In mercuration

Nitration in sulphuric acid is a reaction for which the nature and concentrations of the electrophile, the nitronium ion, are well established. In these solutions compounds reacting one or two orders of magnitude faster than benzene do so at the rate of encounter of the aromatic molecules and the nitronium ion ( 2.5). If there were a connection between selectivity and reactivity in electrophilic aromatic substitutions, then electrophiles such as those operating in mercuration and Friedel-Crafts alkylation should be subject to control by encounter at a lower threshold of substrate reactivity than in nitration this does not appear to occur. 

The occurrence of a hydrogen isotope effect in an electrophilic substitution will certainly render nugatory any attempt to relate the reactivity of the electrophile with the effects of substituents. Such a situation occurs in mercuration in which the large isotope effect = 6) has been attributed to the weakness of the carbon-mercury bond relative to the carbon-hydrogen bond. The following scheme has been formulated for the reaction, and the occurrence of the isotope effect indicates that the magnitudes of A j and are comparable ... 

Inorganic salt solutions Molybdenum has excellent resistance to 3% sodium chloride, 10% aluminium chloride and 10% ammonium chloride at temperatures up to 100°C. It is severely corroded by 20% solutions of ferric and cupric chlorides at 35°C and is subject to pinhole-type pitting in mercuric chloride solutions (Table 5.5). 

The US Bureau of Mines found the chemical and galvanic corrosion behaviour of both the TZM and Mo-30W alloy to be generally equal or superior to that of unalloyed molybdenum in many aqueous solutions of acids, bases and salts. Notable exceptions occurred in 6-1 % nitric acid where both alloys corroded appreciably faster than molybdenum. In mercuric chloride solutions the TZM alloy was susceptible to a type of crevice corrosion which was not due to differential aeration. The alloys were usually not adversely affected by contact with dissimilar metals in galvanic couple experiments, but the dissimilar metals sometimes corroded galvanically. Both alloys were resistant to synthetic sea water spray at 60°C. 

The reaction was first-order in benzene, and approximately first-order in mercuric salt. 

Some progress has been made toward achieving enantioselectivity in mercuration-induced cyclization. Several to-oxazoline (BOX) ligands have been investigated. The... 

Some years later, Kochi et al (Fukuzumi and Kochi, 1981) applied their theory on electron and charge transfers to electrophilic alkene bromination (Kochi, 1988) by comparing the reactivities of various alkenes in bromination and in mercuration. Although the substituent effect trends in the two reactions are totally different, a linear relationship (7) is observed when the reactivities... 

Weeping, J.J., Fleuren, G.J. and Hoedemaeker, J. (1978). Demonstration of antinuclear antibodies in mercuric chloride-induced glomerulopathy in the rat. Lab. Invest. 39 405-411. 

The first product of the oxidation of alcohol is acetaldehyde and an important end-product is fulminic add, which latter can, however, only be isolated if silver or mercury ions are present. With these ions it forms salts—fulminates—which are stable towards nitric add in them, it must be presumed, the linkage with the metal is homopolar and non-ionogenic, as in mercuric cyanide. The formation of fulminic acid takes place because the carbonyl group of the aldehyde confers reactivity on the adjacent methyl group which then forms a point of attack for the nitrous acid. The various stages in the process are indicated by the following formulae ... 

Whether the diminution in mercurous salt concentration of a solution in contact with an expanding mercury surface be regarded as due to the adsorption of the salt on the newly formed surface as imagined by Gibbs and Warburg or as due to the transference of mercurous ions from the aqueous to the metallic phase as postulated by Lippmann and Nemst, we have seen that the number of grm. equivalents removed from the solution per unit increase in 1... 

We are currently trying to answer specifically the question of whether ir-bonded complexes do occur in certain cases where insertion reactions are observed. I think they do because I believe that the same factors which favor stabilization of this type of transition state will also tend to favor formation of 7r-bonded olefin complexes, which are only slightly removed from this. At the moment Bern Tinker is examining the insertion of olefins in mercuric complexes to see whether there is any indication of 7r-bonded intermediates. In his paper, Dr. Heck referred to some unpublished work relevant to this theme. I would certainly be interested in anything more he can tell us about that. 

Again, mercury is apparently a monad in mercurous ohlo ride (calomel, HgCl) and a dyad in mercuric chloride (corrosive sublimate, Hg"Cl,)j but there are strong reasons for believing that the formula of calomel ought to bo doubled, in which case mercury would assume the dyad form in both com pounds ... 

The catalysis of the cleavage of carbon-halogen bonds by complexation with metal ions such as silver or mercuric ion is a well-known phenomenon. The compounds susceptible to this action are alkyl halides capable of forming car-bonium ions. The complexed anions such as in mercuric nitrate, mercuric perchlorate, or hydrated mercuric ion do not exhibit a simple relationship between their effect on the total rate and on the relative distribution of products stemming from water or the anion. This evidence is indicative of the following catalytic mechanism ... 

According to Stettbacher, mercuric azide develops the same vol of gas on deton as MF but it is 20 times more brisant. Wohler Krupko (Ref 3) observed that its sensitivity depended on the cryst size of the azide. Mercuric azide is considered to be more sensitive to impact and friction than MF and is so unstable that it frequently undergoes spontaneous deton at the slightest touch even under w (Refs 5 7). Hitch (Ref 4) noted this sensitivity expecially when the azide was prepd from mercuric nitrate and Na or K azide solns but by careful thermal studies he decompd it quanty into its elements without expln below 300°. Miles (Ref 8) reported that in every case when /3-crysts of Hg(N3)2 were present the material was likely to expl, and in w or more rapidly in mercuric nitrate soln, the /3-type was unstable being transformed to the o-type, as in the parallel case of LA,... 

Double hexagonal closest packing (Sec. 11-5) was first found62 for the oxygen ions in brookite, the orthorhombic form of titanium dioxide, and for the oxygen and fluoride ions in topaz 63 AUSiC F2. It has since been reported for the halogens in one modification of cadmium iodide,64 in mercuric bromide,66 and in mercuric chloride6 and for chloride and... 

At one time solutions of metals in their molten salts were thought to be colloidal in nature, but this has been shown not to be true. However, no completely satisfactory theory has been advanced to account for oil the properties of these solutions. One hypothesis involves reduction of the cation of the molten salt to a lower oxidation state. For example, the solution of mercury in mercuric chloride undoubtedly involves reduction ... 

Insertions into the metal - oxygen bond in mercuric acetate with aromatic isocyanides has given the compound 119 (R = Ph, xylyl), which readily hydrolyzed to give organic acetamide derivatives (480). 

The oxime nitrogen in 307 has been employed as an internal nucleophile in mercuration of a double bond to generate nitrone 308, which instantaneously underwent the dipolar... 

Meanwhile, Reutov et al.4 had reported that reaction (1) followed first-order kinetics, first-order in alkylmercuric bromide and zero-order in mercuric bromide, when anhydrous dimethylsulphoxide (DMSO) was used as the solvent. This report was confirmed by Ingold and co-workers3 and hence is the first authentic record of a reaction following mechanism SE1. Over a six-fold variation in the initial concentration of a-carbethoxybenzylmercuric bromide and a three-fold variation in that of mercuric bromide, only the first-order rate coefficient with respect to the alkylmercuric bromide remained constant3. The rate coefficients reported by the two sets of workers are given in Table 1, together with the reported Arrhenius equations. 

In the above solvents, reaction (42) follows second-order kinetics, first-order in the gold complex and first-order in mercuric salt. The determined second-order rate coefficients are assembled in Table 34 the relative standard deviation in these coefficients is usually about 5 %. 

The alnminium-mercnry couple (prepared by immersing aluminium foil in mercuric clilorido solution) is a halogen carrier of some value, and is used to facilitate substitution in the n.romatic series of compounds, by chlorine and bromine. 

The mercurous acetate product was only slightly soluble. Typical rate curves at constant temperature and pressure define a decrease in mercuric acetate concentration according to a first order kinetic law, finally leveling off at a small constant value. During this last period mercurous acetate was being reduced to metallic mercury. 

Palladation seems to be an electrophilic substitution reaction but it is less selective than mercuration. As in mercuration, the chloride is very much less reactive than the acetate. A curious effect of anion on the... 

Grandberg, Kost, and Zheltikova108 have shown recently that mercuric salts mercurate pyrazoles in the 4-position and also give other complexes with variable quantities of the mercuric salts. The proportion of mercuric salt bound as a complex depends on the basicity of the starting pyrazole. The mercuric group in mercurated pyrazoles behaves in a variety of reactions just as phenyl mercuric chloride.108,219,350... 

A less than the van der Waals distance. This interaction is non-linear and appears to lead to a small distortion in the HgCN angle which is 173°. A similar geometry arises in mercuric cyanide where approximately linear molecules are associated through non-linear Hg N interaction with a Hg—N distance of 2.70 A (Hvoslef, 1958). These situations bear some obvious similarities to the weak non-linear bridges in P(CN)S. 

NOTE Formalin does not preserve tissue proteins by coagulation but it is thought to form cross links with basic amino acids. Ethanol and mercuric chloride-based fixatives are based on coagulation. With few exceptions retrieval should not be performed on ethanol fixed tissues. It should only be conducted with limited controlled protocols in mercuric-chloride-based fixatives. 

Nickel silvers Cu-Zn-Ni alloys containing 5, 10 and 15% Ni did not crack in mercurous nitrate solution for 7 days... 

Cryoscopic determinations in dilute solution with pyridine,7 quinoline,8 and fused bismuth chloride 9 as solvents have proved the constitution of the salt under these conditions to correspond with the simpler formula Cu—Cl. Solutions in mercuric chloride consist of a mixture of single and double molecules.10... 

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