Methyl halides conversion

The effect of monomer concentration was studied using n-pentane solvent and maintaining the total volume of isobutylene plus n-pentane constant. Methyl halide concentration was kept constant so as to maintain constant medium polarity. Attempts were made to keep conversions below 20%. At -30 °C, due to almost explosive polymerizations, conversions could only be maintained below 40%. 

Step (v), conversion of [Fe(NO)2(SMe)2] to the product [Fe2(SMe)2(NO)4], occurs spontaneously under the appropriate conditions of solvent polarity/polarizability (23) [cf. Eq. (20) and Schemes 3 and 4], Step(vi) requires the methylation of [Fe2S2(NO)4]2 " while this has been demonstrated for methylation by methyl halides (3, 24, 29), methylation by biological methyl transfer, e.g., from methionine or S-adenosylmethionine, has yet to be investigated. Thus, although neither of the biosynthetic routes suggested in Scheme 5 has yet been fully investigated, several of the steps [(i), (ii), and (vi)], are established, while others [(iv) and (vi)] are already known to occur under nonbiological conditions. 

The study of the reaction of methyl halides over cationic zeolites, performed using the set-up of Haw, is another example of an in situ NMR study of conversions taking place in batch mode." Methyl halides decompose over cationic zeolites to give ethylene and other hydrocarbons, with the reaction being faster over more basic (nucleophilic) zeolites. NMR indicates the reaction proceeds via reactive methoxy species bound to the framework (observed with a characteristic signal, 5 58 ppm). 

Typical base-catalysed reactions that occur over alkali metal-exchanged zeolites include dehydrogenations, double bond isomerisations, side-chain alkylation of aromatics, conversion of methyl halides and a range of condensations. The reaction of alcohols over zeolites can be used to determine whether acid or base catalysis predominates. Whereas acid forms of zeolites catalyse dehydrations, leading to alkenes and the products of their subsequent reactions, basic sites catalyse dehydrogenations, leading to aldehydes and ketones. 

All of these reactions may be repeated starting with methyl (2/ ,3f )-3-hydroxy-2-methylbutanoate (9a) which is obtained, as shown in Scheme 2, by the double deprotonation of methyl 3-hydroxybutanoate (2b) using lithium di-isopropylamide (LDA) to give the alkoxide-enolate (8) and alkylation with a methyl halide in THF at —After reduction with lithium aluminium hydride, tosyla-tion of the alcohol group and nucleophilic attack by lithium chloride, the (2f ,3f )-l-chloro-2-methyl-3-butanol (10) is available for the sequential metallation reactions and conversion to 1,4-diols or lactones. 

Along with the well-known attempts to increase the conversion of natural gas while avoiding a deep oxidation of the target products by using two-stage schemes with intermediate conversion of natural gas into more easily convertible products, such as s)mgas, methyl halides, or bisulfate, various methods of isolation of the products have been applied. These include continuous extraction in some way or the binding of the products, as well as the separation of CH4 and O2 prior to their direct interaction, for example, on a catalytic permeable membrane, etc. Unfortunately, no feasible methods for the selective adsorption or membrane separation of methanol at temperatures close to the temperature of its formation in the DMTM process have been proposed. 

Murray DK, Chang JW, Haw IF. Conversion of methyl halides to hydrocarbons on basic zeolites. A discovery by in situ NMR. J Am Chem Soc 1993 115 4732-41. 

Electrophilic attack on the sulfur atom of thiiranes by alkyl halides does not give thiiranium salts but rather products derived from attack of the halide ion on the intermediate cyclic salt (B-81MI50602). Treatment of a s-2,3-dimethylthiirane with methyl iodide yields cis-2-butene by two possible mechanisms (Scheme 31). A stereoselective isomerization of alkenes is accomplished by conversion to a thiirane of opposite stereochemistry followed by desulfurization by methyl iodide (75TL2709). Treatment of thiiranes with alkyl chlorides and bromides gives 2-chloro- or 2-bromo-ethyl sulfides (Scheme 32). Intramolecular alkylation of the sulfur atom of a thiirane may occur if the geometry is favorable the intermediate sulfonium ions are unstable to nucleophilic attack and rearrangement may occur (Scheme 33). 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

In this connection it should be mentioned that dihalogenomethyl methyl ethers did not furnish the expected jS-disulfone nor the a-halogeno sulfones as preliminary steps in appreciable amounts surprisingly, sulfonyl halides have been isolated as main products of these conversions ... 

Studies conducted to examine the mode of activation of MAO with bis(imino) pyridine cobalt halide systems have shown some intriguing findings. With regard to 6a/MAO, initial reduction of the cobalt(II) precatalyst to cobalt halide followed by conversion to a cobalt methyl and ultimately to a cobalt cationic species has been demonstrated (see Sect. 2.6) [108, 109], Addition of ethylene affords an eth-... 

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