Hydrochloric exchange reactions

Typical equipment made from tantalum includes heat exchangers, reaction vessels liners, thermowells, and heating elements or heat shields for high temperature vacuum sintering furnaces. Tantalum fabricated parts are found in the manufacturing of pharmaceuticals, explosives, insecticides, dyes, acidic baskets for silver cyanide barrel platers, and in hydrochloric and hydrobromic acid condensers. 

An attempt to directly convert hyellazole (245) to 6-chlorohyellazole (246) by reaction with N-chlorosuccinimide in the presence of a catalytic amount of hydrochloric acid led exclusively to 4-chlorohyellazole. On the other hand, bromination of 245 using NBS and a catalytic amount of hydrobromic acid gave only the expected 6-bromohyellazole (733). Alternatively, a direct one-pot transformation of the iron complex 725 to 6-bromohyellazole (733) was achieved by reaction with an excess of NBS and switching from oxidative cyclization conditions (basic reaction medium) to electrophilic substitution conditions (acidic reaction medium). Finally, a halogen exchange reaction with 4 equivalents of cuprous chloride in N,N-dimethylformamide (DMF) at reflux, transformed 6-bromohyellazole (733) into 6-chlorohyellazole (246) (602) (Scheme 5.73). 

Exchange. During an exchange reaction, partners in compounds exchange their partners. One type of exchange reaction is called a neutralization reaction, the reaction between an acid and a base. The reaction of sodium hydroxide (lye), NaOH, with hydrochloric acid, HC1, to produce NaCl and water is such a reaction. In this case, Na+ switches partners from OH- to Cl, and H+ from Cl to OH. ... 

Halogen exchange reactions may be used to prepare tetrahalotellurates(IV) that are not accessible through reactions of aryl tellurium trihalides and onium halides. Treatment of tetrachloro- or bromotrichlorotellurates with dilute hydrobromic acid produces the tetrabromotellurates. The conversion of bromotellurates to tetrachlorotellurates requires concentrated hydrochloric acid. Chlorine and bromine are easily replaced by iodine when the tellurates are reacted with excess potassium iodide in dilute hydrochloric acid. The iodotellurates cannot be converted to the bromo- or chlorotellurates ... 

Lincoln et al. (292) studied chloride exchange between the free chloride and probably TlClg (see Section II,C,2) by measuring C1 NMR line broadening in aqueous solutions containing concentrated hydrochloric acid, [HCl] = 7 and 11M. Under these conditions the line widths were dominated by quadrupolar relaxation. Only a lower limit for the pseudo-first-order rate constant of the exchange reaction... 

In addition, several Tc(V) complexes based on the 0=Tc(S)4-core have been prepared. The preparation w as achieved by exchange reaction of Tc(V) gluconate with various dithiols in aqueous cthanolic solution. The oxo-dithiolatotechnetatc(V) complexes were mostly precipitated as the Et4N] salts. The complex compounds turned out to be diamagnetic in solution, and have probably square pyramidal structure [117,118,119]. Stereoisomcric complexes derived from mesa and racemic 2.3-dimer-captosuccinic acid dimethylcster were identified by H NMR [120]. The kinetics of the reaction between pcrtcchnetatc and meso- or racemic dimcrcaptosuccinic acid in hydrochloric acid solution were studied. The reaction was found to be first order in each reactant [121]. Also the reaction of pertechnetate with para-substituted benzene thiols was followed and showed a simple second order kinetics. The reaction rate decreased when the substituent became more electron-withdrawing [122]. 

Ligand exchange reactions. From top to bottom copper(ii) ions, copper(ii) ions after addition of concentrated aqueous ammonia, cobalt(ii) ions, cobalt(ii) ions after the addition of concentrated hydrochloric acid... 

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