Halogens, reaction with lime

Toluene from Toluidine.—It is often desirable to obtain tbe hydiocarbon from the base. The process of diazotisntion offers the only convenient method. The diazonium salt may be reduced by alcohol (Reaction 1, p. 162) or, as in the piesent instance, by sodium stannite. Less direct methods are the con-veision of the diazonium compound into (i) the hydrazine (see p. 174), (2) the acid and distillation with lime (p. 200), (3) the halogen derivative and reduction with sodium amalgam, 01, finally (4) the phenol and distillation with zinc dust. 

Other Reactions. Dry hydrated lime adsorbs halogen gases, eg, CI2 and F2, to form hypochlorites and fluorides. It reacts with hydrogen peroxide to form calcium peroxide, a rather unstable compound. At sintering temperatures, quicklime combines with iron to form dicalcium ferrite. 

To study the effects of water and other solvents on titanocene(III)-mediated processes we used the transannular cychzation of epoxygerma-crolides as a model reaction [47]. Thus, we found that in anhydrous, non-halogenated solvents such as THF the reaction led selectively to decalins with an exocyclic double bond (Scheme 5). In an aqueous medium (THF/H2O), however, the characteristic lime green color of Cp2TiCl turned deep blue and the main product was a reduced decalin (Scheme 5). Under these conditions, water (either H2O or D2O) proved to be more effective than the toxic and expensive hydrogen-atom donor 1,4-cyclohexadiene for the reduction of tertiary radicals [47]. This is an unusual phenomenon in free-radical chemistry [48-50], subsequently exploited by us for the selective reduction of aromatic ketones as we shall see later [51,52]. 

The flowsheet of the air-stripping process for bromine recovery from brines (including seawater brines) is shown in Fig. 5 [60]. The stock brine from a reservoir, mbted with H2SO4 and Clj, is directed to the top of the desorber. The bromine-free brine is collected at the bottom of the desorber, neutralized with thiosulfate and lime milk prior to disposal. Release of the chlorine/bromine air mixture from the top of the desorber is directed to the dechlorinating tower (1) where the mixture is treated with diluted FeBrj solution. The halogen exchange is described by the reaction... 

In order to detect the halogens, the substance to be tested is heated in a not too narrow test-tube with a Bunsen flame with an excess of chemically pure lime, the tube while still hot is dipped into a little water, chemically pure nitric acid is added to acid reaction, the solution is then filtered and treated with silver nitrate. 

---