Nitroacetic acid, the most active activated carboxylic acid (ACA) employed so far, is used to transiently increase the conductivity of a water solution. Its dissociation produces ions that act as charge carriers, increasing the conductivity of the system. The subsequent, spontaneous decarboxylation removes such ions from the solution lowering the conductivity to a base value. This conductivity cycle is used to control simple electric circuits.

Abstract

Temporal control of the chemical properties of a molecular system is a main goal of the research focused on dissipative systems, systems chemistry, and smart materials. In this work, we show that nitroacetic acid, a typical activated carboxylic acid (ACA), can be exploited to transiently amplify the electrical conductivity of an aqueous solution. The addition of nitroacetic acid to a water solution induces a transient increase in conductivity, which then decreases over time following the kinetically first order conversion of nitroacetic acid into nitromethane. The rate of the decrease in conductivity can be modulated by varying the temperature or the concentration of an auxiliary base further added to the solution. The time-control of the conductivity is exploited to build a variable resistor which is integrated in simple circuits to operate electrical devices.