[emptyregrets]

I'm doing a reaction where the procedure calls to add one of the reagents slowly over the course of 30 minutes to the reaction flask, but why would you do this instead of adding it all at once?  If necessary, I can copy/paste the procedure here.  Thanks!

[AWK]

The synthesis procedures are usually optimized to achieve the highest possible yields or the lowest amount of by-products.

[Borek]

What if the reaction is strongly exothermic?

What it the reagent can - in the conditions of the reaction - react with not only other reagents present, but also with itself?

etc.

[wildfyr]

Sometimes two reactions can occur. Like if you have 1eq of bis-acid chloride and 1 equivalent of amine, and by adding the amine slowly you minimize the amount of times the acid chloride gets substituted twice because the amine is always low concentration with respect to bis-acid chloride.

[OrganicDan96]

think about concentration and why keeping the concentration of one reagent low might be advantageous in some reactions