Stannous salts, reactions

Stannic and stannous chloride are best prepared by the reaction of chlorine with tin metal. Stannous salts are generally prepared by double decomposition reactions of stannous chloride, stannous oxide, or stannous hydroxide with the appropriate reagents. MetaUic stannates are prepared either by direct double decomposition or by fusion of stannic oxide with the desired metal hydroxide or carbonate. Approximately 80% of inorganic tin chemicals consumption is accounted for by tin chlorides and tin oxides. 

The addition of slaked lime and the initiation of polymerization reactions with 11.Og and feme 01 stannous salts are techniques employed to lemove aminophenols from wastewaters... 

Sulfides. Stannous sulfide SnS, dark brown precipitate, by reaction of stannous salt solution and H2S, insoluble in sodium sulfide solution but soluble in sodium polysulfide solution, forming sodium thiostannate stannic sulfide SnS , yellow precipitate, by reaction of stannic salt solution and H>S, soluble in sodium sulfide solution, forming sodium thiostannate. 

When an excess of nitric acid of 10-50 per cent, strength is treated in the cold with stannous salt soln., hydroxylamine salts are the primary end-product of the reaction, but when the conditions of temp, and cone, are such that the nitric acid and the hydroxylamine salts react, then nitrous oxide is the. chief product together with small amounts of nitHe oxide, nitrogen and traces of nitrogen peroxide. No ammonium salts are formed. When stannous salts are used in excess over the nitric acid, the reaction takes place with hydroxylamine and ammonium salts as the products either in hot or cold soln., but the reaction is very slow in the latter case. When an excess of nitric acid is treated with titanous salt soln., the reaction takes place very rapidly with the formation of nitric oxide as the chief... 

There are two series of compounds of tin and the halogens those related to stannous oxide, SnO, in which the metal has a valence of 2 (stannous salts), and those related to stannic oxide, Sn02, in which it has a valence of 4 (stannic salts). The compounds with lower valence are usually prepared by the action of the halogen acids on the metal. Stannous chloride, for example, is formed when hydrochloric acid reacts with tin. Stannic salts, on the other hand, are prepared by the reaction of tin and the free halogen. In this preparation stannic bromide results from the reaction of bromine and tin. The reaction between the two ele-... 

Numerous applications of standard electrode potentials have been made in various aspects of electrochemistry and analytical chemistry, as well as in thermodynamics. Some of these applications will be considered here, and others will be mentioned later. Just as standard potentials which cannot be determined directly can be calculated from equilibrium constant and free energy data, so the procedure can be reversed and electrode potentials used for the evaluation, for example, of equilibrium constants which do not permit of direct experimental study. Some of the results are of analjrtical interest, as may be shown by the following illustration. Stannous salts have been employed for the reduction of ferric ions to ferrous ions in acid solution, and it is of interest to know how far this process goes toward completion. Although the solutions undoubtedly contain complex ions, particularly those involving tin, the reaction may be represented, approximately, by... 

To 5 c.c. of the original solution add 10 drops of concentrated nitric acid and heat to boiling. Cool the solution and test for a stannous salt. (10) How did you test (11) With what result (12) What has happened to the stannous chloride (13) Will this reaction be brought about by the air (14) What is used in the laboratory to preserve solutions of stannous chloride from change ... 

The reaction between stannous salts and ferric salts occurs formally according to the equation ... 

Catalysis of the flexible polyurethane foaming operation is accompHshed through the use of tertiary amine compounds, often using two different amines to balance the blowing and gelling reactions. Organometallic compoimds, usually stannous salts, are also used to facilitate gelling and promote final cure. 

Tin hydride has been made by the reaction of hydrochloric acid with magnesium-tin alloy (1) or metallic tin (2) by reduction of stannous salts electrolytically (3), by metals (4, 5), or sodium borohydride (6) and by reduction of stannic chloride by atomic hydrogen (7) or metals (S). Perhaps the most practical method involves the reduction of stannic chloride with lithium aluminum hydride under nitrogen (9, 10, 11) containii 0 1% oxygen 12) at — 70° C. The presence of oxygen inhibits the decomposition, which ordinarily occurs at room temperature. This inhibition is at least partially due to the fact that metallic tin is a catalyst for the decomposition, but in the presence of oxygen becomes coated with a film of oxide, which is ineffective as a catalyst 12). 

It is obvious that a route to effective, stoichiometric decomposition of TBPO in the presence of a stannous salt requires complete dissociation or hydrolysis of the latter through a change in reaction condition (e.g., an acidic pH) or the use of a more rapidly hydrolyzed stemnous salt. It should be noted that stannous chloride, which generates an acidic medium on hydrolysis, quantitatively decomposes TBPO. Further, stannous laurate, which contains the lauroate moiety, in the presence of emulsifiers such as sodium lauryl sulfate or dodecylbenzene sulfonate results in a more rapid polymerization rate and a higher conversion of VCM than stannous octoate, indicative of a greater availability of the effective reductant (i.e., a stannous ion). The stannous laurate may be solubilized in the aqueous phase and the resultant mi-... 

Anhydrous stannous chloride, a water-soluble white soHd, is the most economical source of stannous tin and is especially important in redox and plating reactions. Preparation of the anhydrous salt may be by direct reaction of chlorine and molten tin, heating tin in hydrogen chloride gas, or reducing stannic chloride solution with tin metal, followed by dehydration. It is soluble in a number of organic solvents (g/100 g solvent at 23°C) acetone 42.7, ethyl alcohol 54.4, methyl isobutyl carbinol 10.45, isopropyl alcohol 9.61, methyl ethyl ketone 9.43 isoamyl acetate 3.76, diethyl ether 0.49, and mineral spirits 0.03 it is insoluble in petroleum naphtha and xylene (2). 

In the presence of the organic siHcate, the heavy-metal salts trigger the chain extension and cross-linking reactions that lead to siHcone mbber and volatile ethanol as a byproduct. Useful metal soaps iaclude stannous octanoate [1912-83-0], ziac octanoate [557-09-5], dibutyltin dilaurate [77-58-7], and dibutyltin diacetate [1067-33-0]. The reactivity of the different salts varies considerably. Stannous octanoate effects a cure ia 0.5—2 min ziac octanoate may require 24—96 h the dibutyltin dilaurate, 10—20 min. Heat and moisture accelerate the curing rate, but to a lesser degree than ia the case of the polysulfide mbbers. 

Other Octoate Uses. Metal octoates are also used as driers in printing inks. Another appHcation of octoates includes the use of the aluminum salt to gel paint. Stannous, dibutyltin, and bismuth carboxylates find appHcation as catalysts in polyurethane foam appHcations in order to obtain a reaction efficiency suitable for industrial production. In polyurethane foam manufacture the relative rate of polymeriza tion and gas foaming reactions must be controlled so that the setting of the polymer coincides with the maximum expansion of the foam. 

The most common catalyst used in urethane adhesives is a tin(lV) salt, dibutyltin dilaurate. Tin(IV) salts are known to catalyze degradation reactions at high temperatures [30J. Tin(II) salts, such as stannous octoate, are excellent urethane catalysts but can hydrolyze easily in the presence of water and deactivate. More recently, bismuth carboxylates, such as bismuth neodecanoate, have been found to be active urethane catalysts with good selectivity toward the hydroxyl/isocyanate reaction, as opposed to catalyzing the water/isocyanate reaction, which, in turn, could cause foaming in an adhesive bond line [31]. 

Reaction.—Make a solution of 4 grams stannous chloride in TO c.c. cone, hydrochloric acid, add 2 grams aminoazobenzene, and boil for a few minutes. On cooling ciystals of the hydrochlorides of aniline and yi-phenylenediamine separate out. The liquid is filtered and washed with a little cone, hydrochloric acid to remove the tin salts. If the precipitate is dissolved in water and made alkaline with caustic soda, a mixture of liquid aniline and solid/-phenylenediamine is precipitated, from which the former may be removed by filtering, washing, and draining on a porous plate. 

Aniline 77 was converted into its diazonium salt with nitrous acid and this was followed by reduction with stannous chloride to afford the corresponding arylhydrazine 78. Condensation of 78 with 3-cyanopropanal dimethylacetal 79 gave the arylhydrazone 80. Treatment of 80 with PPE resulted in cyclization to indole 81. The nitrile group was then reduced to the primary amine by catalytic hydrogenation. Reaction of the amine with excess formalin and sodium borohydride resulted in Imitrex (82). 

For the reduction of nitro-compounds on a small scale, tin or stannous chloride and concentrated hydrochloric acid are the most suitable reagents. Solids are often difficult to reduce in the absence of a solvent and call for the addition of alcohol or glacial acetic acid. When the addition of water to a sample of the reaction mixture produces a clear solution it is known that the reduction is complete. The base will, of course, be present as hydrochloride, and hydrochlorides are, almost without exception, soluble in water. It should be noted, however, that sparingly soluble double salts with stannous chloride are often formed, but these double salts are usually soluble in boiling water. 

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