Chlorine atomic

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... 

Another teat, which indicates the reactivity of the halogen atom (chlorine and bromine), is based upon the fact that sodium chloride and sodium bromide are sparingly soluble in pure acetone ... 

A more energy-efficient variation of photohalogenation, which has been used since the 1940s to produce chlorinated solvents, is the Kharasch process (45). Ultraviolet radiation is used to photocleave ben2oyl peroxide (see Peroxides and peroxide compounds). The radical products react with sulfuryl chloride (from SO2 and CI2) to Hberate atomic chlorine and initiate a radical chain process in which hydrocarbons become halogenated. Thus, for Ar = aryl,... 

Halogenated compounds tliiochloro hydrocarbons with 5 to 50 C atoms chlorinated hydrocarbons Liihrication-oil and grease distillation vegetable-protein glues... 

In the second reaction, atomic chlorine is again produced by the reaction of the product of the first attack and another ozone molecule. We will consider the first of these reactions in this exercise. 

Compute the enthalpy change for the destruction of ozone by atomic chlorine by subtracting the dissociation energies of O2 and CIO from the dissociation energy for ozone. What model chemistry is required for accurate modeling of each phase of this process The experimental values are given below (in kcal-moT ) ... 

You ll need to run five calculations at each model chemistry oxygen atom, chlorine atom, O2, CIO and ozone (but don t forget that you can obtain lower-level energies from a higher-level calculation). Use the experimental geometries for the various molecules and the following scaled zero-point energy corrections ... 

Advoncsd Exorcise 7,2 aona Destruction by Atomic Chlorine Revisited... 

This technique cannot be applied to reactions which do not happen to be isodesmic (for example, destruction of ozone by atomic chlorine). 

Turning now to the acidic situation, a report on the electrochemical behaviour of platinum exposed to 0-1m sodium bicarbonate containing oxygen up to 3970 kPa and at temperatures of 162 and 238°C is available. Anodic and cathodic polarisation curves and Tafel slopes are presented whilst limiting current densities, exchange current densities and reversible electrode potentials are tabulated. In weak acid and neutral solutions containing chloride ions, the passivity of platinum is always associated with the presence of adsorbed oxygen or oxide layer on the surface In concentrated hydrochloric acid solutions, the possible retardation of dissolution is more likely because of an adsorbed layer of atomic chlorine ... 

It has been proposed that aromatic solvents, carbon disulfide, and sulfur dioxide form a complex with atomic chlorine and that this substantially modifies both its overall reactivity and the specificity of its reactions.126 For example, in reactions of Cl with aliphatic hydrocarbons, there is a dramatic increase in Ihe specificity for abstraction of tertiary or secondary over primary hydrogens in benzene as opposed to aliphatic solvents. At the same time, the overall rate constant for abstraction is reduced by up to two orders of magnitude in the aromatic solvent.1"6 The exact nature of the complex responsible for this effect, whether a ji-coinplex (24) or a chlorocyclohexadienyl radical (25), is not yet resolved.126- 22... 

Example 9.3 Calculate the pressure of atomic chlorine in Cl2(g) at a total pressure of 1.00 bar and a temperature of 2000 K. Do the calculation (a) using the thermodynamic functions in Table 4.3, and (b) using equation (9.58), which requires Cp m expressed as a function of T, obtained from Table 2.1, and compare the results. 

X-ray reflectometry (XR) has already been described in Sect. 2.1 as a technique for polymer surface investigations. If a suitable contrast between components is present buried interfaces may also be investigated (Fig. 4d) [44,61,62]. The contrast is determined by the difference in electron density between materials. It is, in the case of interfaces between polymers, only achieved if one component contains heavy atoms (chlorine, bromine, metals, etc.). Alternatively the location of the interface may be determined by the deposition of heavy markers at the interface. 

CIF3 This compound contains two elements from Group 17 of the periodic table. Chlorine is named first because it is lower in the group, and we add a prefix that specifies the number of fluorine atoms chlorine trifluoride. 

The chlorine electrode contains gaseous chlorine in equilibrium with atomic chlorine adsorbed on the platinum black and a solution of chloride ions. Its potential is given by the equation... 

The atomic mass of chlorine is reported as 35.5 to three significant figures. No single atom of chlorine has that mass because the atomic mass of any element is the weighted average of all the isotopes, not the mass of any one atom. Chlorine is 76% 35C1 and 24% 37C1. 

An alkyl halide (also known as a haloalkane) is an alkane in which one or more hydrogen atoms have been replaced with halogen atoms, such as F, Cl, Br, or I. The functional group of alkyl halides is R—X, where X represents a halogen atom. Alkyl halides are similar in structure, polarity, and reactivity to alcohols. To name an alkyl halide, first name the parent hydrocarbon. Then use the prefix fluoro-, chloro-, bromo-, or iodo-, with a position number, to indicate the presence of a fluorine atom, chlorine atom, bromine atom, or iodine atom. The following Sample Problem shows how to name an alkyl halide. 

Kurlo, M.J. and Knable, G.L. A kinetic investigation of the gas-phase reactions of atomic chlorine ( P) and hydroxyl (X with acetonitrile atmospheric significance and evidence of decreased reactivity between strong electrophiles, J. Phys. Chem., 88(15) 3305-3308, 1984. 

A flashlamp is still needed to produce atomic chlorine by photodissociation, which then reacts with Hj to form atomic hydrogen ... 

At low temperature, propene behaves like another alkene and undergoes a simple addition of a halogen across the double bond to form 1,2-dichlo-ropropane. These conditions minimize the possibility of forming chlorine atoms (chlorine free radicals), and the presence of oxygen traps the few that do form. However, when the conditions promote the formation of chlorine atoms, a substitution occurs to produce 3-chloropropene. 

During the long Antarctic night, appreciable amounts of molecular chlorine, Cl, and hypochlorous acid, HOCl, accumulate within the polar vortex. When the sun returns during the spring (in September in Antarctica), ultraviolet radiation decomposes the accumulated molecular chlorine and hypochlorous acid to produce atomic chlorine. Cl. Atomic chlorine is a free radical. Free radicals are atoms or molecules that contain an unpaired or free electron. The Lewis structures of free radicals contain an odd number of electrons. The unpaired electron in free radicals makes them very reactive. The free radical Cl produced from the decomposition of CI2 and HOCl catalyzes the destruction of ozone as represented by the reaction ... 

In 1974, Cicerone and Stolarski suggested that if there were sources of atomic chlorine in the stratosphere, the following catalytic ozone destruction cycle... 

Figures 4.44 and 4.45 show absorption spectra of some simple chlorofluoro-methanes and ethanes, respectively (Hubrich and Stuhl, 1980). Tables 4.37 and 4.38 give the recommended absorption cross sections for some of these compounds (DeMore et al., 1997). None of these compounds absorb in the actinic region above 290 nm, but do around 180-200 nm, wavelengths only found in the stratosphere. As discussed in Chapter 12, it is photolysis at these short wavelengths to generate atomic chlorine that is responsible, along with bromine and perhaps in some cases, iodine atoms, for the chain destruction of stratospheric ozone.

FIGURE 5.8 (a) Typical decay of resonance fluorescence from atomic chlorine in the presence of CH3SCH3 (8.6 x 1013 molecules cm 3) at 297 K and in 50 Torr N2 as the carrier gas (adapted from Stickel et al., 1992). (b) Typical pseudo-first-order plot of slopes of plots such as those in part (a) against the initial concentration of CH3SCH3 (adapted from Stickel et al., 1992). 

Stelson, A. W and J. H. Seinfeld, Chemical Mass Accounting of Uban Aerosol, Environ. Sci. Technol., 15, 671-679(1981). Stickel, R. E., J. M. Nicovich, S. Wang, Z. Zhao, and P. H. Wine, Kinetic and Mechanistic Study of the Reaction of Atomic Chlorine with Dimethyl Sulfide, J. Phys. Chem., 96, 9875-9883 (1992). Swartz, E J. Boniface, I. Tchertkov, O. V. Rattigan, D. V. Robinson, P. Davidovits, D. R. Worsnop, J. T. Jayne, and C. E. Kolb, Horizontal Bubble Train Apparatus for Heterogeneous Chemistry Studies Uptake of Gas-Phase Formaldehyde, Environ. Sci. Technol, 31, 2634-2641 (1997). 

Zetzsch, C and W. Behnke, Heterogeneous Photochemical Sources of Atomic Chlorine in the Troposphere, Ber. Bunsenges. Phys. Chem., 96, 488-493 (1992). 

Let us first review the oxidants that have been recognized for some time as important in the troposphere, as well as atomic chlorine, for which there is increasing evidence of a contribution in marine regions. 

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