Recrystallization naphthalene

Only if absolutely free from sulfur can aromatic compounds be hydrogenated with platinum metals at low temperatures. Willstatter and Hatt217 hydrogenated twelve times recrystallized naphthalene in glacial acetic acid quantitatively to decalin in presence of platinum black at room temperature and atmospheric pressure. Schroeter218 hydrogenated naphthalene to decalin in precence of nickel catalysts at 40 atm and about 200°, and to tetralin at 15 atm and about 200° ... 

Analysis Determine the melting points of the crude and recrystallized naphthalene, the weight of the latter material, and calculate your percent recovery using Equation 3.1. 

Naphthoquinone reacts in 30 minutes to give l,2,3,4-tetrahydro-l,4-dioxo-naphthalene in 70% yield. After recrystallization from hexane, the product has mp 95-97° 10). 

SimplePHOX 7a proved a useful tool to force the diastereomeric reduction of olefin 31a to pseudopteroxazole precursor 31b in perfect diastereoselectivity and 90% yield with only trace amounts of over-reduced product. NeoPHOX catalyst from ligand 14b, a closely related system to 7a, furnished product 32b in 93% ee, which was then easily recrystallized to enantiopure material with 58% recovery. The R enantiomer of 33b was synthesized by the use of catalyst from ligand 8a in 90% ee and 98% yield with the fully aromatized naphthalene as 2% byproduct. A higher catalyst loading of 2 mol% of catalyst from 7a was used to produce the... 

Naphthyltellurium trichloride (typical procedure) TeCl4 (7.5 g, 27.8 mmol) is added to molten naphthalene (11.0 g, 86 mmol) kept at 110°C under N2. After 12 h at this temperature the greenish solid obtained is pulverized in a mortar and washed thoroughly with hot toluene (15.4 g (54%)). The product is recrystallized from benzene (m.p. 200-202°C). 

After sufficient chloroform has been evaporated to give a solution volume approximating 250 ml., the solution is cooled in an ice bath and the crystalline product collected on a filter. By further concentration of the mother liquor, an additional quantity of naphthalene-1,5-disulfonyl chloride is obtained. A total yield of 85-115 g. (65-88%) of recrystallized material results m.p. 181-183°. 

In a 2-1. round-bottom flask, equipped with a stirrer, are placed 231 g. (0.5 mole) of the addition compound of /3-naphthalene diazonium chloride and mercuric chloride (p. 55), 700 cc. of acetone (b.p. 55-57°) and 189 g. (3 moles) of copper powder (Note 1). The mixture is quickly cooled to 20° and stirred for one hour. The mixture is treated with 700 cc, of concentrated aqueous ammonia solution (sp. gr. 0.9), mixed well, and allowed to stand overnight. The supernatant liquid is decanted the solid is collected on a Buchner funnel and washed successively with 25-cc. portions of water, acetone, and ether. After airdrying, the crude material is recrystallized from xylene, using decolorizing carbon. The crystals thus obtained are slightly yellow (Note 2) and melt at 241.5-243.50. The yield is 51-55 g. (45-48 per cent of the theoretical amount based on the addition compound used). 

C. 2-Bromoacetyl-6-methoxynaphthalene. To a solution of 1 g. (0.005 mole) of 2-acetyl-6-methoxynaphthalene2 in 10 ml. of anhydrous tetrahydrofuran3 (Note 7) contained in a 125-ml. Erlenmeyer flask is added 1.88 g. (0.005 mole) of PTT in small portions. About 10 minutes is required for this operation. A white precipitate forms immediately and the solution becomes pale yellow. After 20 minutes, 50 ml. of cold water is added, and the crystalline precipitate (Note 8) is filtered and washed with 10 ml. of water. The crude, white 2-bromoacetyl-6-methoxy-naphthalene (ca. 1.3 g., m.p. 100-105°) is recrystallized from 32 ml. of cyclohexane to give 1.1 g. (79%) of crystalline product, m.p. 107-109° (lit. 107-1080)4 (Notes 9 and 10). 

Ti(0-f-Bu)4 used in this reaction. Value in parenthesis is after recrystallization. Nps = 2-Naphthalene-sulfonyl. 

Recrystallization from acetone gave 2,3-dihydrospiro[naphthalene-l(4H),3 -piperidine]-2, 4,6 -trione, melting point 197°-199°C. 

Naphthalene endoperoxides have been synthesized with methyl groups located at the 1,4-, 1,8-, 1,2,4-, 1,4,5-, 1,2,3,4-positions, and 1,2,3,4,5,6,7,8-positions in good yield after recrystallization of 58%, 88%, 93%, 54%, 83%, and 69%, respectively [48, 49]. The C—O bond formation preferably takes place at aryl sites bonded by the methyl groups. The stabilities of the endoperoxides were greater with increased numbers of methyl groups on naphthalene [at 25 °C in CDC13, compare... 

The checkers obtained 26.1-26.5 g. (83-84.5%) of 1-(diazoacetyljnaphthalene, m.p. 47-49.5°, when 1-naphthoyl chloride prepared from commercial 1-naphthoic acid was used (ef. Notes 1 and 2). Recrystallization from hexane gave 24.6 g. (78%) of l-(diazoacetyl)naphthalene, m.p. 49.5-52°, that was used in Part B. 

The hexacarbonylniobate(—1) and hexacarbonyltanta-late(—1) anions are well established. The [Nb(CO)6] anion can be prepared at atmospheric pressure of CO from NbCls by using a prereduction step with alkali metal/naphthalene at low temperature, followed by carbonylation of the intermediate at low temperature in DME as solvent. Another method of preparation, also operating at atmospheric pressure of CO, uses the reduction of NbCls with Mg/Zn/pyridine at room temperature and gives yields as high as 48% of recrystallized Na(THF)[Nb(CO)6]. The alkali metal derivatives of [M(CO)6] , M = Nb, Ta, are rapidly oxidized by air the PPN derivatives are stable in air for short periods of time. PPN[Nb(CO)6] and PPN[Ta(CO)6] are isostructural the hexacarbonyl anions possess an almost exact octahedral geometry with the following bond distances Nb-CO, 2.089A Ta-CO, 2.083 A. 

The relative solubilities of compounds are of great importance in connection with recrystallization and extraction. It is difficult to formulate definite rules as to what solvent or type of solvent to use. However, many common solvents are listed in Table 2-5, and their relative behavior with naphthalene will serve as something of a guide as to which solvent to use. 

The cold aqueous solution of the diazonium salt is then added slowly to the decomposition mixture. Considerable frothing occurs, and 4-5 ml. of ether is added from time to time to break the foam. After stirring for 1 hour (Note 3), the mixture is filtered and the crude dark brown precipitate of the 1,4-dinitro-naphthalene is washed several times with water, then with 2% aqueous sodium hydroxide, and again with water. The precipitate is dried and extracted three times with boiling 95% ethanol (450 ml. in all). The extract is concentrated to 75 ml. most of the 1,4-dinitronaphthalene separates and is collected. Additional amounts can be obtained by further concentration. The resulting product melts at 130-132° and weighs 6.0-7.0 g. (52-60%). The product can be purified either by steam distillation (Note 4) or by recrystallization from aqueous ethanol. Pale yellow needles melting at 134° are obtained (Notes 5 and 6). 

SCF technology has spread quickly from molecules such as naphthalene to more complex substances such as polymers, biomolecules, and surfactants. Supercritical fluids can be used to reduce the lower critical solution temperature of polymer solutions in order to remove polymers from liquid solvents(6.26 The technology has been extended to induce crystallization of other substances besides polymers from liquids, and has been named gas recrystallization(4). In other important applications, SCF carbon dioxide has been used to accomplish challenging fractionations of poly(ethylene glycols) selectively based on molecular weight as discussed in this symposium, and of other polymers(. ... 

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