Methanol transesterification with

We first examined the lipase-catalyzed resolution of azirine-2-methanol I, which we expected to have a versatile synthetic utility. As expected for primary alcohols, the enantioselectivity obtained in the transesterification with lipase PS in ether was low (E = 17 at best) at room temperature despite considerable efforts such as screening of lipases, solvents, additives, and acylating agents. 

Chemolysis of ester bonds is performed by hydrolysis or methanolysis. Acidic metha-nolysis, for 24 h at 80 °C, cleaves ester bonds by transesterification, obtaining the fatty acid methyl esters (FAMEs), and has been used to simultaneously study oils, waxes, tannins, resins and polysaccharides in samples collected from embalming materials from Egyptian mummies [17]. Transesterification with trimethyl sulfonium hydroxide in methanol is also used [33,34],... 

Biodiesel is a mixture of methyl esters of fatty acids and is produced from vegetable oils by transesterification with methanol (Fig. 10.1). For every three moles of methyl esters one mole of glycerol is produced as a by-product, which is roughly 10 wt.% of the total product. Transesterification is usually catalyzed with base catalysts but there are also processes with acid catalysts. The base catalysts are the hydroxides and alkoxides of alkaline and alkaline earth metals. The acid catalysts are hydrochloride, sulfuric or sulfonic acid. Some metal-based catalysts can also be exploited, such as titanium alcoholates or oxides of tin, magnesium and zinc. All these catalyst acts as homogeneous catalysts and need to be removed from the product [16, 17]. The advantages of biodiesel as fuel are transportability, heat content (80% of diesel fuel), ready availability and renewability. The... 

The isolated dimethyl sebacate can be sold commercially as is or optionally hydrolyzed to sebacic acid. If a higher molecular weight plasticizer diester is required, a transesterification with -ethyl hexanol, for example, gives the desired product plus two equivalents of methanol which is recycled back to the oxycarbonylation reaction. If the free acid is desired, dimethyl sebacate hydrolysis to sebacic acid is carried out using a strong mineral acid such as sulfuric acid. Hydrolysis is nearly quantitative with a selectivity of about 99.5% to diacid and. 5% to the half-ester acid product. Additional recrystallization is used to improve purity if required. 

Various combinations of Reaction 19 with e.g. transesterification (with methanol) or hydrogenation give access to ethanol, acetic acid and/or methyl acetate. 

Methanol is currently produced from syngas, which has been enriched with C02 and is derived from either a fossil fuel or biomass. A better approach might consist of the direct hydrogenation of pure C02, whilst transesterification with ethylene carbonate implies that ethylene, derived from oil refineries, should be used as the raw material. 

Unsaturated fatty acids or methyl esters are obtained via hydrolysis with water or by transesterification with methanol, while glycerol is produced as a by-product. The structures of some common unsaturated Cig-fatty acids, such as oleic, linoleic, and linolenic are shown in Scheme 1. 

A mixture of methyl or ethyl fatty acid esters that is produced from fats and oils (triglycerides) by transesterification with methanol or ethanol. This mixture can be burned in most diesel engines without modifications, (p. 1205)... 

Many approaches for improving the cold flow properties of biodiesel have been explored. These include blending with petrodiesel, transesterification with medium or branched-chain alcohols instead of methanol or ethanol, crystallization fractionation, and treatment with cold flow improver (CFI) additives. 

Large integrated units combining virgin oil extraction from rapeseed, or soybean, or palm with downstream refining and transesterification with methanol.The minimum step-in size for such plants seems to be 100,000 MT a year (30 million gallon). 

The methyl esters prepared by oxidation of 96 and 97, respectively, with iodine in methanolic potassium hydroxide were converted into atropine-like drugs by transesterification with 2-(dimethylamino)-... 

These compounds 52, 53, 54 and 55 have been deuterium-labelled37 in 33%, 80%, 81% and 70% yield, respectively, starting from the corresponding unlabelled compounds by direct transesterification with perdeuteriated methanol containing 0.1 M NaOH (equation 15). The 2H-labelled methyl esters 52-55 have been used as internal standards for thermospray HPLC mass spectrometric determination of alkaloids produced by Catharanthus roseus, many of which are medicinally important38. 

Addition of the anion of 2-methyl-l,3-cyclopentadione (348) to protoane-monin (349), easily prepared from levulinic acid in four steps (207), led to adduct 350 in low yield due to ready self-condensation (Scheme 39). Transesterification with acidic methanol set the alcohol free, which cyclized spontaneously to the 1 1 mixture of ketals 351 and 352. To enhance the yield of the ketal 352, ketal 351 was recycled by equilibration in acidic methanol. Under Kharash-Grignard conditions, the isopropenyl group added unselectively in 1,4-mode and the ester enolate 353... 

It is worth noting that differences in acid strength between anhydrous Keggin heteropolyacids (H3PW12O40 > H4SiWi2O40 > H3PM012O40 > H4SiMoi204o) measured by ammonia adsorption calorimetry did not correlate simply with the catalytic activity in the reaction of rapeseed oil transesterification with methanol and ethanol [102]. 

Solvolysis (chemolysis) is defined as a techniqne which obtains the raw materials, snch as TPA, DMT, EG monomers and oligomers as the reverse process of PET prodnction by saponification or transesterification with water, methanol or EG. For the process of PET production raw materials of high purity are obligatory. Polycondensation is not a chain reaction, but a step reaction. Impurities can stop the polycondensation at low molar masses, so high-purity standards are also reqnired for the solvolysis prodncts. The choice of process depends on the starting material and the demand for solvolysis prodncts. 

Poly(vinyl alcohol) is made by free-radical polymerization of vinyl acetate and subsequent base-catalyzed transesterification with methanol to yield the alcohol polymer. 

When large quantities are to be processed, the last step (diacetate to diol) is more conveniently carried out as a transesterification, with an excess of methanol and CaO as a catalyst [87]. This process is shown below. It leads to methyl acetate. 

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