The methanol method

The reaction proceeds according to the equation RCOOH -F CH3OH------------RCOOCH3 + H2O 

Several compounds can be used as the catalyst for the esterification reaction. The use of boron trifluoride [151—156] makes it possible, for many systems, to accomplish the 

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An advantage of the acetone/chloroform method as compared to the methanol method is that the aqueous anthocyanin is not contaminated with lipophilic compounds. If the methanol method is used, the concentrated extract can be extracted with hexane, petroleum ether, or diethyl ether to remove unwanted lipophilic compounds after vacuum evaporation of the methanol (Fuleki and Francis, 1968). 

Without going into details of the chromatographic method, a SAR separation (asphaltenes having been eliminated) can be performed in a mixed column of silica followed by alumina. The saturated hydrocarbons are eluted by heptane, the aromatics by a 2 1 volume mixture of heptane and toluene, and the resins by a 1 1 1 mixture of dichloromethane, toluene and methanol. 

Ethyl salicylate (prepared by the same method) has an odour similar to that of methyl salicylate but less intense it is therefore usually impracticable to attempt to distinguish methanol and ethanol by this test alone. 

In general the method is more satisfactory with esters of aromatic acids than with esters of aliphatic acids. Esters of alcohols other than methyl and ethyl are best treated by first converting them into methyl esters thus Heat together under reflux i ml. of the higher ester, 5 ml. of methanol and 0-2 g. of sodium methoxide. [In place of the sodium methoxide, it suffices to add o i g. of metallic sodium to the methanol.] After refluxing, distil off the excess of methanol (b.p, 65 ). The residue is then heated under reflux with benzylamine as described above. 

In Pihkal, Alexander Shulgin mentions that the preparation of MDP-nitropropene can be carried out in cold methanol with aqueous sodium hydroxide as the base. In fact, this method is even more reliable, and gives higher yields than the other method advocated by the dear doctor in his book. 

In many applications in mass spectrometry (MS), the sample to be analyzed is present as a solution in a solvent, such as methanol or acetonitrile, or an aqueous one, as with body fluids. The solution may be an effluent from a liquid chromatography (LC) column. In any case, a solution flows into the front end of a mass spectrometer, but before it can provide a mass spectrum, the bulk of the solvent must be removed without losing the sample (solute). If the solvent is not removed, then its vaporization as it enters the ion source would produce a large increase in pressure and stop the spectrometer from working. At the same time that the solvent is removed, the dissolved sample must be retained so that its mass spectrum can be measured. There are several means of effecting this differentiation between carrier solvent and the solute of interest, and thermospray is just one of them. Plasmaspray is a variant of thermospray in which the basic method of solvent removal is the same, but the number of ions obtained is enhanced (see below). 

Another method used commercially is to grind the gel and extract the water (and residual monomer) with methanol. The methanol is dried and recycled. The dry polymer is ground and screened. 

Transesterification of methyl methacrylate with the appropriate alcohol is often the preferred method of preparing higher alkyl and functional methacrylates. The reaction is driven to completion by the use of excess methyl methacrylate and by removal of the methyl methacrylate—methanol a2eotrope. A variety of catalysts have been used, including acids and bases and transition-metal compounds such as dialkjitin oxides (57), titanium(IV) alkoxides (58), and zirconium acetoacetate (59). The use of the transition-metal catalysts allows reaction under nearly neutral conditions and is therefore more tolerant of sensitive functionality in the ester alcohol moiety. In addition, transition-metal catalysts often exhibit higher selectivities than acidic catalysts, particularly with respect to by-product ether formation. 

Manufacture is either by reaction of molten sodium with methyl alcohol or by the reaction of methyl alcohol with sodium amalgam obtained from the electrolysis of brine in a Castner mercury cell (78). Both these methods produce a solution of sodium methylate in methanol and the product is offered in two forms a 30% solution in methanol, and a soHd, which is a dry, free-flowing white powder obtained by evaporating the methanol. The direct production of dry sodium methylate has been carried out by the introduction of methanol vapors to molten sodium in a heavy duty agitating reactor. The sohd is supphed in polyethylene bags contained in airtight dmms filled in a nitrogen atmosphere. 

The separation and analysis of 1-propanol are straightforward. Gas chromatography is the principal method employed. Other iastmmental techniques, eg, nmr, ir, and classical organic quaHtative analysis, are useful. Molecular sieves (qv) have been used to separate 1-propanol from ethanol and methanol. Commercial purification is accompHshed by distillation (qv). 

Dimethyl succinate [106-65-0] (mp 19°C, bp 196°C at atmospheric pressure) can be produced from methanol and the anhydride or the acid, or by hydrogenation of dimethyl maleate (38,39). The same methods can be used to prepare diethyl succinate [123-25-1] (mp — 18°C, bp 216.5°C at atmospheric pressure) and diisopropyl succinate [924-88-9]. 

Ash is a measure of residual sodium acetate. A simple method consists of dissolving the PVA in water, diluting to a known concentration of about 0.5 wt %, and measuring the electrical conductivity of the solution at 30°C. The amount of sodium acetate is estabUshed by comparing the result to a cahbration curve. A more lengthy method involves the extraction of the PVA with methanol using a Soxhlet extractor. The methanol is evaporated and water is added. The solution is titrated using hydrochloric acid in order to determine the amount of sodium acetate. 

Improvements to the methanol reductant processes may be found in the patent Hterature. These include methods of operation to reduce acidity in the crystallisation 2one of the generator to promote crystallisation of sodium sulfate and to reduce sulfuric acid consumption (48). Other improvements sought are the elimination of formic acid and chlorine impurities from the chlorine dioxide, as weU as methods of recovering acid and sodium hydroxide, or acid and neutral sodium sulfate from the soHd sodium sesquisulfate salt waste stream (48—52). 

RGA Example In order to illustrate use of the RGA method, consider the following steady-state version of a transfer function model for a pilot-scale, methanol-water distillation column (Wood and Berry, Terminal Composition Control of a Binaiy Distillation Column, Chem. Eng. Sci, 28, 1707, 1973) Ku = 12.8, K = -18.9, K. i = 6.6, and Koo = —19.4. It follows that A = 2 and... 

Solvent selection ana screening approaches can be divided into two levels of analysis. The first level focuses on identification of functional groups or chemical famihes that are hkely to give favorable solvent-key component molecular interactions. The second level of analysis identifies and compares individual-candidate solvents. The various methods of analysis are described briefly and illustrated with an example of choosing a solvent for the methanol-acetone separation. 

H2NOH-HC1, Pyr, 60°. This is the standard method for the preparation of oximes. Ethanol or methanol can be used as cosolvents. 

Here the integration method will be shown that was used for the workshop program (Berty et al, 1989) to integrate the UCKRON rate equations. Since this is about methanol synthesis the reaction is shown here with the stochiometric coefficients ... 

The Heck reaction is considered to be the best method for carbon-carbon bond formation by substitution of an olefinic proton. In general, yields are good to very good. Sterically demanding substituents, however, may reduce the reactivity of the alkene. Polar solvents, such as methanol, acetonitrile, N,N-dimethylformamide or hexamethylphosphoric triamide, are often used. Reaction temperatures range from 50 to 160 °C. There are various other important palladium-catalyzed reactions known where organopalladium complexes are employed however, these reactions must not be confused with the Heck reaction. 

The following method is described in U.S. Patent 2,430,891. To a solution of 10 parts of tris-p-methoxyphenyl ethylene in 35 to 40 parts of carbon tetrachloride Is added a solution of 2.0 parts of chlorine in 50 parts of carbon tetrachloride, with stirring, and over a period of Vj hour. The carbon tetrachloride is then removed by distillation on a steam bath and the residual oil is recrystallized from 250 to 400 parts of methanol, decolorizing with charcoal or the like if necessary. Tris-p-methoxyphenyl chloroethylene is obtained in a yield of 65 to 75%. It melts at 113° to 114°C. 

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