Dibutyltin dichloride system

Our attention turned next to a widely used type of commercial stabilizer, dibutyltin di-isooctylthioglycolate. The ligand exchange reaction in the dibutyltin di-isooctylthiogylcolate/dibutyltin dichloride system was studied by both JH and 18C NMR. In the experiments the resonance of the methylene group in the thioglycolate moiety (-S-CH2-COO-) was used to follow the reaction. When Compounds 7 and S (Table III, Experiments 6, 7, and 8) were mixed at 25°C in deutero-... 

Table III. 60-MHz H NMR Data for the Dibutyltin Di-isooctylthioglycolate/Dibutyltin Dichloride System...

Examination of the dibutyltin dilaurate/dibutyltin dichloride system by 13C NMR gave an unexpected result. No evidence was found for the existence of a complete exchange reaction in this case. The only effect noted in the spectra as the concentration of dibutyltin dichloride increased was a linear, downfield shift of the laurate carbonyl resonance... 

Figure 2. The 13C NMR spectra of the carbonyl region for the dibutyltin diisooctylthioglycolate/ dibutyltin dichloride system (Table IV)...

OTCs have severe effects on the immune systems, causing premature atrophy of thymus gland and lymphoid tissues as well as inhibition of spleen cell activity. Inhibition of phagocytosis and cytolysis of polymorphonuclear leukocytes with resultant depression of cell-mediated immune responses have also been demonstrated21-37. The influence of the thymus atrophy-inducing dibutyltin dichloride Bu2SnCl2 on the differentiation and proliferation of immature rat thymocyte subsets were studied in vivo and in vitro. The atrophy results from a depletion of small CD4+CD8+ thymocytes which is caused by a diminished production of immature CD4+CD8+ and CD4+CD8+ thymoblasts. Dibutyltin dichloride inhibits the activation, but not the differentiation of immature CD4+CD8+ thymocytes in vivo and in vitro, suggesting a selective antiproliferative activity of this compound. It also... 

Dibutyltin dichloride (DBTC) is a widespread environmental pollutant that exhibits developmental toxicity in animals 19 and immunotoxic effects in human cells in vitroJ2°l No studies were found in the literature that compared the developmental and immunotoxic effects of DBTC alone to a mixture of DBTC and ethanol. One study, however, found that ethanol co-administered with DBTC increased the toxicity of DBTC in the liver and pancreas of laboratory animals both acutely and chronically. 21 An analysis of this study suggests that the combination of DBTC and ethanol might be expected to show enhanced toxic effects on other body organs and systems. 

Figure I. The 1H NMR spectra for the dibutyltin di-isooctylthioglycolate/di-butyltin dichloride system (Table III)...

We also have obtained ir spectra on the diisooctylthioglycolate system in the absence of solvent. The carbonyl bands of each component can be seen and identified clearly (7 (C=0) at 1740 cm1 and 9 (C=0) at 1680 cm-1). The relative intensities of the two bands vary with the initial concentration of dibutyltin dichloride. 

An even simpler system composed of dibutyltin diacetate and dibutyltin dichloride was examined by both 13C NMR and low-temperature XH NMR because of the report that dibutylchlorotin acetate formed immediately when the reagents were mixed in carbon tetrachloride (16). The 13C spectra of the pure diacetate and the mixed system were obtained using conditions suitable for quantitative analysis. In deuterochloroform, at 30 °C, over a wide range of concentrations, no evidence could be found for the presence of the excess component or the exclusive formation of dibutylchlorotin acetate. The 1H NMR spectra gave similar results and the spectra were unchanged between 50° and — 50° C. 

In both cases yield was markedly dependent on the molar ratio of the reactants, reaching a maximum at a 3 2 ratio of dibutyltin dichloride to dextran-hexose units. This coincides with a 1 1 ratio of reactive Lewis acid to base groups (i.e., equal molar amounts of reactive groups present) and is consistent with results obtained from studying a number of other interfacial condensation systems. 

For both series of reactions, yield dropped dramatically as the ratio of dibutyltin dichloride to dextran exceeded about 2 1. Thus, while the system "tolerated some excess dextran, it is less "forgiving when employing excess stannane. Furthermore, a substantial yield is produced even when the molar ratio of stannane to dextran is low. This is promising for industrial applications where the tin content of the modified dextran may be desired to be maintained at low level. 

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