Methyl chloride, effect

A diagrammatic illustration of the effect of an isotope pattern on a mass spectrum. The two naturally occurring isotopes of chlorine combine with a methyl group to give methyl chloride. Statistically, because their abundance ratio is 3 1, three Cl isotope atoms combine for each Cl atom. Thus, the ratio of the molecular ion peaks at m/z 50, 52 found for methyl chloride in its mass spectrum will also be in the ratio of 3 1. If nothing had been known about the structure of this compound, the appearance in its mass spectrum of two peaks at m/z 50, 52 (two mass units apart) in a ratio of 3 1 would immediately identify the compound as containing chlorine. 

Fig. 5. Effects of product recycle on methane chlorination product distributions where 1 = methyl chloride, 2 = methylene chloride, 3 = chlorine, and...

In practice vapours of the hydrocarbon halide, e.g. methyl chloride, are passed through a heated mixture of the silicon and copper in a reaction tube at a temperature favourable for obtaining the optimum yield of the dichlorosilane, usually 250-280°C. The catalyst not only improves the reactivity and yield but also makes the reaction more reproducible. Presintering of the copper and silicon or alternatively deposition of copper on to the silicon grains by reduction of copper (I) chloride is more effective than using a simple mixture of the two elements. The copper appears to function by forming unstable copper methyl, CUCH3, on reaction with the methyl chloride. The copper methyl then decomposes into free methyl radicals which react with the silicon. 

The direct process is less flexible than the Grignard process and is restricted primarily to the production of the, nevertheless all-important, methyl- and phenyl-chlorosilanes. The main reason for this is that higher alkyl halides than methyl chloride decompose at the reaction temperature and give poor yields of the desired products and also the fact that the copper catalyst is only really effective with methyl chloride. 

The anomeric effect is also present in acyclic systems and stabilizes conformations that allow antiperiplanar (ap) alignment of the C—X bond with a lone-pair orbital of the heteroatom. Anomeric effects are prominent in determining the conformation of acetals and a-alkoxyamines, as well as a-haloethers. MO calculations (4-3IG) have found 4kcal/mol as the difference between the two conformations shown below for methoxy-methyl chloride. ... 

Since many of the uses of antihistamines involve conditions such as rashes, which should be treatable by local application, there is some rationale for developing drugs for topical use. The known side effects of antihistamines could in principle be avoided if the drug were functionalized so as to avoid systemic absorption. The known poor absorption of quaternary salts make such derivatives attractive for nonabsorbable antihistamines for topical use. Thus, reaction of the well-known anti his-taminic drug promethazine (104) with methyl chloride leads... 

Lotti M, Becker CE. 1982. Treatment of acute organophosphate poisoning Evidence of a direct effect on central nervous system by 2-PAM (pyridine-2-aldoxime methyl chloride). J Toxicol Clin Toxicol 19 121-127. 

The reaction of crotonaldehyde and methyl vinyl ketone with thiophenol in the presence of anhydrous hydrogen chloride effects conjugate addition of thiophenol as well as acetal formation. The resulting j3-phenylthio thioacetals are converted to 1-phenylthio-and 2-phenylthio-1,3-butadiene, respectively, upon reaction with 2 equivalents of copper(I) trifluoromethanesulfonate (Table I). The copper(I)-induced heterolysis of carbon-sulfur bonds has also been used to effect pinacol-type rearrangements of bis(phenyl-thio)methyl carbinols. Thus the addition of bis(phenyl-thio)methyllithium to ketones and aldehydes followed by copper(I)-induced rearrangement results in a one-carbon ring expansion or chain-insertion transformation which gives a-phenylthio ketones. Monothioketals of 1,4-diketones are cyclized to 2,5-disubstituted furans by the action of copper(I) trifluoromethanesulfonate. ... 

Levy (Chapter 6) has also explored the use of supercomputers to study detailed properties of biological macromolecule that are only Indirectly accessible to experiment, with particular emphasis on solvent effects and on the Interplay between computer simulations and experimental techniques such as NMR, X-ray structures, and vltratlonal spectra. The chapter by Jorgensen (Chapter 12) summarizes recent work on the kinetics of simple reactions In solutions. This kind of calculation provides examples of how simulations can address questions that are hard to address experimentally. For example Jorgensen s simulations predicted the existence of an Intermediate for the reaction of chloride Ion with methyl chloride In DMF which had not been anticipated experimentally, and they Indicate that the weaker solvation of the transition state as compared to reactants for this reaction In aqueous solution Is not due to a decrease In the number of hydrogen bonds, but rather due to a weakening of the hydrogen bonds. 

Recent experiments11 have shown that for symmetric top molecules, such as methyl chloride, electron impact ionization is more probable at the positive end of the dipole. This follows intuitively from simple electrostatics, since it would be expected that an electron should be more strongly attracted to the positive end of the dipole, leading to a greater ionization probability at this end of the molecule. The effect may be quantified in terms of a steric ratio R. 

Finally, for the PT problem, dynamical friction effects have been examined for a model for a phenol-amine acid-base reaction in methyl chloride solvent [12]. With the quantization of the proton and the O-N vibration, the problem can be reduced to a one-dimensional solvent coordinate problem, similar to the ET case. Again, GH theory is found to agree with the MD results to within the error bars of the computer simulation. 

The experiment with CS2 showed up another extremely interesting effect. Over almost the whole range of compositions the DPs obtained were very significantly greater than those obtained without carbon bisulphide - with methyl chloride as sole diluent. This CS2 effect has been reported previously for the cationic polymerisation of a-methylstyrene [57] and of isobutene [50]. It seems likely that it is due (at least partly) to the fact that CS2 does not act as a transfer agent, whereas most alkyl halides do. 

The effect of the catalyst concentration on the DP of the polymer was investigated at -78° with methyl chloride as solvent at isobutene concentrations of 0.643 and 0.25 mole fraction (approximately 9.5 and 4.6 mole/1) [53]. The catalyst concentration, given as wt.% A1C13 on isobutene (sic ), covers the range 1.5 x 10"3 to 10"1 in these units. Recalculation of the results shows that 1/DP increases linearly with [A1C13] up to a certain value and at higher values remains constant. This corresponds closely to the behaviour reported for the polymerisations of undiluted monomer [53] and can be explained in the same way (see p.159). 

Phenyl carbonochloridate (phenyl chloroformate) effects the dealkylation of tertiary amines A,A-dimethylanilinc yields methyl chloride and the amide 247, and quinuclidine yields the piperidine derivative 248261. 

The reaction of CIO- with methyl chloride can only proceed via the Sn2 process. An inverse KIE of 0.85 is measured (Table 10.3). The reaction with /-butyl chloride presumably proceeds via an E2 mechanism (since Sn2 attack on the Cl substituted carbon is blocked) and the observed KIE of 2.31 (Table 10.3) is consistent with that conclusion. The isotope effects for both species are nearly the same as the effects measured in the condensed phase (compare Tables 10.3 and 10.4) and measure the relative contributions of the two paths. The results indicate that the E2 pathway becomes the dominant channel as the substrate becomes more sterically hindered. 

Nakane ei al. (1964) established equilibrium constants of boron isotope exchange between boron trifluoride gas on one side and boron trifluoride methyl fluoride, methyl chloride, isopropyl chloride and t-butyl chloride. The value of the equilibrium constants, which represents the thermodynamic isotope effect, was related to the polarity, stability and catalytic activity of the complexes. 

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