Preparation of Zinc Amalgam

Preparation of Zinc Amalgam. (Perform the experiment on a tray with high sides ) Put two or three small pieces of pure granulated zinc into a 25-ml porcelain bowl and add 3-4 ml of a 2% mercu-ry(II) nitrate solution acidified with 0.3 ml of concentrated nitric acid. Stir the mixture during 10 minutes, then pour o0 the solution and wash the zinc with water by decantation until the liquid becomes absolutely transparent. Store the zinc amalgam in a jar under water. 

See how zinc amalgam reacts with hydrochloric acid. Touch the zinc amalgam in the acid with a copper wire. What do you observe What is zinc amalgam used for  

Preparation of a Low-Melting Alloy. Put 0.5 g of cadmium, 0.05 g of tin, 1 g of lead, and 2 g of bismuth into a dry test tube. Heat the metal mixture until it melts and cool it. When the alloy solidifies, pour hot water into the test tube. What is observed At what temperature does the prepared alloy melt Note the melting point of the individual metals which the alloy is composed of. Explain the observed phenomenon. 

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Preparation of Zinc Amalgam (260). 2. Preparation of a Low-Melting Alloy (260). 3. Preparation of Zinc Chloride (260). 4. Preparation of Zinc Oxychloride (261). 5. Preparation of Zinc Choride Crystallohydrate (261). 6. Use of Zinc Chloride in Soldering (262). 

Ruthenium(II) [Ru(NH3)50H2] can be most efficiently prepared by zinc amalgam reduction of [RuCl(NH3)5]Cl2 in aqueous solution. More recently, an alternative route avoiding Zn + and Cl" ion has been developed based on the aquation of electrochemically reduced [Ru(03SCF3)(NH3)5] " . Alternative routes include the photolysis and acid-catalysed hydrolysis of [Ru(NH3)g] and the reduction of [Ru(NH3)5(OH2)]. The lability of the aqua ligand in these systems makes [Ru(NH3)jOH2] an excellent starting material for the synthesis of substituted pentaammine complexes, and for the study of their kinetics of formation. 

To 5 ml of solution in a test-tube containing from 0 02 to 0 10 mg of strychnine and 10 per cent w/w of hydrochloric acid, add 0-2 g of zinc amalgam (in 20 mesh and containing 40 per cent of mercury, recently treated by momentary immersion in a 5 per cent aqueous solution of mercuric chloride followed by a brief wash with water). Immerse the tube in a water-bath for seven minutes, cool under the tap and add 0 05 ml of a freshly prepared, approximately 0 1 per cent, aqueous solution of sodium nitrite. Transfer a portion of the red liquid to a 0 5-cm cell and determine the maximum extinction at about 525 rcifji. Prepare a calibration graph under identical conditions. 

Usually prepared by the action of NaCN on benzaldehyde in dilute alcohol. It is oxidized by nitric acid to benzil, and reduced by sodium amalgam to hydrobenzoin PhCHOHCHOHPh by tin amalgam and hydrochloric acid to des-oxybenzoin, PhCH2COPh and by zinc amalgam to stilbene PhCH = CHPh. It gives an oxime, phenylhydrazone and ethanoyl derivative. The a-oxime is used under the name cupron for the estimation of copper and molybdenum. 

Y-Phenylbutyric acid. Prepare amalgamated zinc from 120 g. of zinc wool contained in a 1-litre rovmd-bottomed flask (Section 111,50, IS), decant the liquid as completely as possible, and add in the following order 75 ml. of water, 180 ml. of concentrated hydrochloric acid, 100 ml. of pure toluene (1) and 50 g. of p benzoylpropionic acid. Fit the flask with a reflux condenser connected to a gas absorption device (Fig. II, 8, l,c), and boil the reaction mixture vigorously for 30 hours add three or four 50 ml. portions of concentrated hydrochloric acid at approximately six hour intervals during the refluxing period in order to maintain the concentration of the acid. Allow to cool to room temperature and separate the two layers. Dilute the aqueous portion with about 200 ml. of water and extract with three 75 ml. portions of ether. Combine the toluene layer with the ether extracts, wash with water, and dry over anhydrous magnesium or calcium sulphate. Remove the solvents by distillation under diminished pressure on a water bath (compare Fig. II, 37, 1), transfer the residue to a Claisen flask, and distil imder reduced pressure (Fig. II, 19, 1). Collect the y-phenylbutyric acid at 178-181°/19 mm. this solidifies on coohng to a colourless sohd (40 g.) and melts at 47-48°. 

Fleischer1 prepared benzylaniline by heating aniline with benzyl chloride at i6o°. This reaction may be very violent and always leads to mixtures. Bernthsen and Trompetter 2 reduced thiobenzanilide with zinc and hydrochloric acid or sodium amalgam, while O. Fischer 3 reduced bcnzalaniline with sodium and alcohol, to benzylaniline. Knoevenagel4 obtained a 32 per cent yield of benzylaniline from benzyl alcohol and aniline in the presence of iodine. Ullmann5 describes the preparation of benzylaniline from benzyl chloride and excess of aniline at low temperatures. 

Silver was formerly extracted by cyanide solution of Ag2S, the resulting Ag(CN)2 being treated with zinc to afford the metal roasted ores could also be extracted with mercury to give silver amalgam. Presently much silver is extracted by workup of the anode slime from the preparation of non-ferrous metals (Pb, Cu) pure silver is obtained by electrolysis of AgN03. 

Aliphatic hydrocarbons can be prepared by the reduction of the readily accessible ketones with amalgamated zinc and concentrated hydrochloric acid (Clemmensen method of reduction). This procedure is particularly valuable for the preparation of hydrocarbons with an odd number of carbon atoms where the Wurtz reaction cannot be applied with the higher hydrocarbons some secondary alcohol is produced, which must be removed by repeated distillation from sodium. 

An aluminium-mercury couple acts in the same way as zinc dust. This aluminium amalgam, prepared by the action of mercuric chloride on aluminium (preferably granulated), is also suitable for reducing substances dissolved in ether or alcohol the water which is required is slowly added drop by drop. (The method is that of H. Wislicenus.) The extent of the reduction varies according to the nitro-compound concerned, but corresponds approximately to the effect of zinc dust in a neutral medium. Consequently reduction usually does not proceed beyond the hydroxylamine stage. 

Preparation of the Zinc Amalgam. —Granulated zinc in thin pieces or, still better, zinc foil 0-15 to 0-25 mm. thick and cut into small strips, is left for one hour with frequent shaking in contact with an equal weight of 5 per cent aqueous mercuric chloride solution. The solution is then poured off and the metal washed once with fresh water. 

Another Zinc Reduction. Prepare or activate the zinc as follows 400 g of mossy zinc is treated with 800 ml of 5% aqueous solution of mercuric chloride for 1 hour. Decant the solution off and use the zinc right away. Add. 834 mole of compound to be reduced to the zinc amalgam, followed by as much HCl acid (.834 mole) diluted in as much water as is required to cover all the zinc. Reflux for 6 hours while adding small portions of dilute HCL acid. Cool, separate the upper, wash free of acid (a few portions of dilute sodium hydroxide), dry and distill to get about a 79% yield of product. 

ReCl3(PPh3)(benzil)] reacts with bipy and related ligands or terpy to form a number of rhe-nium(III) and rhenium(II) compounds which are useful precursors for the synthesis of lower-valent rhenium complexes. " Thus, reduction of [Re(bipy)3][PF6]2 with zinc amalgam results in the rhenium(I) compound [Re(bipy)3][PF6] in excellent yields. The corresponding terpyridyl bis-chelate [Re(terpy)2][PF6] has been prepared in a similar manner. " The electrochemistry of the products provides a convenient measure of the chemical reactivity associated with the redox processes. Thus, the one-electron oxidation of [Re(bipy)3]" is reversible at -0.33 V, whereas the Re"/Re" redox couple is irreversible and occurs at relatively low potentials (-1-0.61 V) which is consistent with the instability of [Re(bipy)3] + in solution. However, in the presence of a small coordinating molecule such as CNBu, oxidation to the rhenium(III) state is readily available by the formation of seven-coordinate complexes of the composition [Re(bipy)3(L)]. " ... 

Reduction of oximino esters, i.e. oximes of keto esters, is very useful for the preparation of amino esters. Reductions are very selective since the oximes are easily reduced by catalytic hydrogenation over 10% palladium on carbon in ethanol (yield 78-82%) I094, by aluminum amalgam in ether (yields 52-87%) [750, 70P5], or by zinc dust in acetic acid (yield 77-78%). None of these reagents attacks the ester group. The last mentioned reaction gives an N-acetyl derivative [1096. ... 

Finally, in the recent patent literature, some further processes for the preparation of phosphine were described for example, the treatment of white phosphorus with steam in the presence of phosphoric acid at 275-285 °C. According to a British patent, phosphine is formed when white phosphorus, in aqueous acid, is brought into contact with mercury or zinc amalgam A Japanese patent recommends the treatment of a mixture of white phosphorus and granulated zinc with acids and a small amount of methanol for the preparation of highly pure phosphine. Other patents describe electrolytic processes. Finally, it is mentioned that phosphine is formed by the electrolysis of phosporous and hypophosphorous acid, especially at mercury or lead cathodes. ... 

The compound [(i7s-CsHs)Cr(NO)2] 2 was first prepared in low yields (<5%) by the reduction of (i75-CsHs)Cr(NO)2Cl with sodium tetrahydroborate in a two-phase water-benzene system.6 Recently, this complex was isolated in 75% yield from the zinc amalgam reduction of (i7s-C5Hs)Cr(NO)2Cl in tetrahydrofuran over a period of 21 hours.2 However, [07s-CsH5)Cr(NO)2]2 is synthesized most conveniently by the reduction of the above-mentioned chloro complex with sodium amalgam in benzene as outlined below. 

In 1984, Fried et al. reported the reaction of bromodifluoroacetate with carbonyl substrates in the presence of zinc. The a,a-difluoro /1-hydroxyester was obtained in good yield without isolation of the Reformatsky reagent [240, 241] (Scheme 80) Later, this zinc reagent has also been prepared via reaction of ethyl bromodifluoroacetate with zinc amalgam in triglyme [242] or reaction of methyl iododifluoroacetate with zinc in acetonitrile [243]. 

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