Mercuric acetate, accelerators

The accelerating effect of sodium perchlorate on the rate of mercuration by mercuric acetate in acetic acid arises out of the equilibrium... 

From this equilibrium it follows that 0.1 M sodium perchlorate will produce 6x10"5 M perchloric acid, i.e. sufficient to produce a significant acceleration for mercuration with mercuric acetate in the absence of added perchloric acid, but not otherwise. The acceleration of the rate of mercuration with mercuric perchlorate in 97 % aqueous acetic acid (but not with acetic acid containing a concentration of water of 0.2 M) was attributed to the fact that in the former... 

Sometimes a yellow color (mercuric oxide) appears at this point and disappears as the reaction proceeds. If the yellow color does not disappear in about 10 minutes, 1.5 ml. of 70% perchloric acid per mole of mercuric acetate may be added to accelerate the reaction. Under these conditions even unreactive olefins are completely oxymercurated in about an hour. 

Second-order rate coefficients for reaction (21) (X = I and OAc) were also reported by Abraham and Behbahany30 and are given in Table 20. Kinetic salt effects of added tetra-n-butylammonium perchlorate were studied for reaction (21) (X = I and OAc) both with solvent methanol and solvent tert.-butanol. Reaction (21) (X = 1) was accelerated in both solvents to about the same extent as was reaction (21) (X = Cl), and mechanism SE2(open) was therefore suggested. The reaction of tetraethyltin with mercuric acetate was subject to very large positive salt effects in methanol, perhaps due to anion exchange, but was unaffected by the electrolyte in solvent /er/.-butanol. Abraham and Behbahany30 considered that it was not possible to deduce the mechanism of the acetate reaction and that further work was necessary to decide between mechanism SE2(open) and mechanism SE2(cyclic). 

Other metals, the commonest being lead,2 bismuth, and manganese, in powder form exert a more moderate effect on the decomposition. Mercury would also fall into this class of moderate accelerators, but the catalytic action in this case is remarkable in being periodic or rhythmic. When the concentration of hydrogen ion is reduced to an almost negligible quantity by the addition of a little sodium acetate solution, a clean mercury surface in contact with hydrogen peroxide solution of approximately 10 per cent, concentration, at periodic intervals of about one second, becomes coated with a bronze film which suddenly disappears with a burst of oxygen from the contact layer of the two liquids the substance of the film, which is alternately formed and decomposed, is probably an unstable oxide, possibly mercurous peroxide.3... 

Diacetoxymercuri phenol. —Phenol in concentrated aqueous solution is treated wdth mercuric acetate, wdien a w hite precipitate separates out, the reaction being accelerated if heat is applied. This product crystallises from dilute acetic acid in needles, M.pt. 216° to 217° C. The mother-liquor from this preparation contains o- and p-acetoxymercuri phenols.. Treatment of the diacetoxy compound with sodium chloride gives the dicMoromercuri phenol, a white powder, M.pt. 258° C. with decomposition. ... 

Hofmann-Sand reaction. Olefin mercuration with mercuric salts (halides, acetates, nitrates, or sulfates) in aqueous solution. In alcoholic solutions, the accelerated reaction produces alkoxylalkyl compounds. 

Perchloric acid strongly accelerates aromatic mercuration in acetic acid solution it converts mercuric acetate into a positively charged electrophile.24b,c,d... 

Mercuric perchlorate is a very much more powerful mercurating agent than the more covalent mercuric acetate toluene is only very slowly mercurated by mercuric acetate at room temperature but addition of a little perchloric acid accelerates the reaction by a factor of about 2000.191... 

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