silane - functionalized ultraviolet screening agent precursors comprise compounds of the formula : ## str1 ## wherein r is ## str2 ## r 1 is c 1 - c 6 alkyl , r 2 is c 1 - c 6 alkyl or c 2 - c 6 alkanoyl , r 3 is hydrogen or c 1 - c 6 alkoxyl , x is 0 , 1 or 2 , y is 1 , 2 , or 3 and x + y = 3 . under ultraviolet radiation the compounds rearrange to the corresponding α - hydroxybenzophenones which protect substrates , especially transparent plastics , against degradation .