Benzaldehyde Lab Report

Initially, the conversion of benzyl alcohol in to benzaldehyde was chosen as a model reaction to optimize the reaction conditions. Effect of reaction time and mmol of H2O2 on progress of oxidation reaction was studied (Fig. 4. the experiment was performed with 20 mg catalyst, 10 ml acetonitrile and two different amount of H2O2 1 and 2 mmol for 1mmol benzyl alcohol at reflux condition (85 ºC ) and plotted with respect to the time. With increasing the mole ratio of BzOH : H2O2 from 1:1 to 1:2, the conversion of benzyl alcohol increased from 75% to 93%. The conversion also increased with increasing time of reaction and then remain constant at 180 min. From Fig. 4, it can be deduced that the maximum yield of benzaldehyde was obtained within 2 h when the mole ratio of BzOH: H2O2 was 1:2.

It seems that solvents play a pivotal role in the liquid phase catalytic reaction. The conversion of benzyl alcohol is 5% under solvent-free conditions (Table 1, entry 1). The conversion percentage of benzyl alcohol are different in nonpolar to polar solvents. As demonstrated by Table 1, the conversion of benzyl alcohol is 40%, 62%, 93% and 10% when n-hexane, toluene, acetonitrile and H2O are used as solvent, respectively (Table 1, entries 2-5). This indicates that aprotic acetonitrile with large dielectric constant promote the collisions and dispersion of oxygen source, the alcohol and the catalyst [15]. Furthermore, acetonitrile can form a perhydroxyl anion (OOH-) and activate the hydrogen peroxide. Perhydroxyl anion can attacks the nitrile to produce a peroxy carboximidic acid intermediate, which can act as an oxygen transfer agent and improve the conversion