Zinc compounds preparation

With anhydrides, aluminum chloride reacts to form the acid chloride complex. Zinc chloride is more commonly used with acid anhydrides, although this is restricted practically to acetic and other simple anhydrides that can be used as the reaction solvent. This nevertheless remains a useful reagent for acylations, giving predominantly nonconjugated products. Active zinc compounds prepared from a zinc-copper couple and alkyl halides also promote the acylation of alkenes by acyl chlorides at room temperature. ... 

The zinc alkyls, of which this is an example, are vile-smelling inflammable liquids. They were the first organo-metallic compounds prepared by Frankland in 1849. With water, they decompose giving an alkane ... 

Ligand exchange reactions can be used to prepare perfluoroalkylzinc compounds Solvated trifluoromethylzinc compounds can be synthesized via the reaction of dialkylzincs with bis(trifluoromethyl)mercury [36] (equation 27) A similar exchange process with bis(trif]uorometliyl)cadinium and diraethylzinc gives a mixture of tnfluoromethylcadmium and zinc compounds [77]... 

Zinc phthalocyanine (PcZn) is prepared from phthalonitrile in solvents with a boiling point higher than 200 C, e.g. quinoline277,278 or 1-bromonaphthalene,137 or without solvent in a melt of phthalonitrile.83,116 The zinc compound normally used is zinc(ll) acetate or zinc powder. The reaction of zinc(II) acetate with phthalic acid anhydride, urea and ammonium mo-lybdate(VI) is also successful.262 The metal insertion into a metal-free phthalocyanine is carried out in an alcohol (e.g.. butan-l-ol).127,141,290 This reaction can be catalyzed by an alkali metal alkoxide.112,129... 

The ligand 2,5-bis(2-pyridyl)pyrazine was used in the synthesis of a range of zinc compounds to contrast with copper coordination polymers prepared with this ligand.169 Three zinc compounds were structurally characterized, [ZnCl2L(DMF)], [Zn3(OAc)6L2], and [Zn3Cl6L3] respectively a distorted square planar monomer, a linear trimer, and a triangular arrangement of zinc centers. 

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. 

Zinc hydroxide is used in the preparation of other zinc compounds. Another apphcation is as an absorbent in surgical dressings. 

Zinc oxide occurs in nature as mineral zincite. It is the most important zinc compound and has numerous industrial applications. Zinc oxide is the pigment in white paints. It is used to make enamels, white printing inks, white glue, opaque glasses, rubber products and floor tiles. It is used in cosmetics, soaps, pharmaceuticals, dental cements, storage batteries, electrical equipment, and piezoelectric devices. Other applications are as a flame retardant, as a UV absorber in plastics, and a reagent in analytical chemistry. A major application of zinc oxide is in the preparation of most zinc salts. In medicine, the compound is used as an antiseptic, an astringent and a topical protectant. 

Pyrrolo[2,3-. ]pyridine zinc(ll) and A -(2-pyridyl)pyrrolo[2,3- ]pyridine zinc(ll) compounds have been prepared and characterized by X-ray crystallography <2000IC5248>. The pyrrolo[2,3- ]pyridine zinc compound, formed from pyrrolo[2,3-. ]pyridine and zinc acetate, is a stable compound that can produce a blue light in electroluminescent devices. 

In addition to their use as precursors for alkynylboron, tin or zinc compounds, alkynylmagnesium reagents show a moderate reactivity toward the coupling with haloarenes and haloalkenes. They are often commercially available, or easy to prepare. Their main drawback is their low chemoselectivity and high nucleophilicity, which implies incompatibilities with functional groups such as nitro and carbonyl. 

Pr porstma.-—1. There is only one process of general applies tion for preparing these hydrides it consists in bringing water into contact with the zinc compounds of the respective radicals —... 

More recently, Lange and Naumann have described a new exchange method for the preparation of bis(perfluoroorgano)zinc compounds, which involves the reaction of iodopentafluorobenzene with a dialkylzinc in the presence of a Lewis acid (equation 74)70. 

Methylene difluorocyclopropanes are relatively rare and their rearrangement chemistry has been reviewed recently [14]. In addition, electron deficient alkenes such as sesquiterpenoid methylene lactones may be competent substrates. Two crystal structures of compounds prepared in this way were reported recently [15,16]. Other relatively recent methods use dibromodifluoromethane, a relatively inexpensive and liquid precursor. Dolbier and co-workers described a simple zinc-mediated protocol [17], while Balcerzak and Jonczyk described a useful reproducible phase transfer catalysed procedure (Eq. 6) using bromo-form and dibromodifluoromethane [18]. The only problem here appears to be in separating cyclopropane products from alkene starting material (the authors recommend titration with bromine which is not particularly amenable for small scale use). Schlosser and co-workers have also described a mild ylide-based approach using dibromodifluoromethane [19] which reacts particularly well with highly nucleophilic alkenes such as enol ethers [20], and remarkably, with alkynes [21] to afford labile difluorocyclopropenes (Eq. 7). 

Aluminium and magnesium selenides are very similar light brown powders, unstable in air. Zinc and iron (ferrous) selenides are more stable in air, the zinc compound being citron-yellow and the iron compound black and metallic in appearance.8 The latter becomes brown in air owing to oxidation. Ferric selenide is difficult to obtain pure. Cadmium selenide, which is dark brown, is very stable in colour and is used as a pigment. With thallium, selenium is said to form three distinct compounds,9 but analyses of these compounds have led to discordant results. The selenides of aluminium, chromium and uranium cannot be prepared in the wet way. Nickel selenide, unlike the sulphide, shows no tendency to form a colloidal solution. 

Zinc compounds have long been used in medical and veterinary applications and zinc preparations of a number of drugs1226 are widely used. In this section we focus on insulin1227 and on the toxicology of cadmium. An interesting short review on the general medical and biological aspects of zinc chemistry is available.1228 Nutritional aspects have also been surveyed.1244,1245... 

Support-bound transition metal complexes have mainly been prepared as insoluble catalysts. Table 4.1 lists representative examples of such polymer-bound complexes. Polystyrene-bound molybdenum carbonyl complexes have been prepared for the study of ligand substitution reactions and oxidative eliminations [51], Moreover, well-defined molybdenum, rhodium, and iridium phosphine complexes have been prepared on copolymers of PEG and silica [52]. Several reviews have covered the preparation and application of support-bound reagents, including transition metal complexes [53-59]. Examples of the preparation and uses of organomercury and organo-zinc compounds are discussed in Section 4.1. 

Biaryls have also been prepared by coupling support-bound aryl halides with aryl-zinc compounds (Figure 5.20) or with aryl(fluoro)silanes [203]. As with Suzuki or Stille couplings, these reactions also require transition metal catalysis. An additional strategy for coupling arenes on solid phase is the oxidative dimerization of phenols (Figure 5.20). 

Pure solutions of zinc sulfate can only be used for the preparation of lithopone having a low (up to 30%) percentage of zinc sulfide. Additional zinc compound must be added for the preparation of lithopone having a higher concentration of ZnS. Most often that compound is zinc chloride. One can either use a mixture of sulfuric and hydrochloric acid for the dissolution of zinc-containing raw materials, or direcdy mix separately prepared solutions of zinc sulfate and zinc chloride. The precipitation of 60% of the lithopone can be approximated by the following reaction ... 

For the preparation of basic zinc acetate, Zn40 (CjH Oz) , see reference 3. The zinc compound is more readily hydrolyzed than the beryllium analogue. 

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