Trimethoxybenzaldehyde from Syringaldehyde

At the end of two hours, the heating was discontinued and about 500 mL. of hot water was added to the mixture. The mixture was acidified with concentrated hydrochloric acid and was then extracted three times with about 250 mL. of benzene and the combined extract was washed with water. The benzene was removed by distillation and the solid product was dried in a vacuum oven and weighed. The yield was 106.9 g of 3,4,5-trimethoxybenzaldehyde, representing a yield of 99.3% of the theoretical. Analysis by gas-liquid chromatography (g.l.c.) showed a purity of 99.85% with syringaldehyde as the only detectable impurity. 

20 g ofp-hydroxybenzaldehyde (0.164 mol) was reacted with 29.0 g of dimethyl sulfate (0.230 mol) and 22.0 g of sodium carbonate (0.20 mol) for 2 hr. at 75°-80° C. A total of 12 mL. of water was added in small portions over the last hour. Work-up by addition of water, acidificatior-and benzene extraction yielded 22.27 g ofp-methoxybenzaldehyde (99.9% / containing not more than 0.1% p-hydroxybenzaldehyde. 

---