Tributyltin water-soluble

Recently, there has been much interest in developing water-soluble tributyltin biocides to lessen the costs of application, and to prevent fire hazards when treating material in confined spaces. Bis(tributyltin) oxide itself has a very low aqueous solubility ( 0.001%), but it may be made water-dispersible by the addition of certain (534, 535) quaternary ammonium salts. Formulations of this type, although currently under development as wood preservatives (534), have been used extensively in the United Kingdom for the treatment of stonework to eradicate fungal growths, algae, mosses, and lichens (535). 

TBTO is a colorless liquid of low water solubility and low polarity. Its water solubility varies between <1.0 and >100 mg/L, depending on the pH, temperature, and presence of other anions. These other anions determine the speciation of tributyltin in natural waters. Thus, in sea water, TBT exists largely as hydroxide, chloride, and carbonate, the structures of which are given in Figure 8.5. At pH values below 7.0, the predominant forms are the chloride and the protonated hydroxide at pH8 they are the chloride, hydroxide, and carbonate and at pH values above 10 they are the hydroxide and the carbonate (EHC 116). 

The reactions are commonly initiated with AIBN at ca. 80 °C in a solvent such as benzene or toluene, but alkyl halides have also been reduced at -60 °C with tributyltin hydride under sonication conditions.133-134 Some reductions of halides have been carried out by generating the tin hydride in situ from a molar equivalent of the reducing agent [lithium aluminium hydride, sodium borohydride, or poly(methylhydrosiloxane)] and a catalytic amount of organotin hydride, halide, or oxide. Reduction of halides has also been carried out under aqueous conditions, using 4,4 -azobis(4-cyanovaleric acid) (ACVA) as a water-soluble radical initiator.60... 

Finally, although the use of tributyltin hydride is possible in water with or without a detergent as a solubilizing agent [224], noteworthy is the preparation of a water-soluble tin hydride which can be used for the reduction of alkyl halides in phosphate buffer in the presence of a radical initiator. In this way, water-soluble compounds such as unprotected sugars can be used directly without tedious protection/deprotection steps [225]. 

Among these, carboxylic acid esters have gained importance in the field of wood preservation, because they are of lower volatility and water-solubility, but higher thermal stability than TBTO. From comparison data it can be concluded that the tributyltin (TBT) moiety of the TBT esters determines their antimicrobial effectiveness and also their oral toxicity. This is in line with the fact that the TBT esters tend to dissociate into the hydrated TBT cation and the respective anion. Due to the lower TBT content compared with TBTO greater quantities of TBT carboxylic acid ester therefore have to be used to achieve sufficient antimicrobial effectiveness. 

Second, speciation reactions with anions in the test media have to be carefully considered. When tri- and presumably also diorganotins, are added to seawater or physiological fluids, chemical speciation reactions with all major anions form an equilibrium distribution of products (Tobias 1978). In seawater at concentrations below its water solubility of approximately 1 mg L (Maguire and Tkacz 1983), bis(tributyltin) oxide speciates with all major seawater anions to form a spectrum of products dominated by tributyltin chloride (Laughlin et al. 1986). Similar reactions and equilibria would be... 

A controlled and slow chemical reaction with the seawater at the paint surface occurs and guarantees a constant but very low TBT release The TBT binder, a copolymer of tributyltin methacrylate and methyl methacrylate, hydrolyzes in seawater at a constant linear rate. The binder becomes water soluble as soon as enough TBT has been hydrolyzed. Seawater flowing against the ship s hull polishes off the hydrolyzed remainder of the binder. 

Low solubility agents, such as, tributyltin fluoride (TBTF), had very low solubility in such thermoplastics as polyethylene and low solubility in its acting environment as well. For this porosigen system, water soluble salts and oxides were added to the thermoplastic. As this soluble portion was leached out of the plastic, a porosity system was developed... 

In order to avoid the necessity of adding a quaternary ammonium compound to solubilize the organotin derivative, a number of new, anionic, tributyltin salts of the type (RsR P)" (BuaSnClt) , where R = Ri = "Bu or Ph R = Ph, R = Bz, were prepared (440, 536). Although these contain discrete, trigonal, bipyrEimidal tributyldichloro-stannate anions (440), their solubility in water was found to be very low. 

The solubilities of organotin compounds in water are not well known. At ambient temperatures, their solubilities range from 10 pg/L to about 50 mg/L (Laughlin and Linden 1985 WHO 1980). It has been estimated that the solubility of bis(tributyltin) oxide ranges from 0.7 to 7 mg/L at pH 6 (Maguire et al. 1983). 

Trimethyltin halides are fairly soluble in water, and can often be washed out of a solution of the reaction mixture in an immiscible solvent. If the desired product is polar, it can be separated from tributyltin halides by partition between acetonitrile and hexanes, which are immiscible.52 53... 

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