Heat of chlorination

A surprising trend was noted in vapor-phase heats of chlorination determined at 90 C on fluorine-containing olefins. ... 

A comparison of these heats of chlorination with those of the alkenes gives information about the effects of fluorine atoms on the ethylenic linkage. 

A similar situation holds for the heats of chlorination of some fiuoro-olefins. Thus in the series CFg—CClg, CFg —CFCi, CF2—CF, the heats of chlorination increase from —41-1, through -48 8 to... 

Lacher and his co-workershave also measured the heats of chlorination, in the vapour phase, of a number of fluoro-and fluorochioro-olefins. The heats refer to the reaetions of the type CP -CFR -f Cl - > The results are shown... 

The heat of chlorination of periluorocyelobutcnc, —3 7 4 kcai/ mole refers to the reaction ... 

Radiative stabilization of a most simple kind was first observed [235] on heating of chlorine, bromine and iodine vapour to a temperature above lOOO C. The luminescence spectra of all halogen vapours were found to represent an inversion of their absorption spectra being consistent with process X + X -> Xg hv which is an inversion of photodissociation Xg -f- hv X + X. 

Gunn SR, Green LG, Von Egidy AI. The heat of chlorination of diboron tetrachloride. JPhys Chem. 1959 63 1787-4218. 

Undoubtedly, the degassing technique used in [325] did not result in complete removal of the adsorbed oxygen (this fact was pointed out by the authors). The presence of oxygen on the carbon surface caused a significant decrease in the energy of the C-Cl adsorption bond. On the other hand, it is obvious that the coverage by oxygen in the Keyes-Marshall experiments was considerably lower than in samples subjected to air- or anodic oxidation. Therefore, in our experiments a lower heat of chlorine adsorption could be expected ... 

S = Heat of sublimation of sodium D = Dissociation energy of chlorine / = Ionization energy of sodium = Electron affinity of chlorine Uq = Lattice energy of sodium chloride AHf = Heat of formation of sodium chloride. 

CH2=CHC = CCH = CH2. a colourless liquid which turns yellow on exposure to the air it has a distinct garlic-like odour b.p. 83-5°C. Manufactured by the controlled, low-temperature polymerization of acetylene in the presence of an aqueous solution of copper(I) and ammonium chlorides. It is very dangerous to handle, as it absorbs oxygen from the air to give an explosive peroxide. When heated in an inert atmosphere, it polymerizes to form first a drying oil and finally a hard, brittle insoluble resin. Reacts with chlorine to give a mixture of chlorinated products used as drying oils and plastics. 

Anhydrous hydrogen fluoride (as distinct from an aqueous solution of hydrofluoric acid) does not attack silica or glass. It reacts with metals to give fluorides, for example with heated iron the anhydrous iron(II) fluoride is formed the same product is obtained by displacement of chlorine from iron(II) chloride ... 

The extraction of titanium is still relatively costly first the dioxide Ti02 is converted to the tetrachloride TiCl4 by heating with carbon in a stream of chlorine the tetrachloride is a volatile liquid which can be rendered pure by fractional distillation. The next stage is costly the reduction of the tetrachloride to the metal, with magnesium. must be carried out in a molybdenum-coated iron crucible in an atmospheric of argon at about 1100 K ... 

By the reaction of chlorine with a heated mixture of chrom ium(III) oxide and carbon ... 

The heats of formation of Tt-complexes are small thus, — A//2soc for complexes of benzene and mesitylene with iodine in carbon tetrachloride are 5-5 and i2-o kj mol , respectively. Although substituent effects which increase the rates of electrophilic substitutions also increase the stabilities of the 7r-complexes, these effects are very much weaker in the latter circumstances than in the former the heats of formation just quoted should be compared with the relative rates of chlorination and bromination of benzene and mesitylene (i 3 o6 x 10 and i a-Sq x 10 , respectively, in acetic acid at 25 °C). 

Consider the chlorination of methane to chloromethane The heats of formation of the reac tants and products appear beneath the equation These heats of formation for the chemical com pounds are taken from published tabulations the heat of formation of chlorine as it is for all elements IS zero... 

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... 

The aHphatic iodine derivatives are usually prepared by reaction of an alcohol with hydroiodic acid or phosphoms trHodide by reaction of iodine, an alcohol, and red phosphoms addition of iodine monochloride, monobromide, or iodine to an olefin replacement reaction by heating the chlorine or bromine compound with an alkaH iodide ia a suitable solvent and the reaction of triphenyl phosphite with methyl iodide and an alcohol. The aromatic iodine derivatives are prepared by reacting iodine and the aromatic system with oxidising agents such as nitric acid, filming sulfuric acid, or mercuric oxide. 

The reaction of chlorine gas with a mixture of ore and carbon at 500—1000°C yields volatile chlorides of niobium and other metals. These can be separated by fractional condensation (21—23). This method, used on columbites, is less suited to the chlorination of pyrochlore because of the formation of nonvolatile alkaU and alkaline-earth chlorides which remain in the reaction 2one as a residue. The chlorination of ferroniobium, however, is used commercially. The product mixture of niobium pentachloride, iron chlorides, and chlorides of other impurities is passed through a heated column of sodium chloride pellets at 400°C to remove iron and aluminum by formation of a low melting eutectic compound which drains from the bottom of the column. The niobium pentachloride passes through the column and is selectively condensed the more volatile chlorides pass through the condenser in the off-gas. The niobium pentachloride then can be processed further. 

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