4. Results and discussion
4.1 Solvent effects
The effects of the different organic solvents used in conjunction with the acetophenone reactant were first studied as their different physical and chemical properties could significantly affect the reaction performance, especially when an external electric field is applied. Five primary alcohols, namely 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, and 1-octanol as organic solvents were investigated due to their ability to maintain a stable biphasic reaction system. The experimental results are presented in Figure 1, showing total conversion values and product yields. Table 1 lists the physical and chemical properties of the five solvents. No corresponding aldehyde by-products were detected by GC analysis after the reactions, which confirms the role of sodium formate as hydrogen source and the concept of phase transfer hydrogenation. As we can see, addition of 1-butanol resulted in the best performance on promoting the transfer hydrogenation of acetophenone with conversion of 84.7% and yield of 76.8% after 24 h of reaction under 15 V of positive DC voltage with stainless-steel electrodes. The conversion and yield decreased gradually with the increase of the molecular weight of these homologous alcohol solvents.