Preparation of Zinc Chloride

Preparation of Zinc Chloride. Assemble an apparatus (see Fig. 61), replacing the funnel with a U-tube containing calcium chloride. Weigh 1-2 g of pure granulated zinc in a porcelain boat and place the latter into a refractory tube. Cover the outlet end of the tube 

See what happens to the salt in the air. Transfer a small amount of the product into a porcelain bowl with water. What do you observe Write the equations of the reactions. 

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Preparation of Zinc Chloride Crystallohydrate. Put 5 g of granulated zinc into a 50-mI flask, pour in 12 ml of water, and add 13 ml of concentrated hydrochloric acid in small portions. When the reaction slows down, place the flask on a warm water bath and bring the reaction up to its end. Let the flask with its contents stand up to your next lesson. Filter the solution, and test it for the presence of iron(II) ions. If the reaction is positive, saturate the solution with chlorine. For what purpose Tightly close the flask containing the reaction mixture with a stopper and again let it stand up to your next lesson. Heat the flask in a water bath and introduce moist zinc oxide in small portions up to the complete separation of iron hydroxide. How can you determine that the ions of iron have precipitated completely ... 

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). 

Carry out this preparation precisely as described for the a-compound, but instead of zinc chloride add 2 5 g. of anhydrous powdered sodium acetate (preparation, p. 116) to the acetic anhydride. When this mixture has been heated on the water-bath for 5 minutes, and the greater part of the acetate has dissolved, add the 5 g. of powdered glucose. After heating for I hour, pour into cold water as before. The viscous oil crystallises more readily than that obtained in the preparation of the a-compound. Filter the solid material at the pump, breaking up any lumps as before, wash thoroughly with water and drain. (Yield of crude product, io o-io 5 g.). Recrystallise from rectified spirit until the pure -pentacetylglucose is obtained as colourless crystals, m.p- 130-131° again two recrystallisations are usually sufficient for this purpose. 

The only important precaution in this preparation is to ensure an excess of zinc chloride over sodium cyanide. If the latter is in excess, the zinc cyanide generally precipitates as a sticky mass, which is difficult to filter and unsatisfactory for the preparation of hydroxy-aldehydes. 

The isobomeol so formed melts at 212°, but the determination must be carried out in a sealed tube, as the melting-point is very dose to the temperature of sublimation. It is, however, very rarely that the isobomeol so prepared is free from impurities, and the melting-point will often be found to be as low as 203° to 205°. It is therefore necessary to pare derivatives of the isobomeol in order to identify it with certainty. Kie compound with bromal melts at 71° to 72°. Other compounds will be found mentioned under isobomeol . By dehydration by means of zinc chloride, isobomeol is easily converted into camphene, melting at about 49° to 50°. 

The synthesis of vinylaziridines through reactions between allylic carbenoid reagents and imines (i.e., Darzen-type reactions) was first reported by Mauze in 1980 [13]. Treatment of aldimines or ketimines 16 with gem-chloro(methyl)allyllithium (17) afforded N-substituted vinylaziridines 18 (Scheme 2.6). Similarly, 2,3-trans-N-diphenylphosphinyl-2-vinylaziridines 21 were prepared with good stereoselectivities (trans cis= 10 1 Scheme 2.7) by treatment of a-bromoallyllithium (20) with N-diphenylphosphinyl aldimines 19 in the presence of zinc chloride [14]. 

In ( )-[2-(l-propenyl)-l, 3-dithian-2-yl]lithium, no problem of EjZ selectivity arises. It is easily prepared by deprotonation of the allylic dithiane87,88 with butyllithium in THF, whereas deprotonation of the 2-propylidene-l, 3-dithiane requires the assistance of HMPA. The addition to saturated aldehydes proceeds with excellent y-regioseleetivity and anti selectivity88,89. As often observed in similar cases, aldehydes which bear an, p2-carbon atom adjacent to the carbonyl group give lower selectivities. The stereoselectivity decreases with ketones (2-bu-tanone y/a 84 16, antiisyn 77 23)88. The reaction with ethyl 2-oxopropanoate is merely nonstereoselective90, but addition of zinc chloride improved the syn/anti ratio to 96 4, leading to an efficient synthesis of ( )-crobarbatic acid. 

Instead, the reaction of TMS cyanide with the chiral imine prepared from racemic 2-benzoylaminocyclohexanone and (fi)-l-phenylethylamine or (S)-l-phenylethylamine in the presence of zinc chloride occurred with low stereocontrol, and the two enantiomers of fra s-l,2-diaminocyclohexane car-boxyhc acid were isolated with low yields after several steps [88]. 

A facile exothermic reaction, catalysed by traces of zinc chloride and iron(III) chloride (4 and 40 ppm, respectively) to produce isopropyl propionate and 2-chloropropane (b.p., 35°C) led to pressure build up and bursting of a closed galvanised drum after 24 h. Similar reactions are thermodynamically possible with other acid chlorides and ethers (particularly if secondary or tertiary alkyl ethers), so such mixtures should only be prepared immediately prior to use. 

The parent hexathiaadamantane (185) is obtained preparatively when a solution of formic acid and hydrochloric acid in nitrobenzene is allowed to stand for several weeks in a hydrogen sulfide atmosphere the product which separated is almost insoluble in all common solvents and purification presents a problem. Only large volumes of dimethyl sulfoxide at reflux serve for recrystallization.224 The reaction of thioacetic acid with formic acid in the presence of zinc chloride gives tetramethyl-(186), monomethyl-, dimethyl-and trimethylhexathiaadamantane derivatives (187).225 Other variations include the reaction of thioacetic acid with a /i-diketone,226 and the use of boron trifluoride227 or aluminum chloride as a catalyst.228... 

As the range of components available for use in the azoic dyeing process expanded, research was simultaneously targeted on improvements designed to make the process more attractive to the commercial dyer. The necessity for the dyer to diazotise the Fast Base was removed with the introduction of stabilised diazonium salts [111], known as Fast Salts. Stabilisation was achieved by a judicious selection of the counter-ion to the diazonium cation various anions have found use in commercial Fast Salts and some examples are listed in Table 4-4. Particularly effective is the diazonium tetrachlorozincate, which can be readily prepared by adding an excess of zinc chloride solution to a solution of the diazonium salt. The precipitated complex diazonium salt is usually admixed with an inert diluent, which enhances its stability, and in use the dyer only needs to dissolve the powder in water to prepare the necessary diazonium salt solution. 

How many grams of zinc chloride should be used in preparing 5 L of the mouth wash containing 1/10% w/v of zinc chloride ... 

Dimethyl-p-phenylenediamine (7-6 g.) is dissolved in 70 c.c. of iV-hydrochloric acid, and 35 g. of zinc chloride in 50 c.c. of water are added. With good stirring 12 g. of aluminium sulphate in 20 c.c. of water and then 15 g. of sodium thiosulphate in 20 c.c. of water are poured in. To the solution thus obtained one-third of a solution of 16 g. of sodium dichromate in 30 c.c. of water is at once added and the temperature of the solution is raised as rapidly as possible to 40°. The addition of 6 g. of dimethylaniline dissolved in 8 c.c. of concentrated hydrochloric acid follows, and finally the remainder of the oxidising agent is poured in. Of course, all these solutions are prepared before the experiment is begun. 

Isopropylidene )V-(ethoxycarbonyl-2-pyridyl)aminomethylenemalo-nates (446) were prepared in 66-88% yields in the reactions of Meldrum s acid (421), ethyl 2-aminopyridinecarboxylates, and ethyl orthoformate in the presence of zinc chloride catalyst at 100-120°C for 15 min (78MI5). 

Fumaryl chloride has been prepared from fumaric acid and phthaloyl chloride,3 from maleic acid by the action of thionyl chloride in the presence of zinc chloride, and from maleic anhydride by the use of phthaloyl chloride in the presence of zinc chloride.4... 

An outstandingly reactive diene is l-methoxy-3-(trimethylsilyloxy)-l,3-butadiene ( Danishefsky s diene ) 4, prepared by the action of trimethylsilyl chloride on the ketone 3 in the presence of zinc chloride/triethylamine (equation 7)6. The reaction of diethyl mesoxalate with Danishefsky s diene gives the dihydropyran 5 with the (trimethylsily-loxy)dienes 6 and 7, mixtures of dihydropyrans are obtained, in which the meta-isomers predominate (equations 8 and 9)7. 

A number of secondary high explosives containing both nitramine and nitrate ester functionality have been reported. Aliphatic examples include A-nitrodiethanolamine dinitrate (DINA) (110), prepared from the nitration of diethanolamine with nitric acid-acetic anhydride in the presence of zinc chloride,and A,A -dinitro-A,A -bis(2-hydroxyethyl)oxamide dinitrate (NENO) (111), prepared from the mixed acid nitration of A,lV -bis(2-hydroxyethyl) oxamide . 

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