Thermodynamic driving forces of eight possible elementary steps for Hantzsch ester and six possible elementary steps for H2 to release two hydrogen atoms (2H•) or ions (H− and H+) in acetonitrile were examined using experimental method or the available related thermodynamic data for the first time, which can facilitate chemists to choose a suitable reducing agent between Hantzsch ester and H2 to reduce a given organic unsaturated compound in acetonitrile and make a rational diagnosis on the detailed reaction mechanisms. The focus of this paper is to compare the differences between Hantzsch ester and H2 to release two hydrogen atoms (or ions) on the thermodynamics of elementary steps in acetonitrile. Copyright