C—Cl bond

The broken bonds (boldface=dissociated atom) BDEs (boldface = recommended data reference in parentheses)  

1-Difluoro-l-chloro- ethane CI-CF2CH3 84.8+2.1 355.0 + Review 2005G1A 

3-Chloro-2-methyl-l- propene C1-CH2C(CH3)=CH2 66.2 277.0 Correlation 1995DEN 

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The half-lives for these four compounds taken from the literature allowed the estimation of the Four reaction rates necessai to model their degradation [18], As a first approximation, the rate of hydrolysis of the C-Cl bond of all Four, -triazine compounds was assumed to be the same and to be 5.0 x 10 s on the basis of literature precedence. This approximation seems reasonable as the four structures differ only in the alkyl groups at a site quite remote from the C-CI bond. Furthermore, among the Four reaction steps hydrolysis is the slowest anyway. 

Carbon tetrachloride with four polar C—Cl bonds and a tetrahedral shape has no net dipole moment because the result of the four bond dipoles as shown m Figure 1 7 is zero Dichloromethane on the other hand has a dipole moment of 1 62 D The C—H bond dipoles reinforce the C—Cl bond dipoles... 

Resultant of these two C—Cl bond dipoles IS H-----> in plane of paper... 

Compare the C—C and C—Cl bond distances of acetyl chloride on Learning By Modeling... 

Compare the elec tronic charges at chlorine in chlorocy clohexane and chloroben zene on Learning By Modeling to verify that the C—Cl bond IS more polar in chlorocyclohexane... 

This mechanism not only accounts for the substitution of the more labile chlorine atom on the polymer chain, it also results in the elimination of a new potential initiation site by moving the double bond out of conjugation with any adjacent chlorine atoms. The newly formed C—O or C—S bonds, with AH > 484 kJ/mol (100 kcal/mol), are significantly more thermally stable than even the normal C—Cl bonds in PVC at about 411 kj/mol (85 kcal/mol) (11). 

As chlorination proceeds from methyl chloride to carbon tetrachloride, the length of the C—Cl bond is decreased from 0.1786 nm in the former to 0.1755 nm in the latter (3). At ca 400°C, thermal decomposition of carbon tetrachloride occurs very slowly, whereas at 900—1300°C dissociation is extensive, forming perchloroethylene and hexachloroethane and Hberating some chlorine. Subjecting the vapor to an electric arc also forms perchloroethylene and hexachloroethane, as well as hexachlorobenzene, elementary carbon, and chlorine. 

Polytetrafluoroethylene contains only C—C and C—F bonds. These are both very stable and the polymer is exceptionally inert. A number of other fluorine-containing polymers cU e available which may contain in addition C—H and C—Cl bonds. These are somewhat more reactive and those containing C—H bonds may be cross-linked by peroxides and certain diamines and di-isocyanates. 

Table 1.4. Heterolytic Bond Dissociation Energies for Some C-H and C-Cl Bonds S...

The C—Cl bond is so long that the lone-pair orbital (3p) of chlorine is too far-... 

The IRC calculation confirms that the preceding transition structure does indeed connect these two minima. The C-Cl bond length increases as it proceeds in the forward direction along the reaction path, and this bond decreases in length in the reverse direction (naturally, the C-F bond length changes in the complementary manner). 

It has generally been concluded that the photoinitiation of polymerization by the transition metal carbonyls/ halide system may occur by three routes (1) electron transfer to an organic halide with rupture of C—Cl bond, (2) electron transfer to a strong-attracting monomer such as C2F4, probably with scission of-bond, and (3) halogen atom transfer from monomer molecule or solvent to a photoexcited metal carbonyl species. Of these, (1) is the most frequently encountered. 

Problem 2.4 Look at the following electrostatic potential map of chloromethane, and tell the direction of polarization of the C-Cl bond ... 

Based on these definitions, the chlorination reaction of methane to yield chloromethane is an oxidation because a C-H bond is broken and a C—Cl bond... 

Chloroform, CHCla, is an example of a polar molecule. It has the same bond angles as methane, CH4, and carbon tetrachloride, CCLi- Carbon, with sp3 bonding, forms four tetrahedrally oriented bonds (as in Figure 16-11). However, the cancellation of the electric dipoles of the four C—Cl bonds in CCL does not occur when one of the chlorine atoms is replaced by a hydrogen atom. There is, then, a molecular dipole remaining. The effects of such electric dipoles are important to chemists because they affect chemical properties. We shall examine one of these, solvent action. 

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