Alkylation methyl bromide

Ratio of rate constant k for indicated alkyl bromide to k for methyl bromide at 25 C... 

Mannich polyacrylamides can react with alkylating agents such as methyl chloride [74-87-3], CH Cl, methyl bromide [74-83-9], CH Br, and dimethyl... 

AIBt3, EtSH, 0°, 0.5-1 h, 73-78% yield. Aluminum bromide cleaves aryl and alkyl methyl ethers in high yield methyl esters are stable. 

There are relatively few kinetic data on the Friedel-Crafts reaction. Alkylation of benzene or toluene with methyl bromide or ethyl bromide with gallium bromide as catalyst is first-order in each reactant and in catalyst. With aluminum bromide as catalyst, the rate of reaction changes with time, apparently because of heterogeneity of the reaction mixture. The initial rate data fit the kinetic expression ... 

The real world of Sn reactions is not quite as simple as the discussion has so far suggested. The preceding treatment in terms of two clearly distinct mechanisms, SnI and Sn2, implies that all substitution reactions will follow one or the other of these mechanisms. This is an oversimplification. The strength of the dual mechanism hypothesis and its limitations are revealed by these relative rates of solvolysis of alkyl bromides in 80% ethanol methyl bromide, 2.51 ethyl bromide, 1.00 isopropyl bromide, 1.70 /er/-butyl bromide, 8600. Addition of lyate ions increases the rate for the methyl, ethyl, and isopropyl bromides, whereas the tert-butyl bromide solvolysis rate is unchanged. The reaction with lyate ions is overall second-order for methyl and ethyl, first-order for tert-butyl, and first- or second-order for the isopropyl member, depending upon the concentrations. Similar results are found in other solvents. These data show that the methyl and ethyl bromides solvolyze by the Sn2 mechanism, and tert-butyl bromide by the SnI mech-... 

Me2Br, CH2CI2, 70°, 30-36 h, 72-96% yield." Alkyl methyl ethers are also cleaved, but tertiary methyl ethers are converted to the bromide. 

In a further development on this theme, the thiol, 153, is first alkylated to the corresponding benzyl ether (158). Treatment with sodium methoxide removes the proton on the amide nitrogen to afford the ambient anion (159). This undergoes alkylation with methyl bromide on the ring nitrogen thus it locks amide into the imine form (160). Chlorolysis serves both to oxidize the sulfur to the sulfone stage and to cleave the benzyl ether linkage there is thus obtained the sulfonyl chloride, 161. 

Specially bottled methyl bromide, in an aluminium cylinder under nitrogen pressure, disgorged a black sludge when liquid was discharged. Inversion and venting, to blow free the line, gave a burst of flame from the vent. It is presumed that corrosion of the cylinder produced pyrophoric aluminium alkyls. 

As a result of the inductive and hyperconjugative effects it is to be expected that tertiary carbonium ions will be more stable than secondary carbonium ions, which in turn will be more stable than primary ions. The stabilization of the corresponding transition states for ionization should be in the same order, since the transition state will somewhat resemble the ion. Thus the first order rate constant for the solvolysis of tert-buty bromide in alkaline 80% aqueous ethanol at 55° is about 4000 times that of isopropyl bromide, while for ethyl and methyl bromides the first order contribution to the hydrolysis rate is imperceptible against the contribution from the bimolecular hydrolysis.217 Formic acid is such a good ionizing solvent that even primary alkyl bromides hydrolyze at a rate nearly independent of water concentration. The relative rates at 100° are tertiary butyl, 108 isopropyl, 44.7 ethyl, 1.71 and methyl, 1.00.218>212 One a-phenyl substituent is about as effective in accelerating the ionization as two a-alkyl groups.212 Thus the reactions of benzyl compounds, like those of secondary alkyl compounds, are of borderline mechanism, while benzhydryl compounds react by the unimolecular ionization mechanism. 

Methyl Bromide.—The simplest alkyl bromide is prepared in an esentially similar way (Bygden, J. pr. Ghem., 1911, 83, 421). Since it boils at 4-5° it is difficult to keep in stock, but its direct application in the Grignard reaction, in place of the dearer iodine compound, is very much to be recommended. Uses analogous to those of ethyl bromide. 

The alkyl halides C H2n+1Cl (Br, I) are colourless and usually liquid methyl chloride, methyl bromide, and also ethyl chloride, are gaseous at ordinary temperatures and the members of high molecular weight, such as cetyl iodide C16H22I, are semi-solid, paste-like masses. 

Of the synthetic reactions of the alkyl halides that with potassium cyanide, which enabled H. Kolbe to synthesise acetic acid from a methane derivative, has already been mentioned (cf. the preparations on pp. 137 and 254). Of the simpler syntheses that of Wiirtz may be mentioned here. Metallic sodium removes the halogen from two molecules and the two radicles combine. Thus, in the simplest case, ethane is formed from methyl bromide ... 

This includes bioremediation cases of contaminated sites with several toxic and carcinogenic pollutants, such as petroleum hydrocarbons, PAHs, dichlorobenzene, chlorinated hydrocarbons, carbon tetrachloride, Dicamba, methyl bromide, trinitrotoluene, silicon-based organic compounds, dioxins, alkyl-phenol polyethoxylates, nonylphenol ethoxylates, and polychlorinated biphenyls. The following is a brief summary of each case. 

Furthermore, a double mediatory system consisting of alkyl methyl sulfide and bromide ion was developed, which made the oxidation of alcohols feasible at a lower potential (1.1 V vs SCE) than that of thioanisole (1.60 V vs SCE) [45]. Both the alkyl methyl sulfide and the bromide ion act together as mediators. Under this condition 2-octanol was oxidized to 2-octanone in 85% yield. 

Djalali-Behzad G, Hussain S, Osterman-Golkar S, et al. 1981. Estimation of genetic risks of alkylating agents. VI. Exposure of mice and bacteria to methyl bromide. Mutat Res 84 1-9. 

Methyl bromide is genotoxic in a number of in vivo and in vitro assays and does not require metabolic activationT This is consistent with the fact that it is a direct-acting alkylating agent that can methylate DNA. 

Flexachlorocyclohexane Lindane Flexachloroethane Flexafluoroethane Methyl Bromide Bromomethane Methylene Chloride Dichloromethane Saturated Alkyl Flalides Tetrachloroethane, 1,1,2,2 Trichloroethane, 1,1,2 Trichloroethane, 1,1,1 TCA... 

Methyl Bromide Bromomethane under Saturated Alkyl Halides Methyl Cyclohexane under Alkanes and Cyclic Alkanes Methylene Chloride Dichloromethane under Saturated Alkyl Halides Methyl Hydrazine Monomethylhydrazine under Hydrazine Derivatives Methyl Methacrylate under Esters... 

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