Methyl alcohol ether formation

Berim, A., Schneider, B. and Petersen, M. (2007) Methyl allyl ether formation in plants novel S-adenosyl L-methionine coniferyl alcohol 9-O-methyltransferase from suspension cultures of three Linum species. Plant Mol. Biol, 64, 279-91. 

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. 

Loss of catalytic activity resulting from internal displacements is not usually a serious problem below temperatures of about 100 C. However, highly active R-groups, such as benzyl, methyl and allyl, undergo internal displacement more readily, particularly in the presence of strong nucleopfiles. For instance, the presence phenolates and thiolates may lead to the formation of benzyl alcohol, ethers, or sulphides from benzyl-substituted quaternary ammonium salts. 

The cyclization of y -hydroxy ketones is useful for the formation of pyrans,306,403 both directly and via rearrangement, as illustrated in Eq. 231.153 As with their acyclic counterparts, these cyclizations also occur with the silyl ethers of the hydroxy ketones where Et3SiH/BiBr3 is used with the TBS and TES ethers.342,404 A methyl thiomethyl ether is also capable of undergoing the reductive cyclization 405 In like manner, 1,4-diols and e-hydroxy ketones provide oxepanes, with I ds Si H or PhMe2SiH/TMSOTf being especially effective (Eqs. 232 and 233).336,406 The trimethylsilyl ether of the alcohol also provides the oxepane.306... 

Wender and coworkers conclude that cobalt-catalyzed benzyl alcohol homologation involves the intermediate formation of car-bonium ions (8). However, since the methyl cation (CH3+) is unstable and difficult to form (9), it is more likely that methanol homologation to ethanol proceeds via nucleophilic attack on a protonated methyl alcohol molecule. Protonated dimethyl ether and methyl acetate forms have been invoked also by Braca (10), along with the subsequent formation of methyl-ruthenium moieties, to describe ruthenium catalyzed homologation to ethyl acetate. 

Degradation of methyl terf-butyl ether by bifunctional aluminum in the presence of oxygen was investigated by Lien and Wilkin (2002). Bifunctional aluminum was synthesized by sulfating aluminum metal with sulfuric acid. When the initial methyl terf-butyl ether concentration was 14.4 mg/L, 90% of methyl ferf-butyl ether degraded within 24 h forming acetone, methyl acetate, tert-hniyX alcohol, and ferf-butyl formate. Carbon disulfide was tentatively identified as a reaction product by GC/MS. Product yields were 27.6% for acetone, 18.4% for methyl acetate, 21% for tert-hniyX alcohol, and 6.1% ferf-butyl formate. When the initial concentration of methyl tert-butyl ether was reduced to 1.4 mg/L, 99.5% of methyl terCbutyl ether reacted. Yields of acetone, methyl acetate, and /erf-butyl alcohol were 54.7,17.2, and 13.2, respectively. 

The formation of certain ethers can also be accomplished with hydrogen fluoride. Anisole rather than methylphenol results from a reaction between phenol and methyl alcohol at elevated temperature (Simons and Passino, 40). The addition of an olefin to an alcohol to form an ether was shown to occur in the reaction between cyclohexene and cyclohexanol for form dicyclohexyl ether (Simons and Meunier, 66). 

Protons attached to the C atoms of the 1,2,4-trioxolane moiety of FOZs have chemical shifts at distinctly lower field than alcohols, ethers or esters. For example, the chemical shifts of the ozonide product in equation 100 (Section Vin.C.b.a) are S (CDCI3) 5.7 ppm for the H atoms of the trioxolane partial structure, and 4.1 ppm for the protons at the heads of the other ether bridge . Measurement of the rate of disappearance of these signals can be applied in kinetic studies of modifications in the ozonide structure. The course of ozonization of the methyl esters of the fatty acids of sunflower oil can be followed by observing in H and C NMR spectra the gradual disappearance of the olefinic peaks and the appearance of the 3,5-dialkyl-1,2,4-trioxolane peaks. Formation of a small amount of aldehyde, which at the end of the process turns into carboxylic acid, is also observed . 

Similarly with the raising of the b.p. in violet or reddish-violet soln. of iodine in benzophenone, carbon disulphide, ethyl chloride, chloroform, carbon tetrachloride, ethylene chloride or benzene or in brown soln. of ethyl alcohol, methyl alcohol, thymol, ethyl ether, methylal, or acetone. The values for the last three solvents were rather low, presumably because of the chemical action of solute on solvent. High values with benzene are attributed to the formation of a solid soln. of solvent and solid. Confirmatory results were found by J. Hertz with naphthalene, and by E. Beckmann and P. Wantig with pyridine. The results by I. von Ostromisslensky (o-nitrotoluene), by G. Kriiss and E. Thiele (glacial acetic acid), and by H. Gautier and G. Charpy indicate polymerization, but they are not considered to be reliable. 

Because of their very similar boiling points and azeotrope formation, the components of the C4 fraction cannot be separated by distillation. Instead, other physical and chemical methods must be used. 1,3-Butadiene is recovered by complex formation or by extractive distillation.143-146 Since the reactivity of isobutylene is higher than that of n-butenes, it is separated next by chemical transformations. It is converted with water or methyl alcohol to form, respectively, tert-butyl alcohol and tert-butyl methyl ether, or by oligomerization and polymerization. The remaining n-butenes may be isomerized to yield additional isobutylene. Alternatively, 1-butene in the butadiene-free C4 fraction is isomerized to 2-butenes. The difference between the boiling points of 2-butenes and isobutylene is sufficient to separate them by distillation. n-Butenes and butane may also be separated by extractive distillation.147... 

More recent investigations into the mechanism of formation of pentaerythritol have been made both by Wawzonek and Rees [3] and by Barth, Snow and Wood [4]. Both groups tried to explain the process in terms of the formation of jjw-pen-taerythritol ether (dipentaerythritol), and other ethers, e.g. the methyl ether. The latter is produced whenever the formaldehyde used for the reaction contains methyl alcohol ... 

FORMALDEHYDE. CAS 50-00-0], HCHO. formula weight 30.03. colorless gas with pungent odor, mp — 92 C, bp -2 °C, sp gr 0.815 (at —20"C). The gas is very soluble in H2O. alcohol, and ether. Formaldehyde usually is produced and marketed as a 37% (weight) solution in water. From 3 to 15% methyl alcohol normally is added as a stabilizer 10 prevent paraformaldehyde formation. The commercial trend is 10 furnish a more concentrated product (up 10 50% HCHO hy weight) which contain as... 

In gas-phase methylation reactions over Nafion-H using methyl alcohol as the alkylating agent, the consumption of methyl alcohol was higher than that calculated by product analysis.207,208 This is due to the formation of dimethyl ether as the byproduct [Eq. (5.82)]. Indeed, when neat methyl alcohol is passed over Nafion-H catalyst at temperatures over 150°C, dimethyl ether is the only product formed quantitatively with water as the byproduct.218... 

Whereas the C2—C4 alcohols are not carboxylated under the usual Koch-Haaf conditions, carboxylation can be achieved in the HF-SbF5 superacid system under extremely mild conditions.400 Moreover, Olah and co-workers401 have shown that even methyl alcohol and dimethyl ether can be carboxylated with the superacidic HF-BF3 system to form methyl acetate and acetic acid. In the carboxylation of methyl alcohol the quantity of acetic acid increased at the expense of methyl acetate with increase in reaction time and temperature. The quantity of the byproduct dimethyl ether, in turn, decreased. Dimethyl ether gave the desired products in about 90% yield at 250°C (90% conversion, catalyst/substrate ratio =1 1, 6h). On the basis of experimental observations, first methyl alcohol is dehydrated to dimethyl ether. Protonated dimethyl ether then reacts with CO to yield methyl acetate [Eq. (5.154)]. The most probable pathway suggested to explain the formation of acetic acid involves the intermediate formation of acetic anhydride through acid-catalyzed ester cleavage without the intervention of CO followed by cleavage with HF [Eq. (5.155)]. 

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