Chloromethane reaction studies

Both oxyhydrochlorinatlon of methane and chloromethane oligomerization studies were conducted in essentially the same microreactor system. All the reactants were introduced at pressures slightly above one atmosphere from gas cylinders, and flow rates were controlled by a Brooks four-channel mass-flow controller. The feed stream for the oxyhydrochlorinatlon reaction was sampled before and after an experimental run, while the product stream was continuously sampled on-line during the run to obtain a mass balance. A quadrupole mass spectrometer was used to analyze the feed and product... 

Why Chloromethane 205 The Surface Acidity of T -Alumina 206 Three Types of Surface Site Become Four 208 Interaction of Methanol with the TJ-Alumina Surface 211 The Interaction of Anhydrous HCI with T -Alumina 211 Temperature-Programmed Reaction Studies 213 Summary and Future Outlook 213... 

The mechanism(s) by which these photocatalyzed oxidations are initiated remain uncertain. Early proposals have included involvement of either the photo-produced holes (h+) arising directly from semiconductor photo-excitation, or the (presumed) derivative hydroxyl radical (OH) which was argued to arise from the hole oxidation of adsorbed hydroxyls (h+ + OH-—> OH ). Recent subambient studies [4] with physisorbed chloromethane and oxygen suggest the dioxygen anion (02 ) as a key active species, and the photocatalytic high efficiency chain destruction of TCE is argued to be initiated by chlorine radicals (Cl) [5]. The chlorine-enhanced photocatalytic destruction of air contaminants has been proposed [1, 2, 6] to depend upon reactions initiated by chlorine radicals. 

As it has been shown, there are many ways to assemble the 1,4-(oxa/thia)-2-azole ring. Most of them are performed by inter- or intramolecular cyclization of suitable acyclic precursors. Some of them are found to be suitable for the synthesis of various ring systems, by using readily available, and properly modified reactants. Of particular importance are the following (a) the cyclizations of sulfenamides leading to (oxa/thia)azolium salts (Scheme 33) (b) the cyclization of hydroxamic acids (Scheme 39) (c) the dipolar cycloaddition methodology (Scheme 40) (d) the cyclizations of chlorosulfenyl chlorides (Scheme 46) and (e) the cyclizations of chloromethane sulfonamides (Schemes 47 and 48). Other cyclizations reported are preparative ways used mainly for the synthesis of specific compounds and the scope of these reactions has not been widely studied. 

Alkanes appear to react with platinum(IV) in an identical manner to benzene (34, 84) chloromethane and chloroethane can be detected as the reaction products from methane and ethane, respectively. When propane, butane, or hexane is the reactant, the terminal chloro isomers predominate over the internal isomers. This was interpreted to mean that primary C—H bonds are the most reactive (34), but a more detailed study has shown that this conclusion does not necessarily follow from the experimental results (84). When cyclohexane is the reactant, dehydrogenation (or chlorination and then dehydrohalogenation) occurs to give benzene as one of the reaction products (29, 34, 84). 

An early paper reported that reaction of PtCll- and 1 obeyed the rate law (30) expressed in Eq. (1) through the formation of a methylplatinum intermediate that decomposed in the presence of excess chloride to form chloromethane. Fanchiangef al. made a more detailed study of this reaction and proposed the reaction mechanism shown in Fig. 2, from which... 

The Sn2 reaction in solution. We saw above the application of microsolvation to Sn2 reactions ([14, 15]). Let us now look at the chloride ion-chloromethane Sn2 reaction in water, as studied by a continuum method. Figure 8.2 shows a calculated reaction profile (potential energy surface) from a continuum solvent study of the Sn2 attack of chloride ion on chloromethane (methyl chloride) in water. Calculations were by the author using B3LYP/6-31+G (plus or diffuse functions in the basis set are considered to be very important where anions are involved Section 5.3.3) with the continuum solvent method SM8 [22] as implemented in Spartan [31] some of the data for Fig. 8.2 are given in Table 8.1. Using as the reaction coordinate r the deviation from the transition state C-Cl... 

New quasiphosphonium halides derived from neopentyl diphenyl-phosphinite and dineopentyl phenylphosphonite are reported and it is shown that the attachment of phenyl groups to phosphorus provides enhanced stability. The products, Ph2P(0R)MeX (X = Cl, Br, or I) and PhP(0R)2MeX (X = Br or I) (R = Me3CCH2), are resistant to moist air and can be handled in the open laboratory for the purpose of X-ray diffraction studies (1). The rate of initial reaction between the ester and an alkyl halide increases with the number of phenyl substituents on phosphorus from the diphenyl-phosphinite an adduct with chloromethane can be prepared. 

Davis, D.D., Machado, G., Conaway, B., Oh, Y., Watson, R. (1976) A temperature dependent kinetic study of reaction of hydroxyl radicals with chloromethane, dichloromethane, trichloromethane and bromomethane. J. Chem. Phys. 65, 1268-1274. 

Bottoni also reported the results of computational studies into the abstraction of hydrogen atom by silyl and trichlorosilyl radicals from chloromethane, dichloromethane and chloroform (equation 15)42, and concluded that hydrogen abstraction does not effectively compete with halogen abstraction in the systems investigated. B3LYP/6-31G calculated energy barriers for these reactions fall in the approximate range of 46-72 kJmol-1. 

Kotsinaris et al. 1998), while on Ag and Pt cathodes methane was the main product. Rondinini et al. (2004) observed the preferential formation of methane from poly-chloromethane on silver in ACN, DMF and aquo-organic solvents. Trichloroethene and trichloromethane were hydrodehalogenated in aqueous solution at different pHs by Chen et al. (2003) on platinized and palladized ceramic (ebonex) supports. Main reaction products were ethane, ethene and HC1 for the former substrate, and methane and HC1 for the latter. In a preceding study (Chen et al. 1999) in oxidative conditions, they observed the parallel degradation to carbon-containing products (mainly CO2) and, in neutral or alkaline pH, Cr/CI()3 as the only chloro-containing products. 

In studying the chlorination of methane, we will consider just the first reaction to form chloromethane (common name methyl chloride). This reaction is a substitution Chlorine does not add to methane, but a chlorine atom substitutes for one of the hydrogen atoms, which becomes part of the HC1 by-product. 

We performed extensive studies to determine the Cl-atom rate constant of benzene. n-Butane and ethane were among first molecules that were used as references to measure the relative rate constant of Cl-atom reaction of benzene. By the end of these experiments, the concentration of reference molecules reduced close to the detection limits whereas no decay of benzene outside the uncertainty limits was observed. Although the relative rate technique is particularly powerful in the measurement of reactions with comparable rate constants, for reactions with very different rate constants, this method is less accurate. Since it has become clear that the Cl-atom rate constant of benzene is slow, chloromethane, dichloromethane, and trichloromethane (chloroform) were used as references. These sets of experiments consisted of 20 individual experiments in which the concentration of hydrocarbons ranged from 10 to 15 mTorr and the concentration of CI2 varied from 10 to 100 mTorr. The relative rate constants for chloromethane and dichloromethane have been previously measured by Niki et al. [65]. Specifically, they were combined as a check on the experimental procedures. No difference in the values of the rate... 

Davis, S. R. Ab initio study of the insertion reaction of magnesium into the carbon-halogen bond of fluoro- and chloromethane. J. Am. 

---