Methylene, determination

Several variations of the chemical method are in use. In the one described below, a freshly prepared Fehling s solution is standardised by titrating it directly against a standard solution of pure anhydrous glucose when the end-point is reached, I. e., when the cupric salt in the Fehling s solution is completely reduced to cuprous oxide, the supernatant solution becomes completely decolorised. Some difficulty is often experienced at first in determining the end-point of the reaction, but with practice accurate results can be obtained. The titrations should be performed in daylight whenever possible, unless a Special indicator is used (see under Methylene-blue, p. 463). 

Grote s reagent is useful for the determination of 2-aminothiazoie in blood and wine (145), This thiazole may be extracted from its aqueous solution and then titrated in nonaqueous medium (MeOH) with HCIO4 in the presence of a mixed methyl red-methylene blue indicator (146). 

Brown and Lin reported a quantitative method for methanol based on its effect on the visible spectrum of methylene blue. In the absence of methanol, the visible spectrum for methylene blue shows two prominent absorption bands centered at approximately 610 nm and 660 nm, corresponding to the monomer and dimer, respectively. In the presence of methanol, the intensity of the dimer s absorption band decreases, and that of the monomer increases. For concentrations of methanol between 0 and 30% v/v, the ratio of the absorbance at 663 nm, Asss, to that at 610 nm, Asio, is a linear function of the amount of methanol. Using the following standardization data, determine the %v/v methanol in a sample for which Agio is 0.75 and Ag63 is 1.07. 

It is apparent that it is not particularly easy to determine the exact areas of these features when the various contributions occur together to any significant extent. This is clear from the atactic spectrum, in which slight shoulders on both the methylene and methyl peaks are the only evidence of meso methylenes and iso methyls. 

Miscellaneous Pharmaceutical Processes. Solvent extraction is used for the preparation of many products that ate either isolated from naturally occurring materials or purified during synthesis. Among these are sulfa dmgs, methaqualone [72-44-6] phenobarbital [50-06-6] antihistamines, cortisone [53-06-5] estrogens and other hormones (qv), and reserpine [50-55-5] and alkaloids (qv). Common solvents for these appHcations are chloroform, isoamyl alcohol, diethyl ether, and methylene chloride. Distribution coefficient data for dmg species are important for the design of solvent extraction procedures. These can be determined with a laboratory continuous extraction system (AKUEVE) (244). 

Proton chemical shift data from nuclear magnetic resonance has historically not been very informative because the methylene groups in the hydrocarbon chain are not easily differentiated. However, this can be turned to advantage if a polar group is present on the side chain causing the shift of adjacent hydrogens downfteld. High resolution C-nmr has been able to determine position and stereochemistry of double bonds in the fatty acid chain (62). Broad band nmr has also been shown useful for determination of soHd fat content. 

Methylene iodide [75-11-6], CH2I2, also known as diio dome thane, mol wt 267.87, 94.76% I, mp 6.0°C, and bp 181°C, is a very heavy colorless Hquid. It has a density of 3.325 g/mL at 20°C and a refractive index of 1.7538 at 4°C. It darkens in contact with air, moisture, and light. Its solubiHty in water is 1.42 g/100 g H2O at 20°C it is soluble in alcohol, chloroform, ben2ene, and ether. Methylene iodide is prepared by reaction of sodium arsenite and iodoform with sodium hydroxide reaction of iodine, sodium ethoxide, and hydroiodic acid on iodoform the oxidation of iodoacetic acid with potassium persulfate and by reaction of potassium iodide and methylene chloride (124,125). Diiodoform is used for determining the density and refractive index of minerals. It is also used as a starting material in the manufacture of x-ray contrast media and other synthetic pharmaceuticals (qv). 

The direct microscopic count determines the number of viable and dead microorganisms ia a milk sample. A small amount (0.01 mL) of milk is spread over a 1.0 cm area on a microscope sHde and allowed to dry. After staining with an appropriate dye, usually methylene blue, the sHde is examined with the aid of a microscope (oil immersion lens). The number of bacterial cells and clumps of cells per microscopic field is determined and, by appropriate calculations, is expressed as the number of organisms per milliliter of sample. 

The quaHtative determination of water-soluble perchlorates by precipitation using methylene blue yields a violet precipitate (105). Using potassium, mbidium, or cesium salts for precipitation from ethanol—water solutions can serve as a quaHtative determination of perchlorates (106). 

Properties have been determined for a series of block copolymers based on poly[3,3-bis(ethoxymethyl)oxetane] and poly [3,3-bis(methoxymethyl)oxetane]- (9-tetrahydrofuran. The block copolymers had properties suggestive of a thermoplastic elastomer (308). POX was a good main chain for a weU-developed smectic Hquid crystalline state when cyano- or fluorine-substituted biphenyls were used as mesogenic groups attached through a four-methylene spacer (309,310). Other side-chain Hquid crystalline polyoxetanes were observed with a spacer-separated azo moiety (311) and with laterally attached mesogenic groups (312). 

If an opportunistic preconcentration of the feed is used instead, an entirely different flow sheet results. In this case the MSA composition is a two-phase mixture of methylene chloride and water. Detailed simulations ate requited to determine which of these (or other) 2-ptopanol dehydration flow sheet alternatives is the economically advantaged process. 

In this study we examined the influence of concentration conditions, acidity of solutions, and electrolytes inclusions on the liophilic properties of the surfactant-rich phases of polyethoxylated alkylphenols OP-7 and OP-10 at the cloud point temperature. The liophilic properties of micellar phases formed under different conditions were determined by the estimation of effective hydration values and solvatation free energy of methylene and carboxyl groups at cloud-point extraction of aliphatic acids. It was demonstrated that micellar phases formed from the low concentrated aqueous solutions of the surfactant have more hydrophobic properties than the phases resulting from highly concentrated solutions. The influence of media acidity on the liophilic properties of the surfactant phases was also exposed. 

In this work hybrid method is suggested to determine anionic surfactants in waters. It is based on preconcentration of anionic surfactants as their ion associates with cationic dyes on the membrane filter and measurement of colour intensity by solid-phase spectrophotometry method. Effect of different basic dyes, nature and hydrophobicity of anionic surfactants, size of membrane filter pores, filtration rate on sensitivity of their determination was studied. Various cationic dyes, such as Methylene Blue, Crystal Violet, Malachite Green, Rhodamine 6G, Safranin T, Acridine Yellow were used as counter ions. The difference in reflection between the blank and the sample was significant when Crystal Violet or Rhodamine 6G or Acridine Yellow were used. 

The salts of some enamines crystallize as hydrates. In such cases it is possible that they are derived from either the tautomeric carbinolamine or the amino ketone forms. Amino ketone salts (93) ( = 5, 11) can serve as examples. The proton resonance spectra of 93 show that these salts exist in the open-chain forms in trifluoroacetic acid solution, rather than in the ring-closed forms (94, n = 5, 11). The spectrum of the 6-methylamino-l-phenylhexanone cation shows a multiplet at about 2.15 ppm for phenyl, a triplet for the N-methyl centered at 7.0 ppm and overlapped by signals for the methylene protons at about 8.2 ppm. The spectrum of 93 ( = 11) was similar. These assignments were confirmed by determination of the spectrum in deuterium oxide. Here the N-methyl group of 93 showed a sharp singlet at about 7.4 ppm since the splitting in —NDjMe was much reduced from that of the undeuterated compound. 

During the next fifty years the interest in derivatives of divalent carbon was mainly confined to methylene (CHg) and substituted methylenes obtained by decomposition of the corresponding diazo compounds this phase has been fully reviewed by Huisgen. The first convincing evidence for the formation of dichlorocarbene from chloroform was presented by Hine in 1950. Kinetic studies of the basic hydrolysis of chloroform in aqueous dioxane led to the suggestion that the rate-determining step was loss of chloride ion from the tri-chloromethyl anion which is formed in a rapid pre-equilibrium with hydroxide ions ... 

Unlike the Beckmann rearrangement, the outcome of the Neber rearrangement does not depend on the configuration of the starting oxime derivative E- as well as Z-oxime yield the same product. If the starting oxime derivative contains two different a-methylene groups, the reaction pathway is not determined by the configuration of the oxime, but rather by the relative acidity of the a-methylene protons the more acidic proton is abstracted preferentially. ... 

Gel permeation ehromatography (GPC)/normal-phase HPLC was used by Brown-Thomas et al. (35) to determine fat-soluble vitamins in standard referenee material (SRM) samples of a fortified eoeonut oil (SRM 1563) and a eod liver oil (SRM 1588). The on-line GPC/normal-phase proeedure eliminated the long and laborious extraetion proeedure of isolating vitamins from the oil matrix. In faet, the GPC step permits the elimination of the lipid materials prior to the HPLC analysis. The HPLC eolumns used for the vitamin determinations were a 10 p.m polystyrene/divinylbenzene gel eolumn and a semipreparative aminoeyano eolumn, with hexane, methylene ehloride and methyl tert-butyl ether being employed as solvent. 

B) Acylation of 6-Aminopenicillanic Acid To a solution of the aryl halocarbonyl ketene (0.1 mol) in methylene chloride (sufficient to provide a clear solution and generally from about 5 to 10 ml per gram of ketene) there is added the proper alcohol RjOH (0.1 mol), in this case 5-indanyl alcohol. The reaction mixture is maintained under an atmosphere of nitrogen and stirred for a period of from 20 minutes to 3 hours, care being taken to exclude moisture. The temperature may range from about -70° to about -20°C. The infrared spectrum of the mixture is then taken to determine and confirm the presence of the ketene ester. A solution of 6-aminopenicillanic acid-triethylamine salt (0.1 mol) in methylene chloride (50 ml) is added and the mixture stirred at -70° to -20°C for 10 minutes. The cooling bath is then removed and the reaction mixture stirred continuously and allowed to warm to room temperature. 

The combined acetone extracts were extracted six times with one-fourth volume of ethylene dichloride and the ethylene dichloride extract was evaporated under vacuum to leave the steroid residue. This steroid residue was taken up in a minimum of methylene chloride and applied to the top of a column packed with 30 grams of silica which had been previously triturated with 21 ml of ethylene glycol. Then various developing mixtures, saturated with ethylene glycol, were passed over the column. Cuts were made as each steroid was eluted as determined by the lowering of the absorption of light at 240 mp on the automatic chromatographic fraction cutter. 

The solvents were evaporated in vacuo, and the residue was taken up in 80 ml of 3M hydrochloric acid. After addition of 220 ml of water, the insoluble material was filtered off, washed with 100 ml of water and then dried. The insoluble material weighed 9.5 g and was mainly unreacted bromo compound. The filtrate was reacted with 50 ml of 7 M NaOH, extracted three times with methylene chloride (50 m -t 2 x 25 ml portions), dried over potassium carbonate, and then evaporated. The yield of residue was 26.8 g which corresponds to 71.4% of the theoretical yield. This residue was a colorless solidifying oil and was dissolved in 200 ml chloroform. Hydrogen chloride was bubbled in until a sample of the solution tested acidic to wet pH indicator paper. A precipitate was obtained and recovered by filtration. The precipitate was washed with chloroform and dried. The melting point was determined to be from 246 Cto247.5°C. 

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