Exothermic reactions chlorination

Chlorination of alkanes is less exothermic than fluonnation and bromination less exothermic than chlorination Iodine is unique among the halogens m that its reaction with alkanes is endothermic and alkyl iodides are never prepared by lodmation of alkanes... 

Thus the chlorination of methane is calculated to be an exothermic reaction on the basis of heat of forma tion data... 

A similar analysis for fluorination of methane gives AH° = -426 kJ for its heat of reaction Fluori nation of methane is about four times as exothermic as chlorination A reaction this exothermic if it also occurs at a rapid rate can proceed with explosive violence... 

Bromination of methane is exothermic but less exothermic than chlorination The value calculated from bond dissociation energies is AH° = -30 kJ Al though bromination of methane is energetically fa vorable economic considerations cause most of the methyl bromide prepared commercially to be made from methanol by reaction with hydrogen bromide... 

Chlorination. Historically, the production of zirconium tetrachloride from zircon sand involved first a reduction to carbide nitride (see above) followed by the very exothermic reaction of the cmshed carbide nitride with chlorine gas in a water-cooled vertical shaft furnace ... 

In a 3-I. flask are placed a solution of 184 g. (4.6 moles) of sodium hydroxide in 300-400 cc. of water and sufficient ice to make the total volume about 1500 cc. Chlorine is passed into the solution, keeping the temperature below 0° by means of a salt-ice bath, until the solution is neutral to litmus (Note i). After the addition of a solution of 34 g. of sodium hydroxide in 50 cc. of water, the flask is supported by a clamp and equipped with a thermometer and an efficient stirrer. The solution is warmed to 55°, and 85 g. (0.5 mole) of methyl d-naphthyl ketone (Note 2) is added. The mixture is vigorously stirred and, after the exothermic reaction commences, the temperature is kept at 60-70° (Note 3) by frequent cooling in an ice bath until the temperature no longer tends to rise. This requires thirty to forty minutes. The solution is stirred for thirty minutes longer and then the excess hypochlorite is destroyed by adding a solution of 50 g. of sodium bisulfite in 200 cc. of water (Note 4). After cooling to room temperature, the reaction mixture is transferred to a 4-I. beaker and carefully acidified with 200 cc. 

Hydrochloric acid may conveniently be prepared by combustion of hydrogen with chlorine. In a typical process dry hydrogen chloride is passed into a vapour blender to be mixed with an equimolar proportion of dry acetylene. The presence of chlorine may cause an explosion and thus a device is used to detect any sudden rise in temperature. In such circumstances the hydrogen chloride is automatically diverted to the atmosphere. The mixture of gases is then led to a multi-tubular reactor, each tube of which is packed with a mercuric chloride catalyst on an activated carbon support. The reaction is initiated by heat but once it has started cooling has to be applied to control the highly exothermic reaction at about 90-100°C. In addition to the main reaction the side reactions shown in Figure 12.6 may occur. 

General Incineration (oxidation) is the best-known method for the removal of gaseous industrial waste. Combustible compounds containing carbon, hydrogen, and oxygen are converted to carbon dioxide and water by the overall exothermic reactions [Eq. (13.72)]. When chlorinated or sulfur-containing compounds are present in the effluent, the products of combustion include HCl/CE or S02/S03. ... 

Excess sulfur dioxide feed to a chlorine dioxide reactor, leading to excessive exothermic reaction, combined witli failure of the cooling system... 

An exothermic reaction. Hydrogen, a colorless gas. reacts with chlorine, a pale yellow gas, to form colorless hydrogen chloride gas. 

In chlorinations either a substitution or an addition process can occur with the ultimate reaction pathway(s) determined by a combination of factors, which include the reaction conditions, the positions and natures of any substituents present, and the catalyst used. Uncatalyzed chlorination of benzothiadiazole is an exothermic reaction that gives rise to a mixture of isomeric tetrachloro addition products. These are converted in basic medium into 4,7-dichloro-2,1,3-benzothiadiazole (70RCR923). When an iron(III) catalyst is present 4- and 7-chloro substitution becomes the dominant process. Chlorination of a number of 4-substituted 2,1,3-benzothiadiazoles (43) using an oxidative process gave a combination of chlorinated and oxidized products. The 4-hydroxy, 4-amino-, 4-methyl-amino, and 4-acetoxy derivatives of 43 all formed the chloroquinones (44) (40-61% yields). With the 4-aIkoxy substrates both 44 and some 5,7-dichlorinated product were obtained (88CHE96). 

Chlorine should be introduced slowly at first to prevent an accumulation of unreacted chlorine in the solution and to avoid the risk of a rapid, exothermic reaction. The accumulation of chlorine is indicated by the appearance of its characteristic yellow-green color. 

The side-chain substitution of toluene, p-chlorotoluene, etc. is industrially practised. This reaction is carried out in a photochemical reactor. It is an exothermic reaction in which HCl is produced. The reaction is consecutive, and hence CL first reacts with toluene reacts to form the desired benzyl chloride, which is then converted to benzal chloride, and finally benzotrichloride. We may, however, well be interested in the selectivity to benzyl chloride. An additional complication arises due to nuclear chlorination, which is most undesirable. A distillation-column reactor can offer advantages (Xu and Dudukovic, 1999). 

Copper reacts exothermically with chlorine dissolved in heptane at 0°C. The compounds combust during the reaction. The same happens when dry gaseous chlorine is in contact with the metal in fine leaf form. 

Its oxidising character plays a role in all other reactions. Surprisingly, it is thought to form explosive dichlorine oxide with chlorine. It leads to a and very exothermic reaction with disulphur dichloride and detonations with metals potassium, K-Na alloy, magnesium with phosphorus and anhydrous or hydrated hydrazine. 

Cyanuric chloride dissolved in methanol reacted violently and uncontrollably with the solvent. This was attributed to the absence of an acid acceptor to prevent the initially acid catalysed (and later auto-catalysed) exothermic reaction of all 3 chlorine atoms simultaneously. 

A chlorinated biphenyl heat-transfer liquid was added to a burning batch of naph-thylsodium to help to extinguish it. An exothermic reaction, followed by an explosion occurred. Sodium is known to react violently with many halogenated materials. 

Admixture of damp sulfur and swimming pool chlorine caused a violently exothermic reaction, and ejection of molten sulfur. 

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],... 

Typically, intense chemiluminescence in the UV/Vis spectral region requires highly exothermic reactions such as atomic or radical recombinations (e.g., S + S + M - S2 + M) or reactions of reduced species such as hydrogen atoms, olefins, and certain sulfur and phosphorus compounds with strong oxidants such as ozone, fluorine, and chlorine dioxide. Here we review the chemistry and applications of some of the most intense chemiluminescent reactions having either demonstrated or anticipated analytical utility. 

The destruction of chlorine in a sodium hydroxide solution is a fast exothermic reaction. Hypochlorite, hypobromite and bromate are formed ... 

One surprising physical property of fluorine is its electron affinity which, at — 333 kJmol is lower than that of chlorine, —364 kJmol-1, indicating that the reaction X(g) + e - X (g) is more exothermic for chlorine atoms. In view of the greater reactivity of fluorine a much higher electron affinity might reasonably have been expected. The explanation of this anomaly is found when the steps involved in a complete reaction are considered. For example, with a Group I metal ion M+(g) the steps to form a crystalline solid are,... 

A. Chloromethanesulfonyl chloride. A slurry of 210 g. (1.52 moles) of s-trithiane (Note 1) in a mixture of 1 1. of glacial acetic acid and 210 ml. of water is prepared in a 2-1., three-necked, round-bottomed flask equipped with an efficient mechanical stirrer, a thermometer, a coarsely fritted gas inlet tube (Note 2), and an exit tube by which excess fumes are carried to the rear of the hood. The flask is immersed in an ice bath, and the stirrer is started. A stream of chlorine is introduced at such a rate (Note 3) that the temperature of the mixture is maintained between 40° and 50° by the mildly exothermic reaction. After 1-2 hours a yellow solution results. To this solution is added 300 ml. of water, at which point the temperature rises to ca. 60°. 

Stripping of chlorine from hydroxides such as Cl2Sn(OH)2 could eventually lead to gas-phase SnO or Sn02. However, at the relatively low temperatures typical of tin oxide CVD ( 873-973 K), we do not expect these oxides to form, based on the equilibrium calculations described above. Thus, the formation of tin hydroxides is not only thermodynamically favored (i.e., based on minimization of the Gibbs free energy), but there are also exothermic reaction pathways that we expect to be kinetically favorable. The primary tin carrier in the CVD process could therefore be a tin hydroxide. Complete conversion to Sn02 would most likely occur via reactions on the surface. 

Explosion from Chlorinated Rubber-Zinc Oxide Reaction, An until-now undescribed exothermic reaction — that of chlorinated rubber with zinc oxide was responsible for an expln that leveled the manufg area of Dayton Chemical Products Laboratories,... 

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