Aluminium-mercury couple

If the reduction of nitrobenzene takes place in neutral solution with zinc dust and water in presence of a little calcium or ammonium chloride, or with aluminium-mercury couple and watei, /d-phenylhydio. ylamme is formed (see Prep. 52, p. 14S). 

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. 

The methods used to purify the solvents were as follows. The early batches of ethanol were subjected to a somewhat lengthy series of fractionations involving successive treatment with sulfuric acid, silver nitrate and potassium hydroxide, and aluminium-mercury couple. However, the following simple procedure was found to give equally good results. Three grams of potassium hydroxide pellets were rinsed with ethanol to remove surface impurities and added to 3 liters of boiling ethanol. The ethanol was then immediately fractionated and the middle 50% collected. The n-hexane and the isopentane were purified by ex-... 

Reaction VI. (c) Action of the Aluminium-Mercury Couple, or of certain finely divided Metals on a Mixture of an Aromatic Hydrocarbon and an Alkyl Halide. (J. C. S., 67,826.)—The action of the couple is analogous to that of anhydrous aluminium chloride. Zinc dust or finely divided copper can also be used. 

The reducing agents usually employed are phosphorus and hydriodic acid, or the zinc-copper or the aluminium-mercury couple. The couples have the advantage of readily yielding a pure gas, and are of wide application. 

In the case of aromatic bodies the temperature has an important influence on the part of the molecules the chlorine or bromine will attack in the cold in the presence of carriers, the halogen enters the nucleus, while at the boiling point the side chain is attacked. The carriers most frequently used are iron, aluminium-mercury couple, iodine, halides of phosphorus, antimony, iron, aluminium, sulphur or pyridine. The halogen is always more active in sunlight, or in ultra-violet light. 

The fact that small quantities of tho aluminium-mercury couple can bring about similar condensations, indicates that the chloride acts as a catalyst the formation of diplienyl-methane from benzyl chloride and benzene is an example of this.12... 

Mercuri-biS"3-aminobenzoic acid.—m-Nitrobenzoic acid and mercuric oxide are heated at 200° C. until the reaction is complete. The result is the mercurated nitro compound, and this is reduced in neutral solution with aluminium-mercury couple at 40° to 50° C. to the amine. It has similar properties to the para compound. 

NOTE.—In the preparation of certain compounds by condensation sis the result of the elimination of chlorine and hydrogen, an aluminium-mercury couple gives better results than aluminium chloride. It is probable that a little aluminium chloride is first formed by the action of the metal on the organic halogen compound the presence of mercury makes the aluminium more active. 

An excess of mercuric chloride must be used to prevent the mercury liberated amalgamating with the aluminium, for the couple so formed would act concurrently with, but in a different manner to, the double compound (see the next reaction). 

Figure 6 Apparatus for determination of vapour pressure by dynamic method, A, Monel boiler provided with central thermometer pocket B, aluminium tube-oven C, coupling linking metal connecting tube to glass D, mercury-filled manometer connected to oil-filled line leading to piston gauge E, glass valve with PTFE stem Fisher and Porter Company, U.S.A.) F, reservoir for introduction of the sample G,H, electrical heater windings K,L, control resistor windings, insulated by suitable wrappings from G and H M, platinum resistance thermometer N, connection to vacuum system...

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