why we use ammonium acetate instead of ammonia solution in Hantzsch Dihydropyridine synthesis ?

Answer 1

It's a matter of practicality, as are most things in life.

Ammonia solution is a liquid and can be difficult to work with. Ammonium acetate is a solid, is easily weighed out, and apart from being mildly hygroscopic, is pretty easy to work with. As a general rule, chemists prefer to work with solids over liquids (and certainly gases).

Answer 2

You can use ammonia solution as well; ammonia and ammonium acetate can both serve as a nitrogen donor. It probably just depends on what's handy in your lab.

Answer 3

arg... brain freeze!!