Methanol, esterification with

Surprisingly, there is limited nonproprietary experimental data on methanol esterification with acetic acid (29). Studies have been confined to liquid-phase systems distant from equilibrium (30), in regions where hydrolysis is unimportant. A physical study of the ternary methanol—methyl acetate—water system is useful for design work (31). Methyl acetate and methanol form an azeotrope which boils at 53.8°C and contains 18.7% alcohol An apparent methanol—water azeotrope exists, boiling at 64.4°C and containing about 2.9% water. These azeotropes seriously complicate methyl acetate recovery. Methyl acetate is quite soluble in water, and very soluble in water—methanol mixtures, hence two liquid phases suitable for decanting are seldom found. 

Raw Materials. Eor the first decade of PET manufacture, only DMT could be made sufficiently pure to produce high molecular weight PET. DMT is made by the catalytic air oxidation of -xylene to cmde TA, esterification with methanol, and purification by crystallization and distillation. After about 1965, processes to purify cmde TA by hydrogenation and crystallization became commercial (52) (see Phthalic ACID AND OTHER... 

Herm/es/Djnamit JS obe/Process. On a worldwide basis, the Hercules Inc./Dynamit Nobel AG process is the dorninant technology for the production of dimethyl terephthalate the chemistry was patented in the 1950s (67—69). Modifications in commercial practice have occurred over the years, with several variations being practiced commercially (70—72). The reaction to dimethyl terephthalate involves four steps, which alternate between liquid-phase oxidation and liquid-phase esterification. Two reactors are used. Eirst, -xylene is oxidized with air to -toluic acid in the oxidation reactor, and the contents are then sent to the second reactor for esterification with methanol to methyl -toluate. The toluate is isolated by distillation and returned to the first reactor where it is further oxidized to monomethyl terephthalate, which is then esterified in the second reactor to dimethyl terephthalate. 

Pectins are subdivided according to their degree of esterification (DE), a designation of the percent of carboxyl groups esterified with methanol. Pectins with DE >50% are high methoxyl pectins (HM pectins) [65546-99-8]-, those with DE <50% are low methoxyl pectins (LM pectins) [9049-34-7]. 

Recovery of dilute acetic acid is achieved by esterification with methanol using a sulfonated resin (Dowex 50w) in a packed distillation column (54). Pure methyl acetate is obtained. This reaction is second order in acetic acid, 2ero order in methanol, and partially diffusion controlled. 

Oxidation of ecgonine (2) by means of chromium trioxide was found to afford a keto acid (3). This was formulated as shown based on the fact that the compound undergoes ready themnal decarboxylation to tropinone (4)The latter had been obtained earlier from degradative studies in connection with the structural determination of atropine (5) and its structure established independently. Confirmation for the structure came from the finding that carbonation of the enolate of tropinone does in fact lead back to ecgonine. Reduction, esterification with methanol followed by benzoylation then affords cocaine. 

Hydrogenation of l-0-acetyl-2,4,6-tri-0-benzoyl-2,3-didehydro-3-deoxy-a-D-erythro-hexose (30) gave a crystalline l-0-acetyl-2,4,6-tri-0-benzoyl-3-deoxyhexose in 60% yield, which on de-esterification with methoxide in methanol afforded 3-deoxy- -D-nfeo-hexose (22). It was not possible to hydrogenate the / isomer under the conditions used for the a form, presumably because the large trans-related C-l and C-4 ester groupings prevent the necessary contact with the catalyst. 

C-Disaccharide analogs of trehalose were recently [20c] prepared by using as a key step an aqueous Diels-Alder reaction between the sodium salt of glyoxylic acid and the water soluble homochiral glucopyranosil-l,3-pentadiene 19 (Equation 6.1). A mixture of four diastereoisomers in a 41 24 21 14 proportion was obtained after esterification with methanol and acetylation. The main diaster-eoisomer 20 was isolated and characterized as benzoyl-derivative. 

The second acetamiprid extraction method uses aqueous methanol, and with alkaline methanol to extract acetamiprid and its degradation products which are converted to methyl 6-chloronicotinate (IC-O-Me) through alkaline hydrolysis, oxidation and esterification, prior to column cleanup and GC determination. 

Fatty acid methyl esters (FAME) are currently manufactured mainly by trans-esterification with an alcohol, using a homogeneous base catalyst (NaOH/KOH). Methanol is more suitable for biodiesel manufacturing, but other alcohols can in principle also be used, depending on the feedstock available. The... 

Considering the promising results with 2-ethylhexanol, we tested the applicability of SZ also for esterification with methanol. High conversions can be reached even at 140°C providing that an increased amount of catalyst is used (Figure 33.2). It is worthwhile noting that the esterification with methanol takes place at the highest rates. This can be explained by the alcohols relative sizes. 

Keto acids can be dehydrated to enol lactones (Section III,A,1). They may also undergo esterification with alcohols e.g., /V-methylhydrasteine (104) in methanol at room temperature gave the expected keto ester 126 (R + R = CH2, R1 = CH3) (5,87). Sodium borohydride reduction of keto acid 104 supplies the saturated y-lactone 132 identical with that obtained from enol lactone 98 (5). 

The rate enhancement for the esterification of benzoic acid with methanol was close to 100, when compared with the classical heating under reflux. On the other hand, the rate enhancement for the esterification with n-pentanol, using the same power level (560 W) was only 1.3. The approximate reaction temperature was almost the same for the two alcohols (134 °C and 137 °C respectively). It should be noted, however, that the rate enhancement for the esterification in pentanol increased to 6 times when a higher power level (630 W) was used, the reaction temperature being higher (162 °C). 

The Ester Rule states that in the esterification of hydroxy acids of D-series with methanol, the shift takes place to right but in esterification with ethanol the shift to the right increases. 

The most convenient methods to be used with silica having no pores or very wide ones are the reaction with thionyl chloride, the esterification with methanol or w-butanol and higher alcohols, and ion exchange, e.g., with uranyl ions (however, the general applicability of the latter reagent... 

Dimethylxylaramide 1- To a 250 mL round-bottom flask equipped with a magnetic stirrer was added methanol (50 mL) and the xylaric acid - methanol esterification product (6.7 mmol in 10 mL of methanol) prepared as described above. Triethylamine (6.5 mL, 46 mmol) and methylammonium chloride (1.0 g, 14.7 mmol) were then added to the methanol solution and the reaction mixture was refluxed with stirring overnight. The mixture was concentrated and the residue was washed several times with methanol. The... 

Barbier-type reaction conditions) to yield, after hydrolysis with phosphate buffer and final esterification with methanol under PTSA catalysis, the corresponding functionalized methyl esters 229 (Scheme 77) . 

For example, the reaction of methyl acetate and synthesis gas at 170 C and 5000 psig with a Co-Lil-NPh catalyst results in the formation of acetaldehyde and acetic acid. The rate of acetaldehyde formation is 4.5 M/hr, and the yield based on Equation 15 is nearly 100%. Methane (1-2%) and ethyl acetate (1-2%) are the only by-products. The product mixture does not contain water, methanol or 1,1-dimethoxyethane. The acetic acid can easily be recycled by esterification with methanol in a separate step. 

Methyl />-ethylbenzoate was prepared from ethylbenzene (1 kg.), which was converted into jb-ethylacetophenone by adding aluminum chloride (792 g.), followed by acetyl chloride (462 g.), which was added with stirring at 0-5° over a period of 3 hours. The mixture was stirred for 1 hour longer, allowed to stand overnight, and washed with iced dilute hydrochloric acid. The ethylbenzene was removed by distillation, and the crude product was oxidized to p-ethylbenzoic acid with alkaline hypochlorite.4 Recrystallization of the crude acid from 95% ethanol yielded 350 g. (41%) of the pure acid m.p. 110-112°. Esterification with methanol in the presence of hydrogen chloride 4 yielded methyl />-ethylbenzoate (77-79%). 

A further route to the cycloocta[l,2-c 5,6-c ]difuran system makes use of a Perkin-type reaction. Condensation of furan-3,4-dicarboxaldehyde with furan-3,4-diacetic acid in acetic anhydride and triethylamine at room temperature, followed by esterification with methanol and sulfuric acid, gave... 

The original Garner preparation3 of 5 involves the conversion of serine into the protected methyl ester 3 and controlled reduction of the latter by DIBAL. The reaction sequence employed for the preparation of 3 involves the protection of the amino acid as N-Boc derivative using di-tert-butyl dicarbonate, esterification with methyl iodide or diazomethane, and acetonization with 2,2-dimethoxypropane under acid catalysis. The N-Boc methyl serinate and the ester 3 require purification by vacuum distillation or chromatography. In a modification to this procedure reported by McKillop,2 the esterification reaction of serine is carried out first by methanol/acetyl chloride. The resulting ester is then converted into the N-Boc derivative 2 with di-tert-butyl dicarbonate and the latter transformed into 3 by acetonization. This procedure avoids... 

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