Methyl acetate pyrolysis

With aldehydes, primary alcohols readily form acetals, RCH(OR )2. Acetone also forms acetals (often called ketals), (CH2)2C(OR)2, in an exothermic reaction, but the equiUbrium concentration is small at ambient temperature. However, the methyl acetal of acetone, 2,2-dimethoxypropane [77-76-9] was once made commercially by reaction with methanol at low temperature for use as a gasoline additive (5). Isopropenyl methyl ether [116-11-OJ, useful as a hydroxyl blocking agent in urethane and epoxy polymer chemistry (6), is obtained in good yield by thermal pyrolysis of 2,2-dimethoxypropane. With other primary, secondary, and tertiary alcohols, the equiUbrium is progressively less favorable to the formation of ketals, in that order. However, acetals of acetone with other primary and secondary alcohols, and of other ketones, can be made from 2,2-dimethoxypropane by transacetalation procedures (7,8). Because they hydroly2e extensively, ketals of primary and especially secondary alcohols are effective water scavengers. 

Alcohols can be dehydrated via xanthate esters at temperatures that are much lower than those required for acetate pyrolysis. The preparation of xanthate esters involves reaction of the alkoxide with carbon disulfide. The resulting salt is alkylated with methyl iodide. 

While the direct carbonylation is well accepted by industry, the reductive and oxidative carbonylations are still in the research and development stage. Using Texaco technology (j, 7/ ) the combined synthesis of ethene and ethanol is feasible via homologation of acids according to Figure 3. Ethene can also be obtained from the reductive carbonylation of methyl acetate to ethyl acetate followed by pyrolysis (2 ). Both routes, so far, lack selectivity. 

Nitrogen is passed through a vertical borosilicate combustion tube (20 x 300 mm) that is filled with solid masses and heated at 500°. 4,5-Cyclohexenedi(methyl acetate) (300 g, 1.33 moles) is added in portions at 1.5-min intervals. The product is condensed, washed with water, and dried over potassium carbonate. Thorough fractionation provides 4,5-di-(methylene)cyclohexene (68.1 g) together with starting material and the (2-methylene-4-cyclo-hexenyl)methylacetate that results from partial pyrolysis. 

This reaction was first reported by Kuhn and Roth in 1933. It is a method for quantifying the number of methyl groups attached to the carbon atom in an organic molecule, which involves the oxidation of such an organic compound with chromic acid in the presence of sulfuric acid, followed by steam distillation to collect the generated acetic acid and quantification of the acetic acid via acid/base titration. In addition, the collected acetic acid can be further analyzed by conversion of acetic acid into lithium acetate, pyrolysis of lithium acetate to acetone, and transformation of acetone into iodoform by hypoiodite. Therefore, this reaction is generally known as the Kuhn-Roth C-methyl determination, Kuhn-Roth chromic acid oxidation, Kuhn-Roth degradation, Kuhn-Roth determination, or Kuhn-Roth oxidation. " ... 

The effect of structure on the rate of gas-phase pyrolysis of acetates and carbonates has been found to be similar, the faster rate of the latter being derived equally from lower activation energies and more positive entropies of activation. The a-elimination of acetic acid from methyl acetate derivatives... 

Hydrogenation followed by esterfication will eliminate most of the undesirable characteristics of bio-oils previously listed. Acetic acid is one of the most common carboxylic acids present in bio-oil and is a primary cause of the corrosiveness characteristic. Acetic acid can be reacted with methanol to form methyl acetate. When methyl acetate is hydrogenated using CuGCuCr O as the catalyst, methanol and ethanol are the products. These chemicals have value as fuel or can be introduced into another product stream. About 10-20% of the bio-oil being produced in the pyrolysis unit at MSU can be converted to esters. 

In a typical Knof procedure, 3jS-hydroxyandrost-5-en-17-one acetate is epoxidized with perbenzoic acid (or m-chloroperbenzoic acid ) to a mixture of 5a,6a- and 5)5,6)5-epoxides (75) in 99 % yield. Subsequent oxidation with aqueous chromium trioxide in methyl ethyl ketone affords the 5a-hydroxy-6-ketone (76) in 89% yield. Baeyer-Villiger oxidation of the hydroxy ketone (76) with perbenzoic acid (or w-chloroperbenzoic acid ) gives keto acid (77) in 96% yield as a complex with benzoic acid. The benzoic acid can be removed by sublimation or, more conveniently, by treating the complex with benzoyl chloride and pyridine to give the easily isolated )5-lactone (70) in 40% yield. As described in section III-A, pyrolysis of j5-lactone (70) affords A -B-norsteroid (71). Knof used this reaction sequence to prepare 3)5-hydroxy-B-norandrost-5-en-17-one acetate, B-noran-... 

The pyrolysis of sodium chlorodinuoroacetate is still a widely used, classical method for generating difluorocarbene, especially with enol and allyl acetates [48, 49, 50, 51] (equation 21) A convenient alternative that avoids the hygroscopic salt uses methyl chlorodifluoroacetate with 2 equivalents of a lithium chlonde-hexa-methylphosphoric triamide complex at 75-80 °C in triglyme [52], Yields are excellent with electron-rich olefins but are less satisfactory with moderately nucleophilic alkenes (4-5% yields for 2-bulenes)... 

Figure 11.11 Pyrogram of a paint sample collected from a decorative frame of the Universal Judgement by Bonamico Buffalmacco (fourteenth century, Monumental Cemetery of Pisa, Italy). Pyrolysis was performed with a microfurnace pyrolyser, at 600°C, in the presence of HMDS. 1, Benzene 2, ethyl acrylate 3, methyl methacrylate 4, acetic acid, trimethyl silyl ester 5, pyrrole 6, toluene 7, 2 methylpyrrole 8, 3 methylpyrrole 9, crotonic acid 10, ben zaldehyde 11, phenol 12, 2 methylphenol 13, 4 methylphenol 14, 2,4 dimethyl phenol 15, benzyl nitrile 16, 3 phenylpropionitrile 17, indole 18, phthalate 19, phthalate 20, ben zyl benzoate HMDS pyrolysis products [27]...

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