ZINC COMPOUND

Zinc usually occurs as the sulfide but significant quantities of the oxide, carbonate, siUcate [14374-77-7] and basic compounds of the latter two are also mined (see ZiNC AND ZINC ALLOYS). 

Zinc forms salts with acids but since it is amphoteric, it also forms zincates, eg, [Zn(OH)2 H20] and Z.n([7) ). The tendency of zinc to form stable hydroxy complexes is also important because some basic zinc salts are only slightly soluble in water. Examples are 3Zn(OH)2 ZnSO [12027-98-4] and 4Zn(OH)2 ZnCl2 [11073-22-6] which may precipitate upon neutralization of acidic solutions of the salts. 

Properties of zinc salts of inorganic and organic salts are Hsted in Table 1 with other commercially important zinc chemicals. In the dithiocarbamates, 2-mercaptobenzothiazole, and formaldehyde sulfoxylate, zinc is covalendy bound to sulfur. In compounds such as the oxide, borate, and sihcate, the covalent bonds with oxygen are very stable. Zinc—carbon bonds occur in diorganozinc compounds, eg, diethjizinc [557-20-0]. Such compounds were much used in organic synthesis prior to the development of the more convenient Grignard route (see Grignard reactions). 

The water solubiUty of zinc compounds varies greatly, as shown in Table 1. Water-soluble compounds not Hsted are zinc formate [557-41-5] chlorate [10361-95-2] fluorosihcate [16871 -71 -9] and thiocyanate [557-42-6]. Also, the water-soluble amino and cyanide complexes have many uses. 

Zinc compounds are generally colorless unless the other component, eg, chromate, is colored. The lack of color of most zinc compounds in visible light is a great advantage in that they do not color paint films, plastics, mbber, cosmetics, etc. However, when excited by various types of radiation and at various temperatures, zinc oxide, sulfide, selenide [1315-09-9], and related compounds exhibit luminescence, ie, they emit colored light (see Luminescent materials). Zinc-based phosphors can be produced in many colors, depending upon the added dopants. They are used in television tubes, luminescent glasses, and various specialty products. 

Zinc forms salts with acids but since it is amphoteric, it also forms zincates, eg, [Zn(OH)2 and [Zn(OH)J . The tendency of zinc to form 

The coupling of aryl- and alkenylzinc reagents with various halides has widespread use in the cross-coupling of aromatic rings [101]. The reactions of zinc derivatives of aromatic and heteroaromatic compounds with aryl and heterocyclic halides have wide synthetic applications [103,104], 

The reaction of aryl and alkenyl halides with the Reformatsky reagent 237 in polar solvents affords a-arylacetates [105], Iodides of heterocyclic compounds such as pyridine, quinoline and pyrimidine react smoothly with Reformatsky reagents. The cross-coupling of 237 with 4-iodo-2,6-dimethyl- and 2-iodo-4,6-dimethylpyrimidine (236) occurs smoothly to form 238. But no reaction of 5-iodo-2,4-dimethylpyrimidine (239) takes place [106], 

Triflates are used in this reaction [107]. 5-Phenyltropone 241 is prepared by the coupling of triflate 240 with PhZnCl [108], Instead of rather expensive triflates, triflate equivalents such as phenyl mesylates [100], fluoroalkanesulfonates [109] and the fluorosulfonate 242 [110] are used for the coupling. 

As another alternative to triflates, aryl nonaflates (ONf) are easily prepared from phenol and commerically available perfluorobutane sulfonyl fluoride 243, and used for Pd-catalysed coupling with halides [111]. Aryl nonaflates are more reactive than aryl triflates. / -Iodophcnyl nonaflate (244) gives 245 by chemoselective reaction of the 

The coupling of alkenyl iodides or bromides with alkylzinc reagents is also catalyzed by Co complexes. Using Co(acac)3 as a catalyst precursor, the coupling product 260 is obtained in THF NMP in good yield at room temperature [114], 

Crystal Structure, Mechanical and Thermal Properties Tables 4.1-132 -4.1-139. 

Zinc selenide ZnSe n F43m fee Zinc blende Fig. 4.1-131 

Zinc selenide ZnSe 5.266 Shock wave experiment 

Under normal pressure, ZnS sublimes before melting 

At room temperature, ZnS bulk material consists predominantly of the cubic j ase, often with hexagonal inclusions, leading to polytypic material. Epitaxial ZnS has mostly been grown on GaAs and thus has pseudomorphically assumed the cubic structure of the substrate material. In this section, all data refer to the cubic modification unless explicitly stated otha-wise. 

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Zn — Zn in acid solution —0-76 volts) Apart from possible Zn and Zn2 in some melts all zinc compounds are in the +2 state, generally in octahedral or tetrahedral co-ordination. Readily forms complexes, particularly with O and N ligands. 

Sulfite concentrations for scavenging oxygen ate typically in the 100— 300 mg/L range. Zinc compounds for sulfide scavenging ate used at concentrations of 1.4—14 kg/m (0.5—5 lb/bbl) synthetic magnetite concentrations range to 140 kg/m (50 lb/bbl) and higher if the need arises. 

Whereas the worldwide production of 2inc oxide [1314-13-2] is estimated to be around 500,000 t aimuaHy, only about 75,000—100,000 t are used for pigmentary appHcations by the paint industry. About 250,000 t are consumed by the mbber industry, and the rest is used in the production of plastics, paper, cosmetics, pharmaceutical products, ceramics, and glass (see Zinc compounds). 

Antimicrobial agents are used where there is a need to inhibit bacterial and fungal growth. The additives can consist of copper, germanium, zinc and zinc compounds, metal oxides or sulfides, metal zeofltes, as well as silver and copper oxide-coated inorganic core particles (154—159) (see Industrial ANTIMICROBIAL AGENTS). 

Folate antagonists (eg, methotrexate and certain antiepileptics) are used ia treatment for various diseases, but their adininistration can lead to a functional folate deficiency. Folate utilization can be impaired by a depletion of ziac (see Zinc compounds). In humans, the intestinal bmsh border folate conjugase is a ziac metaHoenzyme (72). One study iadicates that the substantial consumption of alcohol, when combiaed with an iaadequate iatake of folate and methionine, may iacrease the risk of colon cancer (73). Based on this study, it is recommended to avoid excess alcohol consumption and iacrease folate iatake to lower the risk of colon cancer. 

Table 1. Properties, Prices, and Uses of Zinc Compounds...

Zinc compound Formula, synonym CAS Registry No. Sp gi Mp, °C Water Other Price, /kg (Aug. 1981) Uses... 

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