Methane with chlorine

Kandel S A and Zare R N 1998 Reaction dynamics of atomic chlorine with methane importance of methane bending and tortional excitation in controlling reactivity J. Chem. Phys. 109 9719-27... 

Interaction of chlorine with methane is explosive at ambient temperature over yellow mercury oxide [1], and mixtures containing above 20 vol% of chlorine are explosive [2], Mixtures of acetylene and chlorine may explode on initiation by sunlight, other UV source, or high temperatures, sometimes very violently [3], Mixtures with ethylene explode on initiation by sunlight, etc., or over mercury, mercury oxide or silver oxide at ambient temperature, or over lead oxide at 100°C [1,4], Interaction with ethane over activated carbon at 350°C has caused explosions, but added carbon dioxide reduces the risk [5], Accidental introduction of gasoline into a cylinder of liquid chlorine caused a slow exothermic reaction which accelerated to detonation. This effect was verified [6], Injection of liquid chlorine into a naphtha-sodium hydroxide mixture (to generate hypochlorite in situ) caused a violent explosion. Several other incidents involving violent reactions of saturated hydrocarbons with chlorine were noted [7],... 

Figure 4-5 Four-center collision of chlorine with methane as visualized with ball-and-stick models...

The attack of a chlorine atom on a methane hydrogen is not expected to require a precisely oriented collision. Moreover, the interatomic repulsions should be considerably smaller than in the four-center mechanism discussed previously for the reaction of molecular chlorine with methane because only two centers have to come close together (Figure 4-8). The methyl radical resulting from the attack of atomic chlorine on a hydrogen of methane then can remove a chlorine atom from molecular chlorine and form chloromethane and a new chlorine atom ... 

Exercise 4-12 A possible mechanism for the reaction of chlorine with methane would be to have collisions by which a chlorine molecule removes a hydrogen according to the following scheme ... 

THE DETAILED MECHANISM FOR THE REACTION OF CHLORINE WITH METHANE IN BRIGHT SUNLIGHT... 

If enough bond dissociation energies were known, it would seem possible to calculate for any reaction of interest and thus be able to get a rough idea about whether the reaction is favorable. To take the radical substitution reaction of chlorine with methane (Section 5.3) as an example, the bonds formed in this gas-phase reaction (783 kj/mol) are stronger than the bonds broken (681 kJ/mol), so a net release of heat occurs and we calculate that the reaction is exothermic by about -102 kJ/mol (-24 kcal/mol). 

Problem 5.15 Sketch a reaction energy diagram that shows both propagation steps in the radical reaction of chlorine with methane. Is the overall AG for this reaction positive or negative Label the parts of your diagram corresponding to AG° and AG. ... 

Values of A//° for dissociation reactions can be combined to allow prediction of heats of reaction. A familiar example is the calculation of AH° for the reaction of chlorine with methane to produce HCl plus methyl chloride. Using Table 1.11 and the bond dissociation enthalpies of CI2 and HCl/° we can write the following reactions ... 

How do you begin Find the overall equation for the reaction of chlorine with methane, but replace methane with ethane and make any other change that follows from that one. Then do the same for the initiation, propagation, and termination steps, again using the mechanism steps in the chlorination of methane as your model. 

Consider the reaction of chlorine with methane, in which two molecules react to give two molecules of product. For this reaction, = +2.9 J mole deg . The standard entropy change is a small value because the numbers of moles of reactant and products are equal. The TAS° term at 298 K is —860 J mole deg . Since AH° is —102 kj mole , AG° is —103 kj mole ... 

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