Mercury reaction+acids

The mechanism of the mercurydD-catalyzed alkyne hydration reactioi is analogous to the oxymercuration reaction of alkenes (Section 7.4). Elec trophilic addition of mercury(II) ion to the alkyne gives a vinylic cation which reacts with water and loses a proton to yield a mercury-containii enol intermediate. In contrast to alkene oxymercuration, no treatment widi NaBH4 is necessary to remove the mercury the acidic reaction conditions alone are sufficient to effect replacement of mercury by hydrogen (Figure 8.3). 

Protection of OH groups. The Bohn-Schmidt reaction, discovered independently in rival German dye firms (Badische Company, Friedrich Bayer), consists in hydroxylation of an anthraquinone with fuming sulfuric acid and boric acid, often in the presence of a catalytic amount of mercury. Boric acid appears to be beneficial... 

A frequently used route is the mercury- or acid-catalyzed transvinylation of vinyl ethers with allylic alcohols (Saucy-Marbet reaction)152-154. 

Reaction of Thallous Selenide and Bis(organoseleno)mercury with Acid Chlorides... 

Salicyloylguanidines 19, 459 Salts, exclusive of — 19, 739 —, fused, reactions in — 18, 942 —, inner s. Betaines, Mercury-carboxylic acid inner salts —, organic... 

Mercury salts, molybdates, and also vanadates give blue to violet compounds with diphenylcarbazide in acid solution, and therefore interfere with the chromium test. The interference can be prevented by the addition of suitable compounds which lower the ionic concentration of the interfering elements below that required for the diphenylcarbazide reaction. For mercury, it is sufficient to add an excess of hydrochloric acid or alkali chloride the usual low dissociation of mercury chloride is thus even further reduced. (The formation of the complex [HgClJ ions also helps to lower the ionic concentration of mercury.) When chromium is to be detected in the presence of mercury, hydrochloric acid is used to acidify the alkaline chromate solution. In this way, 0.25 y chromium is easily detected by a spot reaction in the presence of 2.5 mg mercury (1 10,000). 

Skeletal rearrangement of alkynyl oxiranes and alkynyl aziridines is an attractive method to synthesize highly substituted furans and pyrroles under mild reaction conditions. Decades ago, mercury(II)/acid-catalyzed reactions of alkynyl oxiranes... 

Tin(IV) in aqueous acid gives a yellow precipitate with hydrogen sulphide, and no reaction with mercury(II) chloride. 

Despite its electrode potential (p. 98), very pure zinc has little or no reaction with dilute acids. If impurities are present, local electrochemical cells are set up (cf the rusting of iron. p. 398) and the zinc reacts readily evolving hydrogen. Amalgamation of zinc with mercury reduces the reactivity by giving uniformity to the surface. Very pure zinc reacts readily with dilute acids if previously coated with copper by adding copper(II) sulphate ... 

A 1500 ml. flask is fitted (preferably by means of a three-necked adaptor) with a rubber-sleeved or mercury-sealed stirrer (Fig. 20, p. 39), a reflux water-condenser, and a dropping-funnel cf. Fig. 23(c), p. 45, in which only a two-necked adaptor is shown or Fig. 23(G)). The dried zinc powder (20 g.) is placed in the flask, and a solution of 28 ml. of ethyl bromoacetate and 32 ml. of benzaldehyde in 40 ml. of dry benzene containing 5 ml. of dry ether is placed in the dropping-funnel. Approximately 10 ml. of this solution is run on to the zinc powder, and the mixture allowed to remain unstirred until (usually within a few minutes) a vigorous reaction occurs. (If no reaction occurs, warm the mixture on the water-bath until the reaction starts.) The stirrer is now started, and the rest of the solution allowed to run in drop-wise over a period of about 30 minutes so that the initial reaction is steadily maintained. The flask is then heated on a water-bath for 30 minutes with continuous stirring, and is then cooled in an ice-water bath. The well-stirred product is then hydrolysed by the addition of 120 ml. of 10% sulphuric acid. The mixture is transferred to a separating-funnel, the lower aqueous layer discarded, and the upper benzene layer then... 

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