Effective zinc compounds

IR and Raman spectroscopy have been commonly used and, for example, the effects of pressure on the Raman spectrum of a zinc compound with a N2C12 coordination sphere around the metal, have been investigated.28 IR spectroscopy has been utilized in studies of the hydration of zinc in aqueous solution and in the hydrated perchlorate salt.29 Gas phase chemistry of zinc complexes has been studied with some gas phase electron diffraction structures including amide and dithiocarbamate compounds.30-32... 

In a review of the course and mechanism of the catalytic decomposition of ammonium perchlorate, the considerable effects of metal oxides in reducing the explosion temperature of the salt are described [1], Solymosi s previous work had shown reductions from 440° to about 270° by dichromium trioxide, to 260° by 10 mol% of cadmium oxide and to 200°C by 0.2% of zinc oxide. The effect of various concentrations of copper chromite , copper oxide, iron oxide and potassium permanganate on the catalysed combustion of the propellant salt was studied [2], Similar studies on the effects of compounds of 11 metals and potassium dichromate in particular, have been reported [3], Presence of calcium carbonate or calcium oxide has a stabilising effect on the salt, either alone or in admixture with polystyrene [4],... 

In the final step of protection, the largest diffusion resistance has been found for the paint modified with zinc phosphate. It reflects the highest difficulties In the mass transport throughout this coating. Also observed Is a positive effect of zinc phosphate on the foirmatlon of sealing and Inhibiting zinc compounds... 

Ethylhexanol is usually produced by subsequent aldolization of butyraldehyde produced in the oxo reaction followed by hydrogenation of the intermediate unsaturated aldehyde.89 In Esso s Aldox process, however, in situ aldol condensation is effected by suitable promoters.11 Magnesium ethoxide and soluble zinc compounds are recommended to promote controlled aldolization during the oxo reaction. The Shell variant uses potassium hydroxide. Serious disadvantages (mixed aldolization with the branched aldehyde, problems associated with recycling of the additives), however, prevented wider use of the Aldox process. 

In the autoxidation of N-butylacetamide all the salicylaldimine chelates showed only inhibitory effects. We also found that two salicylaldimine chelates showed no significant catalytic properties and exhibited only inhibitory effects even in hydrocarbon autoxidation—viz., bis (N-butylsalicylaldimino) zinc and bis (N-butylsalicylaldimino) oxyvanadium-(IV). While there are some well known antioxidants containing zinc (e.g., zinc dialkythiophosphates or zinc dithiocarbamates), this is not a general property for zinc compounds. Zinc acetylacetonate, for example, had no inhibitory effect in the autoxidation of hydrocarbons or amides. 

Phosphate buffer (0.6 M) slightly inhibited lipolysis, but the same concentration of borate and barbiturate buffers was without effect. Zinc chloride, potassium cyanide, manganese sulfate, cysteine, and magnesium chloride retarded milk lapse activity to various degrees. All of these compounds were tested at pH 8.5 with tributyrin as substrate during a 30-min incubation period (Peterson et al 1948). 

Insulin probably exists in the pancreas as a zinc compound, but administration of insulin, per se, is effective in controlling diabetes. The main reason for using a zinc-containing preparation such as neutral protamine zinc insulin is that it is stable, dissolves more slowly and lasts longer than insulin, itself, when given by hypodermic injection. 

The filled 3d subshell is of little direct importance in zinc chemistry, in the sense that it remains intact in all zinc compounds and the 3d orbitals are not thought to take much part in bonding. It does, however, have a profound effect on the 4s electrons, which are rather poorly shielded from the nucleus by the 3d electrons. 

A number of zinc compounds with organic constituents (e.g., zinc salts of organic acids) have therapeutic uses. These include antidandruff zinc pyridinethione, antifungal zinc undecylenate used to treat athlete s foot, zinc stearate and palmitate (zinc soap), and antibacterial zinc bacitracin. Zinc naphthenate is used as a low-toxicity wood preservative, and zinc phenolsulfonate has insecticidal properties and was once used as an intestinal antiseptic. The inhalation of zinc soaps by infants has been known to cause acute fatal pneumonitis characterized by lung lesions similar to, but more serious than, those caused by talc. Zinc pyridine thione (zinc 2-pyridinethiol-l-oxide) has been shown to cause retinal detachment and blindness in dogs this is an apparently species-specific effect because laboratory tests at the same and even much higher dosages in monkeys and rodents do not show the same effect. 

The first examples of microwave-assisted cross-couplings with organo-zinc compounds were reported in 2001, as shown in Scheme 70. Aryl- as well as alkylzinc bromides were effectively coupled with short reaction times [155]. 

Some non-enzymatic antioxidants play a key role in these defense mechanisms. These are often vitamins (A, C, E, K), minerals (zinc, selenium), caretenoids, organosulfur compounds, allyl sulfide, indoles, antioxidant cofactors (coenzyme Qio)> and polyphenols (flavonoids and phenolic acids) [1,37]. Further, there is good evidence that bilirubin and uric acid can act as antioxidants to help neutralize certain free radicals [38]. Alpha-carotene, lycopene, lutein, and zeaxanthine [39] can be considered subgroups of carotenoids [40] that are effective antioxidant compounds. 

Many studies on the direct reaction of methyl chloride with silicon-copper contact mass and other metal promoters added to the silicon-copper contact mass have focused on the reaction mechanisms.7,8 The reaction rate and the selectivity for dimethyldichlorosilane in this direct synthesis are influenced by metal additives, known as promoters, in low concentration. Aluminum, antimony, arsenic, bismuth, mercury, phosphorus, phosphine compounds34 and their metal complexes,35,36 Zinc,37 39 tin38-40 etc. are known to have beneficial effects as promoters for dimethyldichlorosilane formation.7,8 Promoters are not themselves good catalysts for the direct reaction at temperatures < 350 °C,6,8 but require the presence of copper to be effective. When zinc metal or zinc compounds (0.03-0.75 wt%) were added to silicon-copper contact mass, the reaction rate was potentiated and the selectivity of dimethyldichlorosilane was enhanced further.34 These materials are described as structural promoters because they alter the surface enrichment of silicon, increase the electron density of the surface of the catalyst modify the crystal structure of the copper-silicon solid phase, and affect the absorption of methyl chloride on the catalyst surface and the activation energy for the formation of dimethyldichlorosilane.38,39 Cadmium is also a structural promoter for this reaction, but cadmium presents serious toxicity problems in industrial use on a large scale.41,42 Other metals such as arsenic, mercury, etc. are also restricted because of such toxicity problems. In the direct reaction of methyl chloride, tin in... 

Toxicity and health effects Exposure to high concentrations of fumes of zinc compounds such as zinc chloride and zinc oxide causes poisoning among industrial workers. The symptoms include but are not limited to headache, blurred vision, low back pain, vomiting, fever, chills, muscle ache, dry throat, cough, weakness, exhaustion, metallic taste in the mouth, chest tightness, respiratory distress, and decreased pulmonary function. The clinical... 

When the zinc atom is coordinatively unsaturated or when the oxygen atoms bound to zinc have a low electron density rising from mesomeric or inductive effects, the compounds can easily form complexes with coordinative reagents hke pyridine and TMEDA. 

Questionable carcinogen with experimental carcinogenic and tumorigenic data. An experimental teratogen. Other experimental reproductive effects. Human mutation data reported. See also ZINC COMPOUNDS and CARBAMATES. Severe irritant to eyes, nose, and throat. When heated to decomposition it emits very toxic fiimes of NOx and SOx. 

SAFETY PROFILE Poison by ingestion, skin contact, intraperitoneal, and intravenous routes. Moderately toxic by subcutaneous route. An experimental teratogen. Experimental reproductive effects. An eye irritant. When heated to decomposition it emits vety" toxic fumes of NOx, SOx, and ZnO. Used as an antidandruff agent in shampoos. See also ZINC COMPOUNDS and SULFIDES. 

Thietane is a superior inhibitor of corrosion of iron in 10% hydrochloric acid and its effectiveness is said to be due to partial polymerization on the surface of the iron. Addition of chloride ion reduces the inhibition, possibly by inducing ringopening with the formation of sulfhydryl groups. The cyclic sulfide also has been considered as an odorant for natural gas and its absorption by organic soil and clay have been determined. Stabilization of methylchloroform and trichloroethylene by thietane, 2-methylthietane, 3-hydroxythietane, and two spirothietane derivatives has been claimed. Phosphorus and tin derivatives of 3,3-bis-hydroxy-methylthie-tane are reported to be light stabilizers for poly(vinyl chloride), and the dibutyl-tin derivative is a catalyst for the polymerization of aliphatic isocyanates. Mercury and zinc compounds derived from phenylmercury or phenylzinc hydroxide and 3-... 

These condensation compounds are not easily reduced, the follomng reagents being without effect zinc and acetic or hydrochloric acid aluminium powder and sodium hydroxide sodium and alcohol. 

Organozinc compounds add to conjugated systems. The use of chiral ligands is effective for conjugate addition of diaUcylzinc compounds to a,p-unsaturated ketones, esters, and so on, including conjugated lactones." Many dialkyl-zinc compounds can be used, including vinylzinc compounds.Dialkylzinc... 

A recent paper by Cooper et al. [155] reported a fairly strong catalytic effect of an unidentified zinc compound on the reaction of an aromatic isocyanate with 3,3 -dichlorobenzidine. Axelrood et al. [184] found diethylene triamine and stannous octoate to be powerful cateilysts for the reaction of phenyl isocyanate and an aromatic diamine, whereas di-butyltin dilaurate and cobalt naphthenate had only a mild effect in their system. 

Acute oral toxicity in rodents exposed to zinc is low, with LD50 values in the range 30-600 mg kg body weight, depending on the zinc salt administered. Acute effects in rodents following inhalation or intratracheal instillation of zinc compounds include respiratory distress, pulmonary edema, and infiltration of the lung by leukocytes. 

Since Cd(CF3)2DME is ordinarily vastly superior to Hg(CF3)2 as a tii-fluoromethylating agent, it seems only reasonable to assume that trifluoromethyl zinc compounds might well be even more effective. Diligand Zn(CF3)2 complexes have been prepared by a number of routes, including the reactions of Zn(CH3)2 with Hg(CF3)2 (87) orCF3I (88) in basic solvents like pyridine, dimethoxyethane, and acetonitrile. 

Use Zinc salts and other zinc compounds, reducing agent, precipitating agent, purifier, catalyst, rust-resistant paints, bleaches, pyrotechnics, soot removal, pipe-thread compounds, sherardizing, decorative effect in resins, autobody coatings. 

As only limited data are available for zinc distearate the assessment was based on toxicological data of other zinc compounds like zinc gluconate, zinc sulphate or zinc oxide assuming that the availability of zinc ions is controlling the toxicological behaviour. It is further assumed that calcium does not contribute to adverse effects at the expected concentration levels. 

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