solution of 3.6 g of the free base of 3,4-methylenedioxyamphetamine (MDA) in 20 g pyridine, there was added 2.3 g acetic anhydride, and the mixture stirred at room temperature for 0.3 h. This was then poured into 250 mL H,0 and acidified with HC1. This aqueous phase was extracted with 3x75 mL CH2C12, the extracts pooled and washed with dilute HC1, and the solvent removed under vacuum. The pale amber residue of N-acetyl-3,4-methylenedioxyamphetamine weighed 5.2 g as the cmde product, and it was reduced without purification. On standing it slowly formed crystals. Recrystallization from a mixture of EtOAc/ hexane (1 1) gave white crystals with a mp of 92-93 °C. 

Acetic acid (0.2 g) was added to a solution of ethyl-3-amino-2-[[(2 -cyanobiphenyl-4-yl)methyl]amino]benzoate (1 g) in ethylorthocarbonate (5 ml). The mixture was stirred at 80°C for 1 hours. The reaction mixture was concentrated. The solution was washed with an aqueous solution of NaHC03 and water. The solvent was evaporeted to give crystals. Recrystallization from ethyl acetate-benzene afforded colorless crystals l-[(2 -cyanobiphenyl-4-yl)methyl]-2-ethoxybenzimidazole-7-carboxylate (0.79 g, 69%), M.P. 131-132°C. 

Ethyl 2-ethoxy-l-[[2 -(lH-tetrazol-5-yl)biphenyl-4-yl]-methyl]benzimidazole-7-carboxylate (0.24 g) was stirred with 1 N NaOH (1.5 ml) in ethanol (4 ml) for 1 hours at 80°C. The reaction mixture was concentrated, and the concentrate was exrtacted with water and ethyl acetate. The aqueous layer was adjusted to pH 3-4 with 1 N HCI to give crystals. Recrystallization from ethyl acetate-benzene afforded colorless crystals of 2-ethoxy-l-[[2 -(lH-tetrazol-5-yl)biphenyl-4-yl]-methyl]benzimidazole-7-carboxylic acid (0.15 g, 67%), M.P. 183-185°C. 

The light yellow solid which separated was collected by filtration the filtrate was reserved for treatment as described below. Suspension in water of the solid, which weighed 12 grams, and acidification of the mixture with dilute hydrochloric acid produced a gum which soon crystallized. Recrystallization of this solid from ethanol gave 10.2 grams (30%) of 2-diphenylacetyl-l,3-indandione as a light yellow crystalline solid, which melted at 146-147°C. 

The growth kinetics describes the nucleation processes on the atomic scale. Thermally activated processes as adsorption, desorption, and diffusion at the surface and in the volume, nucleation, and crystallization/ recrystallization determine the film structure and can be controlled by the substrate temperature and the growth rate. Using a diagram ln(J ) over 1/ T, R being the deposition rate and T the growth temperature, three different growth modes (epitaxial, polycrystalline, and amorphous) can be... 

Fig. 4.8 Arrangement for surveying a variety of potential solvents for crystallization. A single small crystal is placed on a microscope cover slip. (It may be helpful to mark the location of the crystal by circling it with a felt tipped pen.) The cover slip is then inverted on a short ( 4-6 mm) piece of Tygon tubing mounted on a microscope slide. A few drops of a trial solvent are placed on the side around the periphery of the tubing. They will seep into the space inside the tubing and evaporate, filling it with vapours that may or may not dissolve the crystal. Recrystallization of the sample may be followed on the microscope, and the same sample may be reused many times without loss of material, a Cover slip with crystal in a marked circle, b Microscope slide with a slice of tubing and the coverslip with the crystal (whose size has been exaggerated for clarity).

The above phenylformamidinc (2.1 g) (note the crude product can also be used in the cyclization step) is warmed in a sodium cthoxide solution made by dissolving sodium (0.5 g) in ethanol (15 ml). All of the phenylformamidinc dissolves in 3-5 min.. After 15min a 2- 3-fold volume of water is added to the solution, which is allowed to stand (1 h) to crystallize. Recrystallization from ethanol gives nearly colourless crystals (1.8 g, 85%), m.p. 97-99 C. 

The caffeine can be purified by sublimation as has been done in the experiment in which it was extracted from tea (Fig. 2) or it can be purified by crystallization. Recrystallize the caffeine by dissolving it in the minimum quantity of 30% ethanol in tetrahydrofuran. It can also be crystallized by dissolving the product in a minimum quantity of hot toluene or acetone and adding to this solution ligroin (hexanes) until the solution is cloudy while at the boiling point. In any case allow the solution to cool slowly to room temperature, then cool the mixture in ice, and remove the solvent from the crystals with a Pasteur pipette. Remove the remainder of the solvent under aspirator vacuum, and determine the weight of the caffeine and its melting point. 

Portland cement (containing gypsum) solidifies after 1 to 3 hours. The needle-shaped ettringite crystals recrystallize forming larger needles which bond the cement particles together and solidify the crust. 

A solution of dimethyl 3,3,5,5-tetraphenyl-l,4-pentadiene-l,l-dicarboxylate (200 mg, 0.41 mmol), acetophenone (8.03 g, 66.9 mmol) in benzene (200 mL) was irradiated for 30 min through Pyrex using a 450-W Hanovia medium-pressure lamp. The solvent was removed under vacuum leaving a yellow oil. The sensitizer was removed by bulb-to-bulb distillation at 30 C/0.015 Torr with dry ice cooling of the receiving bulb. The residue consisted of 202 mg (98%) of colorless crystals. Recrystallization (EtjO/hexane) afforded dimethyl 2,2,3,3-tetraphenylcyclopropylmethylidenemalonate yield 161 mg mp 216-217°C. Concentration and silica gel chromatography (5% EtjO/hexane) of the residue afforded an additional 30 mg of the tetraphenylcyclopropane derivative. Total yield 191 mg (95.6%). 

A mixture of 2-diazo-3,4-bis(diphenylmethylene)cyclobutanone (1, 424 mg, 1 mmol) in MeOH (20 mL) and benzene (150 mL) was irradiated (100-W high-pressure Hg lamp) for 2 h. Evaporation of the solvent on a rotary evaporator under vacuum gave an oily residue which was chromatographed (silica gel, benzene), to afford crude crystals. Recrystallization from EtOH afforded the product as colorless prisms yield 372 mg (87%) mp 157-159 X. 

From Lactam 12 To a magnetically stirred slurry of 4-azatricyclo[3.3.2.0 ]deca-6,9-dien-3-one (12, 1.91 g, 0.013 mol) in dry CHjClj (25 mL) was added trimethyloxonium tetrafluoroborate (2.0 g, 0.04 mol) in one portion. During 8 h at rt, a homogeneous solution was obtained. This was carefully treated with 50% aq K2CO3 (5.6 g) the organic portion was filtered through alumina (elution with pentane). Removal of the solvent in vacuo afforded the product yield 1.92 g (92%) as a clear, colorless oil which slowly crystallized. Recrystallization from pentane afforded white needles, mp 49.5-50.5"C. Treatment of an EtjO solution of the product with ethanolic perchloric acid deposited crystals of the perchlorate salt, mp 185.5-186 C (dec. white needles from MeCN/EtjO). 

Since the two inner phenyl groups of 78 are overlapped, 78 becomes chiral in its crystals. Recrystallization of 78 from acetone yielded chiral crystals as orange hexagonal plates (A) and two types of rac-crystals as orange rectangular plates (B, mp 302 °C) and yellow rectangular plates (C, mp 297 °C) [42], X-ray crystal structures of A, B, and C have been analyzed [43], Crystal structures of B and C are completely different. When A was heated at 260 °C, it was converted to C [42], However, when A was put in contact with MeOH vapor, it was converted to B. 

---