A highly active solid superacid of sulfated tin oxide was prepared from tin oxide gel, which was precipitated by the hydrolysis of SnCl 4 and washed with aqueous ammonium acetate solution, followed by exposure to aqueous sulfuric acid and calcining. Differencial thermal analysis suggested that the acetate ion remaining on the surface was replaced with sulfate ion. The acid strength of the sulfated tin oxide estimated by temperature-programmed desorption using argon was higher than that of sulfated zirconia, a well-known solid superacid, the activation energy of Ar desorption by the former being 10.6 kJ mol -1 in comparison with 9.3 kJ mol -1 by the latter. The sulfated tin oxide showed activities much higher than those of the sulfated zirconia for the skeletal isomerization of n-pentane, the Mukaiyama aldol condensation of 1-trimethylsilyloxy-1-cyclohexene with benzaldehyde, and the benzoylation of toluene with benzoic anhydride.

The degradation of organic materials was often observed during XPS measurement. We have evaluated the degradation of silicon wafers modified with 3,3,3-trifluoropropyltrimethoxysilane (F3PTMS-Si), 3-chloropropyltriethoxysilane (CPTES-Si), 3-bromopropyltrimethoxysilane (BPTMS-Si) and 3-iodopropyltrimethoxysilane (IPTMS-Si), and gold substrate modified with 1H,1H,2H,2H-perfluorodecanthiol (PFDT-Au) as reference material in order to investigate influence of C-F, C-Cl, C-Br and C-I bonds in the organic silane monolayers. As a result, the order of damaging factor, β, was IPTMS-Si > BPTMS-Si > CPTES-Si > F3PTMS-Si. It was found that the value of β was related to the chemical bond energy of C-X(X=F, Cl, Br, I).