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.