Chloromethane, 740 table

If more than one electron-withdrawing group is present, the deshielding effects are nearly (but not quite) additive. In the chloromethanes (Table 13-2), the addition of the first chlorine atom causes a shift to 8 3.0, the second chlorine shifts the absorption further to 8 5.3, and the third chlorine moves the chemical shift to 8 7.2 for chloroform. The chemical shift difference is about 2 to 3 ppm each time another chlorine atom is added, but each additional chlorine moves the peak slightly less than the previous one did. 

Production and sales data for methyl chloride, as reported by the U.S. International Trade Commission for the years 1945 to 1989, are given in Table 3. Production grew tremendously in the 1960s and again in the late 1980s. Methanol hydrochlorination was used to produce about 64% of the methyl chloride in 1969 and about 98% by 1974. The principal U.S. producers and their capacities are shown in Table 4 (54). These capacities do not include the 100 + million kg per year used by The Dow Chemical Company, Occidental, and Vulcan to captively produce other chloromethanes. 

Table 3 Hsts the U.S. producers of methylene chloride and their rated yearly capacities. Since the product mix of a typical chloromethanes process is very flexible, production may be adjusted according to the demand for methylene chloride and chloroform. The demand for methylene chloride has taken a broad downturn as a result of the 1985 NTP carcinogenicity tests (Table 4). The 1988 and 1989 demands were 227,000 t and 216,000 t, respectively, with a forecast 1993 demand of 186,000 t. The historical growth rate (1979—1988) was —2.7% pet year. In the future this should decrease even further to —3 to...

Table 4. Occupational exposure limits and guidelines for di-chloromethane ...

Ionic or polar reactions of alkyl halides rarely are observed in the vapor phase because the energy required to dissociate a carbon-halogen bond heterolyti-cally is almost prohibitively high. For example, while the heat of dissociation of chloromethane to a methyl radical and a chlorine atom is 84 kcal mole-1 (Table 4-6), dissociation to a methyl cation and a chloride ion requires about 227 kcal mole-1 ... 

It s relatively easy to measure dipole moments experimentally, and values for some common substances are given in Table 10.1. Once the dipole moment is known, it s then possible to get an idea of the amount of charge separation in a molecule. In chloromethane, for example, the experimentally measured dipole moment is /x = 1.87 D. If we assume that the contributions of the nonpolar C-H bonds are small, then most of the chloromethane dipole moment is due to the C-Cl bond. Since the C-Cl bond distance is 178 pm, we can calculate that the dipole moment of chloromethane would be 1.78 X 4.80 D = 8.54 D if the C-Cl bond were ionic (that is, if a full negative charge on chlorine were separated from a full positive charge on carbon by a distance of 178 pm). But because the measured dipole moment of chloromethane is only 1.87 D, we can conclude that the C-Cl bond is only about (1.87/8.54)(100%) = 22% ionic. Thus, the chlorine atom in chloromethane has an excess of about 0.2 electron, and the carbon atom has a deficiency of about 0.2 electron. 

Chloromethane is the most abundant organohalogen - anthropogenic or natural - in the atmosphere. The myriad natural sources of CH3C1 dwarf the anthropogenic contribution (Table 3.1). Subsequent to the previous survey (7) a number of new natural sources of CH3C1 have been identified, and other reviews have appeared (42, 246, 247). 

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... 

Table 3. Selectivity factor SF-/x2 of calix[4]pyrrole ligands for fluoride anion relative to other anions (X2 = Cl-, Br , I- and H2PO4) in acetonitrile (MeCN), di-chloromethane (DCM), A/,A/-dimethylformamide (DMF), dimethyl sulphoxide (DMSO) and propylene carbonate (PC)...

Table 2-2. Solubilities of methane, ethane, chloromethane, and dimethyl ether in tetrachloro-methane (nonpolar solvent) and acetone (polar solvent) [22].

Acceptor numbers are less than 10 for nonpolar non-HBD solvents, they vary between about 10... 20 for dipolar non-HBD solvents, and they cover a wide range of about 25... 105 for protic solvents cf. Table 2-5). Surprisingly, benzene and tetra-chloromethane have stronger electrophilic properties than diethyl ether and tetrahy-drofuran. Acceptor numbers are also known for binary solvent mixtures [70, 213]. 

Chlorinated naphthalenes are lipophilic compounds with log K(1W values ranging from 3.90 for 1-monoCN up to 6.42 for octaCN, cf. Table 2 [187,188]. Most PCNs are readily soluble in most organic solvents, e. g., diethyl ether, di-chloromethane, hexane, toluene and isooctane. The solubility in more polar solvents such as methanol is low (ng pL )> but high enough for e.g., liquid chromatography on analytical columns [189]. Mono- and diCNs are slightly soluble in water (0.1-3 mg L 1) while the higher chlorinated naphthalenes have very low solubility in water (0.08 pg L-1) [ 187,188]. 

Hydrolysis of DPPC. The catalytic effectiveness of 3, 4, 5, and 6 in the hydrolysis of DPPC was determined in well-stirred suspensions of di-chloromethane-0.5 M aqueous sodium bicarbonate (equation 9 Table III),... 

In the fluorine derivatives of methane and chloromethanes the variation of the GF bond is somewhat complex. As is seen in Table LVIII, the bond length varies from 1 42 A to 1 35 A. 

TABLE 5.2 Calculation of K for Chloromethanes Using Carbon Tetrachloride as an Internal Standard... 

Figure 5.3 Plots of ECD data as In KT3/2 versus TOOO/T. The data are typical for the chloromethanes. An ECD should be able to reproduce these data. They were obtained using a single injection at each temperature. The calculations of the data are illustrated in Table 5.2 using carbon tetrachloride as an internal standard. The data for acetophenone were obtained in a separate experiment.

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