Separation with basic methanol

Table V. Separation of Preasphaltenes by Extraction with Basic Methanol...

Aldehyde 123 was then reacted in a stereoselective Homer-Wadsworth-Emmons reaction with the sodium salt of phosphonate 124 to produce enone 125 (Scheme 3.31). Chemo- and stereoselective rednction of enone 125 with zinc borohydride provided secondary alcohol 126 as a 1 1 mixture of C-15 epimers, which could be separated by chromatography. Next, solvolysis of the acetate in 126 with basic methanol was followed by protection of the two alcohols with dihydropyran in the presence of a catalytic amount of para-toluenesulfonic acid. Reduction with DIBAL-H then provided lactol 127. Wittig reaction of 127 with the nonsta-bilized ylide 128 and snbsequent deprotection produced ( )-prostaglandin F (113). 

A total of 3 g (0.13 moles) of sodium hydride is added to a solution consisting of 10 g of 17 -hydroxy-5a-androstan-3-one (36 mmoles) in 200 ml of benzene and 10 ml of ethyl formate. The reaction mixture is allowed to stand under nitrogen for 3 days followed by dropwise addition of 10 ml of methanol to decompose the excess of sodium hydride. The solution is then diluted with 300 ml water and the layers are separated. The basic aqueous solution is extracted with ether to remove neutral material. The aqueous layer is acidified with 80 ml of 3 A hydrochloric acid and the hydroxymethylene steroid is extracted with benzene and ether. The combined organic extracts are washed with water and saturated sodium chloride solution and then dried over magnesium sulfate and concentrated. The residue, a reddish-yellow oil, crystallized from 10 ml of ether to yield 9.12 g (83%) of 17 -hydroxy-2-hydroxymethylene-5a-androstan-3-one mp 162-162.5°. Recrystallization from chloroform-ether gives an analytical sample mp 165-165.5° [a]o 53° (ethanol) 2 ° 252 mjj. (g 11,500), 307 m u (e 5,800). 

A polyethylene-coated (PEE) silica column was used with water-methanol eluents to achieve the separation and retention of 27 pesticides.40 The retention times of 33 commercial pesticides were determined on an octadecyl (ODS)-derivatized alumina column using water-methanol eluents and compared with retention properties on an ODS-silica column packing.41 More recently, RP-HPLC was used in combination with diode array detection for the identification and quantification of 77 pesticides (acidic, basic, and neutral) in groundwater samples.42... 

Berge and Deye studied the effect of column surface area on the retention of polar solutes [18]. They found that there was a linear relationship between retention and the surface area. 4-Hydroxy benzoic acid was used as a model acidic compound, and sulfamethazine, sulfanilamide, sulfi-somidine, and sulfapyridine were used as the model basic compounds. The separations were carried out on a packed Nucleosil Diol column with a methanol-modified carbon dioxide as the mobile phase. The UV detector was used for the analysis. It was observed that 0.1% acetic acid for the acidic solutes and 0.1% isopropylamine for basic solutes was required in the methanol to achieve the separations. The efficiency was found to be similar for 100-, 300-, and 500-A packing materials. 

Fig. 4 Separation of basic compounds on the alkylpho-sphonate-modified magnesia-zirconia composite column with 35 65 (v/v) methanol-TRIS buffer (5.0 mM TRIS and 50 mM NaCl, pH 10.0) as mobile phase at a flow rate of 1.0 mL/min. 1—Solvent 2—Caffeine 3—Aniline 4—O-toluidine 5— A-methylaniline 6—0-nitroaniline 7— A,A -dimethylaniline 8—P-aminonaphthalene. (From Ref. [25].)...

The production of methyl formate by carbonylation of methanol with basic catalysts [134] can be used to separate carbon monoxide from by-product synthesis gas streams, e.g., steel-mill off-gases [135], to generate clean sources of CO for production of acetic acid by methyl formate isomerization. Therefore methyl formate could be produced near cheap CO sources and then transported to an appropriate site for conversion to acetic acid. This route to acetic acid is potentially competitive with a classic grass-roots methanol carbonylation process. Though the process has not been commercialized, numerous companies have patented the isomerization of methyl formate [136]. 

Nonaqueous capillary electrophoresis has been applied to the separation of basic drugs (316). Efficient, rapid, and versatile conditions were obtained with 20 mM ammonium acetate in acetonitrile-methanol-acetic acid (49 50 1). Baseline separations of 9 morphine analogs, 11 antihistamines, 11 antipsychotics, and 10 stimulants could each be obtained within 6 min. Migration times for individual components had Relative Standard Deviation between 0.8% and 3.5%. Using an internal reference, normalized peak areas were between 2.2% and 9.1%. The precision data was reported to be instrument dependent, since excellent results were obtained only when the instrument had precise evaporation- and temperature-control systems. 

Solvents. Mixtures of chloroform and methanol containing a little water have been the principal solvents used for separations of phospholipids [128,150,163,210]. They have been combined in two-dimensional procedures with basic [1,69, 111, 186] or acidic [1, 111, 127,177] solvents. The solvents customarily employed for TLC of phospholipids can be used also for separating sulpholipids [69,210]. Glycolipids have been chromatographed with chloroform-methanol-water [73, 150, 172, 198] but especially with aqueous propanol [106, 107, 163, 199]. 

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