Chlorine molecules

Step 1 Dissociation of a chlorine molecule into two chlorine atoms... 

Chlorine molecule Two chlorine atoms (b) Cham propagation... 

Direct Chlorination of Ethylene. Direct chlorination of ethylene is generally conducted in Hquid EDC in a bubble column reactor. Ethylene and chlorine dissolve in the Hquid phase and combine in a homogeneous catalytic reaction to form EDC. Under typical process conditions, the reaction rate is controlled by mass transfer, with absorption of ethylene as the limiting factor (77). Ferric chloride is a highly selective and efficient catalyst for this reaction, and is widely used commercially (78). Ferric chloride and sodium chloride [7647-14-5] mixtures have also been utilized for the catalyst (79), as have tetrachloroferrate compounds, eg, ammonium tetrachloroferrate [24411-12-9] NH FeCl (80). The reaction most likely proceeds through an electrophilic addition mechanism, in which the catalyst first polarizes chlorine, as shown in equation 5. The polarized chlorine molecule then acts as an electrophilic reagent to attack the double bond of ethylene, thereby faciHtating chlorine addition (eq. 6) ... 

Chlorine free radicals used for the substitutioa reactioa are obtaiaed by either thermal, photochemical, or chemical means. The thermal method requites temperatures of at least 250°C to iaitiate decomposition of the diatomic chlorine molecules iato chlorine radicals. The large reaction exotherm demands close temperature control by cooling or dilution, although adiabatic reactors with an appropriate diluent are commonly used ia iadustrial processes. Thermal chlorination is iaexpeasive and less sensitive to inhibition than the photochemical process. Mercury arc lamps are the usual source of ultraviolet light for photochemical processes furnishing wavelengths from 300—500 nm. 

Chlorine atoms obtained from the dissociation of chlorine molecules by thermal, photochemical, or chemically initiated processes react with a methane molecule to form hydrogen chloride and a methyl-free radical. The methyl radical reacts with an undissociated chlorine molecule to give methyl chloride and a new chlorine radical necessary to continue the reaction. Other more highly chlorinated products are formed in a similar manner. Chain terrnination may proceed by way of several of the examples cited in equations 6, 7, and 8. The initial radical-producing catalytic process is inhibited by oxygen to an extent that only a few ppm of oxygen can drastically decrease the reaction rate. In some commercial processes, small amounts of air are dehberately added to inhibit chlorination beyond the monochloro stage. 

Aromatic compounds may be chlorinated with chlorine in the presence of a catalyst such as iron, ferric chloride, or other Lewis acids. The halogenation reaction involves electrophilic displacement of the aromatic hydrogen by halogen. Introduction of a second chlorine atom into the monochloro aromatic stmcture leads to ortho and para substitution. The presence of a Lewis acid favors polarization of the chlorine molecule, thereby increasing its electrophilic character. Because the polarization does not lead to complete ionization, the reaction should be represented as shown in equation 26. 

Chlorination of Methane. Methane can be chlorinated thermally, photochemicaHy, or catalyticaHy. Thermal chlorination, the most difficult method, may be carried out in the absence of light or catalysts. It is a free-radical chain reaction limited by the presence of oxygen and other free-radical inhibitors. The first step in the reaction is the thermal dissociation of the chlorine molecules for which the activation energy is about 84 kj/mol (20 kcal/mol), which is 33 kJ (8 kcal) higher than for catalytic chlorination. This dissociation occurs sufficiendy rapidly in the 400 to 500°C temperature range. The chlorine atoms react with methane to form hydrogen chloride and a methyl radical. The methyl radical in turn reacts with a chlorine molecule to form methyl chloride and another chlorine atom that can continue the reaction. The methane raw material may be natural gas, coke oven gas, or gas from petroleum refining. 

The hquid-phase chlorination of benzene is an ideal example of a set of sequential reactions with varying rates from the single-chlorinated molecule to the completely chlorinated molecule containing six chlorines. Classical papers have modeled the chlorination of benzene through the dichlorobenzenes (14,15). A reactor system may be simulated with the relative rate equations and flow equation. The batch reactor gives the minimum ratio of... 

Termination steps are, in general, less likely to occur than the propagation steps. Each of the termination steps requires two free radicals to encounter each other in a medium that contains far- greater quantities of other materials (methane and chlorine molecules) with which they can react. Although some chloromethane undoubtedly arises via direct combination of methyl radicals with chlorine atoms, most of it is formed by the propagation sequence shown in Figure 4.21. 

The Cl atom attacks methane and forms a methyl free radical plus HCI. The methyl radical reacts in a subsequent step with a chlorine molecule, forming methyl chloride and a Cl atom ... 

Using the laws of constant composition and the conservation of mass, complete the molecular picture of hydrogen molecules (O—O) reacting with chlorine molecules ( — ) to give hydrogen chloride ( —O) molecules. 

Then, no further reactions among chlorine molecules occur. 

The ion Fe2+ is converted into ion Fe3+ (oxidation), and the neutral chlorine molecule into negatively charged chloride ions Cl" (reduction) the conversion of Fez+ into Fe3+ requires the loss of one electron, and the transformation of the neutral chlorine molecule into chloride ions necessitates the gain of two electrons. This leads to the view that, for reactions in solutions, oxidation is a process involving a loss of electrons, as in... 

However, Schwarz s suggestion to focus on bonded atoms rather than neutral atoms also runs into a major problem because the atoms of any element typically show a large variety of oxidation states. For example, atoms of chlorine occur in the zero oxidation state in the chlorine molecule, the —1 state in NaCl, +1 in HOC1, +3 in HC102, +5 in HCIO3, and +7 in HCIO4. 

The values for Cl2 are bx = 6.60, b2 = 3.62, both x 10 24 cm3. When these values are substituted in Eq. 43 together with R = 1.99 X 10 8 cm, one obtains ax == 1.79 and a2 = 2.36, both X 10 24 cm3. Thus, although the polarizability of the chlorine molecule is almost twice as great parallel than perpendicular to the axis, the atom is nearly isotropic with slightly greater polarizability perpendicular to the axis. 

Sulfochlorination is a radical chain reaction that is started by photolysis of chlorine molecules ... 

Recall from Section 2.9 that most radicals are very reactive. Because one of the products is another radical, this reaction is a propagation step (a step in which one reactive radical intermediate produces another). In a second propagation step, the methyl radical may react with a chlorine molecule ... 

In column IV there are listed the G2 values calculated from the parameters proposed by von Stackelberg. As an approximation to the configuration of the chlorine molecules spherical shells of uniform density were placed at the centers of the eight cavities formed by the oxygen atoms. It is seen that the calculated values are not compatible with... 

Ions form during the reaction between sodium and chlorine. Each sodium atom loses one electron, leaving one less electron than the number of protons in the nucleus Na Na + e Chlorine molecules decompose into atoms, and the electron lost by a sodium atom becomes attached to a chlorine atom to produce an anion Cl + e Cl ... 

C04-0133. Sodium metal reacts vigorously with chlorine gas to form solid white sodium chloride. Draw a molecular picture showing ten sodium atoms and three chlorine molecules. Then draw another molecular picture of this same system after reaction occurs. 

Chlorine molecules must be broken apart into chlorine atoms. Table gives the bond energy BE) of molecular chlorine, 240 kJ/mol. We need — mole of CI2 to form 1 mole of NaCl, so the energy... 

After dosing methyl radicals and chlorine molecules onto CuaSi samples which were cooled to 180 K, mass spectrometry was used to identify the gas phase reaction products upon heating. The silane products have been identified by monitoring their characteristic ions, which include SiCU" " (m/e=168), CHaSiCla (m/e=148), SiCla" " (m/e=133), (CHa)2SiCl2+ (m/e=128), CHaSiCl2+ (m/e=113), (CHa)2SiCl+ (m/e=93), SKCHala" " (m/e=73). All of these ions are detected. On the other hand, no CHaCl (m/e=53) or SiH4+ (m/e=32) are observed. 

Chlorine molecules are cleaved at high temperatures by photoinduced radical formation. By this means, a gas/liquid reaction can be performed in the side chain of alkyl aromatics quite selectively. The electrophilic ring substitution, instead, is favored using Lewis catalysts in polar solvents at low temperature. 

Basic research consists of exploratory studies into things for which an end use cannot be specified. It might include a study to determine the effect of chlorine molecules on the diffusivity of hydrocarbons or a study of the dissolution of single spheres in a flowing stream. The prospective dollar value of this research cannot be estimated. 

The reaction is the photochemical combination of hydrogen and chlorine. It is clear that chlorine is the only photochemically active constituent. It is, furthermore, very probable that the elementary photochemical act is the dissociation of the chlorine molecule. Rollefson3 has recently studied and discussed the status of this reaction, and has developed the probable mechanism. It will be assumed in what follows that the necessary primary photochemical act is the dissociation of the chlorine molecule. 

The equation states that elementary sodium reacts with elementary chlorine to produce sodium chloride, table salt. (The fact that chlorine is one of the seven elements that occur in diatomic molecules when not combined with other elements is indicated.) The numbers before the Na and NaCI are coefficients, stating how many formula units of these substances are involved. If there is no coefficient in a balanced equation, a coefficient of 1 is implied, and so the absence of a coefficient before the Cl2 implies one Cl2 molecule. The equation thus states that when the two reagents react, they do so in a ratio of two atoms of sodium to one molecule of chlorine, to form two formula units of sodium chloride. In addition, it states that when the two reagents react, they do so in a ratio of 2 mol of sodium to 1 mol of chlorine molecules, to form 2 mol of sodium chloride. The ratios of moles of each reactant and product to every other reactant or product are implied ... 

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