Double chlorides

The central carbon atom is derived from an aromatic aldehyde or a substance capable of generating an aldehyde during the course of the condensation. Malachite green is prepared by heating benzaldehyde under reflux with a slight excess of dimethyl aniline in aqueous acid (Fig. 2). The reaction mass is made alkaline and the excess dimethylaniline is removed by steam distillation. The resulting leuco base is oxidized with freshly prepared lead dioxide to the carbinol base, and the lead is removed by precipitation as the sulfate. Subsequent treatment of the carbinol base with acid produces the dye, which can be isolated as the chloride, the oxalate [2437-29-8] or the zinc chloride double salt [79118-82-4]. 

Hydrochloric acid digestion takes place at elevated temperatures and produces a solution of the mixed chlorides of cesium, aluminum, and other alkah metals separated from the sUiceous residue by filtration. The impure cesium chloride can be purified as cesium chloride double salts such as cesium antimony chloride [14590-08-0] 4CsCl SbCl, cesium iodine chloride [15605 2-2], CS2CI2I, or cesium hexachlorocerate [19153 4-7] Cs2[CeClg] (26). Such salts are recrystaUized and the purified double salts decomposed to cesium chloride by hydrolysis, or precipitated with hydrogen sulfide. Alternatively, solvent extraction of cesium chloride direct from the hydrochloric acid leach Hquor can be used. 

Most aminothiophenes are prepared by the reduction of nitrothio-phenes. Aminothiophenes or their derivatives have also been obtained through the Hofmann rearrangement of the acid amides, which, however, fails with 2-thenamide, in contrast to the 3-isomer. The Beckmann rearrangement of the oxime of 2-acetylthiophene has been applied successfully to the preparation of 2-acetamidothiophene. The free aminothiophenes are very unstable compounds and it has not been possible to distil 3-aminothiophene. They are best stored as the stannic-chloride double salts and give stable acetyl derivatives. 

Condensed thienopyridines have been prepared by reacting the stannic-chloride double salts of 2- and 3 -armnothiophene with methyl vinyl ketone in the presence of FeCU and Additional rings... 

Lead usually has excellent resistance to seawater owing to the formation of a passive film of basic carbonate and carbonate-chloride double salts , which should be compared with its behaviour in solutions of alkali chlorides (see salts p. 4 87). 

Triphenylselenonium chloride may be precipitated from aqueous solution as the zinc chloride double salt.1... 

Absolute ethanol (400 ml.) is vigorously stirred in a 1-1. widenecked Erlenmeyer flask immersed in an ice bath (Note 4). The tropylium hexachlorophosphate-tropylium chloride double salt4 is separated from the reaction mixture by suction filtration, washed briefly with fresh carbon tetrachloride, and transferred as rapidly as possible into the cold, well-stirred ethanol (Note 5). The salt dissolves rapidly and exothermally to give a reddish solution. Fifty milliliters (0.39 mole) of 50% aqueous fluoboric acid is added rapidly to the cold stirred solution (Note 6). The dense white precipitate of tropylium fluoborate that forms is separated by suction filtration, washed with a little cold ethanol and with ether, and air-dried at room temperature (Note 7) weight 34-38 g. (80-89%) decomposition point about 200° A j, HC1 218 mja (log e 4.70), 274 m/i (log e 3.61). The product is 98-100% pure (Notes 8 and 9). 

In this discussion, two mutually canceling simplifications have been made. For the transition value of the radius ratio the phenomenon of double repulsion causes the inter-atomic distances in fluorite type crystals to be increased somewhat, so that R is equal to /3Rx-5, where i has a value of about 1.05 (found experimentally in strontium chloride). Double repulsion is not operative in rutile type crystals, for which R = i M + Rx- From these equations the transition ratio is found to be (4.80/5.04)- /3i — 1 = 0.73, for t = 1.05 that is, it is increased 12%. But Ru and Rx in these equations are not the crystal radii, which we have used above, but are the univalent crystal radii multiplied by the constant of Equation 13 with z placed equal to /2, for M++X2. Hence the univalent crystal radius ratio should be used instead of the crystal radius ratio, which is about 17% smaller (for strontium chloride). Because of its simpler nature the treatment in the text has been presented it is to be emphasized that the complete agreement with the theoretical transition ratio found in Table XVII is possibly to some extent accidental, for perturbing influences might cause the transition to occur for values a few per cent, higher or lower. 

The basic dyes are usually marketed as chlorides, oxalates or zinc chloride double salts in the case of malachite green (6.162), the last-named derivative has the formula 3 [Dye]C1.2ZnCl2.2H20. Acid dyes of this type are often isolated as the sodium salt. 

To the solution of the dye so obtained (and filtered if necessary) a clear concentration solution of zinc chloride (12 g.) is added, and then the zinc chloride double salt of the dye is precipitated by addition of saturated brine. (Test with a spot on filter paper to see whether the solution is nearly colourless.) To purify the dye, which has been collected at the pump and washed with brine, it is redissolved in hot water and, after cooling, salted out as above. Yield 9-10 ... 

The quinaldine can also be separated from the crude mixture of bases by conversion into the zinc chloride double salt in the manner described in the case of quinoline. This furnishes a somewhat smaller yield of a purer preparation. 

Generalized Procedure for Preparation of Diazonium Zinc Chloride Double Salts [45a]... 

When the zinc chloride double salts of diazotized aminocarboxylic esters were subjected to this reaction, only poor to modest yields of the corresponding azo compounds were isolated [45c]. 

Grignard reagents and diazonium zinc chloride double salts have been used to prepare azo compounds. The reaction of arylzinc chloride with a diazonium salt has also been used. By this means, mixed aromatic-aliphatic azo compounds have been prepared. 

These may be prepared by reduction of appropriate nitro compounds. The free amines are unstable, but can be isolated as the tin(IV) chloride double salts, and give stable acetyl derivatives. 2-Acetamidothiophene has been prepared by a Beckmann rearrangement of the oxime of 2-acetylthiophene (63AHC(l)l). 2-Aminothiophene hydrochloride was isolated in 84% yield when cw-4-benzhydrylthiocrotononitrile was treated with hydrogen chloride gas in dry ether (equation 46) (69JHC147). 

Di-o-tolyl methyl tellurium chloride,2 (C7H7)2(CH3)TeCl, is obtained by boiling the corresponding iodide with silver chloride and water. It separates from water as four-sided plates containing two molecules of water of crystallisation, melting at 93° C. and again at 148° C. from chloroform it crystallises with half a molecule of chloroform, and melts at 155° to 156° C. The basic zinc chloride double salt melts with decomposition at 186° to 187° C. 

The formula of the zinc chloride double salt is SC Hg-NjCl, 2ZnCl2, H20. 

Macrae and Wright (96) demonstrated that visible light irradiation of xanthene dyes (eosin, erythrosin, rhodamine B, or RB) in ethanolic solutions of 4-(N,N-diethylamino)benzene-diazonium chloride (as the zinc chloride double salt) resulted in decomposition of the diazonium salt. Electron transfer from the dye excited state(s) to the diazonium salt was postulated and dye-diazonium salt ion pair formation in the ground state was shown to be important. Similar dyes and diazonium salts were claimed by Cerwonka (97) in a photopolymerization process in which vinyl monomers (vinylpyrrolidone, bis(acrylamide)) were crosslinked by visible light. Initiation occurs by the sequence of reactions in eqs. 40-42 ... 

Orthoformic ester has been prepared by the treatment of a mixture of chloroform and alcohol with sodium 1 by the action of dry sodium ethylate on chloroform 2 or on an ether solution of chloroform 3 by the action of alcoholic sodium hydroxide on chloroform 4 and by the action of alcoholic hydrochloric acid on ethyl formimido ester5 or its mercuric chloride double salt.6... 

The product is then transferred to a large flask and distilled with steam to remove unchanged dimethyl-aniline the leuco-base is filtered when cool and recrystallised from alcohol. Almost a quantitative yield is obtained. The zinc chloride double salt of the dye is prepared as follows Ten. gms. of the base is dissolved in dilute hydrochloric acid containing 2 7 gms. of HC1 the liquid is diluted with 800 c.c. of water and 10 gms. of 40 per cent, acetic acid added it is then cooled with ice, and a thin paste of 7 5 gms. of lead peroxide added gradually with shaking. After standing a few minutes, the lead is precipitated by adding 20 per cent, sodium sulphate, and to tho filtrate from lead sulphate is added 8 gms. of zinc chloride dissolved iu a little water. The dye is then salted out by addition of common salt. Yield, abont 7 gms. 

Monographs / Calcium Pantothenate, Calcium Chloride Double Salt / 73... 

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