THE EFFECTS OF SELECTED SOLVENTS ON ALLYLTRIMETHOXYSILANE AND CHLOROPROP YLTRIMETHOXYSILANE AND THE ROLE OF THESE SOLVENTS IN DETERMINING MUTAGENIC POTENTIAL IN SALMONELLA AND ESCHERICHIA COLI

Recently acquired bacterial mutagenicity test data (salmonella/Escherichia coli) indicated that allyltrimethoxysilane (ATMOS) showed mutagenic activity when prepared as a solution in ethanol but was not mutagenic in the same test when prepared in dimethylsulfoxide (DMSO), methanol, or acetone. Chloropropyltrimethoxysilane (CPTMOS)was positivein this assay whether ethanol, methanol, acetone, or DMSO was used as the solvent. A study was carried out to evaluate the effect of the solvent on each methoxysilane as it is prepared for the mutagenicity test. A scheme was used for ATMOS and CPTMOS in which 6 samples were prepared as 10 wt% solutions of either silane in ethanol, DMSO, or acetone(solvents commonly used in the bacterial mutagenicity test)and then analyzed by 29 Si NMR. The samples were then mixed 50:50 with pH 7 phosphatebuffered water and analyzed again over several hours. The solvent interaction with methanol was not investigated but is believed to be unlikely since the only reaction expected would be exchange of methoxy groups between the silane and methanol. These experiments showed that CPTMOS and ATMOS are stable in ethanol, acetone, and DMSO prior to dilution with water. Subsequently, aqueous dilutions of ethanol and acetone solutions of the two silanes did not undergo observable hydrolysis under these conditions. However, both methoxysilanes began hydrolysis immediately when the DMSO solutions were diluted with water. Condensation products were subsequently observed within 40 min. These data together with the differing bacterial mutagenicity test results for ATMOS in ethanol vs. methanol or acetone suggest that (1) the use of DMSO as a solvent for the mutagenicity testing of some methoxysilanes may be inappropriate and (2) alkoxysilanes in general should be tested in the compatible alcohols or other suitable solvent to avoid possible transalkoxylation reactions.