Reactivity in monolayers versus bulk media: Intra- and intermolecular aminolysis of esters

Monolayers possessing reactive amino and p-nitrophenyl ester functional groups at the same or different levels with respect to the monolayer interface have been self-assembled on a gold surface. Intramolecular reactions in these monolayers are at least 1000 times slower than the same processes in the bulk medium. Control experiments with external reagents showed that the monolayer p-nitrophenyl ester group reacts readily with amines from solution, whereas nucleophilicity of the monolayer amino functionality is significantly suppressed. This unusually low reactivity of the amino group was tentatively assigned to its interaction with the gold surface.