Draw a reasonable mechanism for the conversion of vanillin to vanillyl alcohol in the presence of sodium borohydride in aqueous hydroxide followed by the acid work-up in aqueous acid using the curved-arrow formalism (see Fig. 4). Hint: 3-steps.
The first step is an acid-base reaction. Be sure you explain the acid-base chemistry reactions in steps 1 and 3 using appropriate pKa values. Compound [pKa]: Vanillin [7.4]; H2O [15.7]; ROH [17]; HCl [â7].
1. EtOH, HO HO 2. H+, H20 Vanillin Vanillyl alcohol 4-hydroxy-3-methoxybenzyl alcohol 4-hydroxy-3-methoxybenzaldehyde Figure 4. Reduction of vanillin with NaBH4 in the presence of aqueous sodium hydroxide.
