The directing effect of multiple substituents is dominated by the most powerful activator. Which is the most powerful activator for vanillin

- OH group is the most powerful activator

Explanation:

The most powerful activator for Vanillin is the  - OH group and this is due to the effect of the +R  on the  - OH group and also there is more overlapping experienced in -OH groups compared to - OCH3 group

attached below is the reaction scheme

a. possible errors

d. new questions

explanation:

predictions and planning happen before. a summery comes after. errors you get after investigation and new questions propose what you can look for in the future.