Methanol as organic solvent

Since the 1980s, precolumn derivatization methods have gained wider acceptance due to simpler preparation, faster analyses, and better resolution. The separation on reversed-phase C-8 or C-18 columns typically requires low-ultraviolet (UV) mobile phases, such as sodium phosphate or sodium acetate buffers, with acetonitrile or methanol as organic solvents. Separation times range from 15 to 50 min. 

The more distinct the polar/ionic character of the analytes to be separated, the more selective are the phases that are suitable for such interactions. Therefore, phases with strongly acidic silanol groups have the best selectivity for bases. Spherisorb ODSl and Resolve, for example, are able to discriminate strong bases even in an acidic buffer with methanol as organic solvent. In contrast, the bases elute inert or are even excluded in the case of acetonitrile. However, for good selectivity one often has to accept a stronger asymmetry. 

Olefinations using a solid-supported triphenylphosphine were accomplished within 5 min of microwave heating at 150 °C using potassium carbonate as the base and methanol as the solvent (Scheme 7.96). A variety of aldehydes and organic halides were studied with the solid-supported phosphine, yielding the corresponding alkenes in excellent purities. 

The drug substance was a water-soluble base in salt form with a pK of about 9 that was also soluble in most organic solvents. The polymer in the tablet was, however, soluble only in an organic medium like methanol. Other organic solvents such as acetonitrile and dimethylformamide were... 

Water as solvent is good when the use of the so-produced hydrogen peroxide solution is also compatible with the use of water and with the low concentration obtained (typically not more than 1-2 wt%), because the concentration operation is costly and risky. Therefore, for wastewater or some bleaching treatments the methodology could be applied, but for organic syntheses which typically require methanol as the solvent the synthesis in this latter medium is necessary. 

A practical resolution of 3-phenyl-2H-azirine-2-methanol 15 at a very low temperature (-40 °C) was reported by Sakai et al64 to enhance the enantioselectivity in immobilized lipase-catalyzed resolution of 15 using vinyl butanoate as acyl donor in ether as organic solvent. The method was found to be effective in enhancing the enantioselectivity E and affords the primary alcohol (S)-15 with 99% ee and the ester (A)-16 with 91% ee. 

As mobile phase, different buffers at different pH values (mainly 6.8 or 7.4) with organic modifiers are used. Results obtained with methanol as co-solvent were shown by Baczek et al. (2000) to correlate better to octanol-water partitioning data than results using acetonitrile as organic co-solvent. The H-bonding capabilities of the alcohol seem to be the reason for that. 

Methanol can be released from natural sources (e.g., emissions from certain plants, as a by-product of degradation of organic material) as well as from human use of methanol as a solvent. Methanol has a low vapor pressure and will volatilize into air. With... 

The combination of a good catalyst with a preferred solvent for the desired organic reaction can benefit the reaction system. Several solvents were used to study the effects of solvent on reaction rates and product selectivity on the newly-developed low palladium content catalyst. For N-phenylbenzylamine debenzylation, higher hydrogenation activity was obtained by employing methanol as a solvent. THF (tetrahydrofuran), and cyclohexane were found to be less effective. Studer and Blaser [7] studied the solvent effects on catalytic debenzylation of 4-chloro-N,N-dibenzyl anihne and foimd that the overall reaction rate was slower with the use of non-polar solvents. 

The static mode uses both organic solvents such as toluene, methanol, and acetone and solvent mixtures (usually in a 1 1 ratio) including dichloromethane-acetone, acetone-hexane, heptane-acetone, acetone-isohexane, and methanol-water. Water has rarely been used as the extractant in the static mode however, it is the extractant most frequently used in the dynamic mode, both alone and with modifiers such as organic solvents, surfactants, and derivati-zing reagents. 

However, there are some methods for extraction of cellulose from plants. Han and Rowell s (1996) method describes a procedure for extraction of holocellulose, hemicelluloses, cellulose and lignin [18]. The method consists of four principle steps (1) preparation of sample (grinding of the wood), (2) removal of extractives, (3) preparation of holocellulose (removal of lignin), (4) preparation of a-cellulose (removal of hemicellulose). Several other procedures for a-cellulose extraction from wood samples have already been described during the last decades. Older methods used benzene-methanol instead of toluene-ethanol as organic solvent for the second step. Toluene-ethanol works as well as benzene-methanol mixture, and reduces health risks associated with the use of benzene and methanol. 

Different electro-organic reaction systems have been studied. The anodic reactions investigated are mainly the four-electron methoxylation of 4-methoxytoluene [6, 7, 11, 12] and the two-electron methoxylation of furan to 2,5-dimethoxy-2,5-dihydrofuran [10], but also other methoxylation and acetoxylation reactions [11]. Methoxylation reactions are performed in methanol as a solvent, whereas acetoxyla-tions are performed in acetic add. Moreover, Kiipper et al. [7] reported the anodic two-electron decarboxylation of sodium glucanate in an aqueous medium. The cathodic... 

T.Tajima,T. Fuchigami, Development of a novel environmentally friendly electrolytic system by using recyclable solid-supported bases for in situ generation of a supporting electrolyte from methanol as a solvent application for anodic methoxylation of organic compounds, Chem. Ear. J. 2005, 11, 6192-6196. 

The preparation of glycerol-based Ca-synthons and intermediates represents an interesting example where enzymatic transesterification is widely exploited. Alcoholysis of tributyrin with PPL was already shown to produce a chiral diglyceride (Fig. 3). Alcoholysis of trityl-protected dibutyrin with methanol in organic solvents shows some essential features about regio- and enantioselectivity in bifunctional compounds (Fig. 18) (25). Most lipases, such as lipases PS and AK and Novozym 435, first regioselectively produce the primary alcohol from the diester. With lipase AK, the reaction leads to effective kinetic resolution (A), whereas Novozym 435-catalyzed reaction (B) is not enantioselective. However,... 

Many different solvents, such as hydrochloric acid, trichloroacetic acid, and perchloric acid, as well as organic solvents such as methanol, dichloromethane, acetone, and acetonitrile have been used to extract BAs from food samples and for subsequent FIA determination. Which solvent is used depends on the subsequent FIA analysis system to be used, on whether separation columns are used, whether there is derivatization or combination with biosensors, and so on. 

Methanol was one of the earliest organic solvents used in physical and chemical studies. Methanol, like other alcohols, is referred to as latent solvent, whose hidden solvent qualities are brought out by the addition of an active solvent. The presence of a latent solvent increases the tolerance of an active solvent for a nonsolvent. Therefore, latent solvent is also called an extender, because it increases the volume of a solution without decreasing the solvent power [37]. Some important physical properties for methanol as a solvent are listed in Table 3 [3740]. 

There is a growing interest on selection of the mobile phase components such as organic solvent, acid, and pH. The results showed that the use of methanol in a mobile phase, induced very slow elution of flavonoids and isoflavones from the chromatography column, and the peaks were not symmetrical. Furthermore, the use of methanol as an organic modifier significantly decreased the efficiency of the chromatographic column, as compared to acetonitrile, which was observed on the basis of the low number of theoretical plates. 

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